cp.nvim/lua/cp/init.lua

local M = {}

local cache = require('cp.cache')
local config_module = require('cp.config')
local logger = require('cp.log')
local problem = require('cp.problem')
local scrape = require('cp.scrape')
local snippets = require('cp.snippets')

if not vim.fn.has('nvim-0.10.0') then
  logger.log('[cp.nvim]: requires nvim-0.10.0+', vim.log.levels.ERROR)
  return {}
end

local user_config = {}
local config = config_module.setup(user_config)
logger.set_config(config)
local snippets_initialized = false

local state = {
  platform = nil,
  contest_id = nil,
  problem_id = nil,
  saved_layout = nil,
  saved_session = nil,
  test_cases = nil,
  test_states = {},
  run_panel_active = false,
}

local current_diff_layout = nil
local current_mode = nil

local constants = require('cp.constants')
local platforms = constants.PLATFORMS
local actions = constants.ACTIONS

local function set_platform(platform)
  if not vim.tbl_contains(platforms, platform) then
    logger.log(
      ('unknown platform. Available: [%s]'):format(table.concat(platforms, ', ')),
      vim.log.levels.ERROR
    )
    return false
  end

  state.platform = platform
  vim.system({ 'mkdir', '-p', 'build', 'io' }):wait()
  return true
end

---@param contest_id string
---@param problem_id? string
---@param language? string
local function setup_problem(contest_id, problem_id, language)
  if not state.platform then
    logger.log('no platform set. run :CP <platform> <contest> first', vim.log.levels.ERROR)
    return
  end

  local problem_name = contest_id .. (problem_id or '')
  logger.log(('setting up problem: %s'):format(problem_name))

  local ctx = problem.create_context(state.platform, contest_id, problem_id, config, language)

  if vim.tbl_contains(config.scrapers, state.platform) then
    cache.load()
    local existing_contest_data = cache.get_contest_data(state.platform, contest_id)

    if not existing_contest_data then
      local metadata_result = scrape.scrape_contest_metadata(state.platform, contest_id)
      if not metadata_result.success then
        logger.log(
          'failed to load contest metadata: ' .. (metadata_result.error or 'unknown error'),
          vim.log.levels.WARN
        )
      end
    end
  end

  local cached_test_cases = cache.get_test_cases(state.platform, contest_id, problem_id)
  if cached_test_cases then
    state.test_cases = cached_test_cases
    logger.log(('using cached test cases (%d)'):format(#cached_test_cases))
  elseif vim.tbl_contains(config.scrapers, state.platform) then
    local platform_display_name = constants.PLATFORM_DISPLAY_NAMES[state.platform] or state.platform
    logger.log(
      ('Scraping %s %s %s for test cases, this may take a few seconds...'):format(
        platform_display_name,
        contest_id,
        problem_id
      ),
      vim.log.levels.INFO,
      true
    )

    local scrape_result = scrape.scrape_problem(ctx)

    if not scrape_result.success then
      logger.log(
        'scraping failed: ' .. (scrape_result.error or 'unknown error'),
        vim.log.levels.ERROR
      )
      return
    end

    local test_count = scrape_result.test_count or 0
    logger.log(('scraped %d test case(s) for %s'):format(test_count, scrape_result.problem_id))
    state.test_cases = scrape_result.test_cases

    if scrape_result.test_cases then
      cache.set_test_cases(state.platform, contest_id, problem_id, scrape_result.test_cases)
    end
  else
    logger.log(('scraping disabled for %s'):format(state.platform))
    state.test_cases = nil
  end

  vim.cmd('silent only')
  state.run_panel_active = false

  state.contest_id = contest_id
  state.problem_id = problem_id

  vim.cmd.e(ctx.source_file)
  local source_buf = vim.api.nvim_get_current_buf()

  if vim.api.nvim_buf_get_lines(source_buf, 0, -1, true)[1] == '' then
    local has_luasnip, luasnip = pcall(require, 'luasnip')
    if has_luasnip then
      local filetype = vim.api.nvim_get_option_value('filetype', { buf = source_buf })
      local language_name = constants.filetype_to_language[filetype]
      local canonical_language = constants.canonical_filetypes[language_name] or language_name
      local prefixed_trigger = ('cp.nvim/%s.%s'):format(state.platform, canonical_language)

