var fs = require('fs')
var http = require('http')
var qs = require('querystring')
var path = require('path')
var crypto = require('crypto')
var cat = require('pull-cat')
var pull = require('pull-stream')
var paramap = require('pull-paramap')
var marked = require('ssb-marked')
var sort = require('ssb-sort')
var toPull = require('stream-to-pull-stream')
var memo = require('asyncmemo')
var lru = require('lrucache')
var htime = require('human-time')
var emojis = require('emoji-named-characters')
var serveEmoji = require('emoji-server')()

var emojiDir = path.join(require.resolve('emoji-named-characters'), '../pngs')
var appHash = hash([fs.readFileSync(__filename)])

var urlIdRegex = /^(?:\/(([%&])[A-Za-z0-9\/+]{43}=\.sha256)(?:\.([^?]*))?|(\/.*?))(?:\?(.*))?$/

function MdRenderer(opts) {
  marked.Renderer.call(this, {})
  this.opts = opts
}
MdRenderer.prototype = new marked.Renderer() 

MdRenderer.prototype.urltransform = function (href) {
  switch (href && href[0]) {
    case '%': return this.opts.msg_base + href
    case '@': return this.opts.feed_base + href
    case '&': return this.opts.blob_base + href
  }
  return marked.Renderer.prototype.urltransform.call(this, href)
}

MdRenderer.prototype.image = function (href, title, text) {
  return '<img src="' + this.opts.img_base + escape(href) + '"'
    + ' alt="' + text + '"'
    + (title ? ' title="' + title + '"' : '')
    + (this.options.xhtml ? '/>' : '>')
};

function renderEmoji(emoji) {
  var opts = this.renderer.opts
  return emoji in emojis ?
    '<img src="' + opts.emoji_base + escape(emoji) + '.png"'
      + ' alt=":' + escape(emoji) + ':"'
      + ' title=":' + escape(emoji) + ':"'
      + ' class="ssb-emoji" height="16" width="16">'
    : ':' + emoji + ':'
}

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

  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)
    switch (m[2]) {
      case '&': return serveBlob(req, res, sbot, m[1])
      case '%': return serveId(req, res, m[1], m[3], m[5])
      default: return servePath(req, res, m[4])
    }
  }

  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 || '#',
      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, rel: 'root'}),
      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 addAuthorAbout(msg, cb) {
    getAbout(msg.value.author, function (err, about) {
      if (err) return cb(err)
      msg.author = about
      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 && /^invalid/.test(err.message)) return respond(400, err.message)
    if (err) return respond(500, err.message || err)
    if (!has) return respond(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 escape(str) {
  return String(str)
    .replace(/&/g, '&amp;')
    .replace(/</g, '&lt;')
    .replace(/>/g, '&gt;')
    .replace(/"/g, '&quot;')
}

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)
    }
  }
}

function formatMsgs(id, ext, opts) {
  switch (ext || 'html') {
    case 'html': return pull(renderThread(opts), wrapPage(id))
    case 'js': return pull(renderThread(opts), wrapJSEmbed(opts))
    case 'json': return wrapJSON()
    default: return null
  }
}

function wrap(before, after) {
  return function (read) {
    return cat([pull.once(before), read, pull.once(after)])
  }
}

function renderThread(opts) {
  return pull(
    pull.map(renderMsg.bind(this, opts)),
    wrap('<div class="ssb-thread">', '</div>')
  )
}

function wrapPage(id) {
  return wrap('<!doctype html><html><head>'
    + '<meta charset=utf-8>'
    + '<title>' + id + '</title>'
    + '<meta name=viewport content="width=device-width,initial-scale=1">'
    + '<link rel=stylesheet href="/static/base.css">'
    + '<link rel=stylesheet href="/static/nicer.css">'
    + '</head><body>',
    '</body></html>'
  )
}

function wrapJSON() {
  var first = true
  return pull(
    pull.map(JSON.stringify),
    join(','),
    wrap('[', ']')
  )
}

function wrapJSEmbed(opts) {
  return pull(
    wrap('<link rel=stylesheet href="' + opts.base + 'static/base.css">', ''),
    pull.map(docWrite),
    opts.base_token && rewriteBase(new RegExp(opts.base_token, 'g'))
  )
}


function rewriteBase(token) {
  // detect the origin of the script and rewrite the js/html to use it
  return pull(
    replace(token, '" + SSB_VIEWER_ORIGIN + "/'),
    wrap('var SSB_VIEWER_ORIGIN = (function () {'
      + 'var scripts = document.getElementsByTagName("script")\n'
      + 'var script = scripts[scripts.length-1]\n'
      + 'if (!script) return location.origin\n'
      + 'return script.src.replace(/\\/%.*$/, "")\n'
      + '}())\n', '')
  )
}

function join(delim) {
  var first = true
  return pull.map(function (val) {
    if (!first) return delim + String(val)
    first = false
    return val
  })
}

function replace(re, rep) {
  return pull.map(function (val) {
    return String(val).replace(re, rep)
  })
}

function docWrite(str) {
  return 'document.write(' + JSON.stringify(str) + ')\n'
}

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

function renderMsg(opts, msg) {
  var c = msg.value.content || {}
  var name = encodeURIComponent(msg.key)
  return '<div class="ssb-message" id="' + name + '">'
    + '<img class="ssb-avatar-image" alt=""'
      + ' src="' + opts.img_base + escape(msg.author.image) + '"'
      + ' height="32" width="32">'
    + '<a class="ssb-avatar-name"'
      + ' href="' + opts.feed_base + escape(msg.value.author) + '"'
      + '>' + msg.author.name + '</a>'
    + msgTimestamp(msg, name)
    + (c.type === 'post' ? renderPost(opts, c) : renderDefault(c))
    + '</div>'
}

function msgTimestamp(msg, name) {
  var date = new Date(msg.value.timestamp)
  return '<time class="ssb-timestamp" datetime="' + date.toISOString() + '">'
    + '<a href="#' + name + '">'
    + formatDate(date) + '</a></time>'
}

function formatDate(date) {
  // return date.toISOString().replace('T', ' ')
  return htime(date)
}

function renderPost(opts, c) {
  return '<div class="ssb-post">' + marked(c.text, opts.marked) + '</div>'
}

function renderDefault(c) {
  return '<pre>' + JSON.stringify(c, 0, 2) + '</pre>'
}