package jitsi

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

	"github.com/golang-jwt/jwt/v5"
)

type Config struct {
	// Secret is the HMAC-SHA256 shared secret (at least 32 bytes hex-encoded).
	Secret string
	// AppID is the Jitsi App ID (the "iss" and "aud" claim value).
	AppID string
	// AppName is the friendly name shown in the Jitsi client (optional).
	AppName string
	// Domain is the Jitsi Meet domain (e.g. "meet.jit.si").
	Domain string
	// SiteDomain is the public domain of this portal (e.g. "portal.example.com").
	// When set, avatar URLs embedded in the JWT are absolute (https://...) so
	// Jitsi, running on another domain, can load them. When empty, relative
	// URLs are used.
	SiteDomain string
}

type JitsiClaims struct {
	jwt.RegisteredClaims
	Room      string        `json:"room,omitempty"`
	Moderator bool          `json:"moderator"`
	Context   *JitsiContext `json:"context,omitempty"`
}

type JitsiContext struct {
	User *JitsiUser `json:"user,omitempty"`
}

type JitsiUser struct {
	ID     string `json:"id"`
	Name   string `json:"name"`
	Email  string `json:"email,omitempty"`
	Avatar string `json:"avatar,omitempty"`
}

// GenerateSecret creates a new random hex-encoded 32-byte secret.
func GenerateSecret() string {
	b := make([]byte, 32)
	rand.Read(b)
	return hex.EncodeToString(b)
}

// MeetURL returns the full Jitsi Meet URL for a room with a JWT token.
// If Domain is empty it defaults to "meet.jit.si".
func (c *Config) MeetURL(room, jwtToken string) string {
	domain := c.Domain
	if domain == "" {
		domain = "meet.jit.si"
	}
	return fmt.Sprintf("https://%s/%s?jwt=%s", domain, room, jwtToken)
}

// GenerateToken creates a JWT for the given room and user.
// moderator grants Jitsi moderator privileges (mute, kick, etc.) and avatar
// is the user's avatar URL (may be empty).
func (c *Config) GenerateToken(userID, userName, room string, moderator bool, avatar string) (string, error) {
	if c.Secret == "" {
		return "", fmt.Errorf("jitsi secret is not configured")
	}
	if c.AppID == "" {
		return "", fmt.Errorf("jitsi app id is not configured")
	}

	now := time.Now().UTC()
	claims := JitsiClaims{
		RegisteredClaims: jwt.RegisteredClaims{
			Issuer:    c.AppID,
			Subject:   userID,
			Audience:  jwt.ClaimStrings{c.AppID},
			IssuedAt:  jwt.NewNumericDate(now),
			NotBefore: jwt.NewNumericDate(now),
			ExpiresAt: jwt.NewNumericDate(now.Add(1 * time.Hour)),
			ID:        fmt.Sprintf("%s-%d", userID, now.Unix()),
		},
		Room:      room,
		Moderator: moderator,
		Context: &JitsiContext{
			User: &JitsiUser{
				ID:     userID,
				Name:   userName,
				Avatar: avatar,
			},
		},
	}

	token := jwt.NewWithClaims(jwt.SigningMethodHS256, claims)
	return token.SignedString([]byte(c.Secret))
}