/* jslint node: true */
'use strict';

//  ENiGMA½
const Config                = require('./config.js').get;
const FileDb                = require('./database.js').dbs.file;
const getISOTimestampString = require('./database.js').getISOTimestampString;
const FileEntry             = require('./file_entry.js');
const getServer             = require('./listening_server.js').getServer;
const Errors                = require('./enig_error.js').Errors;
const ErrNotEnabled         = require('./enig_error.js').ErrorReasons.NotEnabled;
const StatLog               = require('./stat_log.js');
const User                  = require('./user.js');
const Log                   = require('./logger.js').log;
const getConnectionByUserId = require('./client_connections.js').getConnectionByUserId;
const webServerPackageName  = require('./servers/content/web.js').moduleInfo.packageName;
const Events                = require('./events.js');
const UserProps             = require('./user_property.js');
const SysProps              = require('./system_menu_method.js');

//  deps
const hashids       = require('hashids/cjs');
const moment        = require('moment');
const paths         = require('path');
const async         = require('async');
const fs            = require('graceful-fs');
const mimeTypes     = require('mime-types');
const yazl          = require('yazl');

function notEnabledError() {
    return Errors.General('Web server is not enabled', ErrNotEnabled);
}

class FileAreaWebAccess {
    constructor() {
        this.hashids        = new hashids(Config().general.boardName);
        this.expireTimers   = {};   //  hashId->timer
    }

    startup(cb) {
        const self = this;

        async.series(
            [
                function initFromDb(callback) {
                    return self.load(callback);
                },
                function addWebRoute(callback) {
                    self.webServer = getServer(webServerPackageName);
                    if(!self.webServer) {
                        return callback(Errors.DoesNotExist(`Server with package name "${webServerPackageName}" does not exist`));
                    }

                    if(self.isEnabled()) {
                        const routeAdded = self.webServer.instance.addRoute({
                            method  : 'GET',
                            path    : Config().fileBase.web.routePath,
                            handler : self.routeWebRequest.bind(self),
                        });
                        return callback(routeAdded ? null : Errors.General('Failed adding route'));
                    } else {
                        return callback(null);  //  not enabled, but no error
                    }
                }
            ],
            err => {
                return cb(err);
            }
        );
    }

    shutdown(cb) {
        return cb(null);
    }

    isEnabled() {
        return this.webServer.instance.isEnabled();
    }

    static getHashIdTypes() {
        return {
            SingleFile      : 0,
            BatchArchive    : 1,
        };
    }

    load(cb) {
        //
        //  Load entries, register expiration timers
        //
        FileDb.each(
            `SELECT hash_id, expire_timestamp
            FROM file_web_serve;`,
            (err, row) => {
                if(row) {
                    this.scheduleExpire(row.hash_id, moment(row.expire_timestamp));
                }
            },
            err => {
                return cb(err);
            }
        );
    }

    removeEntry(hashId) {
        //
        //  Delete record from DB, and our timer
        //
        FileDb.run(
            `DELETE FROM file_web_serve
            WHERE hash_id = ?;`,
            [ hashId ]
        );

        delete this.expireTimers[hashId];
    }

    scheduleExpire(hashId, expireTime) {

        //  remove any previous entry for this hashId
        const previous = this.expireTimers[hashId];
        if(previous) {
            clearTimeout(previous);
            delete this.expireTimers[hashId];
        }

        const timeoutMs = expireTime.diff(moment());

        if(timeoutMs <= 0) {
            setImmediate( () => {
                this.removeEntry(hashId);
            });
        } else {
            this.expireTimers[hashId] = setTimeout( () => {
                this.removeEntry(hashId);
            }, timeoutMs);
        }
    }

    loadServedHashId(hashId, cb) {
        FileDb.get(
            `SELECT expire_timestamp FROM
            file_web_serve
            WHERE hash_id = ?`,
            [ hashId ],
            (err, result) => {
                if(err || !result) {
                    return cb(err ? err : Errors.DoesNotExist('Invalid or missing hash ID'));
                }

                const decoded = this.hashids.decode(hashId);

                //  decode() should provide an array of [ userId, hashIdType, id, ... ]
                if(!Array.isArray(decoded) || decoded.length < 3) {
                    return cb(Errors.Invalid('Invalid or unknown hash ID'));
                }

                const servedItem = {
                    hashId          : hashId,
                    userId          : decoded[0],
                    hashIdType      : decoded[1],
                    expireTimestamp : moment(result.expire_timestamp),
                };

                if(FileAreaWebAccess.getHashIdTypes().SingleFile === servedItem.hashIdType) {
                    servedItem.fileIds = decoded.slice(2);
                }

                return cb(null, servedItem);
            }
        );
    }

    getSingleFileHashId(client, fileEntry) {
        return this.getHashId(client, FileAreaWebAccess.getHashIdTypes().SingleFile, [ fileEntry.fileId ] );
    }