      vim.api.nvim_buf_set_lines(0, 0, -1, false, { prefixed_trigger })
      vim.api.nvim_win_set_cursor(0, { 1, #prefixed_trigger })
      vim.cmd.startinsert({ bang = true })

      vim.schedule(function()
        if luasnip.expandable() then
          luasnip.expand()
        else
          vim.api.nvim_buf_set_lines(0, 0, 1, false, { '' })
          vim.api.nvim_win_set_cursor(0, { 1, 0 })
        end
        vim.cmd.stopinsert()
      end)
    else
      vim.api.nvim_input(('i%s<c-space><esc>'):format(state.platform))
    end
  end

  if config.hooks and config.hooks.setup_code then
    config.hooks.setup_code(ctx)
  end

  cache.set_file_state(vim.fn.expand('%:p'), state.platform, contest_id, problem_id, language)

  logger.log(('switched to problem %s'):format(ctx.problem_name))
end

local function scrape_missing_problems(contest_id, missing_problems)
  vim.fn.mkdir('io', 'p')

  logger.log(('scraping %d uncached problems...'):format(#missing_problems))

  local results =
    scrape.scrape_problems_parallel(state.platform, contest_id, missing_problems, config)

  local success_count = 0
  local failed_problems = {}
  for problem_id, result in pairs(results) do
    if result.success then
      success_count = success_count + 1
    else
      table.insert(failed_problems, problem_id)
    end
  end

  if #failed_problems > 0 then
    logger.log(
      ('scraping complete: %d/%d successful, failed: %s'):format(
        success_count,
        #missing_problems,
        table.concat(failed_problems, ', ')
      ),
      vim.log.levels.WARN
    )
  else
    logger.log(('scraping complete: %d/%d successful'):format(success_count, #missing_problems))
  end
end

local function get_current_problem()
  local filename = vim.fn.expand('%:t:r')
  if filename == '' then
    logger.log('no file open', vim.log.levels.ERROR)
    return nil
  end
  return filename
end

local function create_buffer_with_options(filetype)
  local buf = vim.api.nvim_create_buf(false, true)
  vim.api.nvim_set_option_value('bufhidden', 'wipe', { buf = buf })
  vim.api.nvim_set_option_value('readonly', true, { buf = buf })
  vim.api.nvim_set_option_value('modifiable', false, { buf = buf })
  if filetype then
    vim.api.nvim_set_option_value('filetype', filetype, { buf = buf })
  end
  return buf
end

local setup_keybindings_for_buffer

local function toggle_run_panel(is_debug)
  if state.run_panel_active then
    if current_diff_layout then
      current_diff_layout.cleanup()
      current_diff_layout = nil
      current_mode = nil
    end
    if state.saved_session then
      vim.cmd(('source %s'):format(state.saved_session))
      vim.fn.delete(state.saved_session)
      state.saved_session = nil
    end

    state.run_panel_active = false
    logger.log('test panel closed')
    return
  end

  if not state.platform then
    logger.log(
      'No contest configured. Use :CP <platform> <contest> <problem> to set up first.',
      vim.log.levels.ERROR
    )
    return
  end

  local problem_id = get_current_problem()
  if not problem_id then
    return
  end

  local ctx = problem.create_context(state.platform, state.contest_id, state.problem_id, config)
  local run = require('cp.runner.run')

  if not run.load_test_cases(ctx, state) then
    logger.log('no test cases found', vim.log.levels.WARN)
    return
  end

  state.saved_session = vim.fn.tempname()
  vim.cmd(('mksession! %s'):format(state.saved_session))

  vim.cmd('silent only')

  local tab_buf = create_buffer_with_options()
  local main_win = vim.api.nvim_get_current_win()
  vim.api.nvim_win_set_buf(main_win, tab_buf)
  vim.api.nvim_set_option_value('filetype', 'cptest', { buf = tab_buf })

  local test_windows = {
    tab_win = main_win,
  }
  local test_buffers = {
    tab_buf = tab_buf,
  }

  local highlight = require('cp.ui.highlight')
  local diff_namespace = highlight.create_namespace()

  local test_list_namespace = vim.api.nvim_create_namespace('cp_test_list')
  local ansi_namespace = vim.api.nvim_create_namespace('cp_ansi_highlights')

