'use strict';

const assert = require('node:assert'),
    backupTargets = require('../backuptargets.js'),
    BoxError = require('../boxerror.js'),
    DataLayout = require('../datalayout.js'),
    debug = require('debug')('box:backupformat/tgz'),
    { DecryptStream, EncryptStream } = require('../hush.js'),
    fs = require('node:fs'),
    HashStream = require('../hash-stream.js'),
    path = require('node:path'),
    ProgressStream = require('../progress-stream.js'),
    promiseRetry = require('../promise-retry.js'),
    safe = require('safetydance'),
    stream = require('stream/promises'),
    { Transform } = require('node:stream'),
    tar = require('tar-stream'),
    zlib = require('node:zlib');

// In tar, the entry header contains the file size. If we don't provide it those many bytes, the tar will become corrupt
// Linux provides no guarantee of how many bytes can be read from a file. This is the case with sqlite and log files
// which are accessed by other processes when tar is in action. This class handles overflow and underflow
class EnsureFileSizeStream extends Transform {
    constructor(options) {
        super(options);
        this._remaining = options.size;
        this._name = options.name;
    }

    _transform(chunk, encoding, callback) {
        if (this._remaining <= 0) {
            debug(`EnsureFileSizeStream: ${this._name} dropping ${chunk.length} bytes`);
            return callback(null);
        }

        if (this._remaining - chunk.length < 0) {
            debug(`EnsureFileSizeStream: ${this._name} dropping extra ${chunk.length - this._remaining} bytes`);
            chunk = chunk.subarray(0, this._remaining);
            this._remaining = 0;
        } else {
            this._remaining -= chunk.length;
        }

        callback(null, chunk);
    }

    _flush(callback) {
        if (this._remaining > 0) {
            debug(`EnsureFileSizeStream: ${this._name} injecting ${this._remaining} bytes`);
            this.push(Buffer.alloc(this._remaining, 0));
        }
        callback();
    }
}

function addEntryToPack(pack, header, options) {
    assert.strictEqual(typeof pack, 'object');
    assert.strictEqual(typeof header, 'object');
    assert.strictEqual(typeof options, 'object'); // { input }

    return new Promise((resolve, reject) => {
        const packEntry = safe(() => pack.entry(header, function (error) {
            if (error) {
                debug(`addToPack: error adding ${header.name} ${header.type} ${error.message}`);
                reject(new BoxError(BoxError.FS_ERROR, error.message));
            } else {
                debug(`addToPack: added ${header.name} ${header.type}`);
                resolve();
            }
        }));

        if (!packEntry) return reject(new BoxError(BoxError.FS_ERROR, `Failed to add ${header.name}: ${safe.error.message}`));

        if (options?.input) {
            const ensureFileSizeStream = new EnsureFileSizeStream({ name: header.name, size: header.size });
            safe(stream.pipeline(options.input, ensureFileSizeStream, packEntry), { debug }); // background. rely on pack.entry callback for promise completion
        }
    });
}

async function addPathToPack(pack, localPath, dataLayout) {
    assert.strictEqual(typeof pack, 'object');
    assert(dataLayout instanceof DataLayout, 'dataLayout must be a DataLayout');
    assert.strictEqual(typeof localPath, 'string');

    const stats = { fileCount: 0, linkCount: 0, dirCount: 0 };

    const queue = [ localPath ];
    while (queue.length) {
        // if (pack.destroyed || outStream.destroyed) break;
        const dir = queue.shift();
        debug(`tarPack: processing ${dir}`);
        const [readdirError, entries] = await safe(fs.promises.readdir(dir, { withFileTypes: true }));
        if (!entries) {
            debug(`tarPack: skipping directory ${dir}: ${readdirError.message}`);
            continue;
        }
        const subdirs = [];
        for (const entry of entries) {
            const abspath = path.join(dir, entry.name);
            const headerName = dataLayout.toRemotePath(abspath);
            if (entry.isFile()) {
                const [openError, handle] = await safe(fs.promises.open(abspath, 'r'));
                if (!handle) { debug(`tarPack: skipping file, could not open ${abspath}: ${openError.message}`); continue; }
                const [statError, stat] = await safe(handle.stat());
                if (!stat) { debug(`tarPack: skipping file, could not stat ${abspath}: ${statError.message}`); continue; }
                const header = { name: headerName, type: 'file', mode: stat.mode, size: stat.size, uid: process.getuid(), gid: process.getgid() };
                if (stat.size > 8589934590 || entry.name.length > 99) header.pax = { size: stat.size };
                const input = handle.createReadStream({ autoClose: true });
                await addEntryToPack(pack, header, { input });
                ++stats.fileCount;
            } else if (entry.isDirectory()) {
                const header = { name: headerName, type: 'directory', uid: process.getuid(), gid: process.getgid() };
                subdirs.push(abspath);
                await addEntryToPack(pack, header, { /* options */ });
                ++stats.dirCount;
            } else if (entry.isSymbolicLink()) {
                const [readlinkError, target] = await safe(fs.promises.readlink(abspath));
                if (!target) { debug(`tarPack: skipping link, could not readlink ${abspath}: ${readlinkError.message}`); continue; }
                const header = { name: headerName, type: 'symlink', linkname: target, uid: process.getuid(), gid: process.getgid() };
                await addEntryToPack(pack, header, { /* options */ });
                ++stats.linkCount;
            } else {
                debug(`tarPack: ignoring unknown type ${entry.name} ${entry.type}`);
            }
        }