    getBatchArchiveHashId(client, batchId) {
        return this.getHashId(client, FileAreaWebAccess.getHashIdTypes().BatchArchive, batchId);
    }

    getHashId(client, hashIdType, identifier) {
        return this.hashids.encode(client.user.userId, hashIdType, identifier);
    }

    buildSingleFileTempDownloadLink(client, fileEntry, hashId) {
        hashId = hashId || this.getSingleFileHashId(client, fileEntry);

        return this.webServer.instance.buildUrl(`${Config().fileBase.web.path}${hashId}`);
    }

    buildBatchArchiveTempDownloadLink(client, hashId) {
        return this.webServer.instance.buildUrl(`${Config().fileBase.web.path}${hashId}`);
    }

    getExistingTempDownloadServeItem(client, fileEntry, cb) {
        if(!this.isEnabled()) {
            return cb(notEnabledError());
        }

        const hashId = this.getSingleFileHashId(client, fileEntry);
        this.loadServedHashId(hashId, (err, servedItem) => {
            if(err) {
                return cb(err);
            }

            servedItem.url = this.buildSingleFileTempDownloadLink(client, fileEntry);

            return cb(null, servedItem);
        });
    }

    _addOrUpdateHashIdRecord(dbOrTrans, hashId, expireTime, cb) {
        //  add/update rec with hash id and (latest) timestamp
        dbOrTrans.run(
            `REPLACE INTO file_web_serve (hash_id, expire_timestamp)
            VALUES (?, ?);`,
            [ hashId, getISOTimestampString(expireTime) ],
            err => {
                if(err) {
                    return cb(err);
                }

                this.scheduleExpire(hashId, expireTime);

                return cb(null);
            }
        );
    }

    createAndServeTempDownload(client, fileEntry, options, cb) {
        if(!this.isEnabled()) {
            return cb(notEnabledError());
        }

        const hashId        = this.getSingleFileHashId(client, fileEntry);
        const url           = this.buildSingleFileTempDownloadLink(client, fileEntry, hashId);
        options.expireTime  = options.expireTime || moment().add(2, 'days');

        this._addOrUpdateHashIdRecord(FileDb, hashId, options.expireTime, err => {
            return cb(err, url);
        });
    }

    createAndServeTempBatchDownload(client, fileEntries, options, cb) {
        if(!this.isEnabled()) {
            return cb(notEnabledError());
        }

        const batchId       = moment().utc().unix();
        const hashId        = this.getBatchArchiveHashId(client, batchId);
        const url           = this.buildBatchArchiveTempDownloadLink(client, hashId);
        options.expireTime  = options.expireTime || moment().add(2, 'days');

        FileDb.beginTransaction( (err, trans) => {
            if(err) {
                return cb(err);
            }

            this._addOrUpdateHashIdRecord(trans, hashId, options.expireTime, err => {
                if(err) {
                    return trans.rollback( () => {
                        return cb(err);
                    });
                }

                async.eachSeries(fileEntries, (entry, nextEntry) => {
                    trans.run(
                        `INSERT INTO file_web_serve_batch (hash_id, file_id)
                        VALUES (?, ?);`,
                        [ hashId, entry.fileId ],
                        err => {
                            return nextEntry(err);
                        }
                    );
                }, err => {
                    trans[err ? 'rollback' : 'commit']( () => {
                        return cb(err, url);
                    });
                });
            });
        });
    }

    fileNotFound(resp) {
        return this.webServer.instance.fileNotFound(resp);
    }

    routeWebRequest(req, resp) {
        const hashId = paths.basename(req.url);

        Log.debug( { hashId : hashId, url : req.url }, 'File area web request');

        this.loadServedHashId(hashId, (err, servedItem) => {

            if(err) {
                return this.fileNotFound(resp);
            }

            const hashIdTypes = FileAreaWebAccess.getHashIdTypes();
            switch(servedItem.hashIdType) {
                case hashIdTypes.SingleFile :
                    return this.routeWebRequestForSingleFile(servedItem, req, resp);

                case hashIdTypes.BatchArchive :
                    return this.routeWebRequestForBatchArchive(servedItem, req, resp);

                default :
                    return this.fileNotFound(resp);
            }
        });
    }

    routeWebRequestForSingleFile(servedItem, req, resp) {
        Log.debug( { servedItem : servedItem }, 'Single file web request');

        const fileEntry = new FileEntry();

        servedItem.fileId = servedItem.fileIds[0];

        fileEntry.load(servedItem.fileId, err => {
            if(err) {
                return this.fileNotFound(resp);
            }

            const filePath = fileEntry.filePath;
            if(!filePath) {
                return this.fileNotFound(resp);
            }

            fs.stat(filePath, (err, stats) => {
                if(err) {
                    return this.fileNotFound(resp);
                }

                resp.on('close', () => {
                    //  connection closed *before* the response was fully sent
                    //  :TODO: Log and such
                });

                resp.on('finish', () => {
                    //  transfer completed fully
                    this.updateDownloadStatsForUserIdAndSystem(servedItem.userId, stats.size, [ fileEntry ]);
                });

                const headers = {
                    'Content-Type'          : mimeTypes.contentType(filePath) || mimeTypes.contentType('.bin'),
                    'Content-Length'        : stats.size,
                    'Content-Disposition'   : `attachment; filename="${fileEntry.fileName}"`,
                };

                const readStream = fs.createReadStream(filePath);
                resp.writeHead(200, headers);
                return readStream.pipe(resp);
            });
        });
    }

    routeWebRequestForBatchArchive(servedItem, req, resp) {
        Log.debug( { servedItem : servedItem }, 'Batch file web request');

