var fs = require('fs')
var proc = require('child_process')
var pull = require('pull-stream')
var toPull = require('stream-to-pull-stream')
var paramap = require('pull-paramap')
var multicb = require('multicb')
var u = require('./util')
var ssbRef = require('ssb-ref')

exports.help = `
Usage: git ssb reconstruct <msg>...

  Reconstruct pack/idx blobs referenced by git-update messages.
  On success, output the message ids and their pack and index blob ids.

Arguments:
  msg           ssb message id
`

function reconstructBlobsForMsg(sbot, msg, cb) {
  var c = msg.value.content
  if (!c) return cb(new TypeError('Bad message: ' + JSON.stringify(msg)))
  var packs = Array.isArray(c.packs) && c.packs.length === 1 && c.packs
  var idxs = Array.isArray(c.indexes) && c.indexes.length === 1 && c.indexes
  var packId = packs && packs[0] && packs[0].link
  var idxId = idxs && idxs[0] && idxs[0].link
  if (!packId || !idxId) return cb(new TypeError('Message should have ' +
    'exactly one pack link and idx link'))
  var commits = Array.isArray(c.commits) ? c.commits : []
  var commitIds = commits.map(function (commit) { return commit.sha1 })
  var objectIds = Array.isArray(c.object_ids) ? c.object_ids : []
  var allObjectIds = commitIds.concat(objectIds)
  if (c.num_objects && c.num_objects !== allObjectIds.length) {
    return cb(new Error('Message ' + msg.key + ' ' +
      'does not have information to reconstruct its blobs'))
  }
  // replace incorrectly hashed empty blob id
  allObjectIds = allObjectIds.map(function (id) {
    return id === '77e98a59e190ce51ab7ec86deb24492d1434247e'
      ? 'e69de29bb2d1d6434b8b29ae775ad8c2e48c5391' : id
  })
  var tmpName = 'git-ssb-reconstruct'
  var child = proc.spawn('git', ['pack-objects', '-q', tmpName], {
    stdio: ['pipe', 'pipe', process.stderr],
  })
  child.stdin.end(allObjectIds.join('\n'))
  var bufs = []
  child.stdout.on('data', bufs.push.bind(bufs))
  child.on('error', onError)
  function onError(err) {
    if (!cb) return console.trace(err)
    var _cb = cb
    cb = null
    _cb(err)
  }
  var done = multicb()
  child.on('exit', done())
  child.stdout.on('end', done())
  done(function (code) {
    if (code) return onError(new Error('failed to pack git objects. code: ' + code))
    if (!cb) return
    var hash = Buffer.concat(bufs).toString('utf8').trim()
    if (!hash) return cb(new Error('missing hash'))
    var packFile = tmpName + '-' + hash + '.pack'
    var idxFile = tmpName + '-' + hash + '.idx'
    var done = multicb()
    pull(
      toPull(fs.createReadStream(packFile)),
      sbot.blobs.add(packId, done())
    )
    pull(
      toPull(fs.createReadStream(idxFile)),
      sbot.blobs.add(idxId, done())
    )
    done(function (err) {
      var done = multicb()
      fs.unlink(packFile, done())
      fs.unlink(idxFile, done())
      done()(err)
      done(function (err) {
        if (err) return cb(err)
        cb(null, {msg: msg, packId: packId, idxId: idxId})
      })
    })
  })
}

exports.fn = function (argv) {
  if (argv._.length < 1) return u.help('reconstruct')

  var msgIds = argv._
  if (!msgIds.every(ssbRef.isMsgId)) throw 'invalid message ids: ' +
    JSON.stringify(argv._)

  u.getSbot(argv, function (err, sbot) {
    if (err) throw err
    pull(
      pull.values(msgIds),
      paramap(function (id, cb) {
        u.getMsg(sbot, id, function (err, msg) {
          if (err) throw 'failed to get message ' + id + ': ' + (err.stack||err)
          cb(null, msg)
        })
      }, 8),
      paramap(function (msg, cb) {
        u.unbox(sbot, msg, function (err, msg) {
          if (err) throw 'failed to get decrypt message ' + id
          cb(null, msg)
        })
      }, 4),
      pull.asyncMap(function (msg, cb) {
        reconstructBlobsForMsg(sbot, msg, cb)
      }),
      pull.drain(function (obj) {
        console.log(obj.msg.key + ' ' + obj.packId + ' ' + obj.idxId)
      }, function (err) {
        if (err) throw err
        sbot.close()
      })
    )
  })
}