const path = require('path');
const { v4 } = require('uuid');
const mime = require('mime/lite');
const {
  isUUID,
  megabyte,
  FileContext,
  FileSources,
  imageExtRegex,
  EModelEndpoint,
  mergeFileConfig,
} = require('librechat-data-provider');
const { convertToWebP, resizeAndConvert } = require('~/server/services/Files/images');
const { initializeClient } = require('~/server/services/Endpoints/assistant');
const { createFile, updateFileUsage, deleteFiles } = require('~/models/File');
const { isEnabled, determineFileType } = require('~/server/utils');
const { LB_QueueAsyncCall } = require('~/server/utils/queue');
const { getStrategyFunctions } = require('./strategies');
const { logger } = require('~/config');

const { GPTS_DOWNLOAD_IMAGES = 'true' } = process.env;

const processFiles = async (files) => {
  const promises = [];
  for (let file of files) {
    const { file_id } = file;
    promises.push(updateFileUsage({ file_id }));
  }

  // TODO: calculate token cost when image is first uploaded
  return await Promise.all(promises);
};

/**
 * Enqueues the delete operation to the leaky bucket queue if necessary, or adds it directly to promises.
 *
 * @param {Express.Request} req - The express request object.
 * @param {MongoFile} file - The file object to delete.
 * @param {Function} deleteFile - The delete file function.
 * @param {Promise[]} promises - The array of promises to await.
 * @param {OpenAI | undefined} [openai] - If an OpenAI file, the initialized OpenAI client.
 */
function enqueueDeleteOperation(req, file, deleteFile, promises, openai) {
  if (file.source === FileSources.openai) {
    // Enqueue to leaky bucket
    promises.push(
      new Promise((resolve, reject) => {
        LB_QueueAsyncCall(
          () => deleteFile(req, file, openai),
          [],
          (err, result) => {
            if (err) {
              logger.error('Error deleting file from OpenAI source', err);
              reject(err);
            } else {
              resolve(result);
            }
          },
        );
      }),
    );
  } else {
    // Add directly to promises
    promises.push(
      deleteFile(req, file).catch((err) => {
        logger.error('Error deleting file', err);
        return Promise.reject(err);
      }),
    );
  }
}

// TODO: refactor as currently only image files can be deleted this way
// as other filetypes will not reside in public path
/**
 * Deletes a list of files from the server filesystem and the database.
 *
 * @param {Object} params - The params object.
 * @param {MongoFile[]} params.files - The file objects to delete.
 * @param {Express.Request} params.req - The express request object.
 * @param {DeleteFilesBody} params.req.body - The request body.
 * @param {string} [params.req.body.assistant_id] - The assistant ID if file uploaded is associated to an assistant.
 *
 * @returns {Promise<void>}
 */
const processDeleteRequest = async ({ req, files }) => {
  const file_ids = files.map((file) => file.file_id);

  const deletionMethods = {};
  const promises = [];
  promises.push(deleteFiles(file_ids));

  /** @type {OpenAI | undefined} */
  let openai;
  if (req.body.assistant_id) {
    ({ openai } = await initializeClient({ req }));
  }

  for (const file of files) {
    const source = file.source ?? FileSources.local;

    if (source === FileSources.openai && !openai) {
      ({ openai } = await initializeClient({ req }));
    }

    if (req.body.assistant_id) {
      promises.push(openai.beta.assistants.files.del(req.body.assistant_id, file.file_id));
    }

    if (deletionMethods[source]) {
      enqueueDeleteOperation(req, file, deletionMethods[source], promises, openai);
      continue;
    }

    const { deleteFile } = getStrategyFunctions(source);
    if (!deleteFile) {
      throw new Error(`Delete function not implemented for ${source}`);
    }

    deletionMethods[source] = deleteFile;
    enqueueDeleteOperation(req, file, deleteFile, promises, openai);
  }

  await Promise.allSettled(promises);
};

