package handler

import (
	"context"
	"encoding/json"
	"errors"
	"io"
	"net/http"
	"time"
)

const (
	defaultRequestTimeout     = 2 * time.Minute
	reportRequestTimeout      = 10 * time.Minute
	longRunningRequestTimeout = 2 * time.Hour
	defaultJSONBodyLimitBytes = 1 << 20 // 1 MiB
)

func withRequestTimeout(r *http.Request, timeout time.Duration) (context.Context, context.CancelFunc) {
	base := context.Background()
	if r != nil {
		base = r.Context()
	}
	if timeout <= 0 {
		return base, func() {}
	}
	return context.WithTimeout(base, timeout)
}

func decodeJSONBody(w http.ResponseWriter, r *http.Request, dst any) error {
	if r == nil || r.Body == nil {
		return errors.New("request body is required")
	}
	decoder := json.NewDecoder(http.MaxBytesReader(w, r.Body, defaultJSONBodyLimitBytes))
	if err := decoder.Decode(dst); err != nil {
		return err
	}
	var trailing any
	if err := decoder.Decode(&trailing); err != io.EOF {
		if err == nil {
			return errors.New("request body must contain only one JSON object")
		}
		return err
	}
	return nil
}