package timer

import (
	"fmt"
	"strings"
	"time"
)

// Tracker 负责耗时打点追踪
type Tracker struct {
	start time.Time
	last  time.Time
	laps  []Lap
}

type Lap struct {
	Label    string
	Duration time.Duration
	At       time.Time
}

// Start 开始计时
func Start() *Tracker {
	now := time.Now()
	return &Tracker{start: now, last: now}
}

// Record 记录一段耗时 (Lap)，并返回段耗时
func (t *Tracker) Record(label string) time.Duration {
	now := time.Now()
	d := now.Sub(t.last)
	t.last = now
	t.laps = append(t.laps, Lap{Label: label, Duration: d, At: now})
	return d
}

// Stop 结束计时，返回总持续时间
func (t *Tracker) Stop() time.Duration {
	return time.Since(t.start)
}

// Summarize 返回所有记录段
func (t *Tracker) Summarize() []Lap {
	return t.laps
}

// Describe 返回格式化后的统计字符串
func (t *Tracker) Describe() string {
	var sb strings.Builder
	total := t.Stop()
	for i, lap := range t.laps {
		if i > 0 {
			sb.WriteString("; ")
		}
		sb.WriteString(fmt.Sprintf("[%s] %v", lap.Label, lap.Duration))
	}
	if len(t.laps) > 0 {
		sb.WriteString("; ")
	}
	sb.WriteString(fmt.Sprintf("Total: %v", total))
	return sb.String()
}