chore: add issue templates

use `vim.g` for setup

.github/ISSUE_TEMPLATE/bug_report.yaml

@@ -0,0 +1,78 @@
+name: Bug Report
+description: Report a bug
+title: 'bug: '
+labels: [bug]
+body:
+  - type: checkboxes
+    attributes:
+      label: Prerequisites
+      options:
+        - label:
+            I have searched [existing
+            issues](https://github.com/barrettruth/cp.nvim/issues)
+          required: true
+        - label: I have updated to the latest version
+          required: true
+
+  - type: textarea
+    attributes:
+      label: 'Neovim version'
+      description: 'Output of `nvim --version`'
+      render: text
+    validations:
+      required: true
+
+  - type: input
+    attributes:
+      label: 'Operating system'
+      placeholder: 'e.g. Arch Linux, macOS 15, Ubuntu 24.04'
+    validations:
+      required: true
+
+  - type: textarea
+    attributes:
+      label: Description
+      description: What happened? What did you expect?
+    validations:
+      required: true
+
+  - type: textarea
+    attributes:
+      label: Steps to reproduce
+      description: Minimal steps to trigger the bug
+      value: |
+        1.
+        2.
+        3.
+    validations:
+      required: true
+
+  - type: textarea
+    attributes:
+      label: 'Health check'
+      description: 'Output of `:checkhealth cp`'
+      render: text
+
+  - type: textarea
+    attributes:
+      label: Minimal reproduction
+      description: |
+        Save the script below as `repro.lua`, edit if needed, and run:
+        ```
+        nvim -u repro.lua
+        ```
+        Confirm the bug reproduces with this config before submitting.
+      render: lua
+      value: |
+        vim.env.LAZY_STDPATH = '.repro'
+        load(vim.fn.system('curl -s https://raw.githubusercontent.com/folke/lazy.nvim/main/bootstrap.lua'))()
+        require('lazy.nvim').setup({
+          spec = {
+            {
+              'barrett-ruth/cp.nvim',
+              opts = {},
+            },
+          },
+        })
+    validations:
+      required: true

.github/ISSUE_TEMPLATE/config.yaml

@@ -0,0 +1,5 @@
+blank_issues_enabled: false
+contact_links:
+  - name: Questions
+    url: https://github.com/barrettruth/cp.nvim/discussions
+    about: Ask questions and discuss ideas

.github/ISSUE_TEMPLATE/feature_request.yaml

@@ -0,0 +1,30 @@
+name: Feature Request
+description: Suggest a feature
+title: 'feat: '
+labels: [enhancement]
+body:
+  - type: checkboxes
+    attributes:
+      label: Prerequisites
+      options:
+        - label:
+            I have searched [existing
+            issues](https://github.com/barrettruth/cp.nvim/issues)
+          required: true
+
+  - type: textarea
+    attributes:
+      label: Problem
+      description: What problem does this solve?
+    validations:
+      required: true
+
+  - type: textarea
+    attributes:
+      label: Proposed solution
+    validations:
+      required: true
+
+  - type: textarea
+    attributes:
+      label: Alternatives considered

.github/workflows/ci.yaml

@@ -0,0 +1,112 @@
+name: ci
+on:
+  workflow_call:
+  pull_request:
+    branches: [main]
+  push:
+    branches: [main]
+
+jobs:
+  changes:
+    runs-on: ubuntu-latest
+    outputs:
+      lua: ${{ steps.changes.outputs.lua }}
+      python: ${{ steps.changes.outputs.python }}
+    steps:
+      - uses: actions/checkout@v4
+      - uses: dorny/paths-filter@v3
+        id: changes
+        with:
+          filters: |
+            lua:
+              - 'lua/**'
+              - 'spec/**'
+              - 'plugin/**'
+              - 'after/**'
+              - 'ftdetect/**'
+              - '*.lua'
+              - '.luarc.json'
+              - 'stylua.toml'
+              - 'selene.toml'
+            python:
+              - 'scripts/**'
+              - 'scrapers/**'
+              - 'tests/**'
+              - 'pyproject.toml'
+              - 'uv.lock'
+
+  lua-format:
+    runs-on: ubuntu-latest
+    needs: changes
+    if: ${{ needs.changes.outputs.lua == 'true' }}
+    steps:
+      - uses: actions/checkout@v4
+      - uses: JohnnyMorganz/stylua-action@v4
+        with:
+          token: ${{ secrets.GITHUB_TOKEN }}
+          version: 2.1.0
+          args: --check .
+
+  lua-lint:
+    runs-on: ubuntu-latest
+    needs: changes
+    if: ${{ needs.changes.outputs.lua == 'true' }}
+    steps:
+      - uses: actions/checkout@v4
+      - uses: NTBBloodbath/selene-action@v1.0.0
+        with:
+          token: ${{ secrets.GITHUB_TOKEN }}
+          args: --display-style quiet .
+
+  lua-typecheck:
+    runs-on: ubuntu-latest
+    needs: changes
+    if: ${{ needs.changes.outputs.lua == 'true' }}
+    steps:
+      - uses: actions/checkout@v4
+      - uses: mrcjkb/lua-typecheck-action@v0
+        with:
+          checklevel: Warning
+          directories: lua
+          configpath: .luarc.json
+
+  python-format:
+    runs-on: ubuntu-latest
+    needs: changes
+    if: ${{ needs.changes.outputs.python == 'true' }}
+    steps:
+      - uses: actions/checkout@v4
+      - uses: astral-sh/setup-uv@v4
+      - run: uv tool install ruff
+      - run: ruff format --check .
+
+  python-lint:
+    runs-on: ubuntu-latest
+    needs: changes
+    if: ${{ needs.changes.outputs.python == 'true' }}
+    steps:
+      - uses: actions/checkout@v4
+      - uses: astral-sh/setup-uv@v4
+      - run: uv tool install ruff
+      - run: ruff check .
+
+  python-typecheck:
+    runs-on: ubuntu-latest
+    needs: changes
+    if: ${{ needs.changes.outputs.python == 'true' }}
+    steps:
+      - uses: actions/checkout@v4
+      - uses: astral-sh/setup-uv@v4
+      - run: uv sync --dev
+      - run: uvx ty check .
+
+  python-test:
+    runs-on: ubuntu-latest
+    needs: changes
+    if: ${{ needs.changes.outputs.python == 'true' }}
+    steps:
+      - uses: actions/checkout@v4
+      - uses: astral-sh/setup-uv@v4
+      - run: uv sync --dev
+      - run: uv run camoufox fetch
+      - run: uv run pytest tests/ -v

.github/workflows/luarocks.yaml

@@ -1,18 +1,21 @@
-name: Release
+name: luarocks
 
 on:
   push:
     tags:
-      - '*'
-  workflow_dispatch:
+      - 'v*'
 
 jobs:
-  publish-luarocks:
-    name: Publish to LuaRocks
+  ci:
+    uses: ./.github/workflows/ci.yaml
+
+  publish:
+    needs: ci
     runs-on: ubuntu-latest
+
     steps:
       - uses: actions/checkout@v4
-      - name: Publish to LuaRocks
-        uses: nvim-neorocks/luarocks-tag-release@v7
+
+      - uses: nvim-neorocks/luarocks-tag-release@v7
         env:
           LUAROCKS_API_KEY: ${{ secrets.LUAROCKS_API_KEY }}

.github/workflows/quality.yaml

@@ -1,4 +1,4 @@
-name: Code Quality
+name: quality
 
 on:
   pull_request:

.github/workflows/test.yaml

@@ -1,4 +1,4 @@
-name: Tests
+name: tests
 
 on:
   pull_request:

.pre-commit-config.yaml

@@ -25,7 +25,7 @@ repos:
     hooks:
       - id: prettier
         name: prettier
-        files: \.(md|,toml,yaml,sh)$
+        files: \.(md|toml|ya?ml|sh)$
 
   - repo: local
     hooks:

README.md

@@ -19,6 +19,15 @@ https://github.com/user-attachments/assets/e81d8dfb-578f-4a79-9989-210164fc0148
 - **Language agnostic**: Works with any language
 - **Diff viewer**: Compare expected vs actual output with 3 diff modes
 
+## Installation
+
+Install using your package manager of choice or via
+[luarocks](https://luarocks.org/modules/barrettruth/cp.nvim):
+
+```
+luarocks install cp.nvim
+```
+
 ## Optional Dependencies
 
 - [uv](https://docs.astral.sh/uv/) for problem scraping

cp.nvim-scm-1.rockspec

@@ -2,7 +2,7 @@ rockspec_format = '3.0'
 package = 'cp.nvim'
 version = 'scm-1'
 
-source = { url = 'git://github.com/barrett-ruth/cp.nvim' }
+source = { url = 'git://github.com/barrettruth/cp.nvim' }
 build = { type = 'builtin' }
 
 test_dependencies = {

doc/cp.nvim.txt

@@ -205,71 +205,66 @@ Debug Builds ~
 ==============================================================================
 CONFIGURATION                                                      *cp-config*
 
-Here's an example configuration with lazy.nvim:
+Configuration is done via `vim.g.cp_config`. Set this before using the plugin:
 >lua
-    {
-      'barrett-ruth/cp.nvim',
-      cmd = 'CP',
-      build = 'uv sync',
-      opts = {
-        languages = {
-          cpp = {
-            extension = 'cc',
-            commands = {
-              build = { 'g++', '-std=c++17', '{source}', '-o', '{binary}',
-              '-fdiagnostics-color=always' },
-              run   = { '{binary}' },
-              debug = { 'g++', '-std=c++17', '-fsanitize=address,undefined',
-                        '{source}', '-o', '{binary}' },
-            },
-          },
-          python = {
-            extension = 'py',
-            commands = {
-              run   = { 'python', '{source}' },
-              debug = { 'python', '{source}' },
-            },
+    vim.g.cp_config = {
+      languages = {
+        cpp = {
+          extension = 'cc',
+          commands = {
+            build = { 'g++', '-std=c++17', '{source}', '-o', '{binary}',
+            '-fdiagnostics-color=always' },
+            run   = { '{binary}' },
+            debug = { 'g++', '-std=c++17', '-fsanitize=address,undefined',
+                      '{source}', '-o', '{binary}' },
           },
         },
-        platforms = {
-          cses = {
-            enabled_languages = { 'cpp', 'python' },
-            default_language  = 'cpp',
-            overrides = {
-              cpp = { extension = 'cpp', commands = { build = { ... } } }
-            },
-          },
-          atcoder = {
-            enabled_languages = { 'cpp', 'python' },
-            default_language  = 'cpp',
-          },
-          codeforces = {
-            enabled_languages = { 'cpp', 'python' },
-            default_language  = 'cpp',
+        python = {
+          extension = 'py',
+          commands = {
+            run   = { 'python', '{source}' },
+            debug = { 'python', '{source}' },
           },
         },
-        open_url = true,
-        debug = false,
-        ui = {
-          ansi = true,
-          run = {
-            width = 0.3,
-            next_test_key = '<c-n>',  -- or nil to disable
-            prev_test_key = '<c-p>',  -- or nil to disable
+      },
+      platforms = {
+        cses = {
+          enabled_languages = { 'cpp', 'python' },
+          default_language  = 'cpp',
+          overrides = {
+            cpp = { extension = 'cpp', commands = { build = { ... } } }
           },
-          panel = {
-            diff_mode = 'vim',
-            max_output_lines = 50,
-          },
-          diff = {
-            git = {
-              args = { 'diff', '--no-index', '--word-diff=plain',
-                       '--word-diff-regex=.', '--no-prefix' },
-            },
-          },
-          picker = 'telescope',
         },
-      }
+        atcoder = {
+          enabled_languages = { 'cpp', 'python' },
+          default_language  = 'cpp',
+        },
+        codeforces = {
+          enabled_languages = { 'cpp', 'python' },
+          default_language  = 'cpp',
+        },
+      },
+      open_url = true,
+      debug = false,
+      ui = {
+        ansi = true,
+        run = {
+          width = 0.3,
+          next_test_key = '<c-n>',  -- or nil to disable
+          prev_test_key = '<c-p>',  -- or nil to disable
+        },
+        panel = {
+          diff_modes = { 'side-by-side', 'git', 'vim' },
+          max_output_lines = 50,
+        },
+        diff = {
+          git = {
+            args = { 'diff', '--no-index', '--word-diff=plain',
+                     '--word-diff-regex=.', '--no-prefix' },
+          },
+        },
+        picker = 'telescope',
+      },
     }
 <
 
@@ -279,7 +274,7 @@ the default; per-platform overrides can tweak 'extension' or 'commands'.
 
 For example, to run CodeForces contests with Python by default:
 >lua
-    {
+    vim.g.cp_config = {
       platforms = {
         codeforces = {
           default_language  = 'python',
@@ -290,7 +285,7 @@ For example, to run CodeForces contests with Python by default:
 Any language is supported provided the proper configuration. For example, to
 run CSES problems with Rust using the single schema:
 >lua
-    {
+    vim.g.cp_config = {
       languages = {
         rust = {
           extension = 'rs',
@@ -378,8 +373,10 @@ run CSES problems with Rust using the single schema:
 
                                                               *cp.PanelConfig*
     Fields: ~
-        {diff_mode}        (string, default: "none") Diff backend: "none",
-                           "vim", or "git".
+        {diff_modes}       (string[], default: {'side-by-side', 'git', 'vim'})
+                           List of diff modes to cycle through with 't' key.
+                           First element is the default mode.
+                           Valid modes: 'side-by-side', 'git', 'vim'.
         {max_output_lines} (number, default: 50) Maximum lines of test output.
 
                                                                *cp.DiffConfig*
@@ -784,12 +781,15 @@ HIGHLIGHT GROUPS                                               *cp-highlights*
 
 Test Status Groups ~
 
-    CpTestAC        Green foreground for AC status
-    CpTestWA        Red foreground for WA status
-    CpTestTLE       Orange foreground for TLE status
-    CpTestMLE       Orange foreground for MLE status
-    CpTestRTE       Purple foreground for RTE status
-    CpTestNA        Gray foreground for remaining state
+All test status groups link to builtin highlight groups, automatically adapting
+to your colorscheme:
+
+    CpTestAC        Links to DiagnosticOk (AC status)
+    CpTestWA        Links to DiagnosticError (WA status)
+    CpTestTLE       Links to DiagnosticWarn (TLE status)
+    CpTestMLE       Links to DiagnosticWarn (MLE status)
+    CpTestRTE       Links to DiagnosticHint (RTE status)
+    CpTestNA        Links to Comment (pending/unknown status)
 
 ANSI Color Groups ~
 
@@ -848,17 +848,20 @@ PANEL KEYMAPS                                                  *cp-panel-keys*
 
 <c-n>   Navigate to next test case
 <c-p>   Navigate to previous test case
-t       Cycle through diff modes: none → git → vim
+t       Cycle through configured diff modes (see |cp.PanelConfig|)
 q       Exit panel and restore layout
 <c-q>   Exit interactive terminal and restore layout
 
 Diff Modes ~
 
-Three diff backends are available:
+Three diff modes are available:
 
-    none    Nothing
-    vim     Built-in vim diff (default, always available)
-    git     Character-level git word-diff (requires git, more precise)
+    side-by-side    Expected and actual output shown side-by-side (default)
+    vim             Built-in vim diff (always available)
+    git             Character-level git word-diff (requires git, more precise)
+
+Configure which modes to cycle through via |cp.PanelConfig|.diff_modes.
+The first element is used as the default mode.
 