        //
        //  We are going to build an on-the-fly zip file stream of 1:n
        //  files in the batch.
        //
        //  First, collect all file IDs
        //
        const self = this;

        async.waterfall(
            [
                function fetchFileIds(callback) {
                    FileDb.all(
                        `SELECT file_id
                        FROM file_web_serve_batch
                        WHERE hash_id = ?;`,
                        [ servedItem.hashId ],
                        (err, fileIdRows) => {
                            if(err || !Array.isArray(fileIdRows) || 0 === fileIdRows.length) {
                                return callback(Errors.DoesNotExist('Could not get file IDs for batch'));
                            }

                            return callback(null, fileIdRows.map(r => r.file_id));
                        }
                    );
                },
                function loadFileEntries(fileIds, callback) {
                    async.map(fileIds, (fileId, nextFileId) => {
                        const fileEntry = new FileEntry();
                        fileEntry.load(fileId, err => {
                            return nextFileId(err, fileEntry);
                        });
                    }, (err, fileEntries) => {
                        if(err) {
                            return callback(Errors.DoesNotExist('Could not load file IDs for batch'));
                        }

                        return callback(null, fileEntries);
                    });
                },
                function createAndServeStream(fileEntries, callback) {
                    const filePaths = fileEntries.map(fe => fe.filePath);
                    Log.trace( { filePaths : filePaths }, 'Creating zip archive for batch web request');

                    const zipFile = new yazl.ZipFile();

                    zipFile.on('error', err => {
                        Log.warn( { error : err.message }, 'Error adding file to batch web request archive');
                    });

                    filePaths.forEach(fp => {
                        zipFile.addFile(
                            fp,                 //  path to physical file
                            paths.basename(fp), //  filename/path *stored in archive*
                            {
                                compress : false,   //  :TODO: do this smartly - if ext is in set = false, else true via isArchive() or such... mimeDB has this for us.
                            }
                        );
                    });

                    zipFile.end( finalZipSize => {
                        if(-1 === finalZipSize) {
                            return callback(Errors.UnexpectedState('Unable to acquire final zip size'));
                        }

                        resp.on('close', () => {
                            //  connection closed *before* the response was fully sent
                            //  :TODO: Log and such
                        });

                        resp.on('finish', () => {
                            //  transfer completed fully
                            self.updateDownloadStatsForUserIdAndSystem(servedItem.userId, finalZipSize, fileEntries);
                        });

                        const batchFileName = `batch_${servedItem.hashId}.zip`;

                        const headers = {
                            'Content-Type'          : mimeTypes.contentType(batchFileName) || mimeTypes.contentType('.bin'),
                            'Content-Length'        : finalZipSize,
                            'Content-Disposition'   : `attachment; filename="${batchFileName}"`,
                        };

                        resp.writeHead(200, headers);
                        return zipFile.outputStream.pipe(resp);
                    });
                }
            ],
            err => {
                if(err) {
                    //  :TODO: Log me!
                    return this.fileNotFound(resp);
                }

                //  ...otherwise, we would have called resp() already.
            }
        );
    }

    updateDownloadStatsForUserIdAndSystem(userId, dlBytes, fileEntries) {
        async.waterfall(
            [
                function fetchActiveUser(callback) {
                    const clientForUserId = getConnectionByUserId(userId);
                    if(clientForUserId) {
                        return callback(null, clientForUserId.user);
                    }

                    //  not online now - look 'em up
                    User.getUser(userId, (err, assocUser) => {
                        return callback(err, assocUser);
                    });
                },
                function updateStats(user, callback) {
                    StatLog.incrementUserStat(user, UserProps.FileDlTotalCount, 1);
                    StatLog.incrementUserStat(user, UserProps.FileDlTotalBytes, dlBytes);

                    StatLog.incrementSystemStat(SysProps.FileDlTotalCount, 1);
                    StatLog.incrementSystemStat(SysProps.FileDlTotalBytes, dlBytes);

                    return callback(null, user);
                },
                function sendEvent(user, callback) {
                    Events.emit(
                        Events.getSystemEvents().UserDownload,
                        {
                            user    : user,
                            files   : fileEntries,
                        }
                    );
                    return callback(null);
                }
            ]
        );
    }
}

module.exports = new FileAreaWebAccess();