// /components/documents/documentService.js

const path = require('path');
const Document = require('./documentModel');
const User = require('../users/userModel');
const AppError = require('../../utils/AppError');
const config = require('../../config/config');
const {
  commitTempFile,
  generatePresignedUrl,
  deleteFromBucket
} = require('../../utils/s3Client');
const { parsePaginationAndSort, buildFilterQuery, calculateMeta } = require('../../utils/pagination');

const BUCKET = 'documents';

const withAccessUrl = async (doc) => {
  const item = typeof doc.toObject === 'function' ? doc.toObject() : { ...doc };
  item.fileUrl = item.fileUrl || null;
  item.signedUrl = await generatePresignedUrl(item.fileKey, item.bucket || config.S3_DOCUMENTS_BUCKET);
  item.presignedUrl = item.signedUrl;
  item.url = item.fileUrl || item.signedUrl;
  return item;
};

const createDocument = async (data, uploadedBy = null) => {
  const user = await User.findById(data.user);
  if (!user) throw new AppError('USER_NOT_FOUND');
  if (!data.tempFileName) throw new AppError('FILE_REQUIRED');

  const safeName = path.basename(data.tempFileName);
  const targetKey = `documents/doc-${Date.now()}-${safeName}`;
  const { fileKey, bucket, fileUrl } = await commitTempFile(data.tempFileName, targetKey, BUCKET);

  const document = await Document.create({
    user: data.user,
    title: data.title || data.originalName || safeName,
    description: data.description || '',
    fileKey,
    fileName: data.originalName || data.fileName || safeName,
    fileUrl: fileUrl || null,
    bucket,
    mimeType: data.mimeType || '',
    uploadedBy: uploadedBy || null
  });

  if (Array.isArray(user.documents)) {
    user.documents.push(document._id);
    await user.save();
  }

  return withAccessUrl(document);
};

const getDocumentById = async (id) => {
  const document = await Document.findById(id).populate('user', 'name username nationalIdCode');
  if (!document) throw new AppError('DOCUMENT_NOT_FOUND');
  return withAccessUrl(document);
};

const getDocumentsByUser = async (userId) => {
  const documents = await Document.find({ user: userId }).sort({ createdAt: -1 });
  return Promise.all(documents.map(withAccessUrl));
};

const getAllDocuments = async (queryParams) => {
  const { page, limit, skip, sort } = parsePaginationAndSort(queryParams);
  const filter = buildFilterQuery(queryParams, ['title', 'fileName', 'description']);
  if (queryParams.userId) filter.user = queryParams.userId;

  const [documents, totalCount] = await Promise.all([
    Document.find(filter)
      .populate('user', 'name username')
      .sort(sort)
      .skip(skip)
      .limit(limit),
    Document.countDocuments(filter)
  ]);

  const data = await Promise.all(documents.map(withAccessUrl));
  return { data, meta: calculateMeta(totalCount, page, limit) };
};

const updateDocument = async (id, updateData) => {
  const document = await Document.findById(id);
  if (!document) throw new AppError('DOCUMENT_NOT_FOUND');

  if (updateData.tempFileName) {
    const safeName = path.basename(updateData.tempFileName);
    const targetKey = `documents/doc-${Date.now()}-${safeName}`;
    const { fileKey, bucket, fileUrl } = await commitTempFile(updateData.tempFileName, targetKey, BUCKET);
    await deleteFromBucket(document.fileKey, document.bucket || config.S3_DOCUMENTS_BUCKET);
    document.fileKey = fileKey;
    document.bucket = bucket;
    document.fileUrl = fileUrl || null;
    if (updateData.originalName || updateData.fileName) {
      document.fileName = updateData.originalName || updateData.fileName;
    }
    if (updateData.mimeType) document.mimeType = updateData.mimeType;
  }

  if (updateData.title) document.title = updateData.title;
  if (updateData.description !== undefined) document.description = updateData.description;

  await document.save();
  return withAccessUrl(document);
};

const deleteDocument = async (id) => {
  const document = await Document.findById(id);
  if (!document) throw new AppError('DOCUMENT_NOT_FOUND');

  await deleteFromBucket(document.fileKey, document.bucket || config.S3_DOCUMENTS_BUCKET);
  await User.findByIdAndUpdate(document.user, { $pull: { documents: document._id } });
  await Document.findByIdAndDelete(id);
  return null;
};

const getMyDocuments = async (userId, queryParams = {}) => {
  const filter = { user: userId, ...buildFilterQuery(queryParams, ['title', 'fileName']) };
  const { page, limit, skip, sort } = parsePaginationAndSort(queryParams);

  const [documents, totalCount] = await Promise.all([
    Document.find(filter).sort(sort).skip(skip).limit(limit),
    Document.countDocuments(filter)
  ]);

  const data = await Promise.all(documents.map(withAccessUrl));
  return { data, meta: calculateMeta(totalCount, page, limit) };
};

module.exports = {
  createDocument,
  getDocumentById,
  getDocumentsByUser,
  getAllDocuments,
  updateDocument,
  deleteDocument,
  getMyDocuments
};