 The git backend shows character-level changes with [-removed-] and {+added+}
 markers.

lua/cp/config.lua

@@ -18,7 +18,7 @@
 ---@field overrides? table<string, CpPlatformOverrides>
 
 ---@class PanelConfig
----@field diff_mode "none"|"vim"|"git"
+---@field diff_modes string[]
 ---@field max_output_lines integer
 
 ---@class DiffGitConfig
@@ -173,7 +173,7 @@ M.defaults = {
       add_test_key = 'ga',
       save_and_exit_key = 'q',
     },
-    panel = { diff_mode = 'none', max_output_lines = 50 },
+    panel = { diff_modes = { 'side-by-side', 'git', 'vim' }, max_output_lines = 50 },
     diff = {
       git = {
         args = { 'diff', '--no-index', '--word-diff=plain', '--word-diff-regex=.', '--no-prefix' },
@@ -305,7 +305,24 @@ function M.setup(user_config)
   vim.validate({
     hooks = { cfg.hooks, { 'table' } },
     ui = { cfg.ui, { 'table' } },
+    debug = { cfg.debug, { 'boolean', 'nil' }, true },
     open_url = { cfg.open_url, { 'boolean', 'nil' }, true },
+    filename = { cfg.filename, { 'function', 'nil' }, true },
+    scrapers = {
+      cfg.scrapers,
+      function(v)
+        if type(v) ~= 'table' then
+          return false
+        end
+        for _, s in ipairs(v) do
+          if not vim.tbl_contains(constants.PLATFORMS, s) then
+            return false
+          end
+        end
+        return true
+      end,
+      ('one of {%s}'):format(table.concat(constants.PLATFORMS, ',')),
+    },
     before_run = { cfg.hooks.before_run, { 'function', 'nil' }, true },
     before_debug = { cfg.hooks.before_debug, { 'function', 'nil' }, true },
     setup_code = { cfg.hooks.setup_code, { 'function', 'nil' }, true },
@@ -313,14 +330,23 @@ function M.setup(user_config)
     setup_io_output = { cfg.hooks.setup_io_output, { 'function', 'nil' }, true },
   })
 
+  local layouts = require('cp.ui.layouts')
   vim.validate({
     ansi = { cfg.ui.ansi, 'boolean' },
-    diff_mode = {
-      cfg.ui.panel.diff_mode,
+    diff_modes = {
+      cfg.ui.panel.diff_modes,
       function(v)
-        return vim.tbl_contains({ 'none', 'vim', 'git' }, v)
+        if type(v) ~= 'table' then
+          return false
+        end
+        for _, mode in ipairs(v) do
+          if not layouts.DIFF_MODES[mode] then
+            return false
+          end
+        end
+        return true
       end,
-      "diff_mode must be 'none', 'vim', or 'git'",
+      ('one of {%s}'):format(table.concat(vim.tbl_keys(layouts.DIFF_MODES), ',')),
     },
     max_output_lines = {
       cfg.ui.panel.max_output_lines,
@@ -330,6 +356,14 @@ function M.setup(user_config)
       'positive integer',
     },
     git = { cfg.ui.diff.git, { 'table' } },
+    git_args = { cfg.ui.diff.git.args, is_string_list, 'string[]' },
+    width = {
+      cfg.ui.run.width,
+      function(v)
+        return type(v) == 'number' and v > 0 and v <= 1
+      end,
+      'decimal between 0 and 1',
+    },
     next_test_key = {
       cfg.ui.run.next_test_key,
       function(v)
@@ -383,6 +417,13 @@ function M.setup(user_config)
       end,
       'nil or non-empty string',
     },
+    picker = {
+      cfg.ui.picker,
+      function(v)
+        return v == nil or v == 'telescope' or v == 'fzf-lua'
+      end,
+      "nil, 'telescope', or 'fzf-lua'",
+    },
   })
 
   for id, lang in pairs(cfg.languages) do
@@ -443,7 +484,18 @@ function M.get_language_for_platform(platform_id, language_id)
     }
   end
 
-  local effective = cfg.runtime.effective[platform_id][language_id]
+  local platform_effective = cfg.runtime.effective[platform_id]
+  if not platform_effective then
+    return {
+      valid = false,
+      error = string.format(
+        'No runtime config for platform %s (plugin not initialized)',
+        platform_id
+      ),
+    }
+  end
+
+  local effective = platform_effective[language_id]
   if not effective then
     return {
       valid = false,

lua/cp/init.lua

@@ -11,25 +11,25 @@ if vim.fn.has('nvim-0.10.0') == 0 then
   return {}
 end
 
-local user_config = {}
-local config = nil
 local initialized = false
 
+local function ensure_initialized()
+  if initialized then
+    return
+  end
+  local user_config = vim.g.cp_config or {}
+  local config = config_module.setup(user_config)
+  config_module.set_current_config(config)
+  initialized = true
+end
+
 ---@return nil
 function M.handle_command(opts)
+  ensure_initialized()
   local commands = require('cp.commands')
   commands.handle_command(opts)
 end
 
-function M.setup(opts)
-  opts = opts or {}
-  user_config = opts
-  config = config_module.setup(user_config)
-  config_module.set_current_config(config)
-
-  initialized = true
-end
-
 function M.is_initialized()
   return initialized
 end

lua/cp/runner/execute.lua

@@ -177,6 +177,16 @@ function M.compile_problem(debug, on_complete)
   local language = state.get_language() or config.platforms[platform].default_language
   local eff = config.runtime.effective[platform][language]
 
+  local source_file = state.get_source_file()
+  if source_file then
+    local buf = vim.fn.bufnr(source_file)
+    if buf ~= -1 and vim.api.nvim_buf_is_loaded(buf) and vim.bo[buf].modified then
+      vim.api.nvim_buf_call(buf, function()
+        vim.cmd.write({ mods = { silent = true, noautocmd = true } })
+      end)
+    end
+  end
+
   local compile_config = (debug and eff.commands.debug) or eff.commands.build
 
   if not compile_config then
@@ -184,6 +194,8 @@ function M.compile_problem(debug, on_complete)
     return
   end
 