  local function update_buffer_content(bufnr, lines, highlights, namespace)
    local was_readonly = vim.api.nvim_get_option_value('readonly', { buf = bufnr })

    vim.api.nvim_set_option_value('readonly', false, { buf = bufnr })
    vim.api.nvim_set_option_value('modifiable', true, { buf = bufnr })
    vim.api.nvim_buf_set_lines(bufnr, 0, -1, false, lines)
    vim.api.nvim_set_option_value('modifiable', false, { buf = bufnr })
    vim.api.nvim_set_option_value('readonly', was_readonly, { buf = bufnr })

    highlight.apply_highlights(bufnr, highlights, namespace or test_list_namespace)
  end

  local function create_none_diff_layout(parent_win, expected_content, actual_content)
    local expected_buf = create_buffer_with_options()
    local actual_buf = create_buffer_with_options()

    vim.api.nvim_set_current_win(parent_win)
    vim.cmd.split()
    vim.cmd('resize ' .. math.floor(vim.o.lines * 0.35))
    local actual_win = vim.api.nvim_get_current_win()
    vim.api.nvim_win_set_buf(actual_win, actual_buf)

    vim.cmd.vsplit()
    local expected_win = vim.api.nvim_get_current_win()
    vim.api.nvim_win_set_buf(expected_win, expected_buf)

    vim.api.nvim_set_option_value('filetype', 'cptest', { buf = expected_buf })
    vim.api.nvim_set_option_value('filetype', 'cptest', { 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 expected_lines = vim.split(expected_content, '\n', { plain = true, trimempty = true })
    local actual_lines = vim.split(actual_content, '\n', { plain = true, trimempty = true })

    update_buffer_content(expected_buf, expected_lines, {})
    update_buffer_content(actual_buf, actual_lines, {})

    return {
      buffers = { expected_buf, actual_buf },
      windows = { expected_win, actual_win },
      cleanup = function()
        pcall(vim.api.nvim_win_close, expected_win, true)
        pcall(vim.api.nvim_win_close, actual_win, true)
        pcall(vim.api.nvim_buf_delete, expected_buf, { force = true })
        pcall(vim.api.nvim_buf_delete, actual_buf, { force = true })
      end,
    }
  end

  local function create_vim_diff_layout(parent_win, expected_content, actual_content)
    local expected_buf = create_buffer_with_options()
    local actual_buf = create_buffer_with_options()

    vim.api.nvim_set_current_win(parent_win)
    vim.cmd.split()
    vim.cmd('resize ' .. math.floor(vim.o.lines * 0.35))
    local actual_win = vim.api.nvim_get_current_win()
    vim.api.nvim_win_set_buf(actual_win, actual_buf)

    vim.cmd.vsplit()
    local expected_win = vim.api.nvim_get_current_win()
    vim.api.nvim_win_set_buf(expected_win, expected_buf)

    vim.api.nvim_set_option_value('filetype', 'cptest', { buf = expected_buf })
    vim.api.nvim_set_option_value('filetype', 'cptest', { 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 expected_lines = vim.split(expected_content, '\n', { plain = true, trimempty = true })
    local actual_lines = vim.split(actual_content, '\n', { plain = true, trimempty = true })

    update_buffer_content(expected_buf, expected_lines, {})
    update_buffer_content(actual_buf, actual_lines, {})

    vim.api.nvim_set_option_value('diff', true, { win = expected_win })
    vim.api.nvim_set_option_value('diff', true, { win = actual_win })
    vim.api.nvim_win_call(expected_win, function()
      vim.cmd.diffthis()
    end)
    vim.api.nvim_win_call(actual_win, function()
      vim.cmd.diffthis()
    end)
    -- NOTE: diffthis() sets foldcolumn, so override it after
    vim.api.nvim_set_option_value('foldcolumn', '0', { win = expected_win })
    vim.api.nvim_set_option_value('foldcolumn', '0', { win = actual_win })

    return {
      buffers = { expected_buf, actual_buf },
      windows = { expected_win, actual_win },
      cleanup = function()
        pcall(vim.api.nvim_win_close, expected_win, true)
        pcall(vim.api.nvim_win_close, actual_win, true)
        pcall(vim.api.nvim_buf_delete, expected_buf, { force = true })
        pcall(vim.api.nvim_buf_delete, actual_buf, { force = true })
      end,
    }
  end

