package cpu

import (
	"math"
	"runtime"
)

var maxThreads int

// init defaults to 90% of available cores (at least 1).
func init() {
	SetMaxThreads(-1)
}

// SetMaxThreads updates the maximum CPU worker count used by CPU kernels.
// Passing n <= 0 picks 90% of available cores. Clamped to [1, NumCPU].
// It also sets GOMAXPROCS to match to avoid oversubscription.
func SetMaxThreads(n int) {
	cores := runtime.NumCPU()
	if cores < 1 {
		cores = 1
	}
	if n <= 0 || n > cores {
		n = int(math.Ceil(0.9 * float64(cores)))
		if n < 1 {
			n = 1
		}
	}
	maxThreads = n
	runtime.GOMAXPROCS(n)
}

// MaxThreads returns the configured worker count.
func MaxThreads() int {
	return maxThreads
}