+  require('cp.utils').ensure_dirs()
+
   local binary = debug and state.get_debug_file() or state.get_binary_file()
   local substitutions = { source = state.get_source_file(), binary = binary }
 

lua/cp/runner/run_render.lua

@@ -367,14 +367,12 @@ end
 ---@return table<string, table>
 function M.get_highlight_groups()
   return {
-    CpTestAC = { fg = '#10b981' },
-    CpTestWA = { fg = '#ef4444' },
-    CpTestTLE = { fg = '#f59e0b' },
-    CpTestMLE = { fg = '#f59e0b' },
-    CpTestRTE = { fg = '#8b5cf6' },
-    CpTestNA = { fg = '#6b7280' },
-    CpDiffRemoved = { fg = '#ef4444', bg = '#1f1f1f' },
-    CpDiffAdded = { fg = '#10b981', bg = '#1f1f1f' },
+    CpTestAC = { link = 'DiagnosticOk' },
+    CpTestWA = { link = 'DiagnosticError' },
+    CpTestTLE = { link = 'DiagnosticWarn' },
+    CpTestMLE = { link = 'DiagnosticWarn' },
+    CpTestRTE = { link = 'DiagnosticHint' },
+    CpTestNA = { link = 'Comment' },
   }
 end
 

lua/cp/scraper.lua

@@ -186,7 +186,7 @@ function M.scrape_all_tests(platform, contest_id, callback)
         return
       end
       vim.schedule(function()
-        vim.system({ 'mkdir', '-p', 'build', 'io' }):wait()
+        require('cp.utils').ensure_dirs()
         local config = require('cp.config')
         local base_name = config.default_filename(contest_id, ev.problem_id)
         for i, t in ipairs(ev.tests) do

lua/cp/setup.lua

@@ -82,7 +82,7 @@ local function start_tests(platform, contest_id, problems)
     return not vim.tbl_isempty(cache.get_test_cases(platform, contest_id, p.id))
   end, problems)
   if cached_len ~= #problems then
-    logger.log(('Fetching problem test data... (%d/%d)'):format(cached_len, #problems))
+    logger.log(('Fetching %s/%s problem tests...'):format(cached_len, #problems))
     scraper.scrape_all_tests(platform, contest_id, function(ev)
       local cached_tests = {}
       if not ev.interactive and vim.tbl_isempty(ev.tests) then

lua/cp/ui/highlight.lua

@@ -26,7 +26,7 @@ local function parse_diff_line(text)
         line = 0,
         col_start = highlight_start,
         col_end = #result_text,
-        highlight_group = 'CpDiffRemoved',
+        highlight_group = 'DiffDelete',
       })
       pos = removed_end + 1
     else
@@ -38,7 +38,7 @@ local function parse_diff_line(text)
           line = 0,
           col_start = highlight_start,
           col_end = #result_text,
-          highlight_group = 'CpDiffAdded',
+          highlight_group = 'DiffAdd',
         })
         pos = added_end + 1
       else

lua/cp/ui/layouts.lua

@@ -3,7 +3,13 @@ local M = {}
 local helpers = require('cp.helpers')
 local utils = require('cp.utils')
 
-local function create_none_diff_layout(parent_win, expected_content, actual_content)
+M.DIFF_MODES = {
+  ['side-by-side'] = 'side-by-side',
+  vim = 'vim',
+  git = 'git',
+}
+
+local function create_side_by_side_layout(parent_win, expected_content, actual_content)
   local expected_buf = utils.create_buffer_with_options()
   local actual_buf = utils.create_buffer_with_options()
   helpers.clearcol(expected_buf)
@@ -21,8 +27,13 @@ local function create_none_diff_layout(parent_win, expected_content, actual_cont
 
   vim.api.nvim_set_option_value('filetype', 'cp', { buf = expected_buf })
   vim.api.nvim_set_option_value('filetype', 'cp', { buf = actual_buf })
-  vim.api.nvim_set_option_value('winbar', 'Expected', { win = expected_win })
-  vim.api.nvim_set_option_value('winbar', 'Actual', { win = actual_win })
+  local label = M.DIFF_MODES['side-by-side']
+  vim.api.nvim_set_option_value(
+    'winbar',
+    ('expected (diff: %s)'):format(label),
+    { win = expected_win }
+  )
+  vim.api.nvim_set_option_value('winbar', ('actual (diff: %s)'):format(label), { win = actual_win })
 
   local expected_lines = vim.split(expected_content, '\n', { plain = true, trimempty = true })
   local actual_lines = vim.split(actual_content, '\n', { plain = true })
@@ -33,6 +44,7 @@ local function create_none_diff_layout(parent_win, expected_content, actual_cont
   return {
     buffers = { expected_buf, actual_buf },
     windows = { expected_win, actual_win },
+    mode = 'side-by-side',
     cleanup = function()
       pcall(vim.api.nvim_win_close, expected_win, true)
       pcall(vim.api.nvim_win_close, actual_win, true)
@@ -60,8 +72,13 @@ local function create_vim_diff_layout(parent_win, expected_content, actual_conte
 
   vim.api.nvim_set_option_value('filetype', 'cp', { buf = expected_buf })
   vim.api.nvim_set_option_value('filetype', 'cp', { buf = actual_buf })
-  vim.api.nvim_set_option_value('winbar', 'Expected', { win = expected_win })
-  vim.api.nvim_set_option_value('winbar', 'Actual', { win = actual_win })
+  local label = M.DIFF_MODES.vim
+  vim.api.nvim_set_option_value(
+    'winbar',
+    ('expected (diff: %s)'):format(label),
+    { win = expected_win }
+  )
+  vim.api.nvim_set_option_value('winbar', ('actual (diff: %s)'):format(label), { win = actual_win })
 
   local expected_lines = vim.split(expected_content, '\n', { plain = true, trimempty = true })
   local actual_lines = vim.split(actual_content, '\n', { plain = true })
@@ -83,6 +100,7 @@ local function create_vim_diff_layout(parent_win, expected_content, actual_conte
   return {
     buffers = { expected_buf, actual_buf },
     windows = { expected_win, actual_win },
+    mode = 'vim',
     cleanup = function()
       pcall(vim.api.nvim_win_close, expected_win, true)
       pcall(vim.api.nvim_win_close, actual_win, true)
@@ -103,7 +121,8 @@ local function create_git_diff_layout(parent_win, expected_content, actual_conte
   vim.api.nvim_win_set_buf(diff_win, diff_buf)
 
   vim.api.nvim_set_option_value('filetype', 'cp', { buf = diff_buf })
-  vim.api.nvim_set_option_value('winbar', 'Expected vs Actual', { win = diff_win })
+  local label = M.DIFF_MODES.git
+  vim.api.nvim_set_option_value('winbar', ('diff: %s'):format(label), { win = diff_win })
 
   local diff_backend = require('cp.ui.diff')
   local backend = diff_backend.get_best_backend('git')
@@ -121,6 +140,7 @@ local function create_git_diff_layout(parent_win, expected_content, actual_conte
   return {
     buffers = { diff_buf },
     windows = { diff_win },
+    mode = 'git',
     cleanup = function()
       pcall(vim.api.nvim_win_close, diff_win, true)
       pcall(vim.api.nvim_buf_delete, diff_buf, { force = true })
@@ -143,6 +163,7 @@ local function create_single_layout(parent_win, content)
   return {
     buffers = { buf },
     windows = { win },
+    mode = 'single',
     cleanup = function()
       pcall(vim.api.nvim_win_close, win, true)
       pcall(vim.api.nvim_buf_delete, buf, { force = true })
@@ -153,12 +174,14 @@ end
 function M.create_diff_layout(mode, parent_win, expected_content, actual_content)
   if mode == 'single' then
     return create_single_layout(parent_win, actual_content)
-  elseif mode == 'none' then
-    return create_none_diff_layout(parent_win, expected_content, actual_content)
+  elseif mode == 'side-by-side' then
+    return create_side_by_side_layout(parent_win, expected_content, actual_content)
   elseif mode == 'git' then
     return create_git_diff_layout(parent_win, expected_content, actual_content)
-  else
+  elseif mode == 'vim' then
     return create_vim_diff_layout(parent_win, expected_content, actual_content)
+  else
+    return create_side_by_side_layout(parent_win, expected_content, actual_content)
   end
 end
 
@@ -191,12 +214,13 @@ function M.update_diff_panes(
     actual_content = actual_content
   end
 
