local M = {}

local uv = vim.loop

local function load_gitignore_patterns(root)
  local gitignore_path = root .. "/.gitignore"
  local fd = uv.fs_open(gitignore_path, "r", 438)
  if not fd then
    return {}
  end
  local stat = uv.fs_fstat(fd)
  local data = uv.fs_read(fd, stat.size, 0)
  uv.fs_close(fd)
  if not data then return {} end
  local patterns = {}
  for line in data:gmatch("[^\r\n]+") do
    line = line:match("^%s*(.-)%s*$") -- trim
    if line ~= "" and not line:match("^#") then
      patterns[#patterns+1] = line
    end
  end
  return patterns
end

local function should_ignore_file(file, ignore_patterns)
  for _, pattern in ipairs(ignore_patterns) do
    if file:find(pattern, 1, true) then
      return true
    end
  end
  return false
end

local function is_text_file(file)
  local fd = uv.fs_open(file, "r", 438)
  if not fd then
    return false
  end
  local chunk = uv.fs_read(fd, 1024, 0) or ""
  uv.fs_close(fd)
  -- Check for null bytes as a heuristic for binary files
  if chunk:find("\0") then
    return false
  end
  return true
end

local function scandir(dir, ignore_patterns, files)
  files = files or {}
  local fd = uv.fs_opendir(dir, nil, 50)
  if not fd then return files end
  while true do
    local ents = uv.fs_readdir(fd)
    if not ents then break end
    for _, ent in ipairs(ents) do
      local fullpath = dir .. "/" .. ent.name
      if not should_ignore_file(fullpath, ignore_patterns) then
        if ent.type == "file" and is_text_file(fullpath) then
          table.insert(files, fullpath)
        elseif ent.type == "directory" and ent.name ~= ".git" then
          scandir(fullpath, ignore_patterns, files)
        end
      end
    end
  end
  uv.fs_closedir(fd)
  return files
end

function M.get_project_files(directories)
  local root = vim.fn.getcwd()
  local ignore_patterns = load_gitignore_patterns(root)
  local all_files = {}
  for _, dir in ipairs(directories) do
    local abs_dir = dir
    if not abs_dir:match("^/") then
      abs_dir = root .. "/" .. dir
    end
    scandir(abs_dir, ignore_patterns, all_files)
  end

  local rel_files = {}
  for _, f in ipairs(all_files) do
    local rel = vim.fn.fnamemodify(f, ":.")
    table.insert(rel_files, rel)
  end

  return rel_files
end

function M.get_project_structure(directories)
  local files = M.get_project_files(directories)
  local structure = "Files:\n" .. table.concat(files, "\n")
  return structure
end

function M.get_file_contents(files)
  local root = vim.fn.getcwd()
  local sections = {}
  for _, f in ipairs(files) do
    local path = root .. "/" .. f
    local fd = uv.fs_open(path, "r", 438)
    if fd then
      local stat = uv.fs_fstat(fd)
      if stat then
        local data = uv.fs_read(fd, stat.size, 0)
        uv.fs_close(fd)
        if data then
          table.insert(sections, "\nFile: `" .. f .. "`\n```\n" .. data .. "\n```\n")
        end
      else
        uv.fs_close(fd)
      end
    end
  end
  return table.concat(sections, "\n")
end

return M