// Require dependencies
const path = require('path');
const cheerio = require('cheerio');
const df = require('date-format');
const {Feed} = require('feed');
const fs = require('fs-extra');
const GitLab = require('gitlab').Gitlab;
const gulp = require('gulp');
const htmlclean = require('gulp-htmlclean');
const klaw = require('klaw-sync');
const log = require('fancy-log');
const merge2 = require('merge2');
const scss = require('gulp-sass');
const sync = require('browser-sync');

// Require statistic functions
const {avgTime, freqUsers, labelsAlphabet, changedLines, uniqueContributors} = require('./statistics');

// Define paths that are gonna be used commonly
const paths = {
  data: {
    commits: path.join(__dirname, 'data/commits/'),
    issues: {
      open: path.join(__dirname, 'data/issues/open/'),
      closed: path.join(__dirname, 'data/issues/closed/'),
      out: path.join(__dirname, 'data/issues/out/')
    }
  },
  extra: path.join(__dirname, 'src/favicons/**'),
  html: {
    index: path.join(__dirname, 'src/index.html'),
    posts: path.join(__dirname, 'src/posts/*.html')
  },
  out: path.join(__dirname, 'public/'),
  scss: path.join(__dirname, 'src/scss/*.scss')
};

// Define options for Node Sass and Browser Sync
const opts = {
  scss: {
    outputStyle: 'compressed'
  },
  sync: {
    server: {
      baseDir: paths.out
    }
  }
};

// The data to download from specified month, months are zero-based zo January would be 0
// Make sure both of these are **numbers**, if they are strings it won't work properly!
const wantedMonth = new Date().getMonth();
// Since we've passed from 2018 into 2019 we also have to start checking for year now
const wantedYear = new Date().getFullYear();

// Init the months array, probably a way to do this with Dates but this works too
const months = [
  'January',
  'February',
  'March',
  'April',
  'May',
  'June',
  'July',
  'August',
  'September',
  'October',
  'November',
  'December'
];

// Add the year and month to the open/closed/out path so they're easy to identify
const commitsPath = `${paths.data.commits}${wantedYear}/${months[wantedMonth]}/`;
const openIssuesPath = `${paths.data.issues.open}${wantedYear}/${months[wantedMonth]}/`; // Folder
const closedIssuesPath = `${paths.data.issues.closed}${wantedYear}/${months[wantedMonth]}/`; // Folder
const outIssuesPath = `${paths.data.issues.out}${months[wantedMonth]}${wantedYear}`; // Will become table and statistics files

// Make the directories using fs-extra's "mkdir -p" equivalent
// It will make any directory that doesn't yet exist in the path
fs.mkdirpSync(commitsPath);
fs.mkdirpSync(openIssuesPath);
fs.mkdirpSync(closedIssuesPath);
fs.mkdirpSync(paths.data.issues.out);

// Create the browser sync server, it only starts when using `gulp watch` however
const server = sync.create();

// Copy over the HTML, using merge2 to use Gulp's async completion and multiple src's
function buildHTML() {
  return merge2([
    gulp.src(paths.html.index).pipe(htmlclean()).pipe(gulp.dest(paths.out)),
    gulp.src(paths.html.posts).pipe(htmlclean()).pipe(gulp.dest(paths.out + 'posts/'))
  ]);
}

// Build the CSS
function buildCSS() {
  return gulp
    .src(paths.scss)
    .pipe(scss(opts.scss))
    .pipe(gulp.dest(paths.out + 'css/'));
}

// Build the extra stuff, for now only the favicons
function buildExtra() {
  return gulp
    .src(paths.extra)
    .pipe(gulp.dest(paths.out));
}

// Start the Browser Sync server and watch individual file types with appropriate build functions
function watch() {
  server.init(opts.sync);
  gulp.watch([paths.html.index, paths.html.posts], gulp.series(buildHTML, createFeeds, reload));
  gulp.watch(paths.scss, gulp.series(buildCSS, reload));
  gulp.watch(paths.extra, gulp.series(buildExtra, reload));
}

// To use Gulp's async completion system this has to be done, it's ugly but can't do without it
function reload(callback) {
  server.reload();
  callback();
}

function download() {
  // Create the API with the token
  const api = new GitLab({token: require('./config.json').token});

