// Require dependencies
const
  cheerio   = require('cheerio'),
  df        = require('date-format'),
  {Feed}    = require('feed'),
  fs        = require('fs-extra'),
  gitlab    = require('gitlab/dist/es5').default,
  gulp      = require('gulp'),
  htmlclean = require('gulp-htmlclean'),
  klaw      = require('klaw-sync'),
  log       = require('fancy-log'),
  merge2    = require('merge2'),
  path      = require('path'),
  scss      = require('gulp-sass'),
  stylelint = require('gulp-stylelint'),
  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, Stylelint and Browser Sync
const opts = {
  scss: {
    outputStyle: 'compressed',
  },
  stylelint: {
    reporters: [{
      formatter: 'string', console: true,
    }],
  },
  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))
}

// Lint the Scss with Stylelint
function lintSCSS() {
  return gulp
    .src(paths.scss)
    .pipe(stylelint(opts.stylelint))
}

// 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(lintSCSS, 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
    let opened = klaw(openIssuesPath)
    let closed = klaw(closedIssuesPath)

    // Then we want to sort all of these issue files in their arrays
    opened.sort(function(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(function(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.substring(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.substring(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
    let commits = klaw(commitsPath)
    let opened = klaw(openIssuesPath)
    let 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'))
  // 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.substring(0, a.indexOf('-'))) + 1
      const monthB = months.join(',').toLowerCase().split(',').indexOf(b.substring(0, b.indexOf('-'))) + 1
      return monthB - monthA
    }

    return yearB - yearA
  })
  for (const post of posts) {
    // Skip the template, that doesn't need to be included
    if (post.includes('template')) {
      continue
    }

    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.substring(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(lintSCSS, gulp.parallel(buildHTML, buildCSS, buildExtra), createFeeds)
exports.download    = gulp.series(download, gulp.parallel(createIssueTable, createStatistics))
exports.no_download = gulp.parallel(createIssueTable, createStatistics)
exports.lint        = lintSCSS
exports.watch       = gulp.series(lintSCSS, gulp.parallel(buildHTML, buildCSS, buildExtra), createFeeds, watch)