        queue.unshift(...subdirs); // add to front of queue and in order of readdir listing
    }

    return stats;
}

async function tarPack(dataLayout, encryption, uploader, progressCallback) {
    assert(dataLayout instanceof DataLayout, 'dataLayout must be a DataLayout');
    assert.strictEqual(typeof encryption, 'object');
    assert.strictEqual(typeof uploader, 'object');
    assert.strictEqual(typeof progressCallback, 'function');

    const gzip = zlib.createGzip({});
    const ps = new ProgressStream({ interval: 10000 }); // emit '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 backup' }); // 0M@0MBps looks wrong
        progressCallback({ message: `Uploading backup ${transferred}M@${speed}MBps` });
    });

    const pack = tar.pack();

    const hash = new HashStream();

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

    let fileCount = 0;
    for (const localPath of dataLayout.localPaths()) {
        const [error, stats] = await safe(addPathToPack(pack, localPath, dataLayout), { debug });
        if (error) break; // the pipeline will error and we will retry the whole packing all over
        fileCount += stats.fileCount;
    }

    pack.finalize(); // harmless to call if already in error state

    const [error] = await pipeline; // already wrapped in safe()
    if (error) throw new BoxError(BoxError.EXTERNAL_ERROR, `tarPack pipeline error: ${error.message}`);
    debug(`tarPack: pipeline finished: ${JSON.stringify(ps.stats())}`);

    await uploader.finish();
    return {
        stats: { fileCount, ...ps.stats() },
        integrity: { size: ps.stats().transferred, fileCount, sha256: hash.digest('hex') }
    };
}

async function tarExtract(inStream, dataLayout, encryption, progressCallback) {
    assert.strictEqual(typeof inStream, 'object');
    assert(dataLayout instanceof DataLayout, 'dataLayout must be a DataLayout');
    assert.strictEqual(typeof encryption, 'object');
    assert.strictEqual(typeof progressCallback, 'function');

    const extract = tar.extract();
    const now = new Date();
    extract.on('entry', async function (header, entryStream, next) {
        if (path.isAbsolute(header.name)) {
            debug(`tarExtract: ignoring absolute path ${header.name}`);
            return next();
        }
        const abspath = dataLayout.toLocalPath(header.name);
        debug(`tarExtract: ${header.name} ${header.size} ${header.type} to ${abspath}`);
        let error = null;
        if (header.type === 'directory') {
            [error] = await safe(fs.promises.mkdir(abspath, { recursive: true, mode: 0o755 }));
        } else if (header.type === 'file') {
            const output = fs.createWriteStream(abspath);
            [error] = await safe(stream.pipeline(entryStream, output));
            if (!error) [error] = await safe(fs.promises.chmod(abspath, header.mode));
        } else if (header.type === 'symlink') {
            await safe(fs.promises.unlink(abspath)); // remove any link created from previous failed extract
            [error] = await safe(fs.promises.symlink(header.linkname, abspath));
        } else {
            debug(`tarExtract: ignoring unknown entry: ${header.name} ${header.type}`);
            entryStream.resume(); // drain
        }

        if (error) return next(error);

        [error] = await safe(fs.promises.lutimes(abspath, now /* atime */, header.mtime)); // for dirs, mtime will get overwritten
        next(error);
    });
    extract.on('finish', () => debug('tarExtract: extract finished'));

    const gunzip = zlib.createGunzip({});
    const ps = new ProgressStream({ interval: 10000 });
    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 backup' }); // 0M@0MBps looks wrong
        progressCallback({ message: `Downloading ${transferred}M@${speed}MBps` });
    });

    if (encryption) {
        const decrypt = new DecryptStream(encryption);
        const [error] = await safe(stream.pipeline(inStream, ps, decrypt, gunzip, extract));
        if (error) throw new BoxError(BoxError.EXTERNAL_ERROR, `tarExtract pipeline error: ${error.message}`);
    } else {
        const [error] = await safe(stream.pipeline(inStream, ps, gunzip, extract));
        if (error) throw new BoxError(BoxError.EXTERNAL_ERROR, `tarExtract pipeline error: ${error.message}`);
    }

    debug(`tarExtract: pipeline finished: ${JSON.stringify(ps.stats())}`);
}

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');

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

    await promiseRetry({ times: 5, interval: 20000, debug }, async () => {
        progressCallback({ message: `Downloading backup ${remotePath}` });

        const sourceStream = await backupTargets.storageApi(backupTarget).download(backupTarget.config, remotePath);
        await tarExtract(sourceStream, dataLayout, backupTarget.encryption, progressCallback);
    });
}

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');

    debug(`upload: Uploading ${dataLayout.toString()} to ${remotePath}`);

    return await promiseRetry({ times: 5, interval: 20000, debug }, async () => {
        progressCallback({ message: `Uploading backup ${remotePath}` });

        const uploader = await backupTargets.storageApi(backupTarget).upload(backupTarget.config, remotePath);
        const { stats, integrity } = await tarPack(dataLayout, backupTarget.encryption, uploader, progressCallback);

        const integrityMap = new Map([ [path.basename(remotePath), integrity] ]);
        return { stats, integrityMap };
    });
}

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

    return encryption ? '.tar.gz.enc' : '.tar.gz';
}

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

    // exported for testing
    _EnsureFileSizeStream: EnsureFileSizeStream
};