  // Return a new Promise so we can take advantage of Gulp's async completion system
  // We'll reject whenever there is an error and resolve when everything is completed
  return new Promise((resolve, reject) => {
    // The Node GitLab API is a bit weird, first we have to find the project Tildes/Tildes
    api.Projects
      .show('tildes/tildes')
      .catch(error => reject(new Error('There was an error fetching the project:', error)))
      .then(project => {
        log('Found project, downloading issues...');
        // Then once we find the project we can use it and its ID to download the issues
        api.Issues
          .all({projectId: project.id})
          .catch(error => reject(new Error('There was an error downloading the issues:', error)))
          .then(issues => {
            // And then once we've downloaded all the issues we can write them to file appropriately
            log(`Downloaded issues, saving opened and closed issues from ${months[wantedMonth]} ${wantedYear} to file...`);
            for (const issue of issues) {
              const createdDate = new Date(issue.created_at);
              if (createdDate.getFullYear() === wantedYear &&
                  createdDate.getMonth() === wantedMonth) {
                fs.writeFileSync(openIssuesPath + `${issue.iid}.json`, JSON.stringify(issue, null, 2));
              }

              const closedDate = new Date(issue.closed_at);
              if (issue.closed_at !== null &&
                  closedDate.getFullYear() === wantedYear &&
                  closedDate.getMonth() === wantedMonth) {
                fs.writeFileSync(closedIssuesPath + `${issue.iid}.json`, JSON.stringify(issue, null, 2));
              }
            }

            log('Finished writing issues to file.');
            log('Downloading commits...');
          })
          .then(() => {
            api.Commits.all(project.id, {ref_name: 'master', with_stats: true})
              .catch(error => reject(new Error('There was an error downloading the commits:', error)))
              .then(commits => {
                log(`Downloaded commits, saving commits from ${months[wantedMonth]} ${wantedYear} to file...`);
                for (const commit of commits) {
                  const authoredDate = new Date(commit.authored_date);
                  if (authoredDate.getFullYear() === wantedYear &&
                      authoredDate.getMonth() === wantedMonth) {
                    fs.writeFileSync(commitsPath + `${commit.short_id}.json`, JSON.stringify(commit, null, 2));
                  }
                }

                log('Finished writing commits to file.');
                resolve();
              });
          });
      });
  });
}

function createIssueTable() {
  // Using a Promise again for Gulp's async completion
  return new Promise(resolve => {
    // Klaw returns all files in a directory recursively so we're getting all opened and closed issue files
    const opened = klaw(openIssuesPath);
    const closed = klaw(closedIssuesPath);

    // Then we want to sort all of these issue files in their arrays
    opened.sort((a, b) => {
      const aFile = require(a.path);
      const bFile = require(b.path);
      return (aFile.iid > bFile.iid) ? 1 : ((bFile.iid > aFile.iid) ? -1 : 0);
    });

    closed.sort((a, b) => {
      const aFile = require(a.path);
      const bFile = require(b.path);
      return (aFile.iid > bFile.iid) ? 1 : ((bFile.iid > aFile.iid) ? -1 : 0);
    });

    // And then generate the Issue Table HTML, which is kind of a mess to do
    let table = '<article id="issue-table">\n';
    table += '  <h2>Issue Table</h2>\n';

    table += '  <h3 id="opened">Opened</h3>\n';
    table += '  <table>\n';
    table += '    <thead>\n';
    table += '      <tr>\n';
    table += '        <td>Issue</td>\n';
    table += '        <td>Title</td>\n';
    table += '        <td>Author</td>\n';
    table += '        <td>Opened</td>\n';
    table += '        <td>Closed</td>\n';
    table += '      </tr>\n';
    table += '    </thead>\n';
    table += '    <tbody>\n';

    for (const file of opened) {
      const issue = require(file.path);
      table += '      <tr>\n';
      table += `        <td><a href="${issue.web_url}">${issue.iid}</a></td>\n`;

      let title;
      if (issue.title.length >= 50) {
        // We're going to be replacing all instances of <> signs to make sure nobody can add
        // <script></script> in their issue title and run JS on the site or mess up the layout or something
        // I do check myself before I commit and push anything but I'd rather be completely sure.
        title = issue.title.slice(0, 47).replace(/[<>]/g, '') + '...';
      } else {
        title = issue.title.replace(/[<>]/g, '');
      }

      table += `        <td>${title}</td>\n`;
      table += `        <td><a href="${issue.author.web_url}">${issue.author.username}</a></td>\n`;
      table += `        <td>${df.asString('yyyy/MM/dd hh:mm:ss', new Date(issue.created_at))}</td>\n`;