  local function create_git_diff_layout(parent_win, expected_content, actual_content)
    local diff_buf = create_buffer_with_options()

    vim.api.nvim_set_current_win(parent_win)
    vim.cmd.split()
    vim.cmd('resize ' .. math.floor(vim.o.lines * 0.35))
    local diff_win = vim.api.nvim_get_current_win()
    vim.api.nvim_win_set_buf(diff_win, diff_buf)

    vim.api.nvim_set_option_value('filetype', 'cptest', { buf = diff_buf })
    vim.api.nvim_set_option_value('winbar', 'Expected vs Actual', { win = diff_win })

    local diff_backend = require('cp.ui.diff')
    local backend = diff_backend.get_best_backend('git')
    local diff_result = backend.render(expected_content, actual_content)

    if diff_result.raw_diff and diff_result.raw_diff ~= '' then
      highlight.parse_and_apply_diff(diff_buf, diff_result.raw_diff, diff_namespace)
    else
      local lines = vim.split(actual_content, '\n', { plain = true, trimempty = true })
      update_buffer_content(diff_buf, lines, {})
    end

    return {
      buffers = { diff_buf },
      windows = { diff_win },
      cleanup = function()
        pcall(vim.api.nvim_win_close, diff_win, true)
        pcall(vim.api.nvim_buf_delete, diff_buf, { force = true })
      end,
    }
  end

  local function create_single_layout(parent_win, content)
    local buf = create_buffer_with_options()
    local lines = vim.split(content, '\n', { plain = true, trimempty = true })
    update_buffer_content(buf, lines, {})

    vim.api.nvim_set_current_win(parent_win)
    vim.cmd.split()
    vim.cmd('resize ' .. math.floor(vim.o.lines * 0.35))
    local win = vim.api.nvim_get_current_win()
    vim.api.nvim_win_set_buf(win, buf)
    vim.api.nvim_set_option_value('filetype', 'cptest', { buf = buf })

    return {
      buffers = { buf },
      windows = { win },
      cleanup = function()
        pcall(vim.api.nvim_win_close, win, true)
        pcall(vim.api.nvim_buf_delete, buf, { force = true })
      end,
    }
  end

  local function 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 == 'git' then
      return create_git_diff_layout(parent_win, expected_content, actual_content)
    else
      return create_vim_diff_layout(parent_win, expected_content, actual_content)
    end
  end

  local function update_diff_panes()
    local test_state = run.get_run_panel_state()
    local current_test = test_state.test_cases[test_state.current_index]

    if not current_test then
      return
    end

    local expected_content = current_test.expected or ''
    local actual_content = current_test.actual or '(not run yet)'
    local actual_highlights = current_test.actual_highlights or {}
    local is_compilation_failure = current_test.error
      and current_test.error:match('Compilation failed')
    local should_show_diff = current_test.status == 'fail'
      and current_test.actual
      and not is_compilation_failure

    if not should_show_diff then
      expected_content = expected_content
      actual_content = actual_content
    end

    local desired_mode = is_compilation_failure and 'single' or config.run_panel.diff_mode

    if current_diff_layout and current_mode ~= desired_mode then
      local saved_pos = vim.api.nvim_win_get_cursor(0)
      current_diff_layout.cleanup()
      current_diff_layout = nil
      current_mode = nil

      current_diff_layout =
        create_diff_layout(desired_mode, main_win, expected_content, actual_content)
      current_mode = desired_mode

      for _, buf in ipairs(current_diff_layout.buffers) do
        setup_keybindings_for_buffer(buf)
      end

      pcall(vim.api.nvim_win_set_cursor, 0, saved_pos)
      return
    end

    if not current_diff_layout then
      current_diff_layout =
        create_diff_layout(desired_mode, main_win, expected_content, actual_content)
      current_mode = desired_mode

      for _, buf in ipairs(current_diff_layout.buffers) do
        setup_keybindings_for_buffer(buf)
      end
    else
      if desired_mode == 'single' then
        local lines = vim.split(actual_content, '\n', { plain = true, trimempty = true })
        update_buffer_content(
          current_diff_layout.buffers[1],
          lines,
          actual_highlights,
          ansi_namespace
        )
      elseif desired_mode == 'git' then
        local diff_backend = require('cp.ui.diff')
        local backend = diff_backend.get_best_backend('git')
        local diff_result = backend.render(expected_content, actual_content)

