// Package cachedb opens cache.db, the SQLite file in the state directory that
// holds RouteWatch's caches of answers from outside services. It is separate
// from the routes database so that a cache write never queues behind a write
// to that database.
package cachedb

import (
	"context"
	"database/sql"
	_ "embed" // for schema.sql
	"fmt"
	"path/filepath"

	_ "github.com/mattn/go-sqlite3" // CGO SQLite driver
)

const (
	// fileName is the database's file in the state directory.
	fileName = "cache.db"

	// busyTimeoutMs is how long a write waits for another write to finish.
	busyTimeoutMs = 5000
)

//go:embed schema.sql
var schema string

// Open opens cache.db in stateDir, creating the file and its tables when they
// do not exist. The caller closes the database.
func Open(ctx context.Context, stateDir string) (*sql.DB, error) {
	dsn := fmt.Sprintf(
		"file:%s?_journal_mode=WAL&_synchronous=NORMAL&_busy_timeout=%d"+
			"&_txlock=immediate",
		filepath.Join(stateDir, fileName),
		busyTimeoutMs,
	)

	db, err := sql.Open("sqlite3", dsn)
	if err != nil {
		return nil, fmt.Errorf("opening the cache database: %w", err)
	}

	_, err = db.ExecContext(ctx, schema)
	if err != nil {
		_ = db.Close()

		return nil, fmt.Errorf("creating the cache database's tables: %w", err)
	}

	return db, nil
}