'use strict';

exports = module.exports = {
    getBackupFilePath,
    download,
    upload,

    _saveFsMetadata: saveFsMetadata,
    _restoreFsMetadata: restoreFsMetadata
};

const assert = require('assert'),
    async = require('async'),
    BoxError = require('../boxerror.js'),
    DataLayout = require('../datalayout.js'),
    debug = require('debug')('box:backupformat/rsync'),
    fs = require('fs'),
    hush = require('../hush.js'),
    once = require('../once.js'),
    path = require('path'),
    safe = require('safetydance'),
    storage = require('../storage.js'),
    syncer = require('../syncer.js'),
    util = require('util');

function getBackupFilePath(backupConfig, remotePath) {
    assert.strictEqual(typeof backupConfig, 'object');
    assert.strictEqual(typeof remotePath, 'string');

    const rootPath = storage.api(backupConfig.provider).getRootPath(backupConfig);
    return path.join(rootPath, remotePath);
}

function sync(backupConfig, remotePath, dataLayout, progressCallback, callback) {
    assert.strictEqual(typeof backupConfig, 'object');
    assert.strictEqual(typeof remotePath, 'string');
    assert(dataLayout instanceof DataLayout, 'dataLayout must be a DataLayout');
    assert.strictEqual(typeof progressCallback, 'function');
    assert.strictEqual(typeof callback, 'function');

    // the number here has to take into account the s3.upload partSize (which is 10MB). So 20=200MB
    const concurrency = backupConfig.syncConcurrency || (backupConfig.provider === 's3' ? 20 : 10);
    const removeDir = util.callbackify(storage.api(backupConfig.provider).removeDir);
    const remove = util.callbackify(storage.api(backupConfig.provider).remove);

    syncer.sync(dataLayout, function processTask(task, iteratorCallback) {
        debug('sync: processing task: %j', task);
        // the empty task.path is special to signify the directory
        const destPath = task.path && backupConfig.encryptFilenames ? hush.encryptFilePath(task.path, backupConfig.encryption) : task.path;
        const backupFilePath = path.join(getBackupFilePath(backupConfig, remotePath), destPath);

        if (task.operation === 'removedir') {
            debug(`Removing directory ${backupFilePath}`);
            return removeDir(backupConfig, backupFilePath, progressCallback, iteratorCallback);
        } else if (task.operation === 'remove') {
            debug(`Removing ${backupFilePath}`);
            return remove(backupConfig, backupFilePath, iteratorCallback);
        }

        let retryCount = 0;
        async.retry({ times: 5, interval: 20000 }, function (retryCallback) {
            retryCallback = once(retryCallback); // protect again upload() erroring much later after read stream error

            ++retryCount;
            if (task.operation === 'add') {
                progressCallback({ message: `Adding ${task.path}` + (retryCount > 1 ?  ` (Try ${retryCount})` : '') });
                debug(`Adding ${task.path} position ${task.position} try ${retryCount}`);
                const stream = hush.createReadStream(dataLayout.toLocalPath('./' + task.path), backupConfig.encryption);
                stream.on('error', (error) => retryCallback(error.message.includes('ENOENT') ? null : error)); // ignore error if file disappears
                stream.on('progress', function (progress) {
                    const transferred = Math.round(progress.transferred/1024/1024), speed = Math.round(progress.speed/1024/1024);
                    if (!transferred && !speed) return progressCallback({ message: `Uploading ${task.path}` }); // 0M@0MBps looks wrong
                    progressCallback({ message: `Uploading ${task.path}: ${transferred}M@${speed}MBps` }); // 0M@0MBps looks wrong
                });
                // only create the destination path when we have confirmation that the source is available. otherwise, we end up with
                // files owned as 'root' and the cp later will fail
                stream.on('open', function () {
                    storage.api(backupConfig.provider).upload(backupConfig, backupFilePath, stream, function (error) {
                        debug(error ? `Error uploading ${task.path} try ${retryCount}: ${error.message}` : `Uploaded ${task.path}`);
                        retryCallback(error);
                    });
                });
            }
        }, iteratorCallback);
    }, concurrency, function (error) {
        if (error) return callback(new BoxError(BoxError.EXTERNAL_ERROR, error.message));

        callback();
    });
}

// this is not part of 'snapshotting' because we need root access to traverse
async function saveFsMetadata(dataLayout, metadataFile) {
    assert(dataLayout instanceof DataLayout, 'dataLayout must be a DataLayout');
    assert.strictEqual(typeof metadataFile, 'string');

