// pkg/migrate/migrate.go
package migrate

import (
	"context"
	"embed"
	"fmt"
	"io/fs"
	"sort"
	"strconv"
	"strings"

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

func Run(ctx context.Context, conn *pgx.Conn, migrationsFS embed.FS) error {
	// Get already applied migrations
	rows, _ := conn.Query(ctx, "SELECT version FROM schema_migrations")
	defer rows.Close()

	applied := make(map[int64]bool)
	for rows.Next() {
		var version int64
		if err := rows.Scan(&version); err != nil {
			return err
		}
		applied[version] = true
	}

	files, err := migrationsFS.ReadDir("migrations")
	if err != nil {
		return err
	}

	// Apply the migrations sequentially based on their ordinal number
	for _, f := range sortMigrations(files) {
		version, err := strconv.ParseInt(strings.Split(f.Name(), "_")[0], 10, 64)
		if err != nil {
			return fmt.Errorf("invalid migration name: %s", f.Name())
		}

		if applied[version] {
			continue
		}

		// Run migration
		sql, err := migrationsFS.ReadFile("migrations/" + f.Name())
		if err != nil {
			return err
		}

		if _, err := conn.Exec(ctx, string(sql)); err != nil {
			return fmt.Errorf("migration %d failed: %w", version, err)
		}

		if _, err := conn.Exec(ctx,
			"INSERT INTO schema_migrations (version) VALUES ($1)", version,
		); err != nil {
			return err
		}
	}

	return nil
}

// Sort the migration files based on their ordinal number prefix.
func sortMigrations(files []fs.DirEntry) []fs.DirEntry {
	sort.Slice(files, func(i, j int) bool {
		v1, _ := strconv.ParseInt(strings.Split(files[i].Name(), "_")[0], 10, 64)
		v2, _ := strconv.ParseInt(strings.Split(files[j].Name(), "_")[0], 10, 64)
		return v1 < v2
	})
	return files
}