var pull = require('pull-stream')
var paramap = require('pull-paramap')
var qs = require('querystring')
var getFollows = require('./lib/follows')

// One merged view of every custo item the pub knows about.
//
// The selection rule is deliberately "whatever this pub follows", not a list of
// kiosk feed ids: adding a kiosk means following it from the pub, and its items
// appear here on the next cache miss. No code change, no edit to cust.ooo.
//
// ITEMS ONLY. A `nft: "give"` message is a change of custody, not a thing - it
// has no photo of its own and describes an item already on the page, so showing
// it here listed the same object twice. Custody is answered one level down: the
// card links to the item's thread, where the mint and every hand-off since are
// in order.
//
// Two facts about the data that this file depends on, both verified against the
// live log and both easy to get wrong:
//   * `custodisco` is the STRING "true", not a boolean.
//   * no custo message has ever set `content.channel`, so the channel index is
//     useless here and the filter has to look at content fields directly.

var CACHE_MS = 60 * 1000
var PAGE_SIZE = 60

var IMAGE_MD = /!\[[^\]]*\]\((&[A-Za-z0-9+/]{43}=\.sha256)\)/

// The item's photo: a mints's first image mention, falling back to the markdown
// embed in the text for messages whose mentions array is missing or unhelpful.
function itemPhoto (c) {
  if (c && Array.isArray(c.mentions)) {
    for (var i = 0; i < c.mentions.length; i++) {
      var m = c.mentions[i]
      if (!m || typeof m.link !== 'string' || m.link[0] !== '&') continue
      if (typeof m.type === 'string' && !/^image\//.test(m.type)) continue
      return m.link
    }
  }
  var md = IMAGE_MD.exec(String((c && c.text) || ''))
  return md ? md[1] : null
}

// Strip the parts of the post text that are furniture rather than description:
// the image embed itself, and the kiosk's " a #custodisco item " sign-off.
function itemCaption (c) {
  return String((c && c.text) || '')
    .replace(/!\[[^\]]*\]\([^)]*\)/g, ' ')
    .replace(/\s*a\s+#custodisco\s+item\s*$/i, ' ')
    .replace(/\s+/g, ' ')
    .trim()
}

// Every custodisco message carries nft: "mint" or "give" - checked across all
// 407 of them, none lacks the field - so matching "mint" is exact rather than
// merely excluding gives.
function isItem (msg) {
  var c = msg && msg.value && msg.value.content
  return !!c && typeof c === 'object' &&
    c.custodisco === 'true' && c.nft === 'mint'
}

// ctx supplies the pieces that live in index.js's init closure:
//   sbot, defaultOpts, addAuthorAbout, respond, toPull, renderItemGrid, wrapPage
module.exports = function createItemsHandler (ctx) {
  var cache = null   // { at, msgs, feeds }

  // A full log scan takes well under a second on this node (11k messages,
  // 360 KB), so this cache exists to keep a page refresh from redoing it, not
  // because the scan is expensive.
  function load (cb) {
    if (cache && Date.now() - cache.at < CACHE_MS) return cb(null, cache)

    ctx.sbot.whoami(function (err, feed) {
      if (err) return cb(err)
      var me = feed.id
      getFollows(ctx.sbot, me, function (err, sets) {
        if (err) return cb(err)
        var authors = sets.following
        authors[me] = true   // the pub's own items count too

        pull(
          ctx.sbot.createLogStream({ reverse: true }),
          pull.filter(function (msg) {
            return isItem(msg) && authors[msg.value.author] === true
          }),
          pull.collect(function (err, msgs) {
            if (err) return cb(err)
            // Log order is arrival order, which diverges from publish order
            // whenever an old feed is backfilled. Sort so "newest first" and
            // the ?before cursor both mean the same thing.
            msgs.sort(function (a, b) { return b.value.timestamp - a.value.timestamp })
            // Count the feeds that actually contributed an item, not the size
            // of the follow set: the pub follows itself and publishes no items,
            // so the follow set overstates it by one and would keep drifting
            // as feeds are followed for other reasons.
            var contributing = Object.create(null)
            msgs.forEach(function (m) { contributing[m.value.author] = true })

            cache = {
              at: Date.now(),
              msgs: msgs,
              feeds: Object.keys(contributing).length
            }
            cb(null, cache)
          })
        )
      })
    })
  }

  function addItemContext (msg, cb) {
    var c = msg.value.content
    msg.itemPhoto = itemPhoto(c)
    msg.itemCaption = itemCaption(c)
    cb(null, msg)
  }

  return function serveItems (req, res, query) {
    var q = query ? qs.parse(query) : {}
    var showAll = 'showAll' in q
    var before = q.before ? Number(q.before) : null

    load(function (err, data) {
      if (err) return ctx.respond(res, 500, err.stack || err)

      var msgs = data.msgs
      if (before) {
        msgs = msgs.filter(function (m) { return m.value.timestamp < before })
      }
      var page = showAll ? msgs : msgs.slice(0, PAGE_SIZE)
      var last = page[page.length - 1]
      var older = (!showAll && msgs.length > page.length && last)
        ? last.value.timestamp
        : null

      res.writeHead(200, { 'Content-Type': 'text/html' })
      pull(
        pull.values(page),
        paramap(ctx.addAuthorAbout, 8),
        paramap(addItemContext, 8),
        pull(
          ctx.renderItemGrid(ctx.defaultOpts, {
            total: data.msgs.length,
            shown: page.length,
            feeds: data.feeds,
            older: older,
            showAll: showAll
          }),
          ctx.wrapPage('items')
        ),
        ctx.toPull(res, function (err) {
          if (err) console.error('[viewer]', err)
        })
      )
    })
  }
}

module.exports.itemPhoto = itemPhoto
module.exports.itemCaption = itemCaption
module.exports.isItem = isItem