-  local desired_mode = is_compilation_failure and 'single' or config.ui.panel.diff_mode
+  local default_mode = config.ui.panel.diff_modes[1]
+  local desired_mode = is_compilation_failure and 'single' or (current_mode or default_mode)
   local highlight = require('cp.ui.highlight')
   local diff_namespace = highlight.create_namespace()
   local ansi_namespace = vim.api.nvim_create_namespace('cp_ansi_highlights')
 
-  if current_diff_layout and current_mode ~= desired_mode then
+  if current_diff_layout and current_diff_layout.mode ~= desired_mode then
     local saved_pos = vim.api.nvim_win_get_cursor(0)
     current_diff_layout.cleanup()
     current_diff_layout = nil
@@ -251,7 +275,7 @@ function M.update_diff_panes(
           ansi_namespace
         )
       end
-    elseif desired_mode == 'none' then
+    elseif desired_mode == 'side-by-side' then
       local expected_lines = vim.split(expected_content, '\n', { plain = true, trimempty = true })
       local actual_lines = vim.split(actual_content, '\n', { plain = true })
       utils.update_buffer_content(current_diff_layout.buffers[1], expected_lines, {})

lua/cp/ui/views.lua

@@ -13,6 +13,7 @@ local utils = require('cp.utils')
 
 local current_diff_layout = nil
 local current_mode = nil
+local io_view_running = false
 
 function M.disable()
   local active_panel = state.get_active_panel()
@@ -390,6 +391,8 @@ function M.ensure_io_view()
     return
   end
 
+  require('cp.utils').ensure_dirs()
+
   local source_file = state.get_source_file()
   if source_file then
     local source_file_abs = vim.fn.fnamemodify(source_file, ':p')
@@ -622,6 +625,12 @@ local function render_io_view_results(io_state, test_indices, mode, combined_res
 end
 
 function M.run_io_view(test_indices_arg, debug, mode)
+  if io_view_running then
+    logger.log('Tests already running', vim.log.levels.WARN)
+    return
+  end
+  io_view_running = true
+
   logger.log(('%s tests...'):format(debug and 'Debugging' or 'Running'), vim.log.levels.INFO, true)
 
   mode = mode or 'combined'
@@ -633,6 +642,7 @@ function M.run_io_view(test_indices_arg, debug, mode)
       'No platform/contest/problem configured. Use :CP <platform> <contest> [...] first.',
       vim.log.levels.ERROR
     )
+    io_view_running = false
     return
   end
 
@@ -640,6 +650,7 @@ function M.run_io_view(test_indices_arg, debug, mode)
   local contest_data = cache.get_contest_data(platform, contest_id)
   if not contest_data or not contest_data.index_map then
     logger.log('No test cases available.', vim.log.levels.ERROR)
+    io_view_running = false
     return
   end
 
@@ -656,11 +667,13 @@ function M.run_io_view(test_indices_arg, debug, mode)
     local combined = cache.get_combined_test(platform, contest_id, problem_id)
     if not combined then
       logger.log('No combined test available', vim.log.levels.ERROR)
+      io_view_running = false
       return
     end
   else
     if not run.load_test_cases() then
       logger.log('No test cases available', vim.log.levels.ERROR)
+      io_view_running = false
       return
     end
   end
@@ -681,6 +694,7 @@ function M.run_io_view(test_indices_arg, debug, mode)
             ),
             vim.log.levels.WARN
           )
+          io_view_running = false
           return
         end
       end
@@ -698,6 +712,7 @@ function M.run_io_view(test_indices_arg, debug, mode)
 
   local io_state = state.get_io_view_state()
   if not io_state then
+    io_view_running = false
     return
   end
 
@@ -711,6 +726,7 @@ function M.run_io_view(test_indices_arg, debug, mode)
 
   execute.compile_problem(debug, function(compile_result)
     if not vim.api.nvim_buf_is_valid(io_state.output_buf) then
+      io_view_running = false
       return
     end
 
@@ -730,6 +746,7 @@ function M.run_io_view(test_indices_arg, debug, mode)
 
       local ns = vim.api.nvim_create_namespace('cp_io_view_compile_error')
       utils.update_buffer_content(io_state.output_buf, lines, highlights, ns)
+      io_view_running = false
       return
     end
 
@@ -737,6 +754,7 @@ function M.run_io_view(test_indices_arg, debug, mode)
       local combined = cache.get_combined_test(platform, contest_id, problem_id)
       if not combined then
         logger.log('No combined test found', vim.log.levels.ERROR)
+        io_view_running = false
         return
       end
 
@@ -745,18 +763,21 @@ function M.run_io_view(test_indices_arg, debug, mode)
       run.run_combined_test(debug, function(result)
         if not result then
           logger.log('Failed to run combined test', vim.log.levels.ERROR)
+          io_view_running = false
           return
         end
 
         if vim.api.nvim_buf_is_valid(io_state.output_buf) then
           render_io_view_results(io_state, test_indices, mode, result, combined.input)
         end
+        io_view_running = false
       end)
     else
       run.run_all_test_cases(test_indices, debug, nil, function()
         if vim.api.nvim_buf_is_valid(io_state.output_buf) then
           render_io_view_results(io_state, test_indices, mode, nil, nil)
         end
+        io_view_running = false
       end)
     end
   end)
@@ -859,6 +880,9 @@ function M.toggle_panel(panel_opts)
   end
 
   local function refresh_panel()
+    if state.get_active_panel() ~= 'run' then
+      return
+    end
     if not test_buffers.tab_buf or not vim.api.nvim_buf_is_valid(test_buffers.tab_buf) then
       return
     end
@@ -884,6 +908,10 @@ function M.toggle_panel(panel_opts)
         vim.cmd.normal({ 'zz', bang = true })
       end)
     end
+
+    if test_windows.tab_win and vim.api.nvim_win_is_valid(test_windows.tab_win) then
+      vim.api.nvim_set_current_win(test_windows.tab_win)
+    end
   end
 
   local function navigate_test_case(delta)
@@ -900,15 +928,15 @@ function M.toggle_panel(panel_opts)
       M.toggle_panel()
     end, { buffer = buf, silent = true })
     vim.keymap.set('n', 't', function()
-      local modes = { 'none', 'git', 'vim' }
+      local modes = config.ui.panel.diff_modes
       local current_idx = 1
       for i, mode in ipairs(modes) do
-        if config.ui.panel.diff_mode == mode then
+        if current_mode == mode then
           current_idx = i
           break
         end
       end
-      config.ui.panel.diff_mode = modes[(current_idx % #modes) + 1]
+      current_mode = modes[(current_idx % #modes) + 1]
       refresh_panel()
     end, { buffer = buf, silent = true })
     vim.keymap.set('n', '<c-n>', function()
@@ -942,6 +970,9 @@ function M.toggle_panel(panel_opts)
 
   local function finalize_panel()
     vim.schedule(function()
+      if state.get_active_panel() ~= 'run' then
+        return
+      end
       if config.ui.ansi then
         require('cp.ui.ansi').setup_highlight_groups()
       end

lua/cp/utils.lua

@@ -262,4 +262,8 @@ function M.cwd_executables()
   return out
 end
 
+function M.ensure_dirs()
+  vim.system({ 'mkdir', '-p', 'build', 'io' }):wait()
+end
+
 return M

scrapers/atcoder.py

@@ -266,43 +266,31 @@ class AtcoderScraper(BaseScraper):
         return "atcoder"
 
