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')
var packidx = require('pull-git-packidx-parser')

exports.help = `
Usage: git ssb find-object [--repo <id>] <sha1>

  Find a message that introduced the given git object id.
  On success, output the message id.

Arguments:
  sha1          git object id to search for

Options:
  --repo <id>   id, url or remote name of git-ssb repo to search within.
                default: ssb or origin
`

function getBlob(sbot, id, cb) {
  sbot.blobs.size(id, function (err, size) {
    if (err) gotBlob(err)
    else if (size == null) sbot.blobs.want(id, gotBlob)
    else gotBlob(null, true)
    function gotBlob(err, got) {
      if (!err && !got) err = '???'
      if (err) return cb(new Error('failed to get blob ' + id + ': ' + (err.stack||err)))
      cb(null, sbot.blobs.get(id))
    }
  })
}

exports.fn = function (argv) {
  if (argv._.length !== 1) return u.help('find-object')

  var repoId = argv.repo && u.getRemote(argv.repo)
  var objId = argv._[0]
  if (!/^[0-9a-f]{40}$/.test(objId)) throw 'invalid git object id: ' + objId
  var objIdBuf = Buffer.from(objId, 'hex')

  u.getSbot(argv, function (err, sbot) {
    if (err) throw err
    pull(
      u.gitUpdates(sbot, repoId),
      pull.map(function (msg) {
        var c = msg && msg.value && msg.value.content
        return c && Array.isArray(c.indexes) ? c.indexes.map(function (idx) {
          if (idx != null && typeof idx === 'object') idx = idx.link
          if (typeof idx !== 'string') return
          return {msg: msg, idxId: idx}
        }).filter(Boolean) : []
      }),
      pull.flatten(),
      paramap(function (info, cb) {
        // console.error('getting blob', info.idxId)
        getBlob(sbot, info.idxId, function (err, readBlob) {
          if (err) throw 'failed to get index blob ' + info.idxId + ': ' + (err.stack || err)
          // console.error('parsing packidx', info.idxId)
          pull(readBlob, packidx(function (err, idx) {
            if (err) throw 'failed to parse index blob ' + info.idxId + ': ' + (err.stack || err)
            cb(null, {msg: info.msg, idx: idx})
          }))
        })
      }, 8),
      pull.filter(function (info) {
        var offset = info.idx.find(objIdBuf)
        return offset != null
      }),
      pull.drain(function (info) {
        console.log(info.msg.key)
      }, function (err) {
        if (err) throw err
        sbot.close()
      })
    )
  })
}