1 files changed, 155 insertions, 0 deletions
diff --git a/src/download-playlist.js b/src/download-playlist.js
new file mode 100644
index 0000000..bb6b86c
--- /dev/null
+++ b/src/download-playlist.js
@@ -0,0 +1,155 @@
+'use strict'
+
+const fs = require('fs')
+const downloaders = require('./downloaders')
+const path = require('path')
+const processArgv = require('./process-argv')
+const sanitize = require('sanitize-filename')
+
+const {
+  isGroup, isTrack
+} = require('./playlist-utils')
+
+const { promisify } = require('util')
+
+const access = promisify(fs.access)
+const mkdir = promisify(fs.mkdir)
+const readFile = promisify(fs.readFile)
+const readdir = promisify(fs.readdir)
+const stat = promisify(fs.stat)
+const writeFile = promisify(fs.writeFile)
+const ncp = promisify(require('ncp').ncp)
+
+// It's typically bad to attempt to download or copy a million files at once,
+// so we create a "promise delayer" that forces only several promises to run at
+// at one time.
+let delayPromise
+{
+  const INTERVAL = 50
+  const MAX = 5
+
+  let active = 0
+
+  let queue = []
+
+  delayPromise = function(promiseMaker) {
+    return new Promise((resolve, reject) => {
+      queue.push([promiseMaker, resolve, reject])
+    })
+  }
+
+  setInterval(async () => {
+    if (active >= MAX) {
+      return
+    }
+
+    const top = queue.pop()
+
+    if (top) {
+      const [ promiseMaker, resolve, reject ] = top
+
+      active++
+
+      console.log('Going - queue: ' + queue.length)
+
+      try {
+        resolve(await promiseMaker())
+      } catch(err) {
+        reject(err)
+      }
+
+      active--
+    }
+  }, INTERVAL)
+}
+
+async function downloadCrawl(playlist, downloader, outPath = './out/') {
+  // If the output folder doesn't exist, we should create it.
+  let doesExist = true
+  try {
+    doesExist = (await stat(outPath)).isDirectory()
+  } catch(err) {
+    doesExist = false
+  }
+
+  if (!doesExist) {
+    await mkdir(outPath)
+  }
+
+  return Promise.all(playlist.map(async (item) => {
+    if (isGroup(item)) {
+      // TODO: Not sure if this is the best way to pick the next out dir.
+      const out = outPath + sanitize(item[0]) + '/'
+
+      return [item[0], await downloadCrawl(item[1], downloader, out)]
+    } else if (isTrack(item)) {
+      // TODO: How should we deal with songs that don't have an extension?
+      const ext = path.extname(item[1])
+      const base = path.basename(item[1], ext)
+      const out = outPath + base + ext
+
+      // If we've already downloaded a file at some point in previous time,
+      // there's no need to download it again!
+      //
+      // Since we can't guarantee the extension name of the file, we only
+      // compare bases.
+      //
+      // TODO: This probably doesn't work well with things like the YouTube
+      // downloader.
+      const items = await readdir(outPath)
+      const match = items.find(x => path.basename(x, path.extname(x)) === base)
+      if (match) {
+        console.log(`\x1b[32;2mAlready downloaded: ${out}\x1b[0m`)
+        return [item[0], outPath + match]
+      }
+
+      console.log(`\x1b[2mDownloading: ${item[0]} - ${item[1]}\x1b[0m`)
+
+      const downloadFile = await delayPromise(() => downloader(item[1]))
+      // console.log(downloadFile, path.resolve(out))
+
+      try {
+        await delayPromise(() => ncp(downloadFile, path.resolve(out)))
+        console.log(`\x1b[32;1mDownloaded: ${out}\x1b[0m`)
+        return [item[0], out]
+      } catch(err) {
+        console.error(`\x1b[31mFailed: ${out}\x1b[0m`)
+        console.error(err)
+        return false
+      }
+    }
+  })).then(p => p.filter(Boolean))
+}
+
+async function main() {
+  // TODO: Implement command line stuff here
+
+  if (process.argv.length === 2) {
+    console.error('Usage: download-playlist <playlistFile> [opts]')
+    return
+  }
+
+  const playlist = JSON.parse(await readFile(process.argv[2]))
+
+  let downloaderType = 'http'
+
+  processArgv(process.argv.slice(3), {
+    '-downloader': util => {
+      downloaderType = util.nextArg()
+    }
+  })
+
+  const dl = downloaders.makePowerfulDownloader(
+    downloaders.getDownloader(downloaderType)
+  )
+
+  const outPlaylist = await downloadCrawl(playlist, dl)
+
+  await writeFile('out/playlist.json', JSON.stringify(outPlaylist, null, 2))
+
+  console.log('Done - saved playlist to out/playlist.json.')
+  process.exit(0)
+}
+
+main()
+  .catch(err => console.error(err))