local util = require("test-samurai.util")

local runner = {
  name = "go",
}

local function find_block_end(lines, start_idx)
  local depth = 0
  local started = false
  for i = start_idx, #lines do
    local line = lines[i]
    for j = 1, #line do
      local ch = line:sub(j, j)
      if ch == "{" then
        depth = depth + 1
        started = true
      elseif ch == "}" then
        if started then
          depth = depth - 1
          if depth == 0 then
            return i - 1
          end
        end
      end
    end
  end
  return #lines - 1
end

local function find_test_functions(lines)
  local funcs = {}
  for i, line in ipairs(lines) do
    local name = line:match("^%s*func%s+([%w_]+)%s*%(")
    if not name then
      name = line:match("^%s*func%s+%([^)]-%)%s+([%w_]+)%s*%(")
    end
    if name and line:find("%*testing%.T") then
      local start_0 = i - 1
      local end_0 = find_block_end(lines, i)
      table.insert(funcs, {
        name = name,
        start = start_0,
        ["end"] = end_0,
      })
    end
  end
  return funcs
end

local function find_t_runs(lines, func)
  local subtests = {}
  for i = func.start + 1, func["end"] do
    local line = lines[i + 1]
    if line then
      local name = line:match("t%.Run%(%s*['\"]([^'\"]+)['\"]")
      if name then
        local start_idx = i + 1
        local end_0 = find_block_end(lines, start_idx)
        table.insert(subtests, {
          name = name,
          start = start_idx - 1,
          ["end"] = end_0,
        })
      end
    end
  end
  return subtests
end

local function build_run_pattern(spec)
  local name = spec.test_path or ""
  local escaped = name:gsub("(%W)", "%%%1")
  if spec.scope == "function" then
    return "^" .. escaped .. "$|^" .. escaped .. "/"
  else
    return "^" .. escaped .. "$"
  end
end

local function build_pkg_arg(spec)
  local file = spec.file
  local cwd = spec.cwd
  if not file or not cwd or file == "" or cwd == "" then
    return "./..."
  end

  local dir = vim.fs.dirname(file)
  if dir == cwd then
    return "./"
  end

  if file:sub(1, #cwd) ~= cwd then
    return "./..."
  end

  local rel = dir:sub(#cwd + 2)
  if not rel or rel == "" then
    return "./"
  end

  return "./" .. rel
end

function runner.is_test_file(bufnr)
  local path = util.get_buf_path(bufnr)
  if not path or path == "" then
    return false
  end
  return path:sub(-8) == "_test.go"
end

function runner.find_nearest(bufnr, row, _col)
  if not runner.is_test_file(bufnr) then
    return nil, "not a Go test file"
  end

  local lines = util.get_buf_lines(bufnr)
  local funcs = find_test_functions(lines)

  local current
  for _, f in ipairs(funcs) do
    if row >= f.start and row <= f["end"] then
      current = f
      break
    end
  end

  if not current then
    return nil, "cursor not inside a test function"
  end

  local subtests = find_t_runs(lines, current)
  local inside_sub
  for _, sub in ipairs(subtests) do
    if row >= sub.start and row <= sub["end"] then
      inside_sub = sub
      break
    end
  end

  local path = util.get_buf_path(bufnr)
  local root = util.find_root(path, { "go.mod", ".git" })

  if inside_sub then
    local full = current.name .. "/" .. inside_sub.name
    return {
      file = path,
      cwd = root,
      test_path = full,
      scope = "subtest",
      func = current.name,
      subtest = inside_sub.name,
    }
  else
    return {
      file = path,
      cwd = root,
      test_path = current.name,
      scope = "function",
      func = current.name,
    }
  end
end

function runner.build_command(spec)
  local pattern = build_run_pattern(spec)
  local pkg = build_pkg_arg(spec)
  local cmd = { "go", "test", "-v", pkg, "-run", pattern }
  return {
    cmd = cmd,
    cwd = spec.cwd,
  }
end

return runner