var Emitter = require('events').EventEmitter
var util = require('util')

module.exports = Audit

function Audit(options) {
    options = options || {}
    this.iters = options.iterations || 1e3
    this.pause = options.pause || 100
    this.audits = []
}

util.inherits(Audit, Emitter)

Audit.prototype.makeAudit = function(name, audit, async) {

    if (!audit) {
        audit = name
        name = 'Nameless-'+this.audits.length
    }

    this.audits.push({
        name:name,
        fn:audit,
        async:async
    })

    return this
}

Audit.prototype.async = function(name, audit) {
    return this.makeAudit(name, audit, true)
}

Audit.prototype.sync = function(name, audit) {
    return this.makeAudit(name, audit, false)
}

Audit.prototype.runAudit = function(audit, fn) {
    var iters = this.iters
    var times = []
    ;(function next(i) {
        if (i > iters) {
            return fn(audit.name, times)
        }
        var then = Date.now()
        if (audit.async) {
            audit.fn(function() {
                times.push(Date.now() - then)
                next(++i)
            })
        }else {
            var res = audit.fn()
            times.push(Date.now() - then)
            next(++i)
        }
    })(0)
}

Audit.prototype.run = function(fn) {

    var self       = this
    ,   audits     = this.audits
    ,   iters      = this.iters
    ,   pause      = this.pause
    ,   stats      = {}
    ,   count = 0

    ;(function next(i) {
        var audit = audits[i]
        self.emit('auditing', audit.name)
        self.runAudit(audit, function() {
            auditComplete.apply(this, arguments) 
            if (++i >= audits.length) {
                return complete()
            }
            setTimeout(function() {
                next(i) 
            }, pause)
        })
    })(0)

    function complete() {
        self.emit('complete', stats)
    }

    function auditComplete(name, times) {

        var _stats = getStats(times)

        var auditStats = {
            name:name,
            elapsed:_stats.elapsed+'ms',
            iterations:iters,
            opsPerSecond:(iters / _stats.elapsed) * 1000,
            mode:_stats.mode,
            median:_stats.median,
            mean:_stats.mean,
            max:_stats.max,
            min:_stats.min
        }

        self.emit('auditcomplete', auditStats)
        stats[name] = auditStats

    }

}

function getStats(times) {

    var elapsed = times.reduce(function(a, b) {
        return a + b
    })

    var mode = [0, '']
    ,   median = times[~~(times.length/2)]
    ,   mean = elapsed / times.length
    ,   max = [times[0], 0+'ind']
    ,   min = [times[0], 0+'ind']
    ,   maxOcc = 0
    ,   freq = {}

    for (var i=0, len=times.length;i<len;i++) {
        ;(function() {
            var item = times[i]
            var it = (freq[item] || 0) + 1
            freq[item] = it
            if (item > max[0]) {
                max = [item, i+'ind']
            }else if (item < min[0]) {
                min = [item, i+'ind']
            }
        })()
    }

    for (k in freq) {
        if (freq[k] > maxOcc) {
            mode = [k+'ms', freq[k]+'occ'] 
            maxOcc = k
        }
    }

    return {
        elapsed:elapsed,
        frequency:freq,
        mode:mode,
        median:median+'ms',
        mean:mean+'ms',
        max:[max[0]+'ms', max[1]],
        min:[min[0]+'ms', min[1]]
    }
}