package debug

import (
	"runtime"
	"slices"
	"time"
)

// GCStats collect information about recent garbage collections.
type GCStats struct {
	LastGC         time.Time       // time of last collection
	NumGC          int64           // number of garbage collections
	PauseTotal     time.Duration   // total pause for all collections
	Pause          []time.Duration // pause history, most recent first

		case "/gc/cycles/automatic:gc-cycles":
			checkUint64(t, name, samples[i].Value.Uint64(), uint64(mstats.NumGC-mstats.NumForcedGC))
		case "/gc/cycles/forced:gc-cycles":
			checkUint64(t, name, samples[i].Value.Uint64(), uint64(mstats.NumForcedGC))
		case "/gc/cycles/total:gc-cycles":
			checkUint64(t, name, samples[i].Value.Uint64(), uint64(mstats.NumGC))
		case "/gc/pauses:seconds":
			gcPauses = samples[i].Value.Float64Histogram()

	if change > 0 && headroom <= uint64(change) {
		l.overflow += uint64(change) - headroom
		l.bucket.fill = l.bucket.capacity
		if !enabled {
			l.enabled.Store(true)
			l.lastEnabledCycle.Store(memstats.numgc + 1)
		}
		return
	}

	// Handle non-limiting cases.
	if change < 0 && l.bucket.fill <= uint64(-change) {
		// Bucket emptied.
		l.bucket.fill = 0
	} else {
		// All other cases.

	atomic.Store64(&memstats.last_gc_nanotime, uint64(now)) // monotonic time for us
	memstats.pause_ns[memstats.numgc%uint32(len(memstats.pause_ns))] = uint64(work.pauseNS)
	memstats.pause_end[memstats.numgc%uint32(len(memstats.pause_end))] = uint64(unixNow)
	memstats.pause_total_ns += uint64(work.pauseNS)

	// Accumulate CPU stats.
	//

	fmt.Fprintf(w, "# NextGC = %d\n", s.NextGC)
	fmt.Fprintf(w, "# LastGC = %d\n", s.LastGC)
	fmt.Fprintf(w, "# PauseNs = %d\n", s.PauseNs)
	fmt.Fprintf(w, "# PauseEnd = %d\n", s.PauseEnd)
	fmt.Fprintf(w, "# NumGC = %d\n", s.NumGC)
	fmt.Fprintf(w, "# NumForcedGC = %d\n", s.NumForcedGC)
	fmt.Fprintf(w, "# GCCPUFraction = %v\n", s.GCCPUFraction)
	fmt.Fprintf(w, "# DebugGC = %v\n", s.DebugGC)

	// Also flush out MaxRSS on supported platforms.

	dumpint(m.BuckHashSys)
	dumpint(m.GCSys)
	dumpint(m.OtherSys)
	dumpint(m.NextGC)
	dumpint(m.LastGC)
	dumpint(m.PauseTotalNs)
	for i := 0; i < 256; i++ {
		dumpint(m.PauseNs[i])
	}
	dumpint(uint64(m.NumGC))
}

func dumpmemprof_callback(b *bucket, nstk uintptr, pstk *uintptr, size, allocs, frees uintptr) {
	stk := (*[100000]uintptr)(unsafe.Pointer(pstk))
	dumpint(tagMemProf)
	dumpint(uint64(uintptr(unsafe.Pointer(b))))

	a.buckHashSys = memstats.buckhash_sys.load()
	a.gcMiscSys = memstats.gcMiscSys.load()
	a.otherSys = memstats.other_sys.load()
	a.heapGoal = gcController.heapGoal()
	a.gcCyclesDone = uint64(memstats.numgc)
	a.gcCyclesForced = uint64(memstats.numforcedgc)

	systemstack(func() {
		lock(&mheap_.lock)
		a.mSpanSys = memstats.mspan_sys.load()
		a.mSpanInUse = uint64(mheap_.spanalloc.inuse)

		{"MemStats.MSpanInuse", Field, 0},
		{"MemStats.MSpanSys", Field, 0},
		{"MemStats.Mallocs", Field, 0},
		{"MemStats.NextGC", Field, 0},
		{"MemStats.NumForcedGC", Field, 8},
		{"MemStats.NumGC", Field, 0},
		{"MemStats.OtherSys", Field, 2},
		{"MemStats.PauseEnd", Field, 4},
		{"MemStats.PauseNs", Field, 0},
		{"MemStats.PauseTotalNs", Field, 0},
		{"MemStats.StackInuse", Field, 0},

pkg runtime, type MemStats struct, MSpanSys uint64
pkg runtime, type MemStats struct, Mallocs uint64
pkg runtime, type MemStats struct, NextGC uint64
pkg runtime, type MemStats struct, NumGC uint32
pkg runtime, type MemStats struct, PauseNs [256]uint64
pkg runtime, type MemStats struct, PauseTotalNs uint64
pkg runtime, type MemStats struct, StackInuse uint64
pkg runtime, type MemStats struct, StackSys uint64

pkg runtime/debug, func SetGCPercent(int) int
pkg runtime/debug, type GCStats struct
pkg runtime/debug, type GCStats struct, LastGC time.Time
pkg runtime/debug, type GCStats struct, NumGC int64
pkg runtime/debug, type GCStats struct, Pause []time.Duration
pkg runtime/debug, type GCStats struct, PauseQuantiles []time.Duration
pkg runtime/debug, type GCStats struct, PauseTotal time.Duration