// Copyright 2014 The etcd Authors
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//     http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

// the file is borrowed from github.com/rakyll/boom/boomer/print.go

package report

import (
	"fmt"
	"math"
	"sort"
	"strings"
	"time"
)

const (
	barChar = "∎"
)

// Result describes the timings for an operation.
type Result struct {
	Start time.Time
	End   time.Time
	Err   error
}

func (res *Result) Duration() time.Duration { return res.End.Sub(res.Start) }

type report struct {
	results   chan Result
	precision string

	avgTotal float64
	fastest  float64
	slowest  float64
	average  float64
	stddev   float64
	rps      float64
	total    time.Duration

	errorDist map[string]int
	lats      []float64

	sps *secondPoints
}

// Report processes a result stream until it is closed, then produces a
// string with information about the consumed result data.
type Report interface {
	Results() chan<- Result
	Run() <-chan string
	String() string
}

func NewReport(precision string) Report {
	return &report{
		results:   make(chan Result, 16),
		precision: precision,
		errorDist: make(map[string]int),
	}
}

func NewReportSample(precision string) Report {
	r := NewReport(precision).(*report)
	r.sps = newSecondPoints()
	return r
}

func (r *report) Results() chan<- Result { return r.results }

func (r *report) Run() <-chan string {
	donec := make(chan string, 1)
	go func() {
		defer close(donec)
		r.processResults()
		donec <- r.String()
	}()
	return donec
}

func (r *report) String() (s string) {
	if len(r.lats) > 0 {
		s += fmt.Sprintf("\nSummary:\n")
		s += fmt.Sprintf("  Total:\t%s.\n", r.sec2str(r.total.Seconds()))
		s += fmt.Sprintf("  Slowest:\t%s.\n", r.sec2str(r.slowest))
		s += fmt.Sprintf("  Fastest:\t%s.\n", r.sec2str(r.fastest))
		s += fmt.Sprintf("  Average:\t%s.\n", r.sec2str(r.average))
		s += fmt.Sprintf("  Stddev:\t%s.\n", r.sec2str(r.stddev))
		s += fmt.Sprintf("  Requests/sec:\t"+r.precision+"\n", r.rps)
		s += r.histogram()
		s += r.latencies()
		if r.sps != nil {
			s += fmt.Sprintf("%v\n", r.sps.getTimeSeries())
		}
	}
	if len(r.errorDist) > 0 {
		s += r.errors()
	}
	return s
}

func (r *report) sec2str(sec float64) string { return fmt.Sprintf(r.precision+" secs", sec) }

type reportRate struct{ *report }

func NewReportRate(precision string) Report {
	return &reportRate{NewReport(precision).(*report)}
}

func (r *reportRate) String() string {
	return fmt.Sprintf(" Requests/sec:\t"+r.precision+"\n", r.rps)
}

func (r *report) processResult(res *Result) {
	if res.Err != nil {
		r.errorDist[res.Err.Error()]++
		return
	}
	dur := res.Duration()
	r.lats = append(r.lats, dur.Seconds())
	r.avgTotal += dur.Seconds()
	if r.sps != nil {
		r.sps.Add(res.Start, dur)
	}
}

func (r *report) processResults() {
	st := time.Now()
	for res := range r.results {
		r.processResult(&res)
	}
	r.total = time.Since(st)

	r.rps = float64(len(r.lats)) / r.total.Seconds()
	r.average = r.avgTotal / float64(len(r.lats))
	for i := range r.lats {
		dev := r.lats[i] - r.average
		r.stddev += dev * dev
	}
	r.stddev = math.Sqrt(r.stddev / float64(len(r.lats)))
	sort.Float64s(r.lats)
	if len(r.lats) > 0 {
		r.fastest = r.lats[0]
		r.slowest = r.lats[len(r.lats)-1]
	}
}

func (r *report) latencies() string {
	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++
		}
	}
	s := fmt.Sprintf("\nLatency distribution:\n")
	for i := 0; i < len(pctls); i++ {
		if data[i] > 0 {
			s += fmt.Sprintf("  %v%% in %s.\n", pctls[i], r.sec2str(data[i]))
		}
	}
	return s
}

func (r *report) histogram() string {
	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++
		}
	}
	s := fmt.Sprintf("\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
		}
		s += fmt.Sprintf("  "+r.precision+" [%v]\t|%v\n", buckets[i], counts[i], strings.Repeat(barChar, barLen))
	}
	return s
}

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