package auth

import (
	"crypto/sha256"
	"fmt"
	"sync"
	"time"

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

type Manager struct {
	mu         sync.RWMutex
	secret     []byte
	accessTTL  time.Duration
	refreshTTL time.Duration
}

func NewManager(secret string, accessTTL, refreshTTL time.Duration) *Manager {
	m := &Manager{}
	m.Update(secret, accessTTL, refreshTTL)
	return m
}

func (m *Manager) Update(secret string, accessTTL, refreshTTL time.Duration) {
	if m == nil {
		return
	}
	m.mu.Lock()
	defer m.mu.Unlock()
	m.secret = []byte(secret)
	m.accessTTL = accessTTL
	m.refreshTTL = refreshTTL
}

type TokenPair struct {
	AccessToken  string `json:"access_token"`
	RefreshToken string `json:"refresh_token"`
	AccessJTI    string `json:"-"`
	RefreshJTI   string `json:"-"`
	ExpiresAt    int64  `json:"expires_at"`
}

func (m *Manager) Issue(userID, tenantID, primaryWorkspaceID int64, role string) (*TokenPair, error) {
	secret, accessTTL, refreshTTL := m.snapshot()
	now := time.Now()
	accessJTI := uuid.New().String()
	refreshJTI := uuid.New().String()

	accessClaims := Claims{
		UserID:             userID,
		TenantID:           tenantID,
		PrimaryWorkspaceID: primaryWorkspaceID,
		Role:               role,
		RegisteredClaims: jwt.RegisteredClaims{
			ID:        accessJTI,
			Subject:   "access",
			IssuedAt:  jwt.NewNumericDate(now),
			ExpiresAt: jwt.NewNumericDate(now.Add(accessTTL)),
		},
	}
	accessToken, err := jwt.NewWithClaims(jwt.SigningMethodHS256, accessClaims).SignedString(secret)
	if err != nil {
		return nil, fmt.Errorf("sign access token: %w", err)
	}

	refreshClaims := Claims{
		UserID:             userID,
		TenantID:           tenantID,
		PrimaryWorkspaceID: primaryWorkspaceID,
		Role:               role,
		RegisteredClaims: jwt.RegisteredClaims{
			ID:        refreshJTI,
			Subject:   "refresh",
			IssuedAt:  jwt.NewNumericDate(now),
			ExpiresAt: jwt.NewNumericDate(now.Add(refreshTTL)),
		},
	}
	refreshToken, err := jwt.NewWithClaims(jwt.SigningMethodHS256, refreshClaims).SignedString(secret)
	if err != nil {
		return nil, fmt.Errorf("sign refresh token: %w", err)
	}

	return &TokenPair{
		AccessToken:  accessToken,
		RefreshToken: refreshToken,
		AccessJTI:    accessJTI,
		RefreshJTI:   refreshJTI,
		ExpiresAt:    now.Add(accessTTL).Unix(),
	}, nil
}

func (m *Manager) Parse(tokenStr string) (*Claims, error) {
	secret, _, _ := m.snapshot()
	token, err := jwt.ParseWithClaims(tokenStr, &Claims{}, func(t *jwt.Token) (interface{}, error) {
		if _, ok := t.Method.(*jwt.SigningMethodHMAC); !ok {
			return nil, fmt.Errorf("unexpected signing method: %v", t.Header["alg"])
		}
		return secret, nil
	})
	if err != nil {
		return nil, err
	}
	claims, ok := token.Claims.(*Claims)
	if !ok || !token.Valid {
		return nil, fmt.Errorf("invalid token claims")
	}
	return claims, nil
}

func (m *Manager) AccessTTL() time.Duration {
	_, ttl, _ := m.snapshot()
	return ttl
}

func (m *Manager) RefreshTTL() time.Duration {
	_, _, ttl := m.snapshot()
	return ttl
}

func (m *Manager) snapshot() ([]byte, time.Duration, time.Duration) {
	if m == nil {
		return nil, 0, 0
	}
	m.mu.RLock()
	defer m.mu.RUnlock()
	secret := append([]byte(nil), m.secret...)
	return secret, m.accessTTL, m.refreshTTL
}

func HashToken(raw string) string {
	h := sha256.Sum256([]byte(raw))
	return fmt.Sprintf("%x", h)
}