// Package db handles SQLite database setup, pragma configuration, and
// goose migrations.
package db

import (
	"database/sql"
	"embed"
	"errors"
	"fmt"
	"io/fs"
	"log/slog"
	"os"
	"path/filepath"

	"github.com/pressly/goose/v3"
	_ "modernc.org/sqlite"
)

//go:embed migrations/*.sql
var MigrationFS embed.FS

var DB *sql.DB

func Init(dbPath string) (func(), error) {
	if err := os.MkdirAll(filepath.Dir(dbPath), 0o755); err != nil {
		return nil, fmt.Errorf("creating data dir: %w", err)
	}

	// busy_timeout must be first because the connection needs to block on
	// busy before WAL mode is set in case it hasn't been set already.
	pragmas := "?_pragma=busy_timeout(10000)&_pragma=journal_mode(WAL)&_pragma=journal_size_limit(200000000)&_pragma=synchronous(NORMAL)&_pragma=foreign_keys(ON)&_pragma=temp_store(MEMORY)&_pragma=cache_size(-32000)"
	var err error
	DB, err = goose.OpenDBWithDriver("sqlite", dbPath+pragmas)
	if err != nil {
		return nil, fmt.Errorf("opening database: %w", err)
	}

	if err := DB.Ping(); err != nil {
		return nil, errors.Join(fmt.Errorf("pinging database: %w", err), DB.Close())
	}
	slog.Info("db connected", "db", dbPath)

	sub, err := fs.Sub(MigrationFS, "migrations")
	if err != nil {
		return nil, errors.Join(fmt.Errorf("migrations sub fs: %w", err), DB.Close())
	}
	goose.SetBaseFS(sub)

	if err := goose.SetDialect("sqlite3"); err != nil {
		return nil, errors.Join(fmt.Errorf("setting goose dialect: %w", err), DB.Close())
	}
	if err := goose.Up(DB, "."); err != nil {
		return nil, errors.Join(fmt.Errorf("running migrations: %w", err), DB.Close())
	}

	if _, err := DB.Exec("PRAGMA optimize"); err != nil {
		return nil, errors.Join(fmt.Errorf("pragma optimize: %w", err), DB.Close())
	}

	cleanup := func() {
		if _, err := DB.Exec("PRAGMA optimize(0x10002)"); err != nil {
			slog.Error("pragma optimize at shutdown", "error", err)
		}
		if err := DB.Close(); err != nil {
			slog.Error("closing database", "error", err)
		}
	}

	return cleanup, nil
}