     async def scrape_contest_metadata(self, contest_id: str) -> MetadataResult:
-        async def impl(cid: str) -> MetadataResult:
-            try:
-                rows = await asyncio.to_thread(_scrape_tasks_sync, cid)
-            except requests.HTTPError as e:
-                if e.response is not None and e.response.status_code == 404:
-                    return self._create_metadata_error(
-                        f"No problems found for contest {cid}", cid
-                    )
-                raise
-
+        try:
+            rows = await asyncio.to_thread(_scrape_tasks_sync, contest_id)
             problems = _to_problem_summaries(rows)
             if not problems:
-                return self._create_metadata_error(
-                    f"No problems found for contest {cid}", cid
+                return self._metadata_error(
+                    f"No problems found for contest {contest_id}"
                 )
-
             return MetadataResult(
                 success=True,
                 error="",
-                contest_id=cid,
+                contest_id=contest_id,
                 problems=problems,
                 url=f"https://atcoder.jp/contests/{contest_id}/tasks/{contest_id}_%s",
             )
-
-        return await self._safe_execute("metadata", impl, contest_id)
+        except Exception as e:
+            return self._metadata_error(str(e))
 
     async def scrape_contest_list(self) -> ContestListResult:
-        async def impl() -> ContestListResult:
-            try:
-                contests = await _fetch_all_contests_async()
-            except Exception as e:
-                return self._create_contests_error(str(e))
+        try:
+            contests = await _fetch_all_contests_async()
             if not contests:
-                return self._create_contests_error("No contests found")
+                return self._contests_error("No contests found")
             return ContestListResult(success=True, error="", contests=contests)
-
-        return await self._safe_execute("contests", impl)
+        except Exception as e:
+            return self._contests_error(str(e))
 
     async def stream_tests_for_category_async(self, category_id: str) -> None:
         rows = await asyncio.to_thread(_scrape_tasks_sync, category_id)

scrapers/base.py

@@ -1,9 +1,8 @@
+import asyncio
+import sys
 from abc import ABC, abstractmethod
-from typing import Any, Awaitable, Callable, ParamSpec, cast
 
-from .models import ContestListResult, MetadataResult, TestsResult
-
-P = ParamSpec("P")
+from .models import CombinedTest, ContestListResult, MetadataResult, TestsResult
 
 
 class BaseScraper(ABC):
@@ -20,57 +19,65 @@ class BaseScraper(ABC):
     @abstractmethod
     async def stream_tests_for_category_async(self, category_id: str) -> None: ...
 
-    def _create_metadata_error(
-        self, error_msg: str, contest_id: str = ""
-    ) -> MetadataResult:
-        return MetadataResult(
-            success=False,
-            error=f"{self.platform_name}: {error_msg}",
-            contest_id=contest_id,
-            problems=[],
-            url="",
-        )
+    def _usage(self) -> str:
+        name = self.platform_name
+        return f"Usage: {name}.py metadata <id> | tests <id> | contests"
 
-    def _create_tests_error(
-        self, error_msg: str, problem_id: str = "", url: str = ""
-    ) -> TestsResult:
-        from .models import CombinedTest
+    def _metadata_error(self, msg: str) -> MetadataResult:
+        return MetadataResult(success=False, error=msg, url="")
 
+    def _tests_error(self, msg: str) -> TestsResult:
         return TestsResult(
             success=False,
-            error=f"{self.platform_name}: {error_msg}",
-            problem_id=problem_id,
+            error=msg,
+            problem_id="",
             combined=CombinedTest(input="", expected=""),
             tests=[],
             timeout_ms=0,
             memory_mb=0,
-            interactive=False,
         )
 
-    def _create_contests_error(self, error_msg: str) -> ContestListResult:
-        return ContestListResult(
-            success=False,
-            error=f"{self.platform_name}: {error_msg}",
-            contests=[],
-        )
+    def _contests_error(self, msg: str) -> ContestListResult:
+        return ContestListResult(success=False, error=msg)
 
-    async def _safe_execute(
-        self,
-        operation: str,
-        func: Callable[P, Awaitable[Any]],
-        *args: P.args,
-        **kwargs: P.kwargs,
-    ):
-        try:
-            return await func(*args, **kwargs)
-        except Exception as e:
-            if operation == "metadata":
-                contest_id = cast(str, args[0]) if args else ""
-                return self._create_metadata_error(str(e), contest_id)
-            elif operation == "tests":
-                problem_id = cast(str, args[1]) if len(args) > 1 else ""
-                return self._create_tests_error(str(e), problem_id)
-            elif operation == "contests":
-                return self._create_contests_error(str(e))
-            else:
-                raise
+    async def _run_cli_async(self, args: list[str]) -> int:
+        if len(args) < 2:
+            print(self._metadata_error(self._usage()).model_dump_json())
+            return 1
+
+        mode = args[1]
+
+        match mode:
+            case "metadata":
+                if len(args) != 3:
+                    print(self._metadata_error(self._usage()).model_dump_json())
+                    return 1
+                result = await self.scrape_contest_metadata(args[2])
+                print(result.model_dump_json())
+                return 0 if result.success else 1
+
+            case "tests":
+                if len(args) != 3:
+                    print(self._tests_error(self._usage()).model_dump_json())
+                    return 1
+                await self.stream_tests_for_category_async(args[2])
+                return 0
+
+            case "contests":
+                if len(args) != 2:
+                    print(self._contests_error(self._usage()).model_dump_json())
+                    return 1
+                result = await self.scrape_contest_list()
+                print(result.model_dump_json())
+                return 0 if result.success else 1
+
+            case _:
+                print(
+                    self._metadata_error(
+                        f"Unknown mode: {mode}. {self._usage()}"
+                    ).model_dump_json()
+                )
+                return 1
+
+    def run_cli(self) -> None:
+        sys.exit(asyncio.run(self._run_cli_async(sys.argv)))

scrapers/codechef.py

@@ -1,8 +1,8 @@
 #!/usr/bin/env python3
+
 import asyncio
 import json
 import re
-import sys
 from typing import Any
 
 import httpx
@@ -10,13 +10,11 @@ from scrapling.fetchers import Fetcher
 
 from .base import BaseScraper
 from .models import (
-    CombinedTest,
     ContestListResult,
     ContestSummary,
     MetadataResult,
     ProblemSummary,
     TestCase,
-    TestsResult,
 )
 
 BASE_URL = "https://www.codechef.com"
@@ -62,42 +60,40 @@ class CodeChefScraper(BaseScraper):
         return "codechef"
 
     async def scrape_contest_metadata(self, contest_id: str) -> MetadataResult:
-        async with httpx.AsyncClient() as client:
-            try:
+        try:
+            async with httpx.AsyncClient() as client:
                 data = await fetch_json(
                     client, API_CONTEST.format(contest_id=contest_id)
                 )
-            except httpx.HTTPStatusError as e:
-                return self._create_metadata_error(
-                    f"Failed to fetch contest {contest_id}: {e}", contest_id
+            if not data.get("problems"):
+                return self._metadata_error(
+                    f"No problems found for contest {contest_id}"
                 )
-        if not data.get("problems"):
-            return self._create_metadata_error(
-                f"No problems found for contest {contest_id}", contest_id
-            )
-        problems = []
-        for problem_code, problem_data in data["problems"].items():
-            if problem_data.get("category_name") == "main":
-                problems.append(
-                    ProblemSummary(
-                        id=problem_code,
-                        name=problem_data.get("name", problem_code),
+            problems = []
+            for problem_code, problem_data in data["problems"].items():
+                if problem_data.get("category_name") == "main":
+                    problems.append(
+                        ProblemSummary(
+                            id=problem_code,
+                            name=problem_data.get("name", problem_code),
+                        )
                     )
-                )
-        return MetadataResult(
-            success=True,
-            error="",
-            contest_id=contest_id,
-            problems=problems,
-            url=f"{BASE_URL}/{contest_id}",
-        )
+            return MetadataResult(
+                success=True,
+                error="",
+                contest_id=contest_id,
+                problems=problems,
+                url=f"{BASE_URL}/{contest_id}",
+            )
+        except Exception as e:
+            return self._metadata_error(f"Failed to fetch contest {contest_id}: {e}")
 
