'use strict';

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

    _saveFsMetadata: saveFsMetadata,
    _restoreFsMetadata: restoreFsMetadata
};

const assert = require('assert'),
    async = require('async'),
    backupTargets = require('../backuptargets.js'),
    BoxError = require('../boxerror.js'),
    DataLayout = require('../datalayout.js'),
    { DecryptStream } = require('../hush.js'),
    debug = require('debug')('box:backupformat/rsync'),
    { EncryptStream } = require('../hush.js'),
    fs = require('fs'),
    hush = require('../hush.js'),
    path = require('path'),
    paths = require('../paths.js'),
    ProgressStream = require('../progress-stream.js'),
    promiseRetry = require('../promise-retry.js'),
    safe = require('safetydance'),
    shell = require('../shell.js')('backupformat/rsync'),
    stream = require('stream/promises'),
    syncer = require('../syncer.js');

async function addFile(sourceFile, encryption, uploader, progressCallback) {
    assert.strictEqual(typeof sourceFile, 'string');
    assert.strictEqual(typeof encryption, 'object');
    assert.strictEqual(typeof uploader, 'object');
    assert.strictEqual(typeof progressCallback, 'function');

    // make sure file can be opened for reading before we start the pipeline. otherwise, we end up with
    // destinations dirs/file which are owned by root (this process id) and cannot be copied (run as normal user)
    const [openError, sourceHandle] = await safe(fs.promises.open(sourceFile, 'r'));
    if (openError) {
        debug(`addFile: ignoring disappeared file: ${sourceFile}`);
        return;
    }

    const sourceStream = sourceHandle.createReadStream(sourceFile, { autoClose: true });
    const ps = new ProgressStream({ interval: 10000 }); // display a progress every 10 seconds
    ps.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 ${sourceFile}` }); // 0M@0MBps looks wrong
        progressCallback({ message: `Uploading ${sourceFile}: ${transferred}M@${speed}MBps` }); // 0M@0MBps looks wrong
    });

    let pipeline = null;
    if (encryption) {
        const encryptStream = new EncryptStream(encryption);
        pipeline = safe(stream.pipeline(sourceStream, encryptStream, ps, uploader.stream));
    } else {
        pipeline = safe(stream.pipeline(sourceStream, ps, uploader.stream));
    }

    const [error] = await safe(pipeline);
    if (error && error.message.includes('ENOENT')) { // ignore error if file disappears
    }

    if (error) throw new BoxError(BoxError.EXTERNAL_ERROR, `tarPack pipeline error: ${error.message}`);
    // debug(`addFile: pipeline finished: ${JSON.stringify(ps.stats())}`);

    await uploader.finish();
}

async function processSyncerChange(change, backupTarget, remotePath, dataLayout, progressCallback) {
    debug('sync: processing task: %j', change);
    // the empty task.path is special to signify the directory
    const destPath = change.path && backupTarget.encryption?.encryptedFilenames ? hush.encryptFilePath(change.path, backupTarget.encryption) : change.path;
    const backupFilePath = path.join(backupTargets.getBackupFilePath(backupTarget, remotePath), destPath);

    if (change.operation === 'removedir') {
        debug(`Removing directory ${backupFilePath}`);
        await backupTargets.storageApi(backupTarget).removeDir(backupTarget.config, backupFilePath, progressCallback);
    } else if (change.operation === 'remove') {
        debug(`Removing ${backupFilePath}`);
        await backupTargets.storageApi(backupTarget).remove(backupTarget.config, backupFilePath);
    } else if (change.operation === 'add') {
        await promiseRetry({ times: 5, interval: 20000, debug }, async (retryCount) => {
            progressCallback({ message: `Adding ${change.path}` + (retryCount > 1 ?  ` (Try ${retryCount})` : '') });
            debug(`Adding ${change.path} position ${change.position} try ${retryCount}`);

            const uploader = await backupTargets.storageApi(backupTarget).upload(backupTarget.config, backupFilePath);
            await addFile(dataLayout.toLocalPath('./' + change.path), backupTarget.encryption, uploader, progressCallback);
        });
    }
}