/**
 * Processes a file URL using a specified file handling strategy. This function accepts a strategy name,
 * fetches the corresponding file processing functions (for saving and retrieving file URLs), and then
 * executes these functions in sequence. It first saves the file using the provided URL and then retrieves
 * the URL of the saved file. If any error occurs during this process, it logs the error and throws an
 * exception with an appropriate message.
 *
 * @param {Object} params - The parameters object.
 * @param {FileSources} params.fileStrategy - The file handling strategy to use.
 * Must be a value from the `FileSources` enum, which defines different file
 * handling strategies (like saving to Firebase, local storage, etc.).
 * @param {string} params.userId - The user's unique identifier. Used for creating user-specific paths or
 * references in the file handling process.
 * @param {string} params.URL - The URL of the file to be processed.
 * @param {string} params.fileName - The name that will be used to save the file (including extension)
 * @param {string} params.basePath - The base path or directory where the file will be saved or retrieved from.
 * @param {FileContext} params.context - The context of the file (e.g., 'avatar', 'image_generation', etc.)
 * @returns {Promise<MongoFile>} A promise that resolves to the DB representation (MongoFile)
 *  of the processed file. It throws an error if the file processing fails at any stage.
 */
const processFileURL = async ({ fileStrategy, userId, URL, fileName, basePath, context }) => {
  const { saveURL, getFileURL } = getStrategyFunctions(fileStrategy);
  try {
    const { bytes, type, dimensions } = await saveURL({ userId, URL, fileName, basePath });
    const filepath = await getFileURL({ fileName: `${userId}/${fileName}`, basePath });
    return await createFile(
      {
        user: userId,
        file_id: v4(),
        bytes,
        filepath,
        filename: fileName,
        source: fileStrategy,
        type,
        context,
        width: dimensions.width,
        height: dimensions.height,
      },
      true,
    );
  } catch (error) {
    logger.error(`Error while processing the image with ${fileStrategy}:`, error);
    throw new Error(`Failed to process the image with ${fileStrategy}. ${error.message}`);
  }
};

/**
 * Applies the current strategy for image uploads.
 * Saves file metadata to the database with an expiry TTL.
 *
 * @param {Object} params - The parameters object.
 * @param {Express.Request} params.req - The Express request object.
 * @param {Express.Response} params.res - The Express response object.
 * @param {Express.Multer.File} params.file - The uploaded file.
 * @param {ImageMetadata} params.metadata - Additional metadata for the file.
 * @returns {Promise<void>}
 */
const processImageFile = async ({ req, res, file, metadata }) => {
  const source = req.app.locals.fileStrategy;
  const { handleImageUpload } = getStrategyFunctions(source);
  const { file_id, temp_file_id, endpoint } = metadata;
  const { filepath, bytes, width, height } = await handleImageUpload({ req, file, endpoint });
  const result = await createFile(
    {
      user: req.user.id,
      file_id,
      temp_file_id,
      bytes,
      filepath,
      filename: file.originalname,
      context: FileContext.message_attachment,
      source,
      type: 'image/webp',
      width,
      height,
    },
    true,
  );
  res.status(200).json({ message: 'File uploaded and processed successfully', ...result });
};

/**
 * Applies the current strategy for image uploads and
 * returns minimal file metadata, without saving to the database.
 *
 * @param {Object} params - The parameters object.
 * @param {Express.Request} params.req - The Express request object.
 * @param {FileContext} params.context - The context of the file (e.g., 'avatar', 'image_generation', etc.)
 * @returns {Promise<{ filepath: string, filename: string, source: string, type: 'image/webp'}>}
 */
const uploadImageBuffer = async ({ req, context }) => {
  const source = req.app.locals.fileStrategy;
  const { saveBuffer } = getStrategyFunctions(source);
  const { buffer, width, height, bytes } = await resizeAndConvert(req.file.buffer);
  const file_id = v4();
  const fileName = `img-${file_id}.webp`;

  const filepath = await saveBuffer({ userId: req.user.id, fileName, buffer });
  return await createFile(
    {
      user: req.user.id,
      file_id,
      bytes,
      filepath,
      filename: req.file.originalname,
      context,
      source,
      type: 'image/webp',
      width,
      height,
    },
    true,
  );
};

