package main

import (
	"context"
	"database/sql"
	"log/slog"
	"os"
	"os/signal"
	"path/filepath"
	"sort"
	"strings"
	"syscall"

	_ "github.com/jackc/pgx/v5/stdlib"
)

func main() {
	logger := slog.New(slog.NewTextHandler(os.Stdout, nil))
	databaseURL := os.Getenv("DATABASE_URL")
	if databaseURL == "" {
		logger.Error("DATABASE_URL is required")
		os.Exit(1)
	}
	directory := os.Getenv("MIGRATIONS_DIR")
	if directory == "" {
		directory = "migrations"
	}
	ctx, stop := signal.NotifyContext(context.Background(), syscall.SIGINT, syscall.SIGTERM)
	defer stop()
	db, err := sql.Open("pgx", databaseURL)
	if err != nil {
		logger.Error("database open failed", "error", err)
		os.Exit(1)
	}
	defer db.Close()
	if err := migrate(ctx, db, directory, logger); err != nil {
		logger.Error("migration failed", "error", err)
		os.Exit(1)
	}
}

func migrate(ctx context.Context, db *sql.DB, directory string, logger *slog.Logger) error {
	entries, err := os.ReadDir(directory)
	if err != nil {
		return err
	}
	var names []string
	for _, entry := range entries {
		if !entry.IsDir() && strings.HasSuffix(entry.Name(), ".sql") {
			names = append(names, entry.Name())
		}
	}
	sort.Strings(names)
	if _, err := db.ExecContext(ctx, `CREATE TABLE IF NOT EXISTS stow_schema_migrations (name TEXT PRIMARY KEY, applied_at TIMESTAMPTZ NOT NULL DEFAULT now())`); err != nil {
		return err
	}
	for _, name := range names {
		var applied bool
		if err := db.QueryRowContext(ctx, `SELECT EXISTS (SELECT 1 FROM stow_schema_migrations WHERE name=$1)`, name).Scan(&applied); err != nil {
			return err
		}
		if applied {
			continue
		}
		content, err := os.ReadFile(filepath.Join(directory, name))
		if err != nil {
			return err
		}
		tx, err := db.BeginTx(ctx, nil)
		if err != nil {
			return err
		}
		if _, err := tx.ExecContext(ctx, `SELECT pg_advisory_xact_lock(735160)`); err != nil {
			tx.Rollback()
			return err
		}
		if _, err := tx.ExecContext(ctx, string(content)); err != nil {
			tx.Rollback()
			return err
		}
		if _, err := tx.ExecContext(ctx, `INSERT INTO stow_schema_migrations (name) VALUES ($1)`, name); err != nil {
			tx.Rollback()
			return err
		}
		if err := tx.Commit(); err != nil {
			return err
		}
		logger.Info("applied migration", "name", name)
	}
	return nil
}