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

    // the number here has to take into account the s3.upload partSize (which is 10MB). So 20=200MB
    const concurrency = backupTarget.limits?.syncConcurrency || (backupTarget.provider === 's3' ? 20 : 10);

    const cacheFile = path.join(paths.BACKUP_INFO_DIR, backupTarget.id, `${dataLayout.getBasename()}.sync.cache`);
    const changes = await syncer.sync(dataLayout, { cacheFile });
    debug(`sync: processing ${changes.delQueue.length} deletes and ${changes.addQueue.length} additions`);

    const [delError] = await safe(async.eachLimit(changes.delQueue, concurrency, async (change) => await processSyncerChange(change, backupTarget, remotePath, dataLayout, progressCallback)));
    debug('sync: done processing deletes. error: %o', delError);
    if (delError) throw delError;

    const [addError] = await safe(async.eachLimit(changes.addQueue, concurrency, async (change) => await processSyncerChange(change, backupTarget, remotePath, dataLayout, progressCallback)));
    debug('sync: done processing adds. error: %o', addError);
    if (addError) throw addError;

    await syncer.finalize(changes);
}

// 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 (const lp of dataLayout.localPaths()) {
        const [emptyDirsError, emptyDirs] = await safe(shell.spawn('find', [lp, '-type', 'd', '-empty'], { encoding: 'utf8', maxLines: 50000 }));
        if (emptyDirsError && emptyDirsError.stdoutLineCount >= 50000) throw new BoxError(BoxError.FS_ERROR, `Too many empty directories. Run "find ${lp} -type d -empty" to investigate`);
        if (emptyDirsError) throw emptyDirsError;
        if (emptyDirs.length) metadata.emptyDirs = metadata.emptyDirs.concat(emptyDirs.trim().split('\n').map((ed) => dataLayout.toRemotePath(ed)));

        const [execFilesError, execFiles] = await safe(shell.spawn('find', [lp, '-type', 'f', '-executable'], { encoding: 'utf8', maxLines: 20000 }));
        if (execFilesError && execFilesError.stdoutLineCount >= 20000) throw new BoxError(BoxError.FS_ERROR, `Too many executable files. Run "find ${lp} -type f -executable" to investigate`);
        if (execFilesError) throw execFilesError;
        if (execFiles.length) metadata.execFiles = metadata.execFiles.concat(execFiles.trim().split('\n').map((ef) => dataLayout.toRemotePath(ef)));

        const [symlinkFilesError, symlinkFiles] = await safe(shell.spawn('find', [lp, '-type', 'l'], { encoding: 'utf8', maxLines: 20000 }));
        if (symlinkFilesError && symlinkFilesError.stdoutLineCount >= 20000) throw new BoxError(BoxError.FS_ERROR, `Too many symlinks. Run "find ${lp} -type l" to investigate`);
        if (symlinkFilesError) throw symlinkFilesError;

        if (symlinkFiles.length) metadata.symlinks = metadata.symlinks.concat(symlinkFiles.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}`);
    }
}

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

    const encryptedFilenames = backupTarget.encryption?.encryptedFilenames || false;

    debug(`downloadDir: ${backupFilePath} to ${dataLayout.toString()}. encryption filenames: ${encryptedFilenames} content: ${!!backupTarget.encryption}`);

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

        const [mkdirError] = await safe(fs.promises.mkdir(path.dirname(destFilePath), { recursive: true }));
        if (mkdirError) throw new BoxError(BoxError.FS_ERROR, mkdirError.message);

        await promiseRetry({ times: 3, interval: 20000 }, async function () {
            const [downloadError, sourceStream] = await safe(backupTargets.storageApi(backupTarget).download(backupTarget.config, entry.fullPath));
            if (downloadError) {
                progressCallback({ message: `Download ${entry.fullPath} to ${destFilePath} errored: ${downloadError.message}` });
                throw downloadError;
            }

            const ps = new ProgressStream({ interval: 10000 }); // display a progress every 10 seconds
            ps.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` });
            });

            const destStream = fs.createWriteStream(destFilePath);

            const streams = [ sourceStream, ps ];

            if (backupTarget.encryption) {
                const decryptStream = new DecryptStream(backupTarget.encryption);
                streams.push(decryptStream);
            }

            streams.push(destStream);

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

            const [pipelineError] = await safe(stream.pipeline(streams));
            if (pipelineError) {
                progressCallback({ message: `Download error ${entry.fullPath} to ${destFilePath}: ${pipelineError.message}` });
                throw pipelineError;
            }
            progressCallback({ message: `Download finished ${entry.fullPath} to ${destFilePath}` });
        });
    }

    // https://www.digitalocean.com/community/questions/rate-limiting-on-spaces?answer=40441
    const concurrency = backupTarget.limits?.downloadConcurrency || (backupTarget.provider === 's3' ? 30 : 10);
    let marker = null;
    while (true) {
        const batch = await backupTargets.storageApi(backupTarget).listDir(backupTarget.config, backupFilePath, marker === null ? 1 : 1000, marker); // try with one file first. if that works out, we continue faster
        await async.eachLimit(batch.entries, concurrency, downloadFile);
        if (!batch.marker) break;
        marker = batch.marker;
    }
}

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

    const backupFilePath = backupTargets.getBackupFilePath(backupTarget, remotePath);

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

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

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

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

function getFileExtension(encryption) {
    assert.strictEqual(typeof encryption, 'boolean');

    return '';
}