        if diff_result.raw_diff and diff_result.raw_diff ~= '' then
          highlight.parse_and_apply_diff(
            current_diff_layout.buffers[1],
            diff_result.raw_diff,
            diff_namespace
          )
        else
          local lines = vim.split(actual_content, '\n', { plain = true, trimempty = true })
          update_buffer_content(
            current_diff_layout.buffers[1],
            lines,
            actual_highlights,
            ansi_namespace
          )
        end
      elseif desired_mode == 'none' then
        local expected_lines = vim.split(expected_content, '\n', { plain = true, trimempty = true })
        local actual_lines = vim.split(actual_content, '\n', { plain = true, trimempty = true })
        update_buffer_content(current_diff_layout.buffers[1], expected_lines, {})
        update_buffer_content(
          current_diff_layout.buffers[2],
          actual_lines,
          actual_highlights,
          ansi_namespace
        )
      else
        local expected_lines = vim.split(expected_content, '\n', { plain = true, trimempty = true })
        local actual_lines = vim.split(actual_content, '\n', { plain = true, trimempty = true })
        update_buffer_content(current_diff_layout.buffers[1], expected_lines, {})
        update_buffer_content(
          current_diff_layout.buffers[2],
          actual_lines,
          actual_highlights,
          ansi_namespace
        )

        if should_show_diff then
          vim.api.nvim_set_option_value('diff', true, { win = current_diff_layout.windows[1] })
          vim.api.nvim_set_option_value('diff', true, { win = current_diff_layout.windows[2] })
          vim.api.nvim_win_call(current_diff_layout.windows[1], function()
            vim.cmd.diffthis()
          end)
          vim.api.nvim_win_call(current_diff_layout.windows[2], function()
            vim.cmd.diffthis()
          end)
          vim.api.nvim_set_option_value('foldcolumn', '0', { win = current_diff_layout.windows[1] })
          vim.api.nvim_set_option_value('foldcolumn', '0', { win = current_diff_layout.windows[2] })
        else
          vim.api.nvim_set_option_value('diff', false, { win = current_diff_layout.windows[1] })
          vim.api.nvim_set_option_value('diff', false, { win = current_diff_layout.windows[2] })
        end
      end
    end
  end

  local function refresh_run_panel()
    if not test_buffers.tab_buf or not vim.api.nvim_buf_is_valid(test_buffers.tab_buf) then
      return
    end

    local run_render = require('cp.runner.run_render')
    run_render.setup_highlights()

    local test_state = run.get_run_panel_state()
    local tab_lines, tab_highlights = run_render.render_test_list(test_state)
    update_buffer_content(test_buffers.tab_buf, tab_lines, tab_highlights)

    update_diff_panes()
  end

  ---@param delta number 1 for next, -1 for prev
  local function navigate_test_case(delta)
    local test_state = run.get_run_panel_state()
    if #test_state.test_cases == 0 then
      return
    end

    test_state.current_index = test_state.current_index + delta
    if test_state.current_index < 1 then
      test_state.current_index = #test_state.test_cases
    elseif test_state.current_index > #test_state.test_cases then
      test_state.current_index = 1
    end

    refresh_run_panel()
  end

  setup_keybindings_for_buffer = function(buf)
    vim.keymap.set('n', 'q', function()
      toggle_run_panel()
    end, { buffer = buf, silent = true })
    vim.keymap.set('n', config.run_panel.toggle_diff_key, function()
      local modes = { 'none', 'git', 'vim' }
      local current_idx = nil
      for i, mode in ipairs(modes) do
        if config.run_panel.diff_mode == mode then
          current_idx = i
          break
        end
      end
      current_idx = current_idx or 1
      config.run_panel.diff_mode = modes[(current_idx % #modes) + 1]
      refresh_run_panel()
    end, { buffer = buf, silent = true })
    vim.keymap.set('n', config.run_panel.next_test_key, function()
      navigate_test_case(1)
    end, { buffer = buf, silent = true })
    vim.keymap.set('n', config.run_panel.prev_test_key, function()
      navigate_test_case(-1)
    end, { buffer = buf, silent = true })
  end

