package load

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

// Percentiles 是毫秒延迟分位。
type Percentiles struct {
	P50 float64
	P95 float64
	P99 float64
	N   int
}

func calcPercentiles(ms []float64) Percentiles {
	out := Percentiles{N: len(ms)}
	if len(ms) == 0 {
		return out
	}
	cp := append([]float64(nil), ms...)
	sort.Float64s(cp)
	out.P50 = percentileAt(cp, 0.50)
	out.P95 = percentileAt(cp, 0.95)
	out.P99 = percentileAt(cp, 0.99)
	return out
}

func percentileAt(sorted []float64, p float64) float64 {
	n := len(sorted)
	if n == 1 {
		return sorted[0]
	}
	idx := int(math.Ceil(p*float64(n))) - 1
	if idx < 0 {
		idx = 0
	}
	if idx >= n {
		idx = n - 1
	}
	return sorted[idx]
}

// Report 是一次压测输出：提交/送达分位、错误码分布、掉线数。
type Report struct {
	Connections  int
	Alive        int
	Disconnects  int
	Sends        int
	ActualRate   float64
	SubmitMs     Percentiles
	DeliverMs    Percentiles
	Errors       map[string]int
	GroupMembers int
	GroupQueueMs float64
}

func (r Report) Format() string {
	var b strings.Builder
	fmt.Fprintf(&b, "connections: %d  alive: %d  disconnects: %d\n", r.Connections, r.Alive, r.Disconnects)
	fmt.Fprintf(&b, "sends: %d", r.Sends)
	if r.ActualRate > 0 {
		fmt.Fprintf(&b, "  actual_rate: %.2f/s", r.ActualRate)
	}
	b.WriteByte('\n')
	fmt.Fprintf(&b, "submit_ms:  n=%d  p50=%.1f  p95=%.1f  p99=%.1f\n", r.SubmitMs.N, r.SubmitMs.P50, r.SubmitMs.P95, r.SubmitMs.P99)
	fmt.Fprintf(&b, "deliver_ms: n=%d  p50=%.1f  p95=%.1f  p99=%.1f\n", r.DeliverMs.N, r.DeliverMs.P50, r.DeliverMs.P95, r.DeliverMs.P99)
	if r.GroupMembers > 0 {
		fmt.Fprintf(&b, "group: members=%d  queue_ms=%.1f\n", r.GroupMembers, r.GroupQueueMs)
	}
	if len(r.Errors) == 0 {
		b.WriteString("errors: (none)\n")
	} else {
		b.WriteString("errors:")
		keys := make([]string, 0, len(r.Errors))
		for k := range r.Errors {
			keys = append(keys, k)
		}
		sort.Strings(keys)
		for _, k := range keys {
			fmt.Fprintf(&b, " %s=%d", k, r.Errors[k])
		}
		b.WriteByte('\n')
	}
	return b.String()
}

func addError(m map[string]int, code string) {
	if code == "" {
		code = "error"
	}
	m[code]++
}