feat: update git formatting

doc/cp.nvim.txt

@@ -258,7 +258,7 @@ Here's an example configuration with lazy.nvim:
             prev_test_key = '<c-p>',  -- or nil to disable
           },
           panel = {
-            diff_mode = 'vim',
+            diff_modes = { 'side-by-side', 'git', 'vim' },
             max_output_lines = 50,
           },
           diff = {
@@ -378,8 +378,10 @@ run CSES problems with Rust using the single schema:
 
                                                               *cp.PanelConfig*
     Fields: ~
-        {diff_mode}        (string, default: "none") Diff backend: "none",
+        {diff_modes}       (string[], default: {'side-by-side', 'git', 'vim'})
-                           "vim", or "git".
+                           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*
@@ -851,17 +853,20 @@ 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
+    side-by-side    Expected and actual output shown side-by-side (default)
-    vim     Built-in vim diff (default, always available)
+    vim             Built-in vim diff (always available)
-    git     Character-level git word-diff (requires git, more precise)
+    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' },
@@ -313,15 +313,26 @@ function M.setup(user_config)
     setup_io_output = { cfg.hooks.setup_io_output, { 'function', 'nil' }, true },
   })
 
+  local layouts = require('cp.ui.layouts')
+  local valid_modes_str = table.concat(vim.tbl_keys(layouts.DIFF_MODES), ',')
+  if type(cfg.ui.panel.diff_modes) == 'table' then
+    local invalid = {}
+    for _, mode in ipairs(cfg.ui.panel.diff_modes) do
+      if not layouts.DIFF_MODES[mode] then
+        table.insert(invalid, mode)
+      end
+    end
+    if #invalid > 0 then
+      error(
+        ('invalid diff modes [%s] - must be one of: {%s}'):format(
+          table.concat(invalid, ','),
+          valid_modes_str
+        )
+      )
+    end
+  end
   vim.validate({
     ansi = { cfg.ui.ansi, 'boolean' },
-    diff_mode = {
-      cfg.ui.panel.diff_mode,
-      function(v)
-        return vim.tbl_contains({ 'none', 'vim', 'git' }, v)
-      end,
-      "diff_mode must be 'none', 'vim', or 'git'",
-    },
     max_output_lines = {
       cfg.ui.panel.max_output_lines,
       function(v)
@@ -383,6 +394,13 @@ 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 +461,18 @@ 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/ui/layouts.lua

@@ -3,13 +3,13 @@ local M = {}
 local helpers = require('cp.helpers')
 local utils = require('cp.utils')
 
-local MODE_LABELS = {
+M.DIFF_MODES = {
-  none = 'none',
+  ['side-by-side'] = 'side-by-side',
   vim = 'vim',
   git = 'git',
 }
 
-local function create_none_diff_layout(parent_win, expected_content, actual_content)
+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)
@@ -27,9 +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 })
-  local label = MODE_LABELS.none
+  local label = M.DIFF_MODES['side-by-side']
-  vim.api.nvim_set_option_value('winbar', ('expected [%s]'):format(label), { win = expected_win })
+  vim.api.nvim_set_option_value(
-  vim.api.nvim_set_option_value('winbar', ('actual [%s]'):format(label), { win = actual_win })
+    '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 })
@@ -40,7 +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 = 'none',
+    mode = 'side-by-side',
     cleanup = function()
       pcall(vim.api.nvim_win_close, expected_win, true)
       pcall(vim.api.nvim_win_close, actual_win, true)
@@ -68,9 +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 })
-  local label = MODE_LABELS.vim
+  local label = M.DIFF_MODES.vim
-  vim.api.nvim_set_option_value('winbar', ('expected [%s]'):format(label), { win = expected_win })
+  vim.api.nvim_set_option_value(
-  vim.api.nvim_set_option_value('winbar', ('actual [%s]'):format(label), { win = actual_win })
+    '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 })
@@ -113,8 +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 })
-  local label = MODE_LABELS.git
+  local label = M.DIFF_MODES.git
-  vim.api.nvim_set_option_value('winbar', ('diff [%s]'):format(label), { win = diff_win })
+  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')
@@ -166,12 +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
+  elseif mode == 'side-by-side' then
-    return create_none_diff_layout(parent_win, expected_content, actual_content)
+    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
 
@@ -204,12 +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
@@ -264,7 +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

@@ -900,15 +900,15 @@ 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()