package database

import (
	"context"
	"fmt"
)

// List returns every chunk in the index, ordered by chunk hash.
func (r *ChunkRepository) List(ctx context.Context) ([]*Chunk, error) {
	return r.list(ctx, `
		SELECT chunk_hash, size
		FROM chunks
		ORDER BY chunk_hash
	`)
}

// ListInUploadedBlobs returns the chunks that are stored in a blob whose
// upload has completed (uploaded_ts set), ordered by chunk hash. These
// are the only chunks a backup may safely deduplicate against: a chunk
// recorded solely in a blob that was never uploaded refers to data that
// is not in remote storage, so trusting it would silently drop that data
// from later snapshots.
func (r *ChunkRepository) ListInUploadedBlobs(ctx context.Context) ([]*Chunk, error) {
	return r.list(ctx, `
		SELECT DISTINCT c.chunk_hash, c.size
		FROM chunks c
		JOIN blob_chunks bc ON c.chunk_hash = bc.chunk_hash
		JOIN blobs b ON bc.blob_id = b.id
		WHERE b.uploaded_ts IS NOT NULL
		ORDER BY c.chunk_hash
	`)
}

// list runs a chunk-selecting query and scans the (chunk_hash, size) rows.
func (r *ChunkRepository) list(ctx context.Context, query string) ([]*Chunk, error) {
	rows, err := r.db.conn.QueryContext(ctx, query)
	if err != nil {
		return nil, fmt.Errorf("querying chunks: %w", err)
	}

	defer func() {
		err := rows.Close()
		if err != nil {
			Fatalf("failed to close rows: %v", err)
		}
	}()

	var chunks []*Chunk

	for rows.Next() {
		var chunk Chunk

		err := rows.Scan(
			&chunk.ChunkHash,
			&chunk.Size,
		)
		if err != nil {
			return nil, fmt.Errorf("scanning chunk: %w", err)
		}

		chunks = append(chunks, &chunk)
	}

	return chunks, rows.Err()
}