//go:build result_goexit

// Optional runtime.Goexit implementation, enabled with -tags result_goexit.
//
// Expect and Expectf exit the goroutine via runtime.Goexit instead of panic.
// Goexit runs all deferred functions but is invisible to recover() — no
// recover() call anywhere in the call chain can accidentally swallow a result
// failure, making this build safe to use alongside frameworks or user code
// that uses bare recover() inside Go/Run closures.
//
// Cost: error path ≈ 5.5 µs / ~536 B per failure (goroutineID parse +
// sync.Map store/load + Goexit unwind) — about 4× the default panic build.
// Happy-path cost is identical to the default.

package result

import (
	"runtime"
	"sync"
)

// gErrors stores errors set by exitGoroutine before calling runtime.Goexit,
// keyed by goroutine ID. Entries are consumed by the enclosing Async call.
var gErrors sync.Map

// goroutineID returns the current goroutine's numeric ID by parsing the first
// line of runtime.Stack output ("goroutine NNN [...]"). Called only on error
// paths so the runtime.Stack overhead is acceptable.
func goroutineID() uint64 {
	var buf [64]byte
	n := runtime.Stack(buf[:], false)
	var id uint64
	for _, b := range buf[10:n] { // skip "goroutine "
		if b < '0' || b > '9' {
			break
		}
		id = id*10 + uint64(b-'0')
	}
	return id
}

// exitGoroutine stores se in gErrors and exits the goroutine via Goexit.
// The stored error is retrieved by collectGoexitFailure in the enclosing Async.
func exitGoroutine(se *stackError) {
	gErrors.Store(goroutineID(), se)
	runtime.Goexit()
}

// collectGoexitFailure retrieves any failure stored by exitGoroutine for the
// current goroutine, consuming the entry.
func collectGoexitFailure() error {
	if stored, ok := gErrors.LoadAndDelete(goroutineID()); ok {
		return stored.(error)
	}
	return nil
}