var fs = require('fs')
var http = require('http')
var qs = require('querystring')
var path = require('path')
var crypto = require('crypto')
var pull = require('pull-stream')
var paramap = require('pull-paramap')
var sort = require('ssb-sort')
var toPull = require('stream-to-pull-stream')
var memo = require('asyncmemo')
var lru = require('lrucache')
var serveEmoji = require('emoji-server')()
var {
    MdRenderer,
    renderEmoji,
    formatMsgs,
    wrapPage,
    renderThread,
    renderAbout,
    renderShowAll
} = require('./render');

var appHash = hash([fs.readFileSync(__filename)])

var urlIdRegex = /^(?:\/(([%&@]|%25|%26|%40)(?:[A-Za-z0-9\/+]|%2[Ff]|%2[Bb]){43}(?:=|%3[Dd])\.(?:sha256|ed25519))(?:\.([^?]*))?|(\/.*?))(?:\?(.*))?$/

function hash(arr) {
  return arr.reduce(function (hash, item) {
    return hash.update(String(item))
  }, crypto.createHash('sha256')).digest('base64')
}

exports.name = 'viewer'
exports.manifest = {}
exports.version = require('./package').version

exports.init = function (sbot, config) {
  var conf = config.viewer || {}
  var port = conf.port || 8807
  var host = conf.host || config.host || '::'

  var base = conf.base || '/'
  var defaultOpts = {
    base: base,
    msg_base: conf.msg_base || base,
    feed_base: conf.feed_base || base,
    blob_base: conf.blob_base || base,
    img_base: conf.img_base || base,
    emoji_base: conf.emoji_base || (base + 'emoji/'),
  }

  defaultOpts.marked = {
      gfm: true,
      mentions: true,
      tables: true,
      breaks: true,
      pedantic: false,
      sanitize: true,
      smartLists: true,
      smartypants: false,
      emoji: renderEmoji,
      renderer: new MdRenderer(defaultOpts)
  }

  var getMsg = memo({cache: lru(100)}, getMsgWithValue, sbot)
  var getAbout = memo({cache: lru(100)}, require('./lib/about'), sbot)

  http.createServer(serve).listen(port, host, function () {
    console.log('[viewer] Listening on http://' + host + ':' + port)
  })

  function serve(req, res) {
    if (req.method !== 'GET' && req.method !== 'HEAD') {
      return respond(res, 405, 'Method must be GET or HEAD')
    }

    var m = urlIdRegex.exec(req.url)

    if (req.url.startsWith('/user-feed/')) return serveUserFeed(req, res, m[4])
    else if (req.url.startsWith('/channel/')) return serveChannel(req, res, m[4])

    if (m[2] && m[2].length === 3) {
      m[1] = decodeURIComponent(m[1])
      m[2] = m[1][0]
    }
    switch (m[2]) {
      case '%': return serveId(req, res, m[1], m[3], m[5])
      case '@': return serveFeed(req, res, m[1], m[3], m[5])
      case '&': return serveBlob(req, res, sbot, m[1])
      default: return servePath(req, res, m[4])
    }
  }

  function serveFeed(req, res, feedId) {
      console.log("serving feed: " + feedId)

      var showAll = req.url.endsWith("?showAll");

      getAbout(feedId, function (err, about) {
          if (err) return respond(res, 500, err.stack || err)

	  pull(
	      sbot.createUserStream({ id: feedId, reverse: true, limit: showAll ? -1 : 10 }),
	      pull.collect(function (err, logs) {
		  if (err) return respond(res, 500, err.stack || err)
		  res.writeHead(200, {
		      'Content-Type': ctype("html")
		  })
		  pull(
		      pull.values(logs),
		      paramap(addAuthorAbout, 8),
		      paramap(addFollowAbout, 8),
		      paramap(addVoteMessage, 8),
		      paramap(addGitLinks, 8),
		      pull(renderAbout(defaultOpts, about,
				       renderShowAll(showAll, req.url)),
			   wrapPage(about.name)),
		      toPull(res, function (err) {
			  if (err) console.error('[viewer]', err)
		      })
		  )
	      })
	  )
      })
  }

  function serveUserFeed(req, res, url) {
      var feedId = url.substring(url.lastIndexOf('user-feed/')+10, 100)
      console.log("serving user feed: " + feedId)

      var following = []
      var channelSubscriptions = []
      
