// Package probe measures per-phase HTTP request latency.
package probe

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

// Phase holds the measured duration of a single request phase.
type Phase struct {
	Duration time.Duration
	// Present is false when the phase was skipped (e.g. no TLS for http://).
	Present bool
}

// Result holds all timing phases for a single HTTP request.
type Result struct {
	URL      string
	DNS      Phase
	Connect  Phase
	TLS      Phase
	TTFB     Phase // server processing: WroteRequest → GotFirstResponseByte
	Transfer Phase // body read: GotFirstResponseByte → body closed
	Total    Phase

	// StatusCode is the HTTP response status code (0 on error).
	StatusCode int
	// Err is non-nil if the request failed.
	Err error
}

// Measure performs an HTTP GET to url and returns a Result.
// In Step 1 only the Total phase is populated.
func Measure(url string) Result {
	r := Result{URL: url}

	start := time.Now()

	resp, err := http.Get(url) //nolint:noctx
	if err != nil {
		r.Err = err
		r.Total = Phase{Duration: time.Since(start), Present: true}
		return r
	}
	defer resp.Body.Close()

	_, err = io.Copy(io.Discard, resp.Body)

	r.Total = Phase{Duration: time.Since(start), Present: true}
	r.StatusCode = resp.StatusCode
	if err != nil {
		r.Err = err
	}
	return r
}