var pull = require('pull-stream')
var paramap = require('pull-paramap')
var asyncMemo = require('asyncmemo')
var issueSchemas = require('./lib/schemas')
var multicb = require('multicb')

function Cache(fn, ssb) {
  return asyncMemo(fn)
  return function (key, cb) { ac.get(key, cb) }
}

function isUpdateValid(issue, msg) {
  return msg.value.author == issue.author
      || msg.value.author == issue.projectAuthor
}

function truncate(str, len) {
  return str.length > len ? str.substr(0, len) + '...' : str
}

exports.name = 'issues'

exports.manifest = {
  get: 'async',
  list: 'source',
  new: 'async',
  edit: 'async',
  close: 'async',
  reopen: 'async',
  getMention: 'sync',
  isStatusChanged: 'sync'
}

exports.schemas = issueSchemas

function isStatusChanged(msg, issue) {
  var mention = getMention(msg, issue)
  return mention ? mention.open : null
}

function getMention(msg, issue) {
  var c = msg.value.content
  if (msg.key == issue.id || c.issue == issue.id || c.link == issue.id)
    if (c.open != null)
      return c
  if (c.issues) {
    var mention
    for (var i = 0; i < c.issues.length; i++) {
      mention = getMention({value: {
        timestamp: msg.value.timestamp,
        author: msg.value.author,
        content: c.issues[i]
      }}, issue)
      if (mention)
        return mention
    }
  }
}

exports.init = function (ssb) {

  var ssbGet = asyncMemo(ssb.get)
  var liveStreams = []

  var getIssue = asyncMemo(function (id, cb) {
    var issue = {}
    var issueMsg

    ssbGet(id, function (err, msg) {
      msg = {key: id, value: msg}
      if (err) return cb(err)
      issueMsg = msg
      issue.id = msg.key
      issue.msg = msg
      issue.author = msg.value.author
      var c = msg.value.content
      issue.project = c.project
      issue.text = String(c.text)
      issue.created_at = issue.updated_at = msg.value.timestamp
      if (c.project)
        ssbGet(c.project, gotProjectMsg)
      else
        getLinks()
    })

    function gotProjectMsg(err, msg) {
      if (err) return cb(err)
      issue.projectAuthor = msg.author
      getLinks()
    }

    function getLinks() {
      var now = Date.now()
      // compute the result from the past data
      pull(
        ssb.links({dest: id, reverse: true, values: true,
          old: true, live: false, sync: false}),
        pull.drain(onOldMsg, onOldEnd)
      )
      // keep the results up-to-date in the future
      var read = ssb.links({dest: id, values: true,
        old: false, live: true, sync: false})
      liveStreams.push(read)
      pull(
        read,
        pull.drain(onNewMsg, onNewEnd)
      )
    }

    function onOldMsg(msg) {
      if (!msg.value || !isUpdateValid(issue, msg))
        return
      var c = msg.value.content

      // handle updates to issue
      if (msg.key == id || c.issue == id || c.link == id) {
        if (c.open != null && issue.open == null)
          issue.open = c.open
        if (c.title != null && issue.title == null)
          issue.title = c.title
        if (msg.value.timestamp > issue.updated_at)
          issue.updated_at = msg.value.timestamp
      }

      // handle updates via mention
      if (c.issues) {
        for (var i = 0; i < c.issues.length; i++)
          onOldMsg({value: {
            timestamp: msg.value.timestamp,
            author: msg.value.author,
            content: c.issues[i]
          }})
      }

      checkReady()
    }

    function onNewMsg(msg) {
      if (!msg.value || !isUpdateValid(issue, msg))
        return
      var c = msg.value.content

      // handle updates to issue
      if (msg.key == id || c.issue == id || c.link == id) {
        if (c.open != null)
          issue.open = c.open
        if (c.title != null)
          issue.title = c.title
        if (msg.value.timestamp > issue.updated_at)
          issue.updated_at = msg.value.timestamp
      }

      // handle updates via mention
      if (c.issues) {
        for (var i = 0; i < c.issues.length; i++)
          onNewMsg({value: {
            timestamp: msg.value.timestamp,
            author: msg.value.author,
            content: c.issues[i]
          }})
      }
    }

    function checkReady() {
      // call back once all the issue properties are set
      if (issue.open != null && issue.title != null) {
        var _cb = cb
        delete cb
        _cb(null, issue)
      }
    }

    function onOldEnd(err) {
      if (err) {
        if (cb) cb(err)
        else console.error(err)
        return
      }
      // process the root message last
      onOldMsg(issueMsg)
      // if callback hasn't been called yet, the issue is missing a field
      if (cb) {
        if (issue.open == null)
          issue.open = true
        if (issue.title == null)
          issue.title = truncate(issue.text, 40) || issue.id
        checkReady()
      }
    }

    function onNewEnd(err) {
      if (err) {
        if (cb) cb(err)
        else console.error(err)
      }
    }
  })

  function deinit(cb) {
    var done = multicb()
    // cancel all live streams
    liveStreams.forEach(function (read) {
      read(true, done())
    })
    done(cb)
  }

  function listIssues(opts) {
    opts.type = 'issue'
    return pull(
      // TODO: use links2 for this
      ssb.messagesByType(opts),
      pull.unique('key'),
      pull.filter(function (msg) {
        return (!opts.project || opts.project == msg.value.content.project)
          && (!opts.author || opts.author == msg.value.author)
      }),
      paramap(function (msg, cb) {
        getIssue(msg.key, cb)
      }, 8),
      pull.filter(opts.open != null && function (pr) {
        return pr.open == opts.open
      })
    )
  }

  function editIssue(id, opts, cb) {
    var msg
    try { ssb.publish(issueSchemas.edit(id, opts), cb) }
    catch(e) { return cb(e) }
  }

  function closeIssue(id, cb) {
    var msg
    try { ssb.publish(issueSchemas.close(id), cb) }
    catch(e) { return cb(e) }
  }

  function reopenIssue(id, cb) {
    var msg
    try { msg = issueSchemas.reopen(id) }
    catch(e) { return cb(e) }
    ssb.publish(msg, cb)
  }

  function newIssue(opts, cb) {
    var msg
    try { msg = issueSchemas.new(opts.project, opts.title, opts.text) }
    catch(e) { return cb(e) }
    ssb.publish(msg, function (err, msg) {
      if (err) return cb(err)
      getIssue(msg.key, cb)
    })
  }

  return {
    deinit: deinit,
    get: getIssue,
    list: listIssues,
    new: newIssue,
    edit: editIssue,
    close: closeIssue,
    reopen: reopenIssue,
    getMention: getMention,
    isStatusChanged: isStatusChanged
  }
}