// Package messagesvc
// Path: /internal/platform/services/messages
// File: service.go

package messagesvc

import (
	"context"
	"database/sql"
	"errors"
	"time"

	domain "synlotto-website/internal/domain/messages"
)

// Service implements domain.Service.
type Service struct {
	DB      *sql.DB
	Dialect string // "postgres", "mysql", "sqlite"
	Now     func() time.Time
	Timeout time.Duration
}

func New(db *sql.DB, opts ...func(*Service)) *Service {
	s := &Service{
		DB:      db,
		Dialect: "mysql", // default; works with LastInsertId
		Now:     time.Now,
		Timeout: 5 * time.Second,
	}
	for _, opt := range opts {
		opt(s)
	}
	return s
}

// Ensure *Service satisfies the domain interface.
var _ domain.MessageService = (*Service)(nil)

// ToDo: Needs a userId on table or rename the recipiant id.. but then again dont want to expose userids to users for sending.
func (s *Service) ListInbox(userID int64) ([]domain.Message, error) {
	ctx, cancel := context.WithTimeout(context.Background(), s.Timeout)
	defer cancel()

	q := `
		SELECT id, senderId, recipientId, subject, message, is_read, is_archived, created_at
		FROM users_messages
		WHERE recipientId = ? AND is_archived = FALSE
		ORDER BY created_at DESC`
	q = s.bind(q)

	rows, err := s.DB.QueryContext(ctx, q, userID)
	if err != nil {
		return nil, err
	}
	defer rows.Close()

	var out []domain.Message
	for rows.Next() {
		var m domain.Message
		if err := rows.Scan(&m.ID, &m.SenderId, &m.RecipientId, &m.Subject, &m.Body, &m.IsRead, &m.IsArchived, &m.CreatedAt); err != nil {
			return nil, err
		}
		out = append(out, m)
	}

	return out, rows.Err()
}

func (s *Service) ListArchived(userID int64) ([]domain.Message, error) {
	ctx, cancel := context.WithTimeout(context.Background(), s.Timeout)
	defer cancel()

	q := `
		SELECT id, senderId, recipientId, subject, message, is_read, is_archived, created_at
		FROM users_messages
		WHERE recipientId = ? AND is_archived = TRUE
		ORDER BY created_at DESC`
	q = s.bind(q)

	rows, err := s.DB.QueryContext(ctx, q, userID)
	if err != nil {
		return nil, err
	}
	defer rows.Close()

	var out []domain.Message
	for rows.Next() {
		var m domain.Message
		if err := rows.Scan(&m.ID, &m.SenderId, &m.RecipientId, &m.Subject, &m.Body, &m.IsRead, &m.IsArchived, &m.CreatedAt); err != nil {
			return nil, err
		}
		out = append(out, m)
	}
	return out, rows.Err()
}

func (s *Service) GetByID(userID, id int64) (*domain.Message, error) {
	ctx, cancel := context.WithTimeout(context.Background(), s.Timeout)
	defer cancel()

	q := `
		SELECT id, senderId, recipientId, subject, message, is_read, is_archived, created_at
		FROM users_messages
		WHERE recipientId = ? AND id = ?`
	q = s.bind(q)

	var m domain.Message
	err := s.DB.QueryRowContext(ctx, q, userID, id).
		Scan(&m.ID, &m.SenderId, &m.RecipientId, &m.Subject, &m.Body, &m.IsRead, &m.IsArchived, &m.CreatedAt)
	if errors.Is(err, sql.ErrNoRows) {
		return nil, nil
	}
	if err != nil {
		return nil, err
	}
	return &m, nil
}

func (s *Service) Create(userID int64, in domain.CreateMessageInput) (int64, error) {
	ctx, cancel := context.WithTimeout(context.Background(), s.Timeout)
	defer cancel()

	switch s.Dialect {
	case "postgres":
		const q = `
			INSERT INTO messages (id, senderId, recipientId, subject, message, is_read, is_archived, created_at)
			VALUES ($1, $2, $3, $4, $5, FALSE, FALSE, NOW())
			RETURNING id`
		var id int64
		if err := s.DB.QueryRowContext(ctx, q, userID, "", in.RecipientID, in.Subject, in.Body).Scan(&id); err != nil {
			return 0, err
		}
		return id, nil
	default: // mysql/sqlite
		const q = `
			INSERT INTO messages (id, senderId, recipientId, subject, message is_read, is_archived, created_at)
			VALUES (?, ?, ?, ?, ?, FALSE, FALSE, CURRENT_TIMESTAMP)`
		res, err := s.DB.ExecContext(ctx, q, userID, "", in.RecipientID, in.Subject, in.Body)
		if err != nil {
			return 0, err
		}
		return res.LastInsertId()
	}
}

// bind replaces '?' with '$1..' only for Postgres. For MySQL/SQLite it returns q unchanged.
func (s *Service) bind(q string) string {
	if s.Dialect != "postgres" {
		return q
	}
	n := 0
	out := make([]byte, 0, len(q)+8)
	for i := 0; i < len(q); i++ {
		if q[i] == '?' {
			n++
			out = append(out, '$')
			out = append(out, []byte(intToStr(n))...)
			continue
		}
		out = append(out, q[i])
	}
	return string(out)
}

// ToDo: helper dont think it should be here.
func intToStr(n int) string {
	if n == 0 {
		return "0"
	}
	var b [12]byte
	i := len(b)
	for n > 0 {
		i--
		b[i] = byte('0' + n%10)
		n /= 10
	}
	return string(b[i:])
}