package database

import (
	"context"
	"database/sql"
	"errors"
	"fmt"
)

// LocalMetaKeyStorageURL is the key under which the destination store's
// URL is recorded when a mutating command first binds the local index
// to a specific backup destination.
const LocalMetaKeyStorageURL = "storage_url"

// LocalMetaRepository provides keyed access to host-local settings
// stored in the local_meta table.
type LocalMetaRepository struct {
	db *DB
}

func NewLocalMetaRepository(db *DB) *LocalMetaRepository {
	return &LocalMetaRepository{db: db}
}

// Get returns the value stored at key, or the empty string if the key
// is not set. A missing key is not an error — the caller distinguishes
// "unset" (bind on first use) from "set to something" (compare).
func (r *LocalMetaRepository) Get(ctx context.Context, key string) (string, error) {
	var value string
	err := r.db.conn.QueryRowContext(ctx,
		"SELECT value FROM local_meta WHERE key = ?", key,
	).Scan(&value)
	if errors.Is(err, sql.ErrNoRows) {
		return "", nil
	}
	if err != nil {
		return "", fmt.Errorf("reading local_meta %q: %w", key, err)
	}
	return value, nil
}

// Set writes key=value, replacing any prior value.
func (r *LocalMetaRepository) Set(ctx context.Context, key, value string) error {
	_, err := r.db.ExecWithLog(ctx,
		`INSERT INTO local_meta (key, value) VALUES (?, ?)
		 ON CONFLICT(key) DO UPDATE SET value = excluded.value`,
		key, value,
	)
	if err != nil {
		return fmt.Errorf("writing local_meta %q: %w", key, err)
	}
	return nil
}