package store

import (
	"context"
)

// Reaction represents a single emoji reaction on a message.
type Reaction struct {
	MessageID int64
	UserID    int64
	Emoji     string
}

// AddReaction adds a reaction to a message; it is a no-op if it already exists.
func (s *Store) AddReaction(ctx context.Context, messageID, userID int64, emoji string) error {
	_, err := s.pool.Exec(ctx, `
       INSERT INTO message_reactions(message_id, user_id, emoji)
       VALUES($1, $2, $3)
       ON CONFLICT (message_id, user_id, emoji) DO NOTHING
   `, messageID, userID, emoji)
	return err
}

// RemoveReaction removes a reaction from a message; it is a no-op if absent.
func (s *Store) RemoveReaction(ctx context.Context, messageID, userID int64, emoji string) error {
	_, err := s.pool.Exec(ctx, `
       DELETE FROM message_reactions WHERE message_id=$1 AND user_id=$2 AND emoji=$3
   `, messageID, userID, emoji)
	return err
}

// ReactionsForMessages returns all reactions for the given message IDs.
func (s *Store) ReactionsForMessages(ctx context.Context, messageIDs []int64) ([]Reaction, error) {
	if len(messageIDs) == 0 {
		return nil, nil
	}
	rows, err := s.pool.Query(ctx, `
       SELECT message_id, user_id, emoji
       FROM message_reactions
       WHERE message_id = ANY($1)
       ORDER BY message_id, created_at
   `, messageIDs)
	if err != nil {
		return nil, err
	}
	defer rows.Close()

	var reactions []Reaction
	for rows.Next() {
		var r Reaction
		if err := rows.Scan(&r.MessageID, &r.UserID, &r.Emoji); err != nil {
			return nil, err
		}
		reactions = append(reactions, r)
	}
	return reactions, nil
}

// MessageBelongsToConversation reports whether a message belongs to a conversation.
func (s *Store) MessageBelongsToConversation(ctx context.Context, conversationID, messageID int64) (bool, error) {
	var exists bool
	err := s.pool.QueryRow(ctx, `
       SELECT EXISTS(
           SELECT 1 FROM messages WHERE id=$1 AND conversation_id=$2
       )
   `, messageID, conversationID).Scan(&exists)
	if err != nil {
		return false, err
	}
	return exists, nil
}