      getAbout(feedId, function (err, about) {
	  pull(
	      sbot.createUserStream({ id: feedId }),
	      pull.filter((msg) => {
		  return !msg.value ||
		      msg.value.content.type == 'contact' ||
		      (msg.value.content.type == 'channel' &&
		       typeof msg.value.content.subscribed != 'undefined')
	      }),
	      pull.collect(function (err, msgs) {
		  msgs.forEach((msg) => {
		      if (msg.value.content.type == 'contact')
		      {
			  if (msg.value.content.following)
			      following[msg.value.content.contact] = 1
			  else
			      delete following[msg.value.content.contact]
		      }
		      else // channel subscription
		      {
			  if (msg.value.content.subscribed)
			      channelSubscriptions[msg.value.content.channel] = 1
			  else
			      delete channelSubscriptions[msg.value.content.channel]
		      }
		  })
		  
		  serveFeeds(req, res, following, channelSubscriptions, feedId, 'user feed ' + about.name)
	      })
	  )
      })
  }

  function serveFeeds(req, res, following, channelSubscriptions, feedId, name) {
      pull(
	  sbot.createLogStream({ reverse: true, limit: 5000 }),
	  pull.filter((msg) => {
	      return !msg.value ||
		  (msg.value.author in following ||
		   msg.value.content.channel in channelSubscriptions)
	  }),
	  pull.take(150),
	  pull.collect(function (err, logs) {
	      if (err) return respond(res, 500, err.stack || err)
	      res.writeHead(200, {
		  'Content-Type': ctype("html")
	      })
	      pull(
		  pull.values(logs),
		  paramap(addAuthorAbout, 8),
		  paramap(addFollowAbout, 8),
		  paramap(addVoteMessage, 8),
		  paramap(addGitLinks, 8),
		  pull(renderThread(defaultOpts), wrapPage(name)),
		  toPull(res, function (err) {
		      if (err) console.error('[viewer]', err)
		  })
	      )
	  })
      )
  }

  function serveChannel(req, res, url) {
      var channelId = url.substring(url.lastIndexOf('channel/')+8, 100)
      console.log("serving channel: " + channelId)

      var showAll = req.url.endsWith("?showAll")
      
      pull(
	  sbot.query.read({ limit: showAll ? 300 : 10, reverse: true, query: [{$filter: { value: { content: { channel: channelId }}}}]}),
	  pull.collect(function (err, logs) {
	      if (err) return respond(res, 500, err.stack || err)
	      res.writeHead(200, {
		  'Content-Type': ctype("html")
	      })
	      pull(
		  pull.values(logs),
		  paramap(addAuthorAbout, 8),
		  paramap(addVoteMessage, 8),
		  pull(renderThread(defaultOpts,
				    renderShowAll(showAll, req.url)),
		       wrapPage('#' + channelId)),
		  toPull(res, function (err) {
		      if (err) console.error('[viewer]', err)
		  })
	      )
	  })
      )
  }

  function serveId(req, res, id, ext, query) {
    var q = query ? qs.parse(query) : {}
    var includeRoot = !('noroot' in q)
    var base = q.base || conf.base
    var baseToken
    if (!base) {
      if (ext === 'js') base = baseToken = '__BASE_' + Math.random() + '_'
      else base = '/'
    }
    var opts = {
      base: base,
      base_token: baseToken,
      msg_base: q.msg_base || conf.msg_base || base,
      feed_base: q.feed_base || conf.feed_base || base,
      blob_base: q.blob_base || conf.blob_base || base,
      img_base: q.img_base || conf.img_base || base,
      emoji_base: q.emoji_base || conf.emoji_base || (base + 'emoji/'),
    }
    opts.marked = {
      gfm: true,
      mentions: true,
      tables: true,
      breaks: true,
      pedantic: false,
      sanitize: true,
      smartLists: true,
      smartypants: false,
      emoji: renderEmoji,
      renderer: new MdRenderer(opts)
    }

    var format = formatMsgs(id, ext, opts)
    if (format === null) return respond(res, 415, 'Invalid format')

    pull(
      sbot.links({dest: id, values: true }),
      includeRoot && prepend(getMsg, id),
      pull.unique('key'),
      pull.collect(function (err, links) {
        if (err) return respond(res, 500, err.stack || err)
        var etag = hash(sort.heads(links).concat(appHash, ext, qs))
        if (req.headers['if-none-match'] === etag) return respond(res, 304)
        res.writeHead(200, {
          'Content-Type': ctype(ext),
          'etag': etag
        })
        pull(
          pull.values(sort(links)),
          paramap(addAuthorAbout, 8),
          format,
          toPull(res, function (err) {
            if (err) console.error('[viewer]', err)
          })
        )
      })
    )
  }