  vim.keymap.set('n', config.run_panel.next_test_key, function()
    navigate_test_case(1)
  end, { buffer = test_buffers.tab_buf, silent = true })
  vim.keymap.set('n', config.run_panel.prev_test_key, function()
    navigate_test_case(-1)
  end, { buffer = test_buffers.tab_buf, silent = true })

  setup_keybindings_for_buffer(test_buffers.tab_buf)

  if config.hooks and config.hooks.before_run then
    config.hooks.before_run(ctx)
  end

  if is_debug and config.hooks and config.hooks.before_debug then
    config.hooks.before_debug(ctx)
  end

  local execute = require('cp.runner.execute')
  local contest_config = config.contests[state.platform]
  local compile_result = execute.compile_problem(ctx, contest_config, is_debug)
  if compile_result.success then
    run.run_all_test_cases(ctx, contest_config, config)
  else
    run.handle_compilation_failure(compile_result.output)
  end

  refresh_run_panel()

  vim.schedule(function()
    if config.run_panel.ansi then
      local ansi = require('cp.ui.ansi')
      ansi.setup_highlight_groups()
    end
    if current_diff_layout then
      update_diff_panes()
    end
  end)

  vim.api.nvim_set_current_win(test_windows.tab_win)

  state.run_panel_active = true
  state.test_buffers = test_buffers
  state.test_windows = test_windows
  local test_state = run.get_run_panel_state()
  logger.log(
    string.format('test panel opened (%d test cases)', #test_state.test_cases),
    vim.log.levels.INFO
  )
end

---@param contest_id string
---@param language? string
local function setup_contest(contest_id, language)
  if not state.platform then
    logger.log('no platform set', vim.log.levels.ERROR)
    return false
  end

  if not vim.tbl_contains(config.scrapers, state.platform) then
    logger.log('scraping disabled for ' .. state.platform, vim.log.levels.WARN)
    return false
  end

  logger.log(('setting up contest %s %s'):format(state.platform, contest_id))

  local metadata_result = scrape.scrape_contest_metadata(state.platform, contest_id)
  if not metadata_result.success then
    logger.log(
      'failed to load contest metadata: ' .. (metadata_result.error or 'unknown error'),
      vim.log.levels.ERROR
    )
    return false
  end

  local problems = metadata_result.problems
  if not problems or #problems == 0 then
    logger.log('no problems found in contest', vim.log.levels.ERROR)
    return false
  end

  logger.log(('found %d problems, checking cache...'):format(#problems))

  cache.load()
  local missing_problems = {}
  for _, prob in ipairs(problems) do
    local cached_tests = cache.get_test_cases(state.platform, contest_id, prob.id)
    if not cached_tests then
      table.insert(missing_problems, prob)
    end
  end

  if #missing_problems > 0 then
    logger.log(('scraping %d uncached problems...'):format(#missing_problems))
    scrape_missing_problems(contest_id, missing_problems)
  else
    logger.log('all problems already cached')
  end

  state.set_contest_id(contest_id)
  setup_problem(contest_id, problems[1].id, language)

  return true
end

---@param delta number 1 for next, -1 for prev
---@param language? string
local function navigate_problem(delta, language)
  if not state.platform or not state.contest_id then
    logger.log('no contest set. run :CP <platform> <contest> first', vim.log.levels.ERROR)
    return
  end

  cache.load()
  local contest_data = cache.get_contest_data(state.platform, state.contest_id)
  if not contest_data or not contest_data.problems then
    logger.log(
      'no contest metadata found. set up a problem first to cache contest data',
      vim.log.levels.ERROR
    )
    return
  end

  local problems = contest_data.problems
  local current_problem_id = state.problem_id

  if not current_problem_id then
    logger.log('no current problem set', vim.log.levels.ERROR)
    return
  end

  local current_index = nil
  for i, prob in ipairs(problems) do
    if prob.id == current_problem_id then
      current_index = i
      break
    end
  end

  if not current_index then
    logger.log('current problem not found in contest', vim.log.levels.ERROR)
    return
  end

