import axios from 'axios';
import { randomUUID } from 'crypto';
import * as fs from 'fs';
import { parse } from 'node-html-parser';
import config from '../config/config.js';

export namespace DownloaderProvider {
    const bibleserver_endpoint = 'https://www.bibleserver.com';

    export class Downloader {
        private _translation: string;
        private _logs: string[] = [];
        private _status: 'idle' | 'running' | 'completed' | 'error' = 'idle';
        private _books: string[] = [];
        private _data_directory: string = 'data';
        private _operation_id: string = ''
        private _time_start: Date | undefined;
        private _time_end: Date | undefined;

        public get translation() {
            return this._translation
        }

        public get uuid() {
            return this._operation_id
        }

        public get logs() {
            return this._logs
        }

        public get time_start() {
            return this._time_start
        }

        public get time_end() {
            return this._time_end
        }

        constructor(private translation_in: string) {
            this._translation = translation_in;
            this._operation_id = randomUUID()
            this._status = 'idle';
            this.log(`Initialized downloader for translation: ${this._translation}`);
            this.log(`Using bibleserver endpoint: ${bibleserver_endpoint}`);

        }

        public start() {
            this._time_start = new Date();
            this.log(`Starting download for translation: ${this._translation}`);
            this._status = 'running';
            // get all translations from reference file
            try {
                const book_list_file = `${this._data_directory}/books.json`;
                this.log(`Loading book list from ${book_list_file}`);
                this._books = JSON.parse(fs.readFileSync(book_list_file, 'utf-8')).books;
                this.log(`Loaded ${this._books.length} books to download`);
            } catch (error) {
                this.log(`Error loading book list: ${error}`);
                this._status = 'error';
                return;
            }
            // create directory
            try {
                if (!fs.existsSync(`${this._data_directory}/${this._translation}`)) {
                    fs.mkdirSync(`${this._data_directory}/${this._translation}`, { recursive: true });
                    this.log(`Created directory: ${this._data_directory}/${this._translation}`);
                }
            } catch (error) {
                this.log(`Error creating translation directory: ${error}`);
                this._status = 'error';
                return;
            }

            this.fetch_all_books();

        }

        public getStatus(): 'idle' | 'running' | 'completed' | 'error' {
            return this._status;
        }

        private delay(ms: number): Promise<void> {
            return new Promise(resolve => setTimeout(resolve, ms));
        }

        private async fetch_all_books() {
            try {
                for (let book of this._books) {
                    if (fs.existsSync(`${this._data_directory}/${this._translation}/${book}.json`)) {
                        this.log(`Book ${book} already exists for ${this._translation}, skipping`);
                        continue;
                    }
                    this.log(`Fetching book: ${book} for translation: ${this._translation}`);

                    let chapter = 1;
                    let book_content: any[] = [];

                    while (true) {
                        this.log(`Trying to fetch chapter ${chapter} of book ${book}`);
                        await this.delay(config.downloadDelay * 1000); // sleep to prevent DDOS
                        let chapter_content: any = await this.fetch_chapter(book, chapter);
                        if (chapter_content.length === 0) {
                            break;
                        }
                        book_content = book_content.concat(chapter_content);
                        chapter++;
                    }
                    fs.writeFileSync(`${this._data_directory}/${this._translation}/${book}.json`, JSON.stringify(book_content, null, 4));
                    this.log(`Saved book ${book} for translation ${this._translation} with ${book_content.length} verses`);
                    this.log(`Completed fetching book: ${book} for translation: ${this._translation}`);
                }
                this._time_end = new Date();
                this._status = "completed"
            } catch (error) {
                this.log(`Error fetching books: ${error}`);
                this._status = 'error';
                return;
            }
        }

        private async fetch_chapter(book: string, chapter: number) {
            let bibleserver_url = `${bibleserver_endpoint}/${this._translation}/${book}${chapter}`;
            this.log(`Fetching URL from: ${bibleserver_url}`)
            try {
                let response = await axios.get(bibleserver_url)
                this.log("Received response")
                let html = response.data;
                let root = parse(html);
                // verify to avoid redirect
                let book_verify_name = root.querySelector('.chapter')?.querySelector('header')?.querySelector('h1')?.text.trim() || '';
                if (book_verify_name !== `${book} ${chapter}`) {
                    // chapter does not exist, return empty list
                    return [];
                }
                let verse_elements = root.querySelectorAll('.verse');
                let result_array = [];
                for (let verse_element of verse_elements) {
                    verse_element.querySelectorAll('.footnote').forEach(fn => fn.remove()); // remove footnotes
                    let verse_raw = verse_element.querySelector('.verse-number')?.childNodes[0].text
                    // resolve verse ranges
                    if (verse_raw?.includes('-')) {
                        let ranges = verse_raw.split('-');
                        for (let v = parseInt(ranges[0]); v <= parseInt(ranges[1]); v++) {
                            result_array.push({
                                translation: this._translation,
                                book: book,
                                chapter: chapter,
                                verse: v,
                                text: verse_element.querySelector('.verse-content')?.childNodes[0].text || ''
                            });
                        }
                    } else {
                        result_array.push({
                            translation: this._translation,
                            book: book,
                            chapter: chapter,
                            verse: Number(verse_element.querySelector('.verse-number')?.childNodes[0].text) || -1,
                            text: verse_element.querySelector('.verse-content')?.childNodes[0].text || ''
                        });
                    }
                }
                return result_array
            } catch (error: any) {
                if (error.response && error.response.status === 404) {
                    // translation does not exist
                    this.log(`Translation ${this._translation} does not exist for book ${book}`);
                    return [];
                } else {
                    this.log(`Error fetching ${this._translation} ${book} ${chapter}- ${error}`);
                    this.log(`URL: ${bibleserver_url}`);
                    throw (error)
                }
            }
        }

        private log(message: string) {
            let log_entry = `[Downloader<${this._operation_id}>:${this._translation}][${new Date().toISOString()}] ${message}`;
            this._logs.push(log_entry);
            console.log(log_entry);
        }

    }
}