package migrate

import (
	"context"
	"os"
	"path/filepath"
	"sort"
	"strings"

	"github.com/jackc/pgx/v5"
	"github.com/jackc/pgx/v5/pgxpool"
)

const migrationsTable = "laundry_backend.go_schema_migrations"

func Up(ctx context.Context, pool *pgxpool.Pool, dir string) error {
	if _, err := pool.Exec(ctx, `CREATE SCHEMA IF NOT EXISTS laundry_backend`); err != nil {
		return err
	}

	if _, err := pool.Exec(ctx, `
		CREATE TABLE IF NOT EXISTS `+migrationsTable+` (
			version TEXT PRIMARY KEY,
			applied_at TIMESTAMPTZ NOT NULL DEFAULT now()
		)
	`); err != nil {
		return err
	}

	entries, err := os.ReadDir(dir)
	if err != nil {
		return err
	}
	names := make([]string, 0, len(entries))
	for _, e := range entries {
		if e.IsDir() {
			continue
		}
		name := e.Name()
		if strings.HasSuffix(name, ".sql") {
			names = append(names, name)
		}
	}
	sort.Strings(names)

	for _, name := range names {
		if err := applyOne(ctx, pool, dir, name); err != nil {
			return err
		}
	}
	return nil
}

func applyOne(ctx context.Context, pool *pgxpool.Pool, dir, name string) error {
	var exists bool
	if err := pool.QueryRow(ctx, `SELECT EXISTS (SELECT 1 FROM `+migrationsTable+` WHERE version=$1)`, name).Scan(&exists); err != nil {
		return err
	}
	if exists {
		return nil
	}

	sqlBytes, err := os.ReadFile(filepath.Join(dir, name))
	if err != nil {
		return err
	}

	tx, err := pool.BeginTx(ctx, pgx.TxOptions{})
	if err != nil {
		return err
	}
	defer func() { _ = tx.Rollback(ctx) }()

	if _, err := tx.Exec(ctx, string(sqlBytes)); err != nil {
		return err
	}
	if _, err := tx.Exec(ctx, `INSERT INTO `+migrationsTable+` (version) VALUES ($1)`, name); err != nil {
		return err
	}
	return tx.Commit(ctx)
}

var _ = pgx.ErrNoRows