# Code coverage report for index.js

# All files index.js

89.23% Statements 116/130
82.35% Branches 70/85
88.46% Functions 23/26
91.53% Lines 108/118

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     'use strict'
    var Obv = require('obv')

    var STATES = {
      queried: 1,
      checking: 2,
      checked: 3,

      //I realized that this state is maybe not necessary
      //since we actually track this on a per peer basis.
      //requesting: 4,

      responded: 5, //we have received at least one response

      processing: 6,
      processed: 7 //now we can broadcast this
    }

    function each (obj, fn) {
      for(var k in obj)
        fn(obj[k], k, obj)
    }

    function isEmpty (o) {
      for(var k in o) return false
      return true
    }

    module.exports = function (opts) {
      //opts has {check, process, increment, isQuery, isResponse}
      var state = {}
      var localCbs = {}

      var initialWeight = opts.initialWeight || -1
      var increment = opts.increment || function (n) { return Number(n) - 1 }
      var isRequest = opts.isRequest || function (value) { return typeof value === 'number' && value < 0 }
      var isResponse = opts.isResponse || function (value) { return !isRequest(value) }
      var isQuery = opts.isQuery || function () { return true }
      var process = opts.process || function (k, v, cb) { cb (null, v) }
      var compare = opts.compare || function (a, b) {
        return b - a
      }
      var maximum = opts.maximum || -3
      var timeout = opts.timeout || 30e3
      var nextTimeout = 0

      var obv = Obv()
      obv.set(state)
      function next (fn) {
        if(!fn) obv.set(state)
        else obv.once(fn, false)
      }

      function ErrorTimeout() {
        var err = new Error('gossip-query: request timed out')
        err.name = 'request_timeout'
        return err
      }

      function setTimestamp() {
        return Date.now()
      }

      function callback (k, value, err) {
        if (localCbs[k]) {
          var cbs = localCbs[k]
          delete localCbs[k]
          while (cbs.length) cbs.shift()(err, value)
        }
      }

      obv(function () {
        //XXX: I think there could be some bugs in this because
        //obv.set is triggered from inside the loop (if check/process)
        //callback sync, which can happen.

        each(state, function (item, k) {
          //check the local store when new queries are added
          if(item.state === STATES.queried) {
            item.state = STATES.checking
            item.ts = setTimestamp()
            opts.check(k, function (_, value) {
              //igore error
              if(value && !item.value) {
                item.state = STATES.processed
                //UPDATE VALUE
                callback(k, item.value = value)
              }
              else
                item.state = STATES.checked

              item.ts = setTimestamp()

              obv.set(state)
            })
          }

          //process items received
          if(item.value != null && item.state === STATES.responded) {
            item.state = STATES.processing
            item.ts = setTimestamp()
            process(k, item.value, function (err, value) {
              Iif(err) {
                //stay in processing state
                return
              }
              item.state = STATES.processed
              item.ts = setTimestamp()
              //this is the only place that localCbs is called,
              //except for in query(key, cb) if key is already ready.
              Eif(value)
                //UPDATE VALUE
                callback(k, item.value = value)

              obv.set(state)
            })
          }
        })
      })

      function initial (weight) {
        return {
          state: STATES.queried,
          weight: weight,
          value: null,
          requestedBy: {},
          requestedFrom: {},
          respondedTo: {},
          ts: setTimestamp()
        }
      }

      return {
        state: state,
        createStream: function (peerId) {
          return {
            source: function (end, cb) {
              Iif(end) {
                for(var k in state) {
                  delete state[k].respondedTo[peerId]
                  delete state[k].requestedFrom[peerId]
                }
                return
              }
              //read the next pieces of data from the state object.
              ;(function read () {
                var data = {}
                for(var k in state) {
                  if(
                    //this item has been received & processed, respond to any other peers
                    //idea: make respondedTo be a counter, for queries with multiple answers.
                    state[k].state === STATES.processed &&
                    state[k].requestedBy[peerId] &&
                    //responded to != state[k].value.length
                    !state[k].respondedTo[peerId]
                  ) {
                    // change bool to integer, and send data since that index
                    state[k].respondedTo[peerId] = true
                    data[k] = state[k].value
                  }
                  else if(
                    state[k].state === STATES.checked &&
                    !state[k].requestedFrom[peerId]
                  ) {
                    state[k].requestedFrom[peerId] = true
                    data[k] = state[k].weight //the number of hops, etc
                  }
                }
                //next(read) calls read again when something changes in the state.
                if(isEmpty(data)) next(read)
                else cb(null, data)
              })()
            },
            sink: function (read) {
              read(null, function more (end, data) {
                Iif(end) {
                  for(var k in state) {
                    delete state[k].requestedBy[peerId]
                  }
                  //Q: how does the source decide to end?
                  //A: the network connection aborts the stream.
                  return
                }
                //process this message and possibly update the state.
                var update = false
                for(var k in data) {
                  var value = data[k]
                   //ignore invalid requests
                  Iif(!isQuery(k) || !(isRequest(value) || isResponse(value, k)))
                    ;
                  else if(isRequest(data[k])) {
                    //if we already have seen this query:
                    if(compare(data[k], maximum) < 0) {
                      if(!state[k]) {
                        update = true
                        state[k] = initial(increment(data[k]))
                        state[k].requestedBy[peerId] = true
                      }
                      else if (compare(data[k], state[k].weight) < 0){
                        update = true
                        state[k].requestedBy[peerId] = true
                        //update the weight if this peer is closer to us
                        state[k].weight = increment(data[k])
                      }
                    }
                  }
                  else Eif(isResponse(data[k])) {
                    if(state[k].state == STATES.checked) {
                      //what states can it be in here?
                      //what if we are currently processing something and a new response arrives?
                      state[k].state = STATES.responded
                      state[k].value = data[k]
                      update = true
                    }
                  }
                }
                if(update) next()
                read(null, more)
              })
            }
          }
        },

        query: function (k, cb) {
          var update
          //add to state object and update
          Iif(state[k]) {
            if(state[k].state == STATES.processed) cb(null, state[k].value)
            else (localCbs[k] = localCbs[k] || []).push(cb)
          }
          else {
            update = true
            state[k] = initial(initialWeight)
            localCbs[k] = [cb]
          }
         Eif(update) next()
        },
        checkTimeout: function () {
          var ts = Date.now()
          for(var k in state)
            if(state[k].ts + timeout < ts) {
              callback(k, null, ErrorTimeout(k))
              delete state[k]
            }
        },
        progress: function () {
          var prog = {start: 0, current: 0, target: 0}

          for(var k in state) {
            if(Date.now() - state[k].ts < timeout) {
              prog.current += state[k].state
              prog.target += STATES.processed
            }
          }
          return prog
        }
      }
    }