package inbound

import (
	"net"
	"net/http"
	"time"
)

// NewAPIHTTPClient keeps enough loopback connections warm for the bounded CMPP
// Submit window. Go's default of two idle connections per host otherwise causes
// connection churn exactly when SubmitResp latency matters most.
func NewAPIHTTPClient(maxConcurrency int) *http.Client {
	if maxConcurrency < 1 {
		maxConcurrency = 64
	}
	transport := http.DefaultTransport.(*http.Transport).Clone()
	transport.MaxIdleConns = maxConcurrency + 16
	transport.MaxIdleConnsPerHost = maxConcurrency
	transport.MaxConnsPerHost = maxConcurrency
	transport.IdleConnTimeout = 90 * time.Second
	transport.DialContext = (&net.Dialer{
		Timeout:   3 * time.Second,
		KeepAlive: 30 * time.Second,
	}).DialContext
	return &http.Client{Transport: transport, Timeout: defaultHTTPTimeout}
}