    // contains paths prefixed with './'
    const metadata = {
        emptyDirs: [],
        execFiles: [],
        symlinks: []
    };

    // we assume small number of files. spawnSync will raise a ENOBUFS error after maxBuffer
    for (let lp of dataLayout.localPaths()) {
        const emptyDirs = safe.child_process.execSync(`find ${lp} -type d -empty`, { encoding: 'utf8', maxBuffer: 1024 * 1024 * 30 });
        if (emptyDirs === null) throw new BoxError(BoxError.FS_ERROR, `Error finding empty dirs: ${safe.error.message}`);
        if (emptyDirs.length) metadata.emptyDirs = metadata.emptyDirs.concat(emptyDirs.trim().split('\n').map((ed) => dataLayout.toRemotePath(ed)));

        const execFiles = safe.child_process.execSync(`find ${lp} -type f -executable`, { encoding: 'utf8', maxBuffer: 1024 * 1024 * 30 });
        if (execFiles === null) throw new BoxError(BoxError.FS_ERROR, `Error finding executables: ${safe.error.message}`);
        if (execFiles.length) metadata.execFiles = metadata.execFiles.concat(execFiles.trim().split('\n').map((ef) => dataLayout.toRemotePath(ef)));

        const symlinks = safe.child_process.execSync(`find ${lp} -type l`, { encoding: 'utf8', maxBuffer: 1024 * 1024 * 30 });
        if (symlinks === null) throw new BoxError(BoxError.FS_ERROR, `Error finding symlinks: ${safe.error.message}`);
        if (symlinks.length) metadata.symlinks = metadata.symlinks.concat(symlinks.trim().split('\n').map((sl) => {
            const target = safe.fs.readlinkSync(sl);
            return { path: dataLayout.toRemotePath(sl), target };
        }));
    }

    if (!safe.fs.writeFileSync(metadataFile, JSON.stringify(metadata, null, 4))) throw new BoxError(BoxError.FS_ERROR, `Error writing fs metadata: ${safe.error.message}`);
}

async function restoreFsMetadata(dataLayout, metadataFile) {
    assert(dataLayout instanceof DataLayout, 'dataLayout must be a DataLayout');
    assert.strictEqual(typeof metadataFile, 'string');

    debug(`Recreating empty directories in ${dataLayout.toString()}`);

    const metadataJson = safe.fs.readFileSync(metadataFile, 'utf8');
    if (metadataJson === null) throw new BoxError(BoxError.EXTERNAL_ERROR, 'Error loading fsmetadata.json:' + safe.error.message);
    const metadata = safe.JSON.parse(metadataJson);
    if (metadata === null) throw new BoxError(BoxError.EXTERNAL_ERROR, 'Error parsing fsmetadata.json:' + safe.error.message);

    for (const emptyDir of metadata.emptyDirs) {
        const [mkdirError] = await safe(fs.promises.mkdir(dataLayout.toLocalPath(emptyDir), { recursive: true }));
        if (mkdirError) throw new BoxError(BoxError.FS_ERROR, `unable to create path: ${mkdirError.message}`);
    }

    for (const execFile of metadata.execFiles) {
        const [chmodError] = await safe(fs.promises.chmod(dataLayout.toLocalPath(execFile), parseInt('0755', 8)));
        if (chmodError) throw new BoxError(BoxError.FS_ERROR, `unable to chmod: ${chmodError.message}`);
    }

    for (const symlink of (metadata.symlinks || [])) {
        if (!symlink.target) continue;
        // the path may not exist if we had a directory full of symlinks
        const [mkdirError] = await safe(fs.promises.mkdir(path.dirname(dataLayout.toLocalPath(symlink.path)), { recursive: true }));
        if (mkdirError) throw new BoxError(BoxError.FS_ERROR, `unable to symlink (mkdir): ${mkdirError.message}`);
        const [symlinkError] = await safe(fs.promises.symlink(symlink.target, dataLayout.toLocalPath(symlink.path), 'file'));
        if (symlinkError) throw new BoxError(BoxError.FS_ERROR, `unable to symlink: ${symlinkError.message}`);
    }
}