  function addFollowAbout(msg, cb) {
      if (msg.value.content.contact)
	  getAbout(msg.value.content.contact, function (err, about) {
	      if (err) return cb(err)
	      msg.value.content.contactAbout = about
	      cb(null, msg)
	  })
      else
	  cb(null, msg)
  }

  function addVoteMessage(msg, cb) {
      if (msg.value.content.type == 'vote' && msg.value.content.vote.link[0] == '%')
	  getMsg(msg.value.content.vote.link, function (err, linkedMsg) {
	      if (linkedMsg)
		  msg.value.content.vote.linkedText = linkedMsg.value.content.text
	      cb(null, msg)
	  })
      else
	  cb(null, msg)
  }

  function addAuthorAbout(msg, cb) {
    getAbout(msg.value.author, function (err, about) {
      if (err) return cb(err)
      msg.author = about
      cb(null, msg)
    })
  }

  function addGitLinks(msg, cb) {
      if (msg.value.content.type == 'git-update')
	  getMsg(msg.value.content.repo, function (err, gitRepo) {
	      if (gitRepo)
		  msg.value.content.repoName = gitRepo.value.content.name
	      cb(null, msg)
	  })
      else if (msg.value.content.type == 'issue')
	  getMsg(msg.value.content.project, function (err, gitRepo) {
	      if (gitRepo)
		  msg.value.content.repoName = gitRepo.value.content.name
	      cb(null, msg)
	  })
      else
	  cb(null, msg)
  }
}

function serveBlob(req, res, sbot, id) {
  if (req.headers['if-none-match'] === id) return respond(res, 304)
  sbot.blobs.has(id, function (err, has) {
    if (err) {
      if (/^invalid/.test(err.message)) return respond(res, 400, err.message)
      else return respond(res, 500, err.message || err)
    }
    if (!has) return respond(res, 404, 'Not found')
    res.writeHead(200, {
      'Cache-Control': 'public, max-age=315360000',
      'etag': id
    })
    pull(
      sbot.blobs.get(id),
      toPull(res, function (err) {
        if (err) console.error('[viewer]', err)
      })
    )
  })
}

function getMsgWithValue(sbot, id, cb) {
  sbot.get(id, function (err, value) {
    if (err) return cb(err)
    cb(null, {key: id, value: value})
  })
}

function respond(res, status, message) {
  res.writeHead(status)
  res.end(message)
}

function ctype(name) {
  switch (name && /[^.\/]*$/.exec(name)[0] || 'html') {
    case 'html': return 'text/html'
    case 'js': return 'text/javascript'
    case 'css': return 'text/css'
    case 'json': return 'application/json'
  }
}

function servePath(req, res, url) {
  switch (url) {
    case '/robots.txt': return res.end('User-agent: *')
  }
  var m = /^(\/?[^\/]*)(\/.*)?$/.exec(url)
  switch (m[1]) {
    case '/static': return serveStatic(req, res, m[2])
    case '/emoji': return serveEmoji(req, res, m[2])
  }
  return respond(res, 404, 'Not found')
}

function ifModified(req, lastMod) {
  var ifModSince = req.headers['if-modified-since']
  if (!ifModSince) return false
  var d = new Date(ifModSince)
  return d && Math.floor(d/1000) >= Math.floor(lastMod/1000)
}

function serveStatic(req, res, file) {
  serveFile(req, res, path.join(__dirname, 'static', file))
}

function serveFile(req, res, file) {
  fs.stat(file, function (err, stat) {
    if (err && err.code === 'ENOENT') return respond(res, 404, 'Not found')
    if (err) return respond(res, 500, err.stack || err)
    if (!stat.isFile()) return respond(res, 403, 'May only load files')
    if (ifModified(req, stat.mtime)) return respond(res, 304, 'Not modified')
    res.writeHead(200, {
      'Content-Type': ctype(file),
      'Content-Length': stat.size,
      'Last-Modified': stat.mtime.toGMTString()
    })
    fs.createReadStream(file).pipe(res)
  })
}

function prepend(fn, arg) {
  return function (read) {
    return function (abort, cb) {
      if (fn && !abort) {
        var _fn = fn
        fn = null
        return _fn(arg, function (err, value) {
          if (err) return read(err, function (err) {
            cb(err || true)
          })
          cb(null, value)
        })
      }
      read(abort, cb)
    }
  }
}