'use strict';

const { access, cp, mkdir, readdir, readFile, writeFile } = require('fs/promises');
const { exec } = require('child_process');
const { basename, resolve, join } = require('path');
const ParseGemini = require('gemini-to-html/parse');
const RenderGemini = require('gemini-to-html/render');
const { debuglog, promisify } = require('util');
const { ensureDirectoryExists, rmIfExists } = require('./utils');
const { kFileNotFoundError } = require('./constants');

// Generators for the Blog

const StaticGenerator = require('./generators/static');
const HTMLGenerator = require('./generators/html');
const RSSGenerator = require('./generators/rss');
const TXTGenerator = require('./generators/txt');

// Archiving Methods

const GemlogArchiver = require('./archivers/gemlog');

// Remote Handler

const Remote = require('./remote');

const internals = {

  // Promisified functions
  exec: promisify(exec),

  debuglog: debuglog('blog'),

  // constants

  kGeminiRe: /\.gmi$/i,
  kMetadataFilename: 'metadata.json',

  // Strings

  strings: {
    geminiNotFound: 'Gemini file was not found in blog directory. Please update.'
  }
};

/**
 * The Blog class is the blog generator, it's in charge of adding and
 * updating posts, and handling the publishing.
 *
 * @class Blog
 * @param {Blog.tConfiguration} config the initialization options to
 * extend the instance
 */
module.exports = class Blog {

  constructor(config) {

    Object.assign(this, config);
  }

  /**
   * Shifts the blog posts, adds the passed file to slot 0, and
   * generates files.
   *
   * @function add
   * @memberof Blog
   * @param {string} postLocation the path to the blog post file
   * @return {Promise<undefined>} empty promise, returns no value
   * @instance
   */
  async add(postLocation) {

    await ensureDirectoryExists(this.postsDirectory);
    try {
      await this.syncDown();
    }
    catch {};
    await this._shift();
    const firstDirectory = join(this.postsDirectory, '0'); 
    await rmIfExists(firstDirectory);
    await ensureDirectoryExists(firstDirectory);
    await this._update(postLocation);
  }

  /**
   * Update slot 0 with the passed gmi file, and generates files.
   *
   * @function update
   * @memberof Blog
   * @param {string} postLocation the path to the blog post file
   * @return {Promise<undefined>} empty promise, returns no value
   * @instance
   */
  async update(postLocation) {

    try {
      await this.syncDown();
    }
    catch {};
    const metadata = await this._update(postLocation);
  }

  /**
   * Publishes the files to a static host.
   *
   * @function publish
   * @memberof Blog
   * @return {Promise<undefined>} empty promise, returns no value
   * @instance
   */
  async publish(host) {

    internals.debuglog(`Publishing to ${host}`);
    try {
      await internals.exec('which aws');
    }
    catch (err) {
      console.error('Please install and configure AWS CLI to publish.');
    }

    try {
      internals.debuglog(`Copying ephemeral blog from ${this.staticDirectory}`);
      await internals.exec(`rsync -r ${this.staticDirectory}/ ${host}`);
    }
    catch (err) {
      console.error('Failed to publish');
      console.error(err.stderr);
    }

    internals.debuglog('Finished publishing');
  }

  /**
   * Publishes the archive to a host using rsync. Currently assumes
   * gemlog archive.
   *
   * @function publishArchive
   * @memberof Blog
   * @return {Promise<undefined>} empty promise, returns no value
   * @instance
   */
  async publishArchive(host) {

    internals.debuglog(`Publishing archive to ${host}`);
    try {
      await internals.exec('which rsync');
    }
    catch (err) {
      console.error('Please install rsync to publish the archive.');
    }

    try {
      const gemlogPath = resolve(join(__dirname, '../', '.gemlog'));
      internals.debuglog(`Copying archive from ${gemlogPath}`);
      await internals.exec(`rsync -r ${gemlogPath}/ ${host}`);
    }
    catch (err) {
      console.error('Failed to publish archive');
      console.error(err.stderr);
    }

    internals.debuglog('Finished publishing');
  }

  /**
   * Adds a remote
   *
   * @function addRemote
   * @memberof Blog
   * @return {Promise<undefined>} empty promise, returns no value
   * @instance
   */
  async addRemote(remote) {
    await Remote.add(this.remoteConfig, remote)
  }

  /**
   * Removes a remote
   *
   * @function removeRemote
   * @memberof Blog
   * @return {Promise<undefined>} empty promise, returns no value
   * @instance
   */
  async removeRemote() {
    await Remote.remove(this.remoteConfig)
  }


  /**
   * Pulls the posts and archive from the remote
   *
   * @function syncDown
   * @memberof Blog
   * @return {Promise<undefined>} empty promise, returns no value
   * @instance
   */
  async syncDown() {
    internals.debuglog('Pulling remote state');
    await ensureDirectoryExists(this.postsDirectory);
    await Remote.syncDown(this.remoteConfig, this.blogDirectory)
    internals.debuglog('Pulled remote state');
  }

  /**
   * Pushes the posts and archive to the remote
   *
   * @function syncUp
   * @memberof Blog
   * @return {Promise<undefined>} empty promise, returns no value
   * @instance
   */
  async syncUp() {
    internals.debuglog('Pushing remote state');
    await ensureDirectoryExists(this.postsDirectory);
    await Remote.syncUp(this.remoteConfig, this.blogDirectory)
    internals.debuglog('Pushed remote state');
  }