      let closedAt;
      if (issue.closed_at === null) {
        closedAt = '';
      } else {
        closedAt = df.asString('yyyy/MM/dd hh:mm:ss', new Date(issue.closed_at));
      }

      table += `        <td>${closedAt}</td>\n`;
      table += '      </tr>\n';
    }

    table += '    </tbody>\n';
    table += '  </table>\n\n';

    table += '  <h3 id="closed">Closed</h3>\n';
    table += '  <table>\n';
    table += '    <thead>\n';
    table += '      <tr>\n';
    table += '        <td>Issue</td>\n';
    table += '        <td>Title</td>\n';
    table += '        <td>Author</td>\n';
    table += '        <td>Opened</td>\n';
    table += '        <td>Closed</td>\n';
    table += '      </tr>\n';
    table += '    <thead>\n';
    table += '    <tbody>\n';

    for (const file of closed) {
      const issue = require(file.path);
      table += '      <tr>\n';
      table += `        <td><a href="${issue.web_url}">${issue.iid}</a></td>\n`;

      let title;
      if (issue.title.length >= 50) {
        title = issue.title.slice(0, 47).replace(/[<>]/g, '') + '...';
      } else {
        title = issue.title.replace(/[<>]/g, '');
      }

      table += `        <td>${title}\n`;
      table += `        <td><a href="${issue.author.web_url}">${issue.author.username}</a>\n`;
      table += `        <td>${df.asString('yyyy/MM/dd hh:mm:ss', new Date(issue.created_at))}</td>\n`;

      let closedAt;
      if (issue.closed_at === null) {
        closedAt = '';
      } else {
        closedAt = df.asString('yyyy/MM/dd hh:mm:ss', new Date(issue.closed_at));
      }

      table += `        <td>${closedAt}</td>\n`;
      table += '      </tr>\n';
    }

    table += '    </tbody>\n';
    table += '  </table>\n';
    table += '</article>\n';

    // And finally when the HTML is done generating we can write it and resolve that Promise we made
    fs.writeFileSync(outIssuesPath + '_table.html', table, {encoding: 'UTF-8'});
    resolve();
  });
}

function createStatistics() {
  return new Promise(resolve => {
    // Same process as the Issue Table generation
    const commits = klaw(commitsPath);
    const opened = klaw(openIssuesPath);
    const closed = klaw(closedIssuesPath);

    let statistics = '<article id="statistics">\n';
    statistics += '  <h2>Statistics</h2>\n';

    const commitStats = changedLines(commits);
    const contributors = uniqueContributors(commits);

    statistics += `  <p>In the month of ${months[wantedMonth]}, `;
    statistics += `${commits.length} commits were made by ${contributors.length} contributors, `;
    statistics += `changing a total of ${Math.abs(commitStats.total)} (+${commitStats.added}|-${commitStats.deleted}) lines. `;
    statistics += `${opened.length} issues were opened and `;
    statistics += `${closed.length} issues were closed.</p>\n`;

    statistics += `  <p>An average of ${(opened.length / 30).toFixed(2)} issues were opened `;
    statistics += `and ${(closed.length / 30).toFixed(2)} issues were closed each day.</p>\n`;

    statistics += `  <p>The average time to close issues was ${avgTime(closed, 'days')} days `;
    statistics += `or ${avgTime(closed, 'hours')} hours.</p>\n`;

    const topUsers = freqUsers(opened, 3);
    statistics += '  <p>Top 3 issue creators:</p>\n';
    statistics += '  <ol>\n';
    for (const user in topUsers) {
      statistics += '    <li>\n';
      statistics += `      <a href="https://gitlab.com/${user}">${user}</a>`;
      statistics += ' with ';
      statistics += `<a href="https://gitlab.com/tildes/tildes/issues?state=all&author_username=${user}">${topUsers[user]} issues created</a>.\n`;
      statistics += '    </li>\n';
    }

    statistics += '  </ol>\n';

    let labels = labelsAlphabet(opened, true);
    statistics += '  <p>Amount of labels assigned to currently open issues:</p>\n';
    statistics += '  <ul>\n';
    for (const label in labels) {
      statistics += '    <li>\n';
      statistics += `      <a href="https://gitlab.com/tildes/tildes/issues?state=opened&label_name%5B%5D=${label.replace(' ', '+')}")>${label}</a>:`;
      statistics += `${labels[label]} `;
      if (labels[label] === 1) {
        statistics += 'time.\n';
      } else {
        statistics += 'times.\n';
      }

