package ticket

import (
	"crypto/rsa"
	"encoding/base64"
	"errors"
	"github.com/golang-jwt/jwt/v5"
	"github.com/rs/xid"
	"net/http"
	"slices"
	"sorbet/pkg/env"
	"strings"
	"time"
)

var (
	ErrUnauthorized  = errors.New("ticket is unauthorized")
	ErrInvalidTicket = errors.New("invalid ticket")
	ErrTicketExpired = errors.New("ticket is expired")
	ErrNoTicketFound = errors.New("no ticket found")
	ErrBadAudience   = errors.New("bad audience")
)

type Claims struct {
	ID        string           `json:"jti,omitempty"` // ticket编号
	UID       uint             `json:"uid"`           // 用户编号
	Role      string           `json:"role"`          // 账号类型
	Issuer    string           `json:"iss,omitempty"` // 签发人
	Subject   string           `json:"sub,omitempty"` // 主题
	Audience  jwt.ClaimStrings `json:"aud,omitempty"` // 受众
	ExpiresAt *jwt.NumericDate `json:"exp,omitempty"` // 过期时间
	NotBefore *jwt.NumericDate `json:"nbf,omitempty"` // 生效时间
	IssuedAt  *jwt.NumericDate `json:"iat,omitempty"` // 签发时间
}

// GetExpirationTime implements the Claims interface.
func (c *Claims) GetExpirationTime() (*jwt.NumericDate, error) {
	return c.ExpiresAt, nil
}

// GetNotBefore implements the Claims interface.
func (c *Claims) GetNotBefore() (*jwt.NumericDate, error) {
	return c.NotBefore, nil
}

// GetIssuedAt implements the Claims interface.
func (c *Claims) GetIssuedAt() (*jwt.NumericDate, error) {
	return c.IssuedAt, nil
}

// GetAudience implements the Claims interface.
func (c *Claims) GetAudience() (jwt.ClaimStrings, error) {
	return c.Audience, nil
}

// GetIssuer implements the Claims interface.
func (c *Claims) GetIssuer() (string, error) {
	return c.Issuer, nil
}

// GetSubject implements the Claims interface.
func (c *Claims) GetSubject() (string, error) {
	return c.Subject, nil
}

// Verify 验证令牌
func Verify(ticket string, key *rsa.PublicKey, audiences ...string) (*Claims, error) {
	decodeString, err := base64.StdEncoding.DecodeString(ticket)
	if err != nil {
		return nil, err
	}
	claims := new(Claims)
	token, err := jwt.ParseWithClaims(string(decodeString), claims, func(token *jwt.Token) (interface{}, error) {
		if _, ok := token.Method.(*jwt.SigningMethodRSA); !ok {
			return nil, ErrInvalidTicket
		}
		return key, nil
	})
	if err != nil {
		if errors.Is(err, jwt.ErrTokenExpired) {
			return nil, ErrTicketExpired
		}
		return nil, err
	}
	if !token.Valid {
		return nil, ErrInvalidTicket
	}
	var pass bool
	for _, audience := range audiences {
		for _, allow := range claims.Audience {
			if audience == allow {
				pass = true
				goto NEXT
			}
		}
	}
NEXT:
	if !pass && slices.Contains(claims.Audience, "*") {
		pass = true
	}
	if !pass {
		return claims, ErrBadAudience
	}
	return claims, nil
}

// Create 创建令牌
//
// 如果参数
// claims
// 中未给出过期时间，将默认1小时过期
// 如果未给出令牌编号，则自动生成。
func Create(claims *Claims) (string, error) {
	if claims.ID == "" {
		claims.ID = xid.New().String()
	}
	if claims.Issuer == "" {
		claims.Issuer = env.String("TICKET_ISSUER")
	}
	if claims.Subject == "" {
		claims.Issuer = env.String("TICKET_SUBJECT")
	}
	if claims.Audience == nil {
		claims.Audience = env.List("TICKET_AUDIENCE")
	}
	if claims.ExpiresAt == nil {
		ttl := env.Duration("TICKET_TTL", time.Hour)
		claims.ExpiresAt = jwt.NewNumericDate(time.Now().Add(ttl))
	}
	source := []byte(env.String("TICKET_PRIVATE_KEY"))
	privateKey, err := jwt.ParseRSAPrivateKeyFromPEM(source)
	if err != nil {
		return "", err
	}
	token := jwt.NewWithClaims(jwt.SigningMethodRS256, claims)
	signedString, err := token.SignedString(privateKey)
	if err != nil {
		return "", err
	}
	return base64.StdEncoding.EncodeToString([]byte(signedString)), nil
}

type Finder func(r *http.Request) string

func DefaultFinder(r *http.Request) string {
	if s := FromHeader(r); s != "" {
		return s
	}
	if s := FromCookie(r); s != "" {
		return s
	}
	return FromQuery(r)
}

func FromCookie(r *http.Request) string {
	cookie, err := r.Cookie("ticket")
	if err != nil {
		return ""
	}
	return cookie.Value
}

func FromHeader(r *http.Request) string {
	bearer := r.Header.Get("Authorization")
	if len(bearer) > 7 && strings.ToUpper(bearer[0:6]) == "BEARER" {
		return bearer[7:]
	}
	return ""
}

func FromQuery(r *http.Request, keys ...string) string {
	q := r.URL.Query()
	for _, key := range keys {
		s := q.Get(key)
		if s != "" {
			return s
		}
	}
	return q.Get("ticket")
}