package main

import (
	"fmt"
	"runtime"
	"sort"
	"strings"
	"sync"
	"time"

	"github.com/astaxie/bat/httplib"
)

type result struct {
	err           error
	statusCode    int
	duration      time.Duration
	contentLength int64
}

func RunBench(b *httplib.BeegoHttpRequest) {
	runtime.GOMAXPROCS(runtime.NumCPU())
	start := time.Now()
	results := make(chan *result, benchN)
	var wg sync.WaitGroup
	wg.Add(benchN)

	jobs := make(chan int, benchN)
	for i := 0; i < benchC; i++ {
		go func() {
			worker(&wg, jobs, results, b)
		}()
	}
	for i := 0; i < benchN; i++ {
		jobs <- i
	}
	close(jobs)

	wg.Wait()
	printReport(benchN, results, "", time.Now().Sub(start))
	close(results)
}

func worker(wg *sync.WaitGroup, ch chan int, results chan *result, b *httplib.BeegoHttpRequest) {
	for _ = range ch {
		s := time.Now()
		code := 0
		size := int64(0)
		resp, err := b.SendOut()
		if err == nil {
			size = resp.ContentLength
			code = resp.StatusCode
			resp.Body.Close()
		}
		wg.Done()

		results <- &result{
			statusCode:    code,
			duration:      time.Now().Sub(s),
			err:           err,
			contentLength: size,
		}
	}
}

const (
	barChar = "∎"
)

type report struct {
	avgTotal float64
	fastest  float64
	slowest  float64
	average  float64
	rps      float64

	results chan *result
	total   time.Duration

	errorDist      map[string]int
	statusCodeDist map[int]int
	lats           []float64
	sizeTotal      int64

	output string
}

func printReport(size int, results chan *result, output string, total time.Duration) {
	r := &report{
		output:         output,
		results:        results,
		total:          total,
		statusCodeDist: make(map[int]int),
		errorDist:      make(map[string]int),
	}
	r.finalize()
}

func (r *report) finalize() {
	for {
		select {
		case res := <-r.results:
			if res.err != nil {
				r.errorDist[res.err.Error()]++
			} else {
				r.lats = append(r.lats, res.duration.Seconds())
				r.avgTotal += res.duration.Seconds()
				r.statusCodeDist[res.statusCode]++
				if res.contentLength > 0 {
					r.sizeTotal += res.contentLength
				}
			}
		default:
			r.rps = float64(len(r.lats)) / r.total.Seconds()
			r.average = r.avgTotal / float64(len(r.lats))
			r.print()
			return
		}
	}
}

func (r *report) print() {
	sort.Float64s(r.lats)

	if r.output == "csv" {
		r.printCSV()
		return
	}

	if len(r.lats) > 0 {
		r.fastest = r.lats[0]
		r.slowest = r.lats[len(r.lats)-1]
		fmt.Printf("\nSummary:\n")
		fmt.Printf("  Total:\t%4.4f secs.\n", r.total.Seconds())
		fmt.Printf("  Slowest:\t%4.4f secs.\n", r.slowest)
		fmt.Printf("  Fastest:\t%4.4f secs.\n", r.fastest)
		fmt.Printf("  Average:\t%4.4f secs.\n", r.average)
		fmt.Printf("  Requests/sec:\t%4.4f\n", r.rps)
		if r.sizeTotal > 0 {
			fmt.Printf("  Total Data Received:\t%d bytes.\n", r.sizeTotal)
			fmt.Printf("  Response Size per Request:\t%d bytes.\n", r.sizeTotal/int64(len(r.lats)))
		}
		r.printStatusCodes()
		r.printHistogram()
		r.printLatencies()
	}

	if len(r.errorDist) > 0 {
		r.printErrors()
	}
}

func (r *report) printCSV() {
	for i, val := range r.lats {
		fmt.Printf("%v,%4.4f\n", i+1, val)
	}
}

// Prints percentile latencies.
func (r *report) printLatencies() {
	pctls := []int{10, 25, 50, 75, 90, 95, 99}
	data := make([]float64, len(pctls))
	j := 0
	for i := 0; i < len(r.lats) && j < len(pctls); i++ {
		current := i * 100 / len(r.lats)
		if current >= pctls[j] {
			data[j] = r.lats[i]
			j++
		}
	}
	fmt.Printf("\nLatency distribution:\n")
	for i := 0; i < len(pctls); i++ {
		if data[i] > 0 {
			fmt.Printf("  %v%% in %4.4f secs.\n", pctls[i], data[i])
		}
	}
}

func (r *report) printHistogram() {
	bc := 10
	buckets := make([]float64, bc+1)
	counts := make([]int, bc+1)
	bs := (r.slowest - r.fastest) / float64(bc)
	for i := 0; i < bc; i++ {
		buckets[i] = r.fastest + bs*float64(i)
	}
	buckets[bc] = r.slowest
	var bi int
	var max int
	for i := 0; i < len(r.lats); {
		if r.lats[i] <= buckets[bi] {
			i++
			counts[bi]++
			if max < counts[bi] {
				max = counts[bi]
			}
		} else if bi < len(buckets)-1 {
			bi++
		}
	}
	fmt.Printf("\nResponse time histogram:\n")
	for i := 0; i < len(buckets); i++ {
		// Normalize bar lengths.
		var barLen int
		if max > 0 {
			barLen = counts[i] * 40 / max
		}
		fmt.Printf("  %4.3f [%v]\t|%v\n", buckets[i], counts[i], strings.Repeat(barChar, barLen))
	}
}

// Prints status code distribution.
func (r *report) printStatusCodes() {
	fmt.Printf("\nStatus code distribution:\n")
	for code, num := range r.statusCodeDist {
		fmt.Printf("  [%d]\t%d responses\n", code, num)
	}
}

func (r *report) printErrors() {
	fmt.Printf("\nError distribution:\n")
	for err, num := range r.errorDist {
		fmt.Printf("  [%d]\t%s\n", num, err)
	}
}