      statistics += '    </li>\n';
    }

    statistics += '  </ul>\n';

    labels = labelsAlphabet(closed, false);
    statistics += '  <p>Amount of labels assigned to closed issues:</p>\n';
    statistics += '  <ul>\n';
    for (const label in labels) {
      statistics += '    <li>\n';
      statistics += `      <a href="https://gitlab.com/tildes/tildes/issues?state=opened&label_name%5B%5D=${label.replace(' ', '+')}")>${label}</a>:`;
      statistics += `${labels[label]} `;
      if (labels[label] === 1) {
        statistics += 'time.\n';
      } else {
        statistics += 'times.\n';
      }

      statistics += '    </li>\n';
    }

    statistics += '  </ul>\n';
    statistics += '</article>\n';

    fs.writeFileSync(outIssuesPath + '_statistics.html', statistics, {encoding: 'UTF-8'});
    resolve();
  });
}

function createFeeds() {
  const feed = new Feed({
    title: 'Tildes Issue Log',
    description: 'Monthly blog highlighting the changes of Tildes.net',
    id: 'https://til.bauke.xyz',
    link: 'https://til.bauke.xyz',
    language: 'en',
    image: 'https://til.bauke.xyz/android-chrome-192x192.png',
    favicon: 'https://til.bauke.xyz/favicon.ico',
    copyright: 'AGPL-3.0-or-later Tildes Issue Log Contributors https://gitlab.com/Bauke/tildes-issue-log',
    generator: 'https://github.com/jpmonette/feed',
    feedLinks: {
      atom: 'https://til.bauke.xyz/feed.atom',
      json: 'https://til.bauke.xyz/feed.json',
      rss: 'https://til.bauke.xyz/feed.rss'
    },
    author: {
      name: 'Bauke',
      email: 'me@bauke.xyz',
      link: 'https://bauke.xyz'
    }
  });
  const posts = fs.readdirSync(path.join(paths.out, 'posts'));
  // Remove the template, that doesn't need to be included
  posts.splice(posts.indexOf('template.html'), 1);
  // Sort the posts descending year and month
  posts.sort((a, b) => {
    const yearA = Number(a.replace(/\D/g, ''));
    const yearB = Number(b.replace(/\D/g, ''));
    if (yearA === yearB) {
      const monthA = months.join(',').toLowerCase().split(',').indexOf(a.slice(0, a.indexOf('-'))) + 1;
      const monthB = months.join(',').toLowerCase().split(',').indexOf(b.slice(0, b.indexOf('-'))) + 1;
      return monthB - monthA;
    }

    return yearB - yearA;
  });
  for (let i = 0; i < 5; i++) {
    const post = posts[i];
    const html = fs.readFileSync(path.join(paths.out, 'posts', post), 'UTF8');
    const $ = cheerio.load(html);
    const title = $('#wrapper>h1').text();
    const id = `https://til.bauke.xyz/posts/${post}`;
    const date = new Date(Date.UTC(
      Number(post.replace(/\D/g, '')),
      // Add one to the month since UTC months are 0 based and since we set the
      // day as 0 we'll get the Date back as the last day of the previous month
      months.join(',').toLowerCase().split(',').indexOf(post.slice(0, post.indexOf('-'))) + 1,
      0, 23, 59, 59
    ));
    const content = $('#post')
      .html()
      .replace(/<article id="toc">.+?<\/article>/g, ''); // Remove the TOC
    feed.addItem({
      title,
      id,
      link: id,
      date,
      published: date,
      description: `${title}'s Issue Log`,
      content,
      image: 'https://til.bauke.xyz/android-chrome-192x192.png'
    });
  }

  fs.writeFileSync(path.join(paths.out, 'feed.atom'), feed.atom1());
  fs.writeFileSync(path.join(paths.out, 'feed.json'), feed.json1());
  fs.writeFileSync(path.join(paths.out, 'feed.rss'), feed.rss2());
  return Promise.resolve();
}

exports.build = gulp.series(gulp.parallel(buildHTML, buildCSS, buildExtra), createFeeds);
exports.download = gulp.series(download, gulp.parallel(createIssueTable, createStatistics));
exports.no_download = gulp.parallel(createIssueTable, createStatistics);
exports.watch = gulp.series(gulp.parallel(buildHTML, buildCSS, buildExtra), createFeeds, watch);