/**
 * Applies the current strategy for file uploads.
 * Saves file metadata to the database with an expiry TTL.
 * Files must be deleted from the server filesystem manually.
 *
 * @param {Object} params - The parameters object.
 * @param {Express.Request} params.req - The Express request object.
 * @param {Express.Response} params.res - The Express response object.
 * @param {Express.Multer.File} params.file - The uploaded file.
 * @param {FileMetadata} params.metadata - Additional metadata for the file.
 * @returns {Promise<void>}
 */
const processFileUpload = async ({ req, res, file, metadata }) => {
  const isAssistantUpload = metadata.endpoint === EModelEndpoint.assistants;
  const source = isAssistantUpload ? FileSources.openai : req.app.locals.fileStrategy;
  const { handleFileUpload } = getStrategyFunctions(source);
  const { file_id, temp_file_id } = metadata;

  /** @type {OpenAI | undefined} */
  let openai;
  if (source === FileSources.openai) {
    ({ openai } = await initializeClient({ req }));
  }

  const { id, bytes, filename, filepath } = await handleFileUpload(req, file, openai);

  if (isAssistantUpload && !metadata.message_file) {
    await openai.beta.assistants.files.create(metadata.assistant_id, {
      file_id: id,
    });
  }

  const result = await createFile(
    {
      user: req.user.id,
      file_id: id ?? file_id,
      temp_file_id,
      bytes,
      filepath: isAssistantUpload ? `https://api.openai.com/v1/files/${id}` : filepath,
      filename: filename ?? file.originalname,
      context: isAssistantUpload ? FileContext.assistants : FileContext.message_attachment,
      source,
      type: file.mimetype,
    },
    true,
  );
  res.status(200).json({ message: 'File uploaded and processed successfully', ...result });
};

/**
 * Retrieves and processes an OpenAI file based on its type.
 *
 * @param {Object} params - The params passed to the function.
 * @param {OpenAIClient} params.openai - The params passed to the function.
 * @param {string} params.file_id - The ID of the file to retrieve.
 * @param {string} params.basename - The basename of the file (if image); e.g., 'image.jpg'.
 * @param {boolean} [params.unknownType] - Whether the file type is unknown.
 * @returns {Promise<{file_id: string, filepath: string, source: string, bytes?: number, width?: number, height?: number} | null>}
 * - Returns null if `file_id` is not defined; else, the file metadata if successfully retrieved and processed.
 */
async function retrieveAndProcessFile({ openai, file_id, basename: _basename, unknownType }) {
  if (!file_id) {
    return null;
  }

  if (openai.attachedFileIds?.has(file_id)) {
    return {
      file_id,
      // filepath: TODO: local source filepath?,
      source: FileSources.openai,
    };
  }

  let basename = _basename;
  const downloadImages = isEnabled(GPTS_DOWNLOAD_IMAGES);

  /**
   * @param {string} file_id - The ID of the file to retrieve.
   * @param {boolean} [save] - Whether to save the file metadata to the database.
   */
  const retrieveFile = async (file_id, save = false) => {
    const _file = await openai.files.retrieve(file_id);
    const filepath = `/api/files/download/${file_id}`;
    const file = {
      ..._file,
      type: mime.getType(_file.filename),
      filepath,
      usage: 1,
      file_id,
      context: _file.purpose ?? FileContext.message_attachment,
      source: FileSources.openai,
    };

    if (save) {
      await createFile(file, true);
    } else {
      try {
        await updateFileUsage({ file_id });
      } catch (error) {
        logger.error('Error updating file usage', error);
      }
    }

    return file;
  };

