package jwt

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

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

	"gitlab.com/dynaweb/ains-microservices/pkg/config"
)

var (
	ErrInvalidToken = errors.New("invalid token")
	ErrExpiredToken = errors.New("expired token")
	ErrWrongType    = errors.New("wrong token type")
)

const (
	TypeAccess  = "access"
	TypeRefresh = "refresh"
)

type Claims struct {
	UserID int64  `json:"uid"`
	Role   string `json:"role"`
	State  string `json:"state,omitempty"`
	PPD    string `json:"ppd,omitempty"`
	School string `json:"school,omitempty"`
	Type   string `json:"typ"`
	jwt.RegisteredClaims
}

type Manager struct {
	secret     []byte
	issuer     string
	accessTTL  time.Duration
	refreshTTL time.Duration
}

func NewManager(cfg *config.Config) *Manager {
	return &Manager{
		secret:     []byte(cfg.JWT.Secret),
		issuer:     cfg.JWT.Issuer,
		accessTTL:  cfg.JWT.AccessTTL,
		refreshTTL: cfg.JWT.RefreshTTL,
	}
}

type Identity struct {
	UserID int64
	Role   string
	State  string
	PPD    string
	School string
}

func (m *Manager) IssueAccess(id Identity) (string, error) {
	return m.issue(id, TypeAccess, m.accessTTL)
}

func (m *Manager) IssueRefresh(id Identity) (string, error) {
	return m.issue(id, TypeRefresh, m.refreshTTL)
}

func (m *Manager) issue(id Identity, tokenType string, ttl time.Duration) (string, error) {
	now := time.Now()
	claims := Claims{
		UserID: id.UserID,
		Role:   id.Role,
		State:  id.State,
		PPD:    id.PPD,
		School: id.School,
		Type:   tokenType,
		RegisteredClaims: jwt.RegisteredClaims{
			Issuer:    m.issuer,
			Subject:   "user",
			ID:        newID(),
			IssuedAt:  jwt.NewNumericDate(now),
			NotBefore: jwt.NewNumericDate(now),
			ExpiresAt: jwt.NewNumericDate(now.Add(ttl)),
		},
	}
	return jwt.NewWithClaims(jwt.SigningMethodHS256, claims).SignedString(m.secret)
}

func newID() string {
	b := make([]byte, 16)
	if _, err := rand.Read(b); err != nil {
		return time.Now().UTC().Format("20060102150405.000000000")
	}
	return hex.EncodeToString(b)
}

func (m *Manager) Parse(tokenString string) (*Claims, error) {
	claims := &Claims{}
	token, err := jwt.ParseWithClaims(tokenString, claims, func(t *jwt.Token) (any, error) {
		if _, ok := t.Method.(*jwt.SigningMethodHMAC); !ok {
			return nil, ErrInvalidToken
		}
		return m.secret, nil
	})
	if err != nil {
		if errors.Is(err, jwt.ErrTokenExpired) {
			return nil, ErrExpiredToken
		}
		return nil, ErrInvalidToken
	}
	if !token.Valid {
		return nil, ErrInvalidToken
	}
	return claims, nil
}

func (m *Manager) ParseAccess(tokenString string) (*Claims, error) {
	claims, err := m.Parse(tokenString)
	if err != nil {
		return nil, err
	}
	if claims.Type != TypeAccess {
		return nil, ErrWrongType
	}
	return claims, nil
}

func (m *Manager) ParseRefresh(tokenString string) (*Claims, error) {
	claims, err := m.Parse(tokenString)
	if err != nil {
		return nil, err
	}
	if claims.Type != TypeRefresh {
		return nil, ErrWrongType
	}
	return claims, nil
}