package db

import (
	"context"
	"database/sql"
)

// PrunableTarget holds the data needed to delete the file and clean the database.
type PrunableTarget struct {
	MessageID int64
	BlobHash  string
}

// GetPrunableTargets reports whether it is safe to remove a file from the db perspective
func (db *DB) GetPrunableTargets(ctx context.Context) ([]PrunableTarget, error) {
	rows, err := db.read.QueryContext(
		ctx, `SELECT id, blob_address 
FROM messages 
WHERE id NOT IN (SELECT message_id FROM mailbox_messages)`)

	if err != nil {
		return nil, err
	}

	defer func(rows *sql.Rows) {
		_ = rows.Close()
	}(rows)

	out := make([]PrunableTarget, 0)
	for rows.Next() {
		var pt PrunableTarget
		if err := rows.Scan(&pt.MessageID, &pt.BlobHash); err != nil {
			return nil, err
		}
		out = append(out, pt)
	}

	return out, nil
}

// DeleteMessage deletes the message which is usually part of the pruning process
func (db *DB) DeleteMessage(ctx context.Context, id int64) error {
	_, err := db.read.ExecContext(ctx, `DELETE FROM messages WHERE id = ?`, id)
	return err
}