import fs from 'node:fs';

export class RssGenerator {
  maxItem = 10;
  items = [];
  channel = {};

  constructor(options) {
    this.options = options;
  }

  // TODO: move to pass an option parameter and iterate over the key/values
  setChannel (title, description, link, pubDate) {
    this.channel.title = title;
    this.channel.description = description;
    this.channel.link = link;
    this.channel.pubDate = pubDate;
    
    return this;
  }

  addItem (item) {
    if (!this.isItemValid(item)) {
      console.error('[RssGenerator] addItem: item invalid.', item);
      return this;
    }

    this.items.push(item);
    
    if (this.items.lenght > this.maxItem) {
      this.items.shift();
    }

    return this;
  }
  
  isItemValid(item) {
    return true;
  }

  generateFile() {
    let data = '';

    data += '<rss version=\"2.0\" xmlns:atom=\"http://www.w3.org/2005/Atom\"><channel>';
    data += this.#generateChannelInfos();
    data += this.#generateItems();
    data += '</channel></rss>';

    this.#saveFile(data);
    return this;
  }

  #generateChannelInfos() {
    let infos = '';

    infos += `<title>${this.channel.title}</title>\n`;
    infos += `<description>${this.channel.description}</description>\n`;
    infos += `<link>${this.channel.link}</link>\n`;
    infos += `<pubDate>${RssGenerator.formatDate(this.channel.pubDate)}</pubDate>\n`;
    infos += `<atom:link href="${this.channel.link}/rss.xml" rel="self" type="application/rss+xml" />\n`;

    return infos;
  }

  #generateItems() {
    let data = '';

    for (const item of this.items) {
      data += '<item>\n';
      data += `<title>${item.title}</title>\n`;
      data += `<link>${item.link}</link>\n`;
      data += `<guid>${item.link}</guid>\n`;
      data += `<description>${item.description}</description>\n`;
      data += '</item>\n';
    }

    return data;
  }

  static formatDate(date) {
    return new Intl.DateTimeFormat("en-GB", {
      hour12: false,
      weekday: "short",
      year: "numeric",
      month: "short",
      day: "2-digit",
      hour: "2-digit",
      minute: "2-digit",
      second: "2-digit",
      timeZone: "Europe/London",
    }).formatToParts(date)
      .filter(el => el.type !== "literal") 
      .reduce((acc, cur) => {
        switch (cur.type) {
          case "weekday":
            acc += `${cur.value}, `;
            break;
          case "hour":
          case "minute":
            acc += `${cur.value}:`;
            break;
          case "timeZoneName":
            acc += cur.value;
            break;
          default:
            acc += `${cur.value} `;
            break;
        }
        return acc;
      }, '')
      .concat(" GMT");
  }

  #saveFile(data) {
    try {
      fs.writeFileSync(this.options.filePath, data, { encoding: 'utf8' });
    } catch (err) {
      console.error('[RssGenerator] saveFile - ERROR');
      console.error(err);
    }
  }
}