local M = {}

local uv = vim.loop

-- Converts a .gitignore-style pattern to a Lua pattern
local function gitignore_to_lua_pattern(gip)
  -- Trim spaces
  gip = gip:gsub("^%s*(.-)%s*$", "%1")

  -- Escape magic chars in Lua patterns
  local magic_chars = "().^$+%-*?[]"
  gip = gip:gsub("["..magic_chars.."]", "%%%1")

  -- Convert ** to .- (match any path, including dirs)
  gip = gip:gsub("%%%%%*%%%%%*", ".*")

  -- Convert * to [^/]* (match anything except /)
  gip = gip:gsub("%%%%%*", "[^/]*")

  -- If pattern starts with /, ensure it matches start of string
  if gip:sub(1,1) == "/" then
    gip = "^" .. gip:sub(2)
  else
    -- Otherwise allow matching anywhere
    gip = gip
  end

  -- If pattern ends with /, ensure it matches a directory
  if gip:sub(-1) == "/" then
    gip = gip .. ".*"
  end

  return gip
end

local function load_gitignore_patterns(root, conf)
  local gitignore_path = root .. "/.gitignore"
  local fd = uv.fs_open(gitignore_path, "r", 438)
  if not fd then
    if conf.debug then
      vim.api.nvim_out_write("[chatgpt_nvim:context] No .gitignore found.\n")
    end
    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*$")
    if line ~= "" and not line:match("^#") then
      table.insert(patterns, gitignore_to_lua_pattern(line))
    end
  end
  if conf.debug then
    vim.api.nvim_out_write("[chatgpt_nvim:context] Loaded " .. #patterns .. " gitignore patterns.\n")
  end
  return patterns
end

local function should_ignore_file(file, ignore_patterns, conf)
  for _, pattern in ipairs(ignore_patterns) do
    if file:match(pattern) then
      if conf.debug then
        vim.api.nvim_out_write("[chatgpt_nvim:context] Ignoring file/dir: " .. file .. " (matched pattern: " .. pattern .. ")\n")
      end
      return true
    end
  end
  return false
end

local function is_text_file(file, conf)
  local fd = uv.fs_open(file, "r", 438)
  if not fd then
    if conf.debug then
      vim.api.nvim_out_write("[chatgpt_nvim:context] Could not open file: " .. file .. " for reading.\n")
    end
    return false
  end
  local chunk = uv.fs_read(fd, 1024, 0) or ""
  uv.fs_close(fd)
  if chunk:find("\0") then
    if conf.debug then
      vim.api.nvim_out_write("[chatgpt_nvim:context] File appears binary: " .. file .. "\n")
    end
    return false
  end
  return true
end

local function scandir(dir, ignore_patterns, files, conf)
  local fd = uv.fs_opendir(dir, nil, 50)
  if not fd then
    if conf.debug then
      vim.api.nvim_out_write("[chatgpt_nvim:context] Could not open dir: " .. dir .. "\n")
    end
    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, conf) then
        if ent.type == "file" and is_text_file(fullpath, conf) then
          table.insert(files, fullpath)
        elseif ent.type == "directory" and ent.name ~= ".git" then
          scandir(fullpath, ignore_patterns, files, conf)
        elseif ent.type == "link" then
          local link_target = uv.fs_readlink(fullpath)
          if link_target then
            local st = uv.fs_stat(link_target)
            if st and st.type == "directory" then
              table.insert(files, fullpath .. " (symlink to directory " .. link_target .. ")")
            else
              table.insert(files, fullpath .. " (symlink to file " .. link_target .. ")")
            end
          else
            table.insert(files, fullpath .. " (symlink)")
          end
        end
      end
    end
  end
  uv.fs_closedir(fd)
  return files
end

function M.get_project_files(directories, conf)
  local root = vim.fn.getcwd()
  local ignore_patterns = load_gitignore_patterns(root, conf)
  if conf.ignore_files then
    for _, pattern in ipairs(conf.ignore_files) do
      table.insert(ignore_patterns, gitignore_to_lua_pattern(pattern))
    end
  end
  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, conf)
  end

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

  if conf.debug then
    vim.api.nvim_out_write("[chatgpt_nvim:context] Found " .. #rel_files .. " project files.\n")
  end

  return rel_files
end

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

function M.get_file_contents(files, conf)
  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
    else
      if conf.debug then
        vim.api.nvim_out_write("[chatgpt_nvim:context] Could not open file for content: " .. f .. "\n")
      end
    end
  end
  return table.concat(sections, "\n")
end

-- NEW FUNCTION: Build the project prompt by optionally including file contents.
function M.get_project_prompt(directories, conf)
  local structure = M.get_project_structure(directories, conf)
  if conf.include_file_contents then
    local files = M.get_project_files(directories, conf)
    local contents = M.get_file_contents(files, conf)
    local total_chars = #contents
    if total_chars > conf.prompt_char_limit then
      vim.notify("Total file contents (" .. total_chars .. " characters) exceed the prompt limit (" .. conf.prompt_char_limit .. "). Please disable 'include_file_contents' in your config.", vim.log.levels.ERROR)
      return structure
    else
      return structure .. "\n" .. contents
    end
  else
    return structure
  end
end

return M