// Package auth implements login, JWT session issuance/validation, and logout,
// ported from archivmail's internal/auth pattern. LDAP and TOTP are
// intentionally left out of this initial scaffold; they can be re-added later
// following the same shape archivmail uses (Manager.SetTenantLDAP etc.).
package auth

import (
	"context"
	"crypto/rand"
	"encoding/hex"
	"errors"
	"fmt"
	"strings"
	"time"

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

	"archivdms/internal/audit"
	"archivdms/internal/ldapauth"
	"archivdms/internal/ldapstore"
	"archivdms/internal/tenantstore"
	"archivdms/internal/userstore"
)

// Session holds the claims extracted from a validated JWT.
type Session struct {
	UserID   int64
	Username string
	Email    string
	Role     string
	JTI      string
	TenantID *int64
}

// Manager handles login, token issuance, validation, and logout.
type Manager struct {
	store     *userstore.Store
	jwtSecret []byte

	// ldap is nil until SetLDAP wires the directory integration. When nil the
	// login flow is local-only (bcrypt).
	ldap *ldapComponent
}

// ldapComponent bundles the dependencies for LDAP authentication. Kept behind
// a pointer so a deployment without LDAP configured pays zero cost.
type ldapComponent struct {
	store   *ldapstore.Store
	authn   *ldapauth.Authenticator
	tenants *tenantstore.Store
	audlog  *audit.Logger
	limiter *keyedRateLimiter
}

// New creates a new auth Manager.
func New(store *userstore.Store, jwtSecret string) *Manager {
	return &Manager{store: store, jwtSecret: []byte(jwtSecret)}
}

// SetLDAP wires the LDAP directory integration into the auth manager. Called
// once at startup after the ldapstore/tenantstore/audit dependencies exist.
func (m *Manager) SetLDAP(ldapSt *ldapstore.Store, authn *ldapauth.Authenticator, tenants *tenantstore.Store, audlog *audit.Logger) {
	m.ldap = &ldapComponent{
		store:   ldapSt,
		authn:   authn,
		tenants: tenants,
		audlog:  audlog,
		// 10 attempts burst, refilled at 1 / 6s per key (~10/min sustained).
		limiter: newKeyedRateLimiter(10, 1.0/6.0),
	}
}

// Login verifies credentials and returns a signed JWT token. Kept for callers
// that do not have request context (client IP); prefer LoginFrom.
func (m *Manager) Login(username, password string) (token string, user *userstore.User, err error) {
	return m.LoginFrom(context.Background(), username, password, "")
}

// LoginFrom verifies credentials, honouring each account's auth_source and,
// where applicable, the tenant's LDAP configuration. ip is used for
// rate-limiting and audit context.
//
// Decision matrix:
//   - account exists, auth_source=local : bcrypt only, LDAP never attempted.
//   - account exists, auth_source=ldap  : LDAP bind only, no local-password fallback.
//   - account absent, tenant LDAP enabled: LDAP bind + JIT provisioning.
//   - otherwise                          : fail (with bcrypt timing burn).
func (m *Manager) LoginFrom(ctx context.Context, identifier, password, ip string) (string, *userstore.User, error) {
	rec, err := m.store.FindForLogin(ctx, identifier)
	switch {
	case err == nil && rec.AuthSource == userstore.AuthSourceLDAP:
		if m.ldap == nil {
			return "", nil, fmt.Errorf("auth: login: invalid credentials")
		}
		return m.ldapLogin(ctx, derefTenant(rec.User.TenantID), identifier, password, ip, rec.User)

	case err == nil:
		if !rec.User.Active {
			return "", nil, fmt.Errorf("auth: login: invalid credentials")
		}
		if cErr := userstore.CompareLocalPassword(rec.Hash, password); cErr != nil {
			return "", nil, fmt.Errorf("auth: login: invalid credentials")
		}
		return m.issueToken(rec.User)

	case errors.Is(err, userstore.ErrUserNotFound):
		// Possible just-in-time LDAP provisioning.
		if tid := m.jitTenant(ctx, identifier); tid != nil {
			return m.ldapLogin(ctx, *tid, identifier, password, ip, nil)
		}
		m.store.BurnPasswordTiming(password)
		return "", nil, fmt.Errorf("auth: login: invalid credentials")