  local new_index = current_index + delta

  if new_index < 1 or new_index > #problems then
    local msg = delta > 0 and 'at last problem' or 'at first problem'
    logger.log(msg, vim.log.levels.WARN)
    return
  end

  local new_problem = problems[new_index]

  setup_problem(state.contest_id, new_problem.id, language)
end

local function handle_pick_action()
  if not config.picker then
    logger.log(
      'No picker configured. Set picker = "telescope" or picker = "fzf-lua" in config',
      vim.log.levels.ERROR
    )
    return
  end

  if config.picker == 'telescope' then
    local ok = pcall(require, 'telescope')
    if not ok then
      logger.log(
        'Telescope not available. Install telescope.nvim or change picker config',
        vim.log.levels.ERROR
      )
      return
    end
    local ok_cp, telescope_cp = pcall(require, 'cp.pickers.telescope')
    if not ok_cp then
      logger.log('Failed to load telescope integration', vim.log.levels.ERROR)
      return
    end
    telescope_cp.platform_picker()
  elseif config.picker == 'fzf-lua' then
    local ok, _ = pcall(require, 'fzf-lua')
    if not ok then
      logger.log(
        'fzf-lua not available. Install fzf-lua or change picker config',
        vim.log.levels.ERROR
      )
      return
    end
    local ok_cp, fzf_cp = pcall(require, 'cp.pickers.fzf_lua')
    if not ok_cp then
      logger.log('Failed to load fzf-lua integration', vim.log.levels.ERROR)
      return
    end
    fzf_cp.platform_picker()
  end
end

local function handle_cache_command(cmd)
  if cmd.subcommand == 'clear' then
    cache.load()
    if cmd.platform then
      if vim.tbl_contains(platforms, cmd.platform) then
        cache.clear_platform(cmd.platform)
        logger.log(('cleared cache for %s'):format(cmd.platform), vim.log.levels.INFO, true)
      else
        logger.log(
          ('unknown platform: %s. Available: %s'):format(
            cmd.platform,
            table.concat(platforms, ', ')
          ),
          vim.log.levels.ERROR
        )
      end
    else
      cache.clear_all()
      logger.log('cleared all cache', vim.log.levels.INFO, true)
    end
  end
end

local function restore_from_current_file()
  local current_file = vim.fn.expand('%:p')
  if current_file == '' then
    logger.log('No file is currently open', vim.log.levels.ERROR)
    return false
  end

  cache.load()
  local file_state = cache.get_file_state(current_file)
  if not file_state then
    logger.log(
      'No cached state found for current file. Use :CP <platform> <contest> <problem> first.',
      vim.log.levels.ERROR
    )
    return false
  end

  logger.log(
    ('Restoring from cached state: %s %s %s'):format(
      file_state.platform,
      file_state.contest_id,
      file_state.problem_id or 'N/A'
    )
  )

  if not set_platform(file_state.platform) then
    return false
  end

  state.contest_id = file_state.contest_id
  state.problem_id = file_state.problem_id

  setup_problem(file_state.contest_id, file_state.problem_id, file_state.language)

  return true
end

local function parse_command(args)
  if #args == 0 then
    return {
      type = 'restore_from_file',
    }
  end

  local language = nil
  local debug = false

  for i, arg in ipairs(args) do
    local lang_match = arg:match('^--lang=(.+)$')
    if lang_match then
      language = lang_match
    elseif arg == '--lang' then
      if i + 1 <= #args then
        language = args[i + 1]
      else
        return { type = 'error', message = '--lang requires a value' }
      end
    elseif arg == '--debug' then
      debug = true
    end
  end

  local filtered_args = vim.tbl_filter(function(arg)
    return not (arg:match('^--lang') or arg == language or arg == '--debug')
  end, args)

  local first = filtered_args[1]

  if vim.tbl_contains(actions, first) then
    if first == 'cache' then
      local subcommand = filtered_args[2]
      if not subcommand then
        return { type = 'error', message = 'cache command requires subcommand: clear' }
      end
      if subcommand == 'clear' then
        local platform = filtered_args[3]
        return {
          type = 'cache',
          subcommand = 'clear',
          platform = platform,
        }
      else
        return { type = 'error', message = 'unknown cache subcommand: ' .. subcommand }
      end
    else
      return { type = 'action', action = first, language = language, debug = debug }
    end
  end

