package circuitbreaker

import (
	"time"

	"git.codelab.vc/pkg/httpx/internal/clock"
)

type options struct {
	failureThreshold int           // consecutive failures to trip
	openDuration     time.Duration // how long to stay open before half-open
	halfOpenMax      int           // max concurrent requests in half-open
	clk              clock.Clock   // time source (real by default)
}

func defaults() options {
	return options{
		failureThreshold: 5,
		openDuration:     30 * time.Second,
		halfOpenMax:      1,
		clk:              clock.System(),
	}
}

// Option configures a Breaker.
type Option func(*options)

// withClock sets the clock used for state-transition timing. Unexported; for
// deterministic tests.
func withClock(c clock.Clock) Option {
	return func(o *options) {
		if c != nil {
			o.clk = c
		}
	}
}

// WithFailureThreshold sets the number of consecutive failures required to
// trip the breaker from Closed to Open. Default is 5.
func WithFailureThreshold(n int) Option {
	return func(o *options) {
		if n > 0 {
			o.failureThreshold = n
		}
	}
}

// WithOpenDuration sets how long the breaker stays in the Open state before
// transitioning to HalfOpen. Default is 30s.
func WithOpenDuration(d time.Duration) Option {
	return func(o *options) {
		if d > 0 {
			o.openDuration = d
		}
	}
}

// WithHalfOpenMax sets the maximum number of concurrent probe requests
// allowed while the breaker is in the HalfOpen state. Default is 1.
func WithHalfOpenMax(n int) Option {
	return func(o *options) {
		if n > 0 {
			o.halfOpenMax = n
		}
	}
}