  // Adds the passed path to slot 0, and generates files.

  async _update(postLocation) {

    const metadata = await this._getMetadata();
    await ensureDirectoryExists(this.postsDirectory);
    await this._copyPost(postLocation);
    await this._writeMetadata(metadata);

    await this._archive(postLocation);

    await this.generate();
    try {
      await this.syncUp();
    }
    catch {};
  }


  // Parses Gemini for each page, copies assets and generates index.

  async generate() {

    internals.debuglog('Generating output');

    const posts = await this._readPosts();

    await StaticGenerator(this.postsDirectory, this.staticDirectory, posts);
    await HTMLGenerator(this.templatesDirectory, this.staticDirectory, posts);
    await RSSGenerator(this.templatesDirectory, this.staticDirectory, posts);
    await TXTGenerator(this.templatesDirectory, this.staticDirectory, posts);

    await GemlogArchiver(this.archiveDirectory);
  }

  // Reads the posts into an array

  async _readPosts() {

    internals.debuglog('Reading posts');
    const posts = [];

    for (let i = 0; i < this.maxPosts; ++i) {
      try {
        posts.push(await this._readPost(i));
      }
      catch (error) {
        if (error.code === kFileNotFoundError) {
          internals.debuglog(`Skipping ${i}`);
          continue;
        }

        throw error;
      }
    }

    return posts;
  }

  // Reads an individual post

  async _readPost(index=0) {
      const postSourcePath = join(this.postsDirectory, `${index}`);

      internals.debuglog(`Reading ${postSourcePath}`);

      await access(postSourcePath);

      const metadata = await this._getMetadata(index);

      const postContentPath = await this._findBlogContent(postSourcePath);
      internals.debuglog(`Reading ${postContentPath}`);
      const postContent = await readFile(postContentPath, { encoding: 'utf8' });

      internals.debuglog('Parsing Gemini');
      return {
        ...metadata,
        location: postSourcePath,
        index,
        html: RenderGemini(ParseGemini(postContent)),
        raw: postContent
      };
  }

  // Shift the posts, delete any remainder.

  async _shift() {


    for (let i = this.maxPosts - 1; i >= 1; --i) {
      const targetPath = join(this.postsDirectory, `${i}`);
      const sourcePath = join(this.postsDirectory, `${i - 1}`);

      try {
        internals.debuglog(`Archiving ${targetPath}`);
        await rmIfExists(targetPath);
        await access(sourcePath); // check the source path

        internals.debuglog(`Shifting blog post ${sourcePath} to ${targetPath}`);
        await cp(sourcePath, targetPath, { recursive: true });
      }
      catch (error) {
        if (error.code === kFileNotFoundError) {
          internals.debuglog(`Skipping ${sourcePath}: Does not exist.`);
          continue;
        }

        throw error;
      }
    }
  }

  // Moves older posts to the archive

  async _archive() {
    internals.debuglog('Archiving post');
    const post = await this._readPost(0);
    await ensureDirectoryExists(this.archiveDirectory);

    const targetPath = join(this.archiveDirectory, post.id);

    internals.debuglog(`Removing ${targetPath}`);
    await rmIfExists(targetPath);
    internals.debuglog(`Adding ${post.location} to ${targetPath}`);
    await ensureDirectoryExists(targetPath);
    await cp(post.location, targetPath, { recursive: true });
    internals.debuglog(`Added ${post.location} to ${targetPath}`);
  }

  // Attempts to read existing metadata. Otherwise generates new set.

  async _getMetadata(index = 0) {

    const metadataTarget = join(this.postsDirectory, String(index), internals.kMetadataFilename);

    try {
      internals.debuglog(`Looking for metadata at ${metadataTarget}`);
      return JSON.parse(await readFile(metadataTarget, { encoding: 'utf8' }));
    }
    catch (e) {
      internals.debuglog(`Metadata not found or unreadable. Generating new set.`);
      const createdOn = Date.now();
      const metadata = {
        id: String(createdOn),
        createdOn
      };

      return metadata;
    }
  }

  // Writes metadata. Assumes post 0 since it only gets written
  // on create

  async _writeMetadata(metadata) {

    const metadataTarget = join(this.postsDirectory, '0', internals.kMetadataFilename);
    internals.debuglog(`Writing ${metadataTarget}`);
    await writeFile(metadataTarget, JSON.stringify(metadata, null, 2));
  }

  // Copies a post file to the latest slot.

  async _copyPost(postLocation) {

    internals.debuglog(`Copying ${postLocation}`);
    const targetPath = join(this.postsDirectory, '0');
    const postName = basename(postLocation);
    const targetPost = join(targetPath, postName);

    await rmIfExists(targetPath);
    await ensureDirectoryExists(targetPath);
    await cp(postLocation, targetPost, { recursive: true });
    internals.debuglog(`Added ${postLocation} to ${targetPath}`);
  }

  // Looks for a `.gmi` file in the blog directory, and returns the path

  async _findBlogContent(directory) {

    const entries = await readdir(directory);

    const geminiEntries = entries
      .filter((entry) => internals.kGeminiRe.test(entry))
      .map((entry) => join(directory, entry));

    if (geminiEntries.length > 0) {
      internals.debuglog(`Found gemini file: ${geminiEntries[0]}`);
      return geminiEntries[0];
    }

    throw new Error(internals.strings.geminiNotFound);
  }
};