	default:
		return "", nil, fmt.Errorf("auth: login: %w", err)
	}
}

// jitTenant returns the tenant ID an unknown identifier may be provisioned
// into: the identifier's email domain must map to a tenant that has an enabled
// LDAP config. Returns nil when JIT is not applicable.
func (m *Manager) jitTenant(ctx context.Context, identifier string) *int64 {
	if m.ldap == nil {
		return nil
	}
	at := strings.LastIndex(identifier, "@")
	if at < 0 || at == len(identifier)-1 {
		return nil
	}
	domain := strings.ToLower(identifier[at+1:])
	tid, err := m.ldap.tenants.GetTenantIDByDomain(ctx, domain)
	if err != nil || tid == nil {
		return nil
	}
	cfg, err := m.ldap.store.Get(ctx, *tid)
	if err != nil || !cfg.Enabled {
		return nil
	}
	return tid
}

// ldapLogin performs the LDAP bind, applies role mapping, JIT-provisions or
// re-synchronises the local user, and issues a token. existing may be nil (JIT).
func (m *Manager) ldapLogin(ctx context.Context, tenantID int64, loginName, password, ip string, existing *userstore.User) (string, *userstore.User, error) {
	tid := tenantID
	logFail := func(detail string) {
		m.ldap.audlog.Log(audit.Entry{
			EventType: audit.EventLdapLoginFailed, Username: loginName, IPAddress: ip,
			TenantID: &tid, Success: false, Detail: detail,
		})
	}

	// Rate limit per (tenant, loginName) and per source IP.
	userKey := fmt.Sprintf("u:%d:%s", tenantID, strings.ToLower(loginName))
	if !m.ldap.limiter.allow(userKey) || (ip != "" && !m.ldap.limiter.allow("ip:"+ip)) {
		logFail("rate_limited")
		return "", nil, fmt.Errorf("auth: login: too many attempts")
	}

	cfg, bindPw, err := m.ldap.store.GetWithSecret(ctx, tenantID)
	if err != nil {
		logFail("config_unavailable")
		return "", nil, fmt.Errorf("auth: login: invalid credentials")
	}
	if !cfg.Enabled {
		logFail("ldap_disabled")
		return "", nil, fmt.Errorf("auth: login: invalid credentials")
	}

	res, err := m.ldap.authn.Authenticate(ctx, cfg, bindPw, loginName, password)
	if err != nil {
		logFail("bind_failed")
		return "", nil, fmt.Errorf("auth: login: invalid credentials")
	}

	// Role mapping: admin group membership -> domain_admin, else user.
	// LDAP can NEVER confer superadmin.
	role := userstore.RoleUser
	if res.IsAdmin {
		role = userstore.RoleDomainAdmin
	}

	var user *userstore.User
	if existing == nil {
		username := res.Username
		if username == "" {
			username = loginName
		}
		email := res.Email
		if email == "" {
			email = loginName
		}
		user, err = m.store.CreateLDAPUser(ctx, userstore.LDAPUserRequest{
			Username: username, Email: email, Role: role, LdapUID: res.Username, TenantID: &tid,
		})
		if err != nil {
			logFail("provision_failed")
			return "", nil, fmt.Errorf("auth: login: provisioning failed")
		}
	} else {
		if existing.Role != role && existing.Role != userstore.RoleSuperAdmin {
			m.ldap.audlog.Log(audit.Entry{
				EventType: audit.EventLdapRoleSync, Username: existing.Username, IPAddress: ip,
				TenantID: &tid, Success: true,
				Detail:   fmt.Sprintf("role %s -> %s", existing.Role, role),
			})
		}
		// Never downgrade a superadmin via LDAP (defensive; LDAP accounts are
		// never superadmin, but guard against manual DB edits).
		syncRole := role
		if existing.Role == userstore.RoleSuperAdmin {
			syncRole = userstore.RoleSuperAdmin
		}
		email := res.Email
		if email == "" {
			email = existing.Email
		}
		if err := m.store.SyncLDAPUser(ctx, existing.ID, email, syncRole); err != nil {
			logFail("sync_failed")
			return "", nil, fmt.Errorf("auth: login: sync failed")
		}
		user, err = m.store.GetByID(existing.ID)
		if err != nil {
			logFail("reload_failed")
			return "", nil, fmt.Errorf("auth: login: reload failed")
		}
	}

	m.ldap.audlog.Log(audit.Entry{
		EventType: audit.EventLdapLoginSuccess, Username: user.Username, IPAddress: ip,
		TenantID: &tid, Success: true, Detail: "role:" + user.Role,
	})
	return m.issueToken(user)
}

