package repository

import (
	"context"
	"errors"
	"strings"

	"gorm.io/gorm"

	"github.com/dhao2001/mygo/internal/model"
)

// isDuplicateKeyError checks if the error indicates a unique constraint violation.
func isDuplicateKeyError(err error) bool {
	return errors.Is(err, gorm.ErrDuplicatedKey) || strings.Contains(strings.ToLower(err.Error()), "unique constraint failed")
}

// UserRepository provides access to user records.
type UserRepository interface {
	Create(ctx context.Context, user *model.User) error
	FindByID(ctx context.Context, id string) (*model.User, error)
	FindByEmail(ctx context.Context, email string) (*model.User, error)
	FindByUsername(ctx context.Context, username string) (*model.User, error)
	Update(ctx context.Context, user *model.User) error
	Delete(ctx context.Context, id string) error
	List(ctx context.Context, offset, limit int) ([]model.User, int64, error)
}

type userRepository struct {
	db *gorm.DB
}

// NewUserRepository creates a UserRepository backed by GORM.
func NewUserRepository(db *gorm.DB) UserRepository {
	return &userRepository{db: db}
}

func (r *userRepository) Create(ctx context.Context, user *model.User) error {
	result := r.db.WithContext(ctx).Create(user)
	if result.Error != nil {
		if isDuplicateKeyError(result.Error) {
			return model.ErrDuplicate
		}
		return result.Error
	}
	return nil
}

func (r *userRepository) FindByID(ctx context.Context, id string) (*model.User, error) {
	var user model.User
	result := r.db.WithContext(ctx).First(&user, "id = ?", id)
	if errors.Is(result.Error, gorm.ErrRecordNotFound) {
		return nil, model.ErrNotFound
	}
	if result.Error != nil {
		return nil, result.Error
	}
	return &user, nil
}

func (r *userRepository) FindByEmail(ctx context.Context, email string) (*model.User, error) {
	var user model.User
	result := r.db.WithContext(ctx).First(&user, "email = ?", email)
	if errors.Is(result.Error, gorm.ErrRecordNotFound) {
		return nil, model.ErrNotFound
	}
	if result.Error != nil {
		return nil, result.Error
	}
	return &user, nil
}

func (r *userRepository) FindByUsername(ctx context.Context, username string) (*model.User, error) {
	var user model.User
	result := r.db.WithContext(ctx).First(&user, "username = ?", username)
	if errors.Is(result.Error, gorm.ErrRecordNotFound) {
		return nil, model.ErrNotFound
	}
	if result.Error != nil {
		return nil, result.Error
	}
	return &user, nil
}

func (r *userRepository) Update(ctx context.Context, user *model.User) error {
	result := r.db.WithContext(ctx).Save(user)
	if result.Error != nil {
		if isDuplicateKeyError(result.Error) {
			return model.ErrDuplicate
		}
		return result.Error
	}
	return nil
}

func (r *userRepository) Delete(ctx context.Context, id string) error {
	result := r.db.WithContext(ctx).Delete(&model.User{}, "id = ?", id)
	if result.Error != nil {
		return result.Error
	}
	return nil
}

func (r *userRepository) List(ctx context.Context, offset, limit int) ([]model.User, int64, error) {
	var users []model.User
	var total int64

	if err := r.db.WithContext(ctx).Model(&model.User{}).Count(&total).Error; err != nil {
		return nil, 0, err
	}

	result := r.db.WithContext(ctx).Offset(offset).Limit(limit).Find(&users)
	if result.Error != nil {
		return nil, 0, result.Error
	}

	return users, total, nil
}