     async def scrape_contest_list(self) -> ContestListResult:
         async with httpx.AsyncClient() as client:
             try:
                 data = await fetch_json(client, API_CONTESTS_ALL)
             except httpx.HTTPStatusError as e:
-                return self._create_contests_error(f"Failed to fetch contests: {e}")
+                return self._contests_error(f"Failed to fetch contests: {e}")
             all_contests = data.get("future_contests", []) + data.get(
                 "past_contests", []
             )
@@ -110,7 +106,7 @@ class CodeChefScraper(BaseScraper):
                         num = int(match.group(1))
                         max_num = max(max_num, num)
             if max_num == 0:
-                return self._create_contests_error("No Starters contests found")
+                return self._contests_error("No Starters contests found")
             contests = []
             sem = asyncio.Semaphore(CONNECTIONS)
 
@@ -252,68 +248,5 @@ class CodeChefScraper(BaseScraper):
                 print(json.dumps(payload), flush=True)
 
 
-async def main_async() -> int:
-    if len(sys.argv) < 2:
-        result = MetadataResult(
-            success=False,
-            error="Usage: codechef.py metadata <contest_id> OR codechef.py tests <contest_id> OR codechef.py contests",
-            url="",
-        )
-        print(result.model_dump_json())
-        return 1
-    mode: str = sys.argv[1]
-    scraper = CodeChefScraper()
-    if mode == "metadata":
-        if len(sys.argv) != 3:
-            result = MetadataResult(
-                success=False,
-                error="Usage: codechef.py metadata <contest_id>",
-                url="",
-            )
-            print(result.model_dump_json())
-            return 1
-        contest_id = sys.argv[2]
-        result = await scraper.scrape_contest_metadata(contest_id)
-        print(result.model_dump_json())
-        return 0 if result.success else 1
-    if mode == "tests":
-        if len(sys.argv) != 3:
-            tests_result = TestsResult(
-                success=False,
-                error="Usage: codechef.py tests <contest_id>",
-                problem_id="",
-                combined=CombinedTest(input="", expected=""),
-                tests=[],
-                timeout_ms=0,
-                memory_mb=0,
-            )
-            print(tests_result.model_dump_json())
-            return 1
-        contest_id = sys.argv[2]
-        await scraper.stream_tests_for_category_async(contest_id)
-        return 0
-    if mode == "contests":
-        if len(sys.argv) != 2:
-            contest_result = ContestListResult(
-                success=False, error="Usage: codechef.py contests"
-            )
-            print(contest_result.model_dump_json())
-            return 1
-        contest_result = await scraper.scrape_contest_list()
-        print(contest_result.model_dump_json())
-        return 0 if contest_result.success else 1
-    result = MetadataResult(
-        success=False,
-        error=f"Unknown mode: {mode}. Use 'metadata <contest_id>', 'tests <contest_id>', or 'contests'",
-        url="",
-    )
-    print(result.model_dump_json())
-    return 1
-
-
-def main() -> None:
-    sys.exit(asyncio.run(main_async()))
-
-
 if __name__ == "__main__":
-    main()
+    CodeChefScraper().run_cli()

scrapers/codeforces.py

@@ -4,7 +4,6 @@ import asyncio
 import json
 import logging
 import re
-import sys
 from typing import Any
 
 import requests
@@ -13,13 +12,11 @@ from scrapling.fetchers import Fetcher
 
 from .base import BaseScraper
 from .models import (
-    CombinedTest,
     ContestListResult,
     ContestSummary,
     MetadataResult,
     ProblemSummary,
     TestCase,
-    TestsResult,
 )
 
 # suppress scrapling logging - https://github.com/D4Vinci/Scrapling/issues/31)
@@ -89,14 +86,14 @@ def _extract_samples(block: Tag) -> tuple[list[TestCase], bool]:
     if not st:
         return [], False
 
-    input_pres: list[Tag] = [  # type: ignore[misc]
-        inp.find("pre")  # type: ignore[misc]
-        for inp in st.find_all("div", class_="input")  # type: ignore[union-attr]
+    input_pres: list[Tag] = [
+        inp.find("pre")
+        for inp in st.find_all("div", class_="input")
         if isinstance(inp, Tag) and inp.find("pre")
     ]
     output_pres: list[Tag] = [
-        out.find("pre")  # type: ignore[misc]
-        for out in st.find_all("div", class_="output")  # type: ignore[union-attr]
+        out.find("pre")
+        for out in st.find_all("div", class_="output")
         if isinstance(out, Tag) and out.find("pre")
     ]
     input_pres = [p for p in input_pres if isinstance(p, Tag)]
@@ -209,49 +206,46 @@ class CodeforcesScraper(BaseScraper):
         return "codeforces"
 
     async def scrape_contest_metadata(self, contest_id: str) -> MetadataResult:
-        async def impl(cid: str) -> MetadataResult:
-            problems = await asyncio.to_thread(_scrape_contest_problems_sync, cid)
+        try:
+            problems = await asyncio.to_thread(
+                _scrape_contest_problems_sync, contest_id
+            )
             if not problems:
-                return self._create_metadata_error(
-                    f"No problems found for contest {cid}", cid
+                return self._metadata_error(
+                    f"No problems found for contest {contest_id}"
                 )
             return MetadataResult(
                 success=True,
                 error="",
-                contest_id=cid,
+                contest_id=contest_id,
                 problems=problems,
                 url=f"https://codeforces.com/contest/{contest_id}/problem/%s",
             )
-
-        return await self._safe_execute("metadata", impl, contest_id)
+        except Exception as e:
+            return self._metadata_error(str(e))
 
     async def scrape_contest_list(self) -> ContestListResult:
-        async def impl() -> ContestListResult:
-            try:
-                r = requests.get(API_CONTEST_LIST_URL, timeout=TIMEOUT_SECONDS)
-                r.raise_for_status()
-                data = r.json()
-                if data.get("status") != "OK":
-                    return self._create_contests_error("Invalid API response")
+        try:
+            r = requests.get(API_CONTEST_LIST_URL, timeout=TIMEOUT_SECONDS)
+            r.raise_for_status()
+            data = r.json()
+            if data.get("status") != "OK":
+                return self._contests_error("Invalid API response")
 
-                contests: list[ContestSummary] = []
-                for c in data["result"]:
-                    if c.get("phase") != "FINISHED":
-                        continue
-                    cid = str(c["id"])
-                    name = c["name"]
-                    contests.append(
-                        ContestSummary(id=cid, name=name, display_name=name)
-                    )
+            contests: list[ContestSummary] = []
+            for c in data["result"]:
+                if c.get("phase") != "FINISHED":
+                    continue
+                cid = str(c["id"])
+                name = c["name"]
+                contests.append(ContestSummary(id=cid, name=name, display_name=name))
 
-                if not contests:
-                    return self._create_contests_error("No contests found")
+            if not contests:
+                return self._contests_error("No contests found")
 