func derefTenant(t *int64) int64 {
	if t == nil {
		return 0
	}
	return *t
}

func (m *Manager) issueToken(user *userstore.User) (string, *userstore.User, error) {
	jti := generateJTI()
	now := time.Now()

	claims := jwt.MapClaims{
		"sub":   user.Username,
		"email": user.Email,
		"role":  user.Role,
		"uid":   user.ID,
		"jti":   jti,
		"iat":   now.Unix(),
		"exp":   now.Add(8 * time.Hour).Unix(),
	}
	if user.TenantID != nil {
		claims["tenant_id"] = *user.TenantID
	}

	token := jwt.NewWithClaims(jwt.SigningMethodHS256, claims)
	signed, err := token.SignedString(m.jwtSecret)
	if err != nil {
		return "", nil, fmt.Errorf("auth: sign token: %w", err)
	}
	return signed, user, nil
}

// ValidateToken parses and validates the token, checking the blacklist.
func (m *Manager) ValidateToken(tokenStr string) (*Session, error) {
	token, err := jwt.Parse(tokenStr, func(t *jwt.Token) (interface{}, error) {
		if _, ok := t.Method.(*jwt.SigningMethodHMAC); !ok {
			return nil, fmt.Errorf("auth: unexpected signing method: %v", t.Header["alg"])
		}
		return m.jwtSecret, nil
	})
	if err != nil {
		return nil, fmt.Errorf("auth: invalid token: %w", err)
	}
	if !token.Valid {
		return nil, errors.New("auth: token not valid")
	}

	claims, ok := token.Claims.(jwt.MapClaims)
	if !ok {
		return nil, errors.New("auth: bad claims")
	}

	jti, _ := claims["jti"].(string)
	blacklisted, err := m.store.IsBlacklisted(jti)
	if err != nil {
		return nil, fmt.Errorf("auth: blacklist check: %w", err)
	}
	if blacklisted {
		return nil, errors.New("auth: token revoked")
	}

	username, _ := claims["sub"].(string)
	email, _ := claims["email"].(string)
	role, _ := claims["role"].(string)

	var userID int64
	switch v := claims["uid"].(type) {
	case float64:
		userID = int64(v)
	case int64:
		userID = v
	}

	var tenantID *int64
	switch v := claims["tenant_id"].(type) {
	case float64:
		id := int64(v)
		tenantID = &id
	case int64:
		id := v
		tenantID = &id
	}

	return &Session{
		UserID:   userID,
		Username: username,
		Email:    email,
		Role:     role,
		JTI:      jti,
		TenantID: tenantID,
	}, nil
}

// Logout revokes the token by adding its JTI to the blacklist.
func (m *Manager) Logout(tokenStr string) error {
	token, err := jwt.Parse(tokenStr, func(t *jwt.Token) (interface{}, error) {
		if _, ok := t.Method.(*jwt.SigningMethodHMAC); !ok {
			return nil, fmt.Errorf("auth: unexpected signing method")
		}
		return m.jwtSecret, nil
	})
	if err != nil {
		return fmt.Errorf("auth: logout parse: %w", err)
	}
	claims, ok := token.Claims.(jwt.MapClaims)
	if !ok {
		return errors.New("auth: bad claims on logout")
	}
	jti, _ := claims["jti"].(string)
	var exp time.Time
	switch v := claims["exp"].(type) {
	case float64:
		exp = time.Unix(int64(v), 0)
	case int64:
		exp = time.Unix(v, 0)
	default:
		exp = time.Now().Add(8 * time.Hour)
	}
	return m.store.BlacklistToken(jti, exp)
}

// HasRole returns true when userRole satisfies the required role level.
// Hierarchy: superadmin > domain_admin > user
func HasRole(userRole, required string) bool {
	levels := map[string]int{
		userstore.RoleUser:        1,
		userstore.RoleDomainAdmin: 2,
		userstore.RoleSuperAdmin:  3,
	}
	return levels[userRole] >= levels[required]
}

// generateJTI returns a cryptographically random identifier for a JWT.
func generateJTI() string {
	b := make([]byte, 16)
	if _, err := rand.Read(b); err != nil {
		return fmt.Sprintf("%d", time.Now().UnixNano())
	}
	return hex.EncodeToString(b)
}

// GetUserStore returns the underlying user store.
func (m *Manager) GetUserStore() *userstore.Store {
	return m.store
}