package middlewares

import (
	"crypto/rand"
	"encoding/hex"

	"github.com/gofiber/fiber/v2"
)

// RequestID echoes the caller's X-Request-Id on every response, errors
// included, and mints one when the caller did not send it. The customer app
// funnels all failures into a single retryable error state, so a support
// conversation about "it failed" has nothing to correlate on unless the id the
// client already holds comes back on the failing response too.
//
// Also stashed in c.Locals("requestid") so handlers can log it alongside the
// real error they are hiding behind a customer-safe message.
func RequestID() fiber.Handler {
	return func(c *fiber.Ctx) error {
		id := c.Get("X-Request-Id")
		if id == "" {
			b := make([]byte, 8)
			if _, err := rand.Read(b); err == nil {
				id = hex.EncodeToString(b)
			}
		}
		if id != "" {
			c.Locals("requestid", id)
			c.Set("X-Request-Id", id)
		}
		return c.Next()
	}
}