package transport

import (
	"cmp"
	"errors"
	"fmt"
	"net/http"
	"slices"
)

var ErrUnsupportedRequest = errors.New("unsupported request")

type Properties uint8

const (
	// PropertiesFree indicates that the transport is free.
	// This means that requests made with this transport don't cost any money.
	PropertiesFree Properties = 1 << iota
	// PropertiesReliable indicates that the transport is reliable.
	// This means that requests made with this transport are guaranteed to be
	// successful if the server is reachable.
	PropertiesReliable
)

func (p Properties) IsReliable() bool {
	return p&PropertiesReliable != 0
}

func (p Properties) IsFree() bool {
	return p&PropertiesFree != 0
}

type Transport interface {
	fmt.Stringer

	Do(req *http.Request) (*http.Response, error)
	Properties() Properties
}

// SortTransports sorts the transports by their properties.
//
// The transports are sorted in the following order:
// 1. Free transports
// 2. Reliable transports
func SortTransports(transports []Transport) {
	priorities := map[Properties]int{
		PropertiesFree | PropertiesReliable: 0,
		PropertiesFree:                      1,
		PropertiesReliable:                  2,
	}
	slices.SortStableFunc(transports, func(a, b Transport) int {
		iPriority := priorities[a.Properties()]
		jPriority := priorities[b.Properties()]
		return cmp.Compare(iPriority, jPriority)
	})
}

func FilterTransports(transport []Transport, props Properties) []Transport {
	var filtered []Transport
	for _, tp := range transport {
		if tp.Properties()&props == props {
			filtered = append(filtered, tp)
		}
	}
	return filtered
}