local M = {}
local uv = vim.loop

local config = require('chatgpt_nvim.config')

local function ensure_dir(path)
  local st = uv.fs_stat(path)
  if st and st.type == 'directory' then
    return true
  end
  local parent = path:match("(.*)/")
  if parent and parent ~= "" then
    ensure_dir(parent)
  end
  uv.fs_mkdir(path, 511)
  return true
end

function M.get_clipboard_content()
  local conf = config.load()
  local content = vim.fn.getreg('+')
  if conf.debug then
    vim.api.nvim_out_write("[chatgpt_nvim:handler] Clipboard content length: " .. #content .. "\n")
  end
  return content
end

function M.write_file(filepath, content)
  local conf = config.load()
  local dir = filepath:match("(.*)/")
  if dir and dir ~= "" then
    ensure_dir(dir)
  end
  local fd = uv.fs_open(filepath, "w", 438)
  if not fd then
    vim.api.nvim_err_writeln("Could not open file for writing: " .. filepath)
    if conf.debug then
      vim.api.nvim_out_write("[chatgpt_nvim:handler] Failed to open file for writing: " .. filepath .. "\n")
    end
    return
  end
  uv.fs_write(fd, content, -1)
  uv.fs_close(fd)
  if conf.debug then
    vim.api.nvim_out_write("[chatgpt_nvim:handler] Successfully wrote file: " .. filepath .. "\n")
  end
end

function M.delete_file(filepath)
  local conf = config.load()
  local st = uv.fs_stat(filepath)
  if st then
    local success, err = uv.fs_unlink(filepath)
    if not success then
      vim.api.nvim_err_writeln("Could not delete file: " .. filepath .. " - " .. (err or "unknown error"))
      if conf.debug then
        vim.api.nvim_out_write("[chatgpt_nvim:handler] Failed to delete file: " .. filepath .. "\n")
      end
    else
      if conf.debug then
        vim.api.nvim_out_write("[chatgpt_nvim:handler] Deleted file: " .. filepath .. "\n")
      end
    end
  else
    vim.api.nvim_err_writeln("File not found, cannot delete: " .. filepath)
    if conf.debug then
      vim.api.nvim_out_write("[chatgpt_nvim:handler] File not found for deletion: " .. filepath .. "\n")
    end
  end
end

-- Applies a unified diff to the specified file.
function M.apply_diff(filepath, diff_content)
  local conf = config.load()
  local tmp_original = vim.fn.tempname()
  local tmp_patch = vim.fn.tempname()

  -- 1) Read original file (or empty if it doesn't exist)
  local fd_in = uv.fs_open(filepath, "r", 438)
  local original_data = ""
  if fd_in then
    local stat = uv.fs_fstat(fd_in)
    original_data = uv.fs_read(fd_in, stat.size, 0)
    uv.fs_close(fd_in)
  end

  -- 2) Write original content to a temp file
  local fd_orig = uv.fs_open(tmp_original, "w", 438)
  if fd_orig then
    uv.fs_write(fd_orig, original_data, -1)
    uv.fs_close(fd_orig)
  end

  -- 3) Write diff to a temp file
  local fd_patch = uv.fs_open(tmp_patch, "w", 438)
  if fd_patch then
    uv.fs_write(fd_patch, diff_content, -1)
    uv.fs_close(fd_patch)
  else
    return false, "Could not open temporary file to write patch."
  end

  if conf.debug then
    vim.api.nvim_out_write("[chatgpt_nvim:handler] Applying diff to: " .. filepath .. "\n")
    vim.api.nvim_out_write("[chatgpt_nvim:handler] Original file contents saved at: " .. tmp_original .. "\n")
    vim.api.nvim_out_write("[chatgpt_nvim:handler] Patch file saved at: " .. tmp_patch .. "\n")
    vim.api.nvim_out_write("[chatgpt_nvim:handler] Patch contents:\n" .. diff_content .. "\n")
  end

  -- 4) Attempt to run 'patch'
  local patch_cmd = "patch -u --reject-file=- " .. vim.fn.shellescape(tmp_original)
    .. " < " .. vim.fn.shellescape(tmp_patch)
  local handle = io.popen(patch_cmd)
  if not handle then
    return false, "Failed to run patch command."
  end
  local result = handle:read("*a")
  local success_close, errmsg = handle:close()

  if conf.debug then
    vim.api.nvim_out_write("[chatgpt_nvim:handler] Patch command was: " .. patch_cmd .. "\n")
    vim.api.nvim_out_write("[chatgpt_nvim:handler] Patch command output:\n" .. (result or "") .. "\n")
    if not success_close then
      vim.api.nvim_out_write("[chatgpt_nvim:handler] Patch command closed with error: " .. (errmsg or "unknown") .. "\n")
    else
      vim.api.nvim_out_write("[chatgpt_nvim:handler] Patch command succeeded.\n")
    end
  end

  if not success_close then
    if conf.debug then
      vim.api.nvim_out_write("[chatgpt_nvim:handler] Patch command failed: " .. (errmsg or "unknown") .. "\n")
    end
    return false, errmsg
  end

  -- If successful, read the patched file and write it back
  if conf.debug then
    local debug_read = uv.fs_open(tmp_original, "r", 438)
    if debug_read then
      local debug_stat = uv.fs_fstat(debug_read)
      local debug_data = uv.fs_read(debug_read, debug_stat.size, 0)
      uv.fs_close(debug_read)
      vim.api.nvim_out_write("[chatgpt_nvim:handler] Post-patch temp file:\n" .. debug_data .. "\n")
      vim.api.nvim_out_write("[chatgpt_nvim:handler] End of patched temp file content.\n")
    end
  end

  local fd_out = uv.fs_open(tmp_original, "r", 438)
  if fd_out then
    local stat_out = uv.fs_fstat(fd_out)
    local new_data = uv.fs_read(fd_out, stat_out.size, 0)
    uv.fs_close(fd_out)

    M.write_file(filepath, new_data)
    if conf.debug then
      vim.api.nvim_out_write("[chatgpt_nvim:handler] Successfully applied patch to: " .. filepath .. "\n")
    end
  else
    return false, "Could not read patched file."
  end

  return true
end

function M.finish()
  print("Finished processing files.")
end

return M