package user

import (
	"encoding/json"
	"errors"
	"time"

	"github.com/shopspring/decimal"
	"go.uber.org/zap"
	"gorm.io/gorm"

	"openteam/server/internal/config"
	"openteam/server/internal/pkg/jwt"
	"openteam/server/internal/pkg/password"
	"openteam/server/internal/store"
)

var (
	ErrUserExists     = errors.New("username or email already exists")
	ErrBadCredentials = errors.New("invalid username/email or password")
	ErrUserDisabled   = errors.New("account disabled")
	ErrInvalidRefresh = errors.New("invalid refresh token")
)

type Service struct {
	db  *gorm.DB
	cfg *config.Config
	log *zap.Logger
}

func NewService(db *gorm.DB, cfg *config.Config, log *zap.Logger) *Service {
	return &Service{db: db, cfg: cfg, log: log}
}

type RegisterInput struct {
	Username   string `json:"username" binding:"required,min=3,max=64"`
	Email      string `json:"email" binding:"required,email"`
	Password   string `json:"password" binding:"required,min=8,max=128"`
	InviteCode string `json:"inviteCode"`
}

type TokenPair struct {
	AccessToken  string `json:"accessToken"`
	TokenType    string `json:"tokenType"`
	ExpiresIn    int64  `json:"expiresIn"`
	RefreshToken string `json:"refreshToken"`
}

// Register creates a user. Returns a token pair plus the created user.
func (s *Service) Register(in RegisterInput) (*store.User, *TokenPair, error) {
	if s.cfg.Registration.Mode == "invite" {
		// Invite mode: validate the invite code before allowing signup.
		ok, err := s.validateInviteCode(in.InviteCode)
		if err != nil {
			return nil, nil, err
		}
		if !ok {
			return nil, nil, errors.New("invalid invite code")
		}
	}

	hash, err := password.Hash(in.Password)
	if err != nil {
		return nil, nil, err
	}
	u := &store.User{
		Username:     in.Username,
		Email:        in.Email,
		PasswordHash: hash,
		Role:         "user",
		Balance:      decimalZero(),
		Status:       "active",
		InviteCode:   in.InviteCode,
	}
	if err := s.db.Create(u).Error; err != nil {
		if errors.Is(err, gorm.ErrDuplicatedKey) {
			return nil, nil, ErrUserExists
		}
		return nil, nil, err
	}
	pair, err := s.issuePair(u)
	if err != nil {
		return nil, nil, err
	}
	return u, pair, nil
}

type LoginInput struct {
	Account  string `json:"account" binding:"required"` // username or email
	Password string `json:"password" binding:"required"`
}

// Login authenticates by username or email and returns a token pair.
func (s *Service) Login(in LoginInput) (*store.User, *TokenPair, error) {
	var u store.User
	err := s.db.Where("username = ? OR email = ?", in.Account, in.Account).First(&u).Error
	if errors.Is(err, gorm.ErrRecordNotFound) {
		return nil, nil, ErrBadCredentials
	}
	if err != nil {
		return nil, nil, err
	}
	ok, err := password.Verify(in.Password, u.PasswordHash)
	if err != nil || !ok {
		return nil, nil, ErrBadCredentials
	}
	if u.Status != "active" {
		return nil, nil, ErrUserDisabled
	}
	now := time.Now()
	u.LastLoginAt = &now
	s.db.Model(&u).Update("last_login_at", now)
	pair, err := s.issuePair(&u)
	if err != nil {
		return nil, nil, err
	}
	return &u, pair, nil
}

// Refresh issues a new access token from a valid refresh token.
func (s *Service) Refresh(refreshToken string) (*TokenPair, error) {
	claims, err := jwt.Parse(s.cfg.Auth.JWTSecret, refreshToken)
	if err != nil || claims.Type != "refresh" {
		return nil, ErrInvalidRefresh
	}
	var u store.User
	if err := s.db.First(&u, claims.UserID).Error; err != nil {
		return nil, ErrInvalidRefresh
	}
	if u.Status != "active" {
		return nil, ErrUserDisabled
	}
	return s.issuePair(&u)
}

// GetByID loads a user.
func (s *Service) GetByID(id int64) (*store.User, error) {
	var u store.User
	if err := s.db.First(&u, id).Error; err != nil {
		return nil, err
	}
	return &u, nil
}

// GetPublic returns a user DTO without secrets.
func GetPublic(u *store.User) map[string]any {
	return map[string]any{
		"id":         u.ID,
		"username":   u.Username,
		"email":      u.Email,
		"role":       u.Role,
		"balance":    u.Balance.String(),
		"status":     u.Status,
		"createdAt":  u.CreatedAt,
		"lastLoginAt": u.LastLoginAt,
	}
}

func (s *Service) validateInviteCode(code string) (bool, error) {
	var conf store.SystemConfig
	if err := s.db.First(&conf, "key = ?", "invite_codes").Error; err != nil {
		return false, nil
	}
	var codes map[string]bool
	if len(conf.Value) > 0 {
		if err := json.Unmarshal(conf.Value, &codes); err != nil {
			return false, err
		}
	}
	return codes[code], nil
}

func (s *Service) issuePair(u *store.User) (*TokenPair, error) {
	access, err := jwt.SignAccess(s.cfg.Auth.JWTSecret, u.ID, u.Username, u.Role, s.cfg.Auth.AccessTokenTTL)
	if err != nil {
		return nil, err
	}
	refresh, err := jwt.SignRefresh(s.cfg.Auth.JWTSecret, u.ID, s.cfg.Auth.RefreshTokenTTL)
	if err != nil {
		return nil, err
	}
	return &TokenPair{
		AccessToken: access,
		TokenType:   "Bearer",
		ExpiresIn:   int64(s.cfg.Auth.AccessTokenTTL.Seconds()),
		RefreshToken: refresh,
	}, nil
}

func decimalZero() decimal.Decimal {
	return decimal.NewFromInt(0)
}