/* ssb-exec
 * © 2019 cel @f/6sQ6d2CMxRUhLpspgGIulDxDCwYD7DzFzPNr7u5AU=.ed25519
 *
 * Usage of the works is permitted provided that this instrument is
 * retained with the works, so that any entity that uses the works is
 * notified of this instrument.
 *
 * DISCLAIMER: THE WORKS ARE WITHOUT WARRANTY.
 */

var url = require('url')
var path = require('path')
var fs = require('fs')

var blobsDir = path.resolve(__dirname, '../../blobs')

exports.requireBlob = function (id) {
  var m = /^\&([0-9a-zA-Z\/+=]{44})\.(sha256)$/.exec(id)
  if (!m) throw new Error('invalid blob id: ' + id)
  var hex = new Buffer(m[1], 'base64').toString('hex')
  return require(path.join(blobsDir, m[2], hex.substr(0, 2), hex.substr(2)))
}

exports.name = 'exec'
exports.version = '1.0.0'
exports.manifest = {
}
exports.init = function (sbot, config) {
  if (!sbot.ws || !sbot.ws.use) return console.trace('missing ssb-ws')
  var prefix = '/exec'
  var dir = path.join(config.path, 'exec')
  blobsDir = path.join(config.path, 'blobs')
  var mtimes = {}
  console.log('[exec] init. dir:', dir, 'prefix:', prefix)

  function getModule(resolved, tried, cb) {
    try {
      var module = require(resolved)
      return cb(null, module)
    } catch(e) {
      if (tried || !e || !(e.code === 'ENOENT' || e.code === 'MODULE_NOT_FOUND')) return cb(e)
      var m = /(sha256)\/([0-9a-f]{2})\/([0-9a-f]{62})/.exec(e.path || e.message)
      if (!m) return cb(e)
      var blobId = '&' + new Buffer(m[2] + m[3], 'hex').toString('base64') + '.' + m[1]
      if (!sbot.blobs) return cb(new Error('Missing ssb-blobs plugin'))
      if (typeof sbot.blobs.want !== 'function') return cb(new Error('missing blobs.want method'))
      return sbot.blobs.want(blobId, function (err, has) {
        if (err) return cb(new Error('Unable to get blob: ' + (err.stack || err)))
        if (!has) return cb(new Error('Unable to get blob'))
        getModule(resolved, true, cb)
      })
    }
  }

  sbot.ws.use(function (req, res, next) {
    if (prefix !== req.url.substr(0, prefix.length)) return next()
    if (prefix === req.url) {
      res.writeHead(302, {Location: path.basename(prefix) + '/'})
      return res.end()
    }
    try {
      req.uri = url.parse(req.url.substr(prefix.length), true)
      var file = path.normalize(path.join(dir, req.uri.pathname))
      if (dir !== file.substr(0, dir.length)) {
        res.writeHead(403)
        return res.end('Forbidden')
      }
      var resolved = require.resolve(file)
      var prevMtime = mtimes[resolved]
      var mtime = fs.statSync(resolved).mtime.getTime()
      if (mtime !== prevMtime) {
        delete require.cache[resolved]
        mtimes[resolved] = mtime
      }
      getModule(resolved, false, gotModule)
    } catch(e) {
      return gotError(e)
    }

    function gotError(err) {
      try {
        res.writeHead(err.code === 'ENOENT' || err.code === 'MODULE_NOT_FOUND' ? 404 : 500)
      } finally {
        res.end(err.stack || err)
      }
    }

    function gotModule(err, module) {
      if (err) return gotError(err)
      try {
        module(req, res, sbot, config)
      } catch(e) {
        gotError(e)
      }
    }
  })
}