package utils

import (
	"crypto/hmac"
	"crypto/sha256"
	"encoding/base64"
	"fmt"
	"strconv"
	"time"
)

const (
	// DefaultSignKey is the signing key from the Android app
	DefaultSignKey = "p93jhgh689SBReK6ghtw62"
	// DesktopSignKey is the signing key from the desktop app
	DesktopSignKey = "kzqU4XhfCaY6B6JTHODeq5"
	// DesktopClient is the X-Yandex-Music-Client header value for desktop
	DesktopClient = "YandexMusicDesktopAppWindows/5.95.0"
)

// Sign represents a request signature
type Sign struct {
	Timestamp int64
	Value     string
}

// GetSignRequest creates a signature for a track request
func GetSignRequest(trackID string, key string) Sign {
	if key == "" {
		key = DefaultSignKey
	}

	timestamp := time.Now().Unix()
	message := trackID + strconv.FormatInt(timestamp, 10)

	h := hmac.New(sha256.New, []byte(key))
	h.Write([]byte(message))
	sign := base64.StdEncoding.EncodeToString(h.Sum(nil))

	return Sign{
		Timestamp: timestamp,
		Value:     sign,
	}
}

// GetFileInfoSign creates a signature for file info requests
func GetFileInfoSign(trackID, quality string, codecs []string, transport, key string) Sign {
	if key == "" {
		key = DesktopSignKey
	}

	timestamp := time.Now().Unix()
	message := fmt.Sprintf("%d%s%s%s%s", timestamp, trackID, quality, joinCodecs(codecs), transport)

	h := hmac.New(sha256.New, []byte(key))
	h.Write([]byte(message))
	sign := base64.StdEncoding.EncodeToString(h.Sum(nil))
	// Remove last character as in Python
	if len(sign) > 0 {
		sign = sign[:len(sign)-1]
	}

	return Sign{
		Timestamp: timestamp,
		Value:     sign,
	}
}

func joinCodecs(codecs []string) string {
	result := ""
	for _, c := range codecs {
		result += c
	}
	return result
}