---@class TestCase
---@field index number
---@field input string
---@field expected string
---@field status "pending"|"pass"|"fail"|"running"|"timeout"
---@field actual string?
---@field time_ms number?
---@field error string?
---@field selected boolean
---@field code number?
---@field ok boolean?
---@field signal string?
---@field timed_out boolean?

---@class TestPanelState
---@field test_cases TestCase[]
---@field current_index number
---@field buffer number?
---@field namespace number?
---@field is_active boolean
---@field saved_layout table?

local M = {}
local constants = require('cp.constants')
local logger = require('cp.log')

---@type TestPanelState
local test_panel_state = {
  test_cases = {},
  current_index = 1,
  buffer = nil,
  namespace = nil,
  is_active = false,
  saved_layout = nil,
}

---@param index number
---@param input string
---@param expected string
---@return TestCase
local function create_test_case(index, input, expected)
  return {
    index = index,
    input = input,
    expected = expected,
    status = 'pending',
    actual = nil,
    time_ms = nil,
    error = nil,
    selected = true,
  }
end

---@param platform string
---@param contest_id string
---@param problem_id string?
---@return TestCase[]
local function parse_test_cases_from_cache(platform, contest_id, problem_id)
  local cache = require('cp.cache')
  cache.load()
  local cached_test_cases = cache.get_test_cases(platform, contest_id, problem_id)

  if not cached_test_cases or #cached_test_cases == 0 then
    return {}
  end

  local test_cases = {}

  for i, test_case in ipairs(cached_test_cases) do
    local index = test_case.index or i
    local expected = test_case.expected or test_case.output or ''
    table.insert(test_cases, create_test_case(index, test_case.input, expected))
  end

  return test_cases
end

---@param input_file string
---@param expected_file string
---@return TestCase[]
local function parse_test_cases_from_files(input_file, expected_file)
  if vim.fn.filereadable(input_file) == 0 or vim.fn.filereadable(expected_file) == 0 then
    return {}
  end

  local base_name = vim.fn.fnamemodify(input_file, ':r')
  local test_cases = {}
  local i = 1

  while true do
    local individual_input_file = base_name .. '.' .. i .. '.cpin'
    local individual_expected_file = base_name .. '.' .. i .. '.cpout'

    if
      vim.fn.filereadable(individual_input_file) == 1
      and vim.fn.filereadable(individual_expected_file) == 1
    then
      local input_content = table.concat(vim.fn.readfile(individual_input_file), '\n')
      local expected_content = table.concat(vim.fn.readfile(individual_expected_file), '\n')

      table.insert(test_cases, create_test_case(i, input_content, expected_content))
      i = i + 1
    else
      break
    end
  end

  if #test_cases == 0 then
    local input_content = table.concat(vim.fn.readfile(input_file), '\n')
    local expected_content = table.concat(vim.fn.readfile(expected_file), '\n')
    return { create_test_case(1, input_content, expected_content) }
  end

  return test_cases
end

---@param ctx ProblemContext
---@param contest_config ContestConfig
---@param test_case TestCase
---@return table
local function run_single_test_case(ctx, contest_config, test_case)
  local language = vim.fn.fnamemodify(ctx.source_file, ':e')
  local language_name = constants.filetype_to_language[language] or contest_config.default_language
  local language_config = contest_config[language_name]

  if not language_config then
    return {
      status = 'fail',
      actual = '',
      error = 'No language configuration',
      time_ms = 0,
    }
  end

  local function substitute_template(cmd_template, substitutions)
    local result = {}
    for _, arg in ipairs(cmd_template) do
      local substituted = arg
      for key, value in pairs(substitutions) do
        substituted = substituted:gsub('{' .. key .. '}', value)
      end
      table.insert(result, substituted)
    end
    return result
  end

  local function build_command(cmd_template, executable, substitutions)
    local cmd = substitute_template(cmd_template, substitutions)
    if executable then
      table.insert(cmd, 1, executable)
    end
    return cmd
  end

  local substitutions = {
    source = ctx.source_file,
    binary = ctx.binary_file,
    version = tostring(language_config.version or ''),
  }

  if language_config.compile and vim.fn.filereadable(ctx.binary_file) == 0 then
    logger.log('binary not found, compiling first...')
    local compile_cmd = substitute_template(language_config.compile, substitutions)
    local compile_result = vim.system(compile_cmd, { text = true }):wait()
    if compile_result.code ~= 0 then
      return {
        status = 'fail',
        actual = '',
        error = 'Compilation failed: ' .. (compile_result.stderr or 'Unknown error'),
        time_ms = 0,
      }
    end
  end

  local run_cmd = build_command(language_config.test, language_config.executable, substitutions)

  local stdin_content = test_case.input .. '\n'

  local start_time = vim.uv.hrtime()
  local result = vim
    .system(run_cmd, {
      stdin = stdin_content,
      timeout = contest_config.timeout_ms or 2000,
      text = true,
    })
    :wait()
  local execution_time = (vim.uv.hrtime() - start_time) / 1000000

  local actual_output = (result.stdout or ''):gsub('\n$', '')
  local expected_output = test_case.expected:gsub('\n$', '')
  local ok = actual_output == expected_output

  local status
  local timed_out = result.code == 143 or result.code == 124
  if timed_out then
    status = 'timeout'
  elseif result.code == 0 and ok then
    status = 'pass'
  else
    status = 'fail'
  end

  local signal = nil
  if result.code >= 128 then
    signal = constants.signal_codes[result.code]
  end

  return {
    status = status,
    actual = actual_output,
    error = result.code ~= 0 and result.stderr or nil,
    time_ms = execution_time,
    code = result.code,
    ok = ok,
    signal = signal,
    timed_out = timed_out,
  }
end

---@param ctx ProblemContext
---@param state table
---@return boolean
function M.load_test_cases(ctx, state)
  local test_cases = parse_test_cases_from_cache(state.platform, state.contest_id, state.problem_id)

  if #test_cases == 0 then
    test_cases = parse_test_cases_from_files(ctx.input_file, ctx.expected_file)
  end

  test_panel_state.test_cases = test_cases
  test_panel_state.current_index = 1

  logger.log(('loaded %d test case(s)'):format(#test_cases))
  return #test_cases > 0
end

---@param ctx ProblemContext
---@param contest_config ContestConfig
---@param index number
---@return boolean
function M.run_test_case(ctx, contest_config, index)
  local test_case = test_panel_state.test_cases[index]
  if not test_case then
    return false
  end

  logger.log(('running test case %d'):format(index))
  test_case.status = 'running'

  local result = run_single_test_case(ctx, contest_config, test_case)

  test_case.status = result.status
  test_case.actual = result.actual
  test_case.error = result.error
  test_case.time_ms = result.time_ms
  test_case.code = result.code
  test_case.ok = result.ok
  test_case.signal = result.signal
  test_case.timed_out = result.timed_out

  return true
end

---@param ctx ProblemContext
---@param contest_config ContestConfig
---@return TestCase[]
function M.run_all_test_cases(ctx, contest_config)
  local results = {}
  for i, _ in ipairs(test_panel_state.test_cases) do
    M.run_test_case(ctx, contest_config, i)
    table.insert(results, test_panel_state.test_cases[i])
  end
  return results
end

---@return TestPanelState
function M.get_test_panel_state()
  return test_panel_state
end

return M