  // If image downloads are not enabled or no basename provided, return only the file metadata
  if (!downloadImages || (!basename && !downloadImages)) {
    return await retrieveFile(file_id, true);
  }

  let data;
  try {
    const response = await openai.files.content(file_id);
    data = await response.arrayBuffer();
  } catch (error) {
    logger.error('Error downloading file from OpenAI:', error);
    return await retrieveFile(file_id);
  }

  if (!data) {
    return await retrieveFile(file_id);
  }
  const dataBuffer = Buffer.from(data);

  /**
   * @param {Buffer} dataBuffer
   * @param {string} fileExt
   */
  const processAsImage = async (dataBuffer, fileExt) => {
    // Logic to process image files, convert to webp, etc.
    const _file = await convertToWebP(openai.req, dataBuffer, 'high', `${file_id}${fileExt}`);
    const file = {
      ..._file,
      type: 'image/webp',
      usage: 1,
      file_id,
      source: FileSources.openai,
    };
    createFile(file, true);
    return file;
  };

  /** @param {Buffer} dataBuffer */
  const processOtherFileTypes = async (dataBuffer) => {
    // Logic to handle other file types
    logger.debug('[retrieveAndProcessFile] Non-image file type detected');
    return { filepath: `/api/files/download/${file_id}`, bytes: dataBuffer.length };
  };

  // If the filetype is unknown, inspect the file
  if (unknownType || !path.extname(basename)) {
    const detectedExt = await determineFileType(dataBuffer);
    if (detectedExt && imageExtRegex.test('.' + detectedExt)) {
      return await processAsImage(dataBuffer, detectedExt);
    } else {
      return await processOtherFileTypes(dataBuffer);
    }
  }

  // Existing logic for processing known image types
  if (downloadImages && basename && path.extname(basename) && imageExtRegex.test(basename)) {
    return await processAsImage(dataBuffer, path.extname(basename));
  } else {
    logger.debug('[retrieveAndProcessFile] Not an image or invalid extension: ', basename);
    return await processOtherFileTypes(dataBuffer);
  }
}

/**
 * Filters a file based on its size and the endpoint origin.
 *
 * @param {Object} params - The parameters for the function.
 * @param {Express.Request} params.req - The request object from Express.
 * @param {Express.Multer.File} params.file - The file uploaded to the server via multer.
 * @param {boolean} [params.image] - Whether the file expected is an image.
 * @returns {void}
 *
 * @throws {Error} If a file exception is caught (invalid file size or type, lack of metadata).
 */
function filterFile({ req, file, image }) {
  const { endpoint, file_id, width, height } = req.body;

  if (!file_id) {
    throw new Error('No file_id provided');
  }

  /* parse to validate api call, throws error on fail */
  isUUID.parse(file_id);

  if (!endpoint) {
    throw new Error('No endpoint provided');
  }

  const fileConfig = mergeFileConfig(req.app.locals.fileConfig);

  const { fileSizeLimit, supportedMimeTypes } =
    fileConfig.endpoints[endpoint] ?? fileConfig.endpoints.default;

  if (file.size > fileSizeLimit) {
    throw new Error(
      `File size limit of ${fileSizeLimit / megabyte} MB exceeded for ${endpoint} endpoint`,
    );
  }

  const isSupportedMimeType = fileConfig.checkType(file.mimetype, supportedMimeTypes);

  if (!isSupportedMimeType) {
    throw new Error('Unsupported file type');
  }

  if (!image) {
    return;
  }

  if (!width) {
    throw new Error('No width provided');
  }

  if (!height) {
    throw new Error('No height provided');
  }
}

module.exports = {
  filterFile,
  processFiles,
  processFileURL,
  processImageFile,
  uploadImageBuffer,
  processFileUpload,
  processDeleteRequest,
  retrieveAndProcessFile,
};