/* Copyright IBM Corp. 2018 */
import { createWriteStream } from 'graceful-fs';
import { join, normalize, parse } from 'path';
import * as request from 'request';
import { defer, fromEvent, Observable, of } from 'rxjs';
import { filter, first, mapTo, mergeMap, takeUntil, tap } from 'rxjs/operators';
import { Entry, Parse } from 'unzip';

import { rxMkdirp } from './rx.walk';

const random_ua = require('random-ua');

function _skipPrefix(aName: string, aCount: number): string | null {
    // current name
    let idx = 0;
    for (let i = 0; i < aCount; ++i) {
        // find the next separator
        const nextIdx = aName.indexOf('/', idx);
        if (nextIdx >= idx) {
            idx = nextIdx + 1;
        } else {
            return null;
        }
    }
    // split
    return aName.substring(idx);
}

function _rxExtractEntry(aEntry: Entry, aDstDir: string, aSkip: number): Observable<string> {
    // skip the prefix
    const path = _skipPrefix(aEntry.path, aSkip);
    if (!path) {
        // nothing
        return of('').pipe(
            tap(() => aEntry.autodrain()),
            filter(() => false)
        );
    }
    // create filename
    const fileName = normalize(join(aDstDir, path));
    // handle directories
    if (aEntry.type === 'Directory') {
        // create the directory
        return rxMkdirp(fileName).pipe(
            tap(() => aEntry.autodrain()),
            filter(() => false)
        );
    } else {
        // parent path
        const parsedFileName = parse(fileName);
        const dirName = parsedFileName.dir;
        // create later
        return rxMkdirp(dirName).pipe(
            mergeMap(() => {
                // construct the stream
                const stream: any = aEntry.pipe(createWriteStream(fileName));
                // attach
                return fromEvent(stream, 'close').pipe(first());
            }),
            // map to the target name
            mapTo(fileName)
        );
    }
}

function _rxUnzipFromUrl(aSrcUrl: string, aDstDir: string, aSkip: number = 0): Observable<string> {
    // the options
    const options = {
        url: aSrcUrl,
        headers: {
            'User-Agent': random_ua.generate()
        }
    };
    // defer
    return defer(() => {
        // construct the stream
        const stream = request(options).pipe(Parse());
        // handle
        const onEntry = fromEvent<Entry>(stream, 'entry');
        const onClose = fromEvent(stream, 'close');
        // return the full stream
        return onEntry.pipe(
            takeUntil(onClose),
            mergeMap(entry => _rxExtractEntry(entry, aDstDir, aSkip))
        );
    });
}

export {
    _rxUnzipFromUrl as rxUnzipFromUrl
};