package db

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

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

func RunMigrations(ctx context.Context, pool *pgxpool.Pool, dir string) error {
	if _, err := pool.Exec(ctx, `
		create table if not exists schema_migrations (
			filename text primary key,
			applied_at timestamptz not null default now()
		)
	`); err != nil {
		return fmt.Errorf("create schema_migrations: %w", err)
	}

	entries, err := os.ReadDir(dir)
	if err != nil {
		return fmt.Errorf("read migrations dir: %w", err)
	}

	var files []string
	for _, entry := range entries {
		if entry.IsDir() || filepath.Ext(entry.Name()) != ".sql" {
			continue
		}
		files = append(files, entry.Name())
	}
	sort.Strings(files)

	for _, name := range files {
		var exists bool
		if err := pool.QueryRow(ctx, `select exists(select 1 from schema_migrations where filename = $1)`, name).Scan(&exists); err != nil {
			return fmt.Errorf("check migration %s: %w", name, err)
		}
		if exists {
			continue
		}

		body, err := os.ReadFile(filepath.Join(dir, name))
		if err != nil {
			return fmt.Errorf("read migration %s: %w", name, err)
		}

		tx, err := pool.Begin(ctx)
		if err != nil {
			return fmt.Errorf("begin migration %s: %w", name, err)
		}

		if _, err := tx.Exec(ctx, string(body)); err != nil {
			_ = tx.Rollback(ctx)
			return fmt.Errorf("execute migration %s: %w", name, err)
		}

		if _, err := tx.Exec(ctx, `insert into schema_migrations (filename) values ($1)`, name); err != nil {
			_ = tx.Rollback(ctx)
			return fmt.Errorf("record migration %s: %w", name, err)
		}

		if err := tx.Commit(ctx); err != nil {
			return fmt.Errorf("commit migration %s: %w", name, err)
		}
	}

	return nil
}