-                return ContestListResult(success=True, error="", contests=contests)
-            except Exception as e:
-                return self._create_contests_error(str(e))
-
-        return await self._safe_execute("contests", impl)
+            return ContestListResult(success=True, error="", contests=contests)
+        except Exception as e:
+            return self._contests_error(str(e))
 
     async def stream_tests_for_category_async(self, category_id: str) -> None:
         html = await asyncio.to_thread(_fetch_problems_html, category_id)
@@ -281,73 +275,5 @@ class CodeforcesScraper(BaseScraper):
             )
 
 
-async def main_async() -> int:
-    if len(sys.argv) < 2:
-        result = MetadataResult(
-            success=False,
-            error="Usage: codeforces.py metadata <contest_id> OR codeforces.py tests <contest_id> OR codeforces.py contests",
-            url="",
-        )
-        print(result.model_dump_json())
-        return 1
-
-    mode: str = sys.argv[1]
-    scraper = CodeforcesScraper()
-
-    if mode == "metadata":
-        if len(sys.argv) != 3:
-            result = MetadataResult(
-                success=False,
-                error="Usage: codeforces.py metadata <contest_id>",
-                url="",
-            )
-            print(result.model_dump_json())
-            return 1
-        contest_id = sys.argv[2]
-        result = await scraper.scrape_contest_metadata(contest_id)
-        print(result.model_dump_json())
-        return 0 if result.success else 1
-
-    if mode == "tests":
-        if len(sys.argv) != 3:
-            tests_result = TestsResult(
-                success=False,
-                error="Usage: codeforces.py tests <contest_id>",
-                problem_id="",
-                combined=CombinedTest(input="", expected=""),
-                tests=[],
-                timeout_ms=0,
-                memory_mb=0,
-            )
-            print(tests_result.model_dump_json())
-            return 1
-        contest_id = sys.argv[2]
-        await scraper.stream_tests_for_category_async(contest_id)
-        return 0
-
-    if mode == "contests":
-        if len(sys.argv) != 2:
-            contest_result = ContestListResult(
-                success=False, error="Usage: codeforces.py contests"
-            )
-            print(contest_result.model_dump_json())
-            return 1
-        contest_result = await scraper.scrape_contest_list()
-        print(contest_result.model_dump_json())
-        return 0 if contest_result.success else 1
-
-    result = MetadataResult(
-        success=False,
-        error="Unknown mode. Use 'metadata <contest_id>', 'tests <contest_id>', or 'contests'",
-        url="",
-    )
-    print(result.model_dump_json())
-    return 1
-
-
-def main() -> None:
-    sys.exit(asyncio.run(main_async()))
-
-
 if __name__ == "__main__":
-    main()
+    CodeforcesScraper().run_cli()

scrapers/cses.py

@@ -3,20 +3,17 @@
 import asyncio
 import json
 import re
-import sys
 from typing import Any
 
 import httpx
 
 from .base import BaseScraper
 from .models import (
-    CombinedTest,
     ContestListResult,
     ContestSummary,
     MetadataResult,
     ProblemSummary,
     TestCase,
-    TestsResult,
 )
 
 BASE_URL = "https://cses.fi"
@@ -261,73 +258,5 @@ class CSESScraper(BaseScraper):
                 print(json.dumps(payload), flush=True)
 
 
-async def main_async() -> int:
-    if len(sys.argv) < 2:
-        result = MetadataResult(
-            success=False,
-            error="Usage: cses.py metadata <category_id> OR cses.py tests <category> OR cses.py contests",
-            url="",
-        )
-        print(result.model_dump_json())
-        return 1
-
-    mode: str = sys.argv[1]
-    scraper = CSESScraper()
-
-    if mode == "metadata":
-        if len(sys.argv) != 3:
-            result = MetadataResult(
-                success=False,
-                error="Usage: cses.py metadata <category_id>",
-                url="",
-            )
-            print(result.model_dump_json())
-            return 1
-        category_id = sys.argv[2]
-        result = await scraper.scrape_contest_metadata(category_id)
-        print(result.model_dump_json())
-        return 0 if result.success else 1
-
-    if mode == "tests":
-        if len(sys.argv) != 3:
-            tests_result = TestsResult(
-                success=False,
-                error="Usage: cses.py tests <category>",
-                problem_id="",
-                combined=CombinedTest(input="", expected=""),
-                tests=[],
-                timeout_ms=0,
-                memory_mb=0,
-            )
-            print(tests_result.model_dump_json())
-            return 1
-        category = sys.argv[2]
-        await scraper.stream_tests_for_category_async(category)
-        return 0
-
-    if mode == "contests":
-        if len(sys.argv) != 2:
-            contest_result = ContestListResult(
-                success=False, error="Usage: cses.py contests"
-            )
-            print(contest_result.model_dump_json())
-            return 1
-        contest_result = await scraper.scrape_contest_list()
-        print(contest_result.model_dump_json())
-        return 0 if contest_result.success else 1
-
-    result = MetadataResult(
-        success=False,
-        error=f"Unknown mode: {mode}. Use 'metadata <category>', 'tests <category>', or 'contests'",
-        url="",
-    )
-    print(result.model_dump_json())
-    return 1
-
-
-def main() -> None:
-    sys.exit(asyncio.run(main_async()))
-
-
 if __name__ == "__main__":
-    main()
+    CSESScraper().run_cli()

tests/conftest.py

@@ -232,33 +232,35 @@ def run_scraper_offline(fixture_text):
             case _:
                 raise AssertionError(f"Unknown scraper: {scraper_name}")
 
+    scraper_classes = {
+        "cses": "CSESScraper",
+        "atcoder": "AtcoderScraper",
+        "codeforces": "CodeforcesScraper",
+        "codechef": "CodeChefScraper",
+    }
+
     def _run(scraper_name: str, mode: str, *args: str):
         mod_path = ROOT / "scrapers" / f"{scraper_name}.py"
         ns = _load_scraper_module(mod_path, scraper_name)
         offline_fetches = _make_offline_fetches(scraper_name)
 
         if scraper_name == "codeforces":
-            fetchers.Fetcher.get = offline_fetches["Fetcher.get"]  # type: ignore[assignment]
+            fetchers.Fetcher.get = offline_fetches["Fetcher.get"]
             requests.get = offline_fetches["requests.get"]
         elif scraper_name == "atcoder":
             ns._fetch = offline_fetches["_fetch"]
             ns._get_async = offline_fetches["_get_async"]
         elif scraper_name == "cses":
-            httpx.AsyncClient.get = offline_fetches["__offline_fetch_text"]  # type: ignore[assignment]
+            httpx.AsyncClient.get = offline_fetches["__offline_fetch_text"]
         elif scraper_name == "codechef":
-            httpx.AsyncClient.get = offline_fetches["__offline_get_async"]  # type: ignore[assignment]
-            fetchers.Fetcher.get = offline_fetches["Fetcher.get"]  # type: ignore[assignment]
+            httpx.AsyncClient.get = offline_fetches["__offline_get_async"]
+            fetchers.Fetcher.get = offline_fetches["Fetcher.get"]
 
-        main_async = getattr(ns, "main_async")
-        assert callable(main_async), f"main_async not found in {scraper_name}"
+        scraper_class = getattr(ns, scraper_classes[scraper_name])
+        scraper = scraper_class()
 
         argv = [str(mod_path), mode, *args]
-        old_argv = sys.argv
-        sys.argv = argv
-        try:
-            rc, out = _capture_stdout(main_async())
-        finally:
-            sys.argv = old_argv
+        rc, out = _capture_stdout(scraper._run_cli_async(argv))
 
         json_lines: list[Any] = []
         for line in (_line for _line in out.splitlines() if _line.strip()):