import Axios from 'axios';
import * as electron from 'electron';
import log from 'electron-log';  //tslint:disable-line:match-default-export-name
import * as fs from 'fs';
import * as path from 'path';
import {promisify} from 'util';

const dictDir = path.join(electron.app.getPath('userData'), 'spellchecker');
fs.mkdirSync(dictDir, {recursive: true});

const downloadedPath = path.join(dictDir, 'downloaded.json');
const downloadUrl = 'https://client.f-list.net/dicts/';
type File = {name: string, hash: string};
type DictionaryIndex = {[key: string]: {dic: File, aff: File} | undefined};
let availableDictionaries: DictionaryIndex | undefined;
let downloadedDictionaries: {[key: string]: File | undefined} = {};
const writeFile = promisify(fs.writeFile);

export async function getAvailableDictionaries(): Promise<ReadonlyArray<string>> {
    if(availableDictionaries === undefined)
        try {
            availableDictionaries = (await Axios.get<DictionaryIndex>(`${downloadUrl}index.json`)).data;
            if(fs.existsSync(downloadedPath))
                downloadedDictionaries = <{[key: string]: File}>JSON.parse(fs.readFileSync(downloadedPath, 'utf-8'));
        } catch(e) {
            availableDictionaries = {};
            log.error(`Error loading dictionaries: ${e}`);
        }
    return Object.keys(availableDictionaries).sort();
}

export async function ensureDictionary(lang: string): Promise<void> {
    await getAvailableDictionaries();
    const dict = availableDictionaries![lang];
    if(dict === undefined) return;
    async function ensure(type: 'aff' | 'dic'): Promise<void> {
        const file = dict![type];
        const filePath = path.join(dictDir, `${lang}.${type}`);
        const downloaded = downloadedDictionaries[file.name];
        if(downloaded === undefined || downloaded.hash !== file.hash || !fs.existsSync(filePath)) {
            const dictionary = (await Axios.get<string>(`${downloadUrl}${file.name}`, {responseType: 'arraybuffer'})).data;
            await writeFile(filePath, Buffer.from(dictionary));
            downloadedDictionaries[file.name] = file;
            await writeFile(downloadedPath, JSON.stringify(downloadedDictionaries));
        }
    }
    await ensure('aff');
    await ensure('dic');
}