  if vim.tbl_contains(platforms, first) then
    if #filtered_args == 1 then
      return {
        type = 'platform_only',
        platform = first,
        language = language,
      }
    elseif #filtered_args == 2 then
      return {
        type = 'contest_setup',
        platform = first,
        contest = filtered_args[2],
        language = language,
      }
    elseif #filtered_args == 3 then
      return {
        type = 'full_setup',
        platform = first,
        contest = filtered_args[2],
        problem = filtered_args[3],
        language = language,
      }
    else
      return { type = 'error', message = 'Too many arguments' }
    end
  end

  if state.platform and state.contest_id then
    cache.load()
    local contest_data = cache.get_contest_data(state.platform, state.contest_id)
    if contest_data and contest_data.problems then
      local problem_ids = vim.tbl_map(function(prob)
        return prob.id
      end, contest_data.problems)
      if vim.tbl_contains(problem_ids, first) then
        return { type = 'problem_switch', problem = first, language = language }
      end
    end
    return {
      type = 'error',
      message = ("invalid subcommand '%s'"):format(first),
    }
  end

  return { type = 'error', message = 'Unknown command or no contest context' }
end

function M.handle_command(opts)
  local cmd = parse_command(opts.fargs)

  if cmd.type == 'error' then
    logger.log(cmd.message, vim.log.levels.ERROR)
    return
  end

  if cmd.type == 'restore_from_file' then
    restore_from_current_file()
    return
  end

  if cmd.type == 'action' then
    if cmd.action == 'run' then
      toggle_run_panel(cmd.debug)
    elseif cmd.action == 'next' then
      navigate_problem(1, cmd.language)
    elseif cmd.action == 'prev' then
      navigate_problem(-1, cmd.language)
    elseif cmd.action == 'pick' then
      handle_pick_action()
    end
    return
  end

  if cmd.type == 'cache' then
    handle_cache_command(cmd)
    return
  end

  if cmd.type == 'platform_only' then
    set_platform(cmd.platform)
    return
  end

  if cmd.type == 'contest_setup' then
    if set_platform(cmd.platform) then
      setup_contest(cmd.contest, cmd.language)
    end
    return
  end

  if cmd.type == 'full_setup' then
    if set_platform(cmd.platform) then
      state.set_contest_id(cmd.contest)
      local problem_ids = {}
      local has_metadata = false

      if vim.tbl_contains(config.scrapers, cmd.platform) then
        local metadata_result = scrape.scrape_contest_metadata(cmd.platform, cmd.contest)
        if not metadata_result.success then
          logger.log(
            'failed to load contest metadata: ' .. (metadata_result.error or 'unknown error'),
            vim.log.levels.ERROR
          )
          return
        end

        logger.log(
          ('loaded %d problems for %s %s'):format(
            #metadata_result.problems,
            cmd.platform,
            cmd.contest
          ),
          vim.log.levels.INFO,
          true
        )
        problem_ids = vim.tbl_map(function(prob)
          return prob.id
        end, metadata_result.problems)
        has_metadata = true
      else
        cache.load()
        local contest_data = cache.get_contest_data(cmd.platform, cmd.contest)
        if contest_data and contest_data.problems then
          problem_ids = vim.tbl_map(function(prob)
            return prob.id
          end, contest_data.problems)
          has_metadata = true
        end
      end

      if has_metadata and not vim.tbl_contains(problem_ids, cmd.problem) then
        logger.log(
          ("Invalid problem '%s' for contest %s %s"):format(cmd.problem, cmd.platform, cmd.contest),
          vim.log.levels.ERROR
        )
        return
      end

      setup_problem(cmd.contest, cmd.problem, cmd.language)
    end
    return
  end

  if cmd.type == 'problem_switch' then
    setup_problem(state.contest_id, cmd.problem, cmd.language)
    return
  end
end

function M.setup(opts)
  opts = opts or {}
  user_config = opts
  config = config_module.setup(user_config)
  logger.set_config(config)
  if not snippets_initialized then
    snippets.setup(config)
    snippets_initialized = true
  end
end

function M.get_current_context()
  return {
    platform = state.platform,
    contest_id = state.contest_id,
    problem_id = state.problem_id,
  }
end

function M.is_initialized()
  return true
end

return M