function downloadDir(backupConfig, backupFilePath, dataLayout, progressCallback, callback) {
    assert.strictEqual(typeof backupConfig, 'object');
    assert.strictEqual(typeof backupFilePath, 'string');
    assert(dataLayout instanceof DataLayout, 'dataLayout must be a DataLayout');
    assert.strictEqual(typeof progressCallback, 'function');
    assert.strictEqual(typeof callback, 'function');

    debug(`downloadDir: ${backupFilePath} to ${dataLayout.toString()}`);

    function downloadFile(entry, done) {
        let relativePath = path.relative(backupFilePath, entry.fullPath);
        if (backupConfig.encryptFilenames) {
            const { error, result } = hush.decryptFilePath(relativePath, backupConfig.encryption);
            if (error) return done(new BoxError(BoxError.CRYPTO_ERROR, 'Unable to decrypt file'));
            relativePath = result;
        }
        const destFilePath = dataLayout.toLocalPath('./' + relativePath);

        fs.mkdir(path.dirname(destFilePath), { recursive: true }, function (error) {
            if (error) return done(new BoxError(BoxError.FS_ERROR, error.message));

            async.retry({ times: 5, interval: 20000 }, function (retryCallback) {
                storage.api(backupConfig.provider).download(backupConfig, entry.fullPath, function (error, sourceStream) {
                    if (error) {
                        progressCallback({ message: `Download ${entry.fullPath} to ${destFilePath} errored: ${error.message}` });
                        return retryCallback(error);
                    }

                    let destStream = hush.createWriteStream(destFilePath, backupConfig.encryption);

                    // protect against multiple errors. must destroy the write stream so that a previous retry does not write
                    let closeAndRetry = once((error) => {
                        if (error) progressCallback({ message: `Download ${entry.fullPath} to ${destFilePath} errored: ${error.message}` });
                        else progressCallback({ message: `Download ${entry.fullPath} to ${destFilePath} finished` });
                        sourceStream.destroy();
                        destStream.destroy();
                        retryCallback(error);
                    });

                    destStream.on('progress', function (progress) {
                        const transferred = Math.round(progress.transferred/1024/1024), speed = Math.round(progress.speed/1024/1024);
                        if (!transferred && !speed) return progressCallback({ message: `Downloading ${entry.fullPath}` }); // 0M@0MBps looks wrong
                        progressCallback({ message: `Downloading ${entry.fullPath}: ${transferred}M@${speed}MBps` });
                    });
                    destStream.on('error', closeAndRetry);

                    sourceStream.on('error', closeAndRetry);

                    progressCallback({ message: `Downloading ${entry.fullPath} to ${destFilePath}` });

                    sourceStream.pipe(destStream, { end: true }).on('done', closeAndRetry);
                });
            }, done);
        });
    }

    storage.api(backupConfig.provider).listDir(backupConfig, backupFilePath, 1000, function (entries, iteratorDone) {
        // https://www.digitalocean.com/community/questions/rate-limiting-on-spaces?answer=40441
        const concurrency = backupConfig.downloadConcurrency || (backupConfig.provider === 's3' ? 30 : 10);

        async.eachLimit(entries, concurrency, downloadFile, iteratorDone);
    }, callback);
}

async function download(backupConfig, remotePath, dataLayout, progressCallback) {
    assert.strictEqual(typeof backupConfig, 'object');
    assert.strictEqual(typeof remotePath, 'string');
    assert(dataLayout instanceof DataLayout, 'dataLayout must be a DataLayout');
    assert.strictEqual(typeof progressCallback, 'function');

    debug(`download: Downloading ${remotePath} to ${dataLayout.toString()}`);

    const backupFilePath = getBackupFilePath(backupConfig, remotePath);
    const downloadDirAsync = util.promisify(downloadDir);

    await downloadDirAsync(backupConfig, backupFilePath, dataLayout, progressCallback);
    await restoreFsMetadata(dataLayout, `${dataLayout.localRoot()}/fsmetadata.json`);
}

async function upload(backupConfig, remotePath, dataLayout, progressCallback) {
    assert.strictEqual(typeof backupConfig, 'object');
    assert.strictEqual(typeof remotePath, 'string');
    assert.strictEqual(typeof dataLayout, 'object');
    assert.strictEqual(typeof progressCallback, 'function');

    const syncAsync = util.promisify(sync);

    await saveFsMetadata(dataLayout, `${dataLayout.localRoot()}/fsmetadata.json`);
    await syncAsync(backupConfig, remotePath, dataLayout, progressCallback);
}