package store

import (
	"embed"
	"fmt"
	"sort"
	"strconv"
	"strings"
	"time"
)

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

func (s *Store) applyMigrations() error {
	if _, err := s.db.Exec(`
		CREATE TABLE IF NOT EXISTS schema_migrations (
			version    INTEGER PRIMARY KEY,
			applied_at INTEGER NOT NULL
		)
	`); err != nil {
		return fmt.Errorf("bootstrap schema_migrations: %w", err)
	}

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

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

	for _, name := range files {
		version, err := migrationVersion(name)
		if err != nil {
			return err
		}

		applied, err := s.isMigrationApplied(version)
		if err != nil {
			return err
		}
		if applied {
			continue
		}

		sqlBytes, err := migrationFS.ReadFile("migrations/" + name)
		if err != nil {
			return fmt.Errorf("read migration %s: %w", name, err)
		}

		if _, err := s.db.Exec(string(sqlBytes)); err != nil {
			return fmt.Errorf("apply migration %s: %w", name, err)
		}

		if _, err := s.db.Exec(
			`INSERT INTO schema_migrations (version, applied_at) VALUES (?, ?)`,
			version, time.Now().Unix(),
		); err != nil {
			return fmt.Errorf("record migration %s: %w", name, err)
		}
	}

	return nil
}

func migrationVersion(name string) (int, error) {
	prefix := strings.SplitN(name, "_", 2)[0]
	version, err := strconv.Atoi(prefix)
	if err != nil {
		return 0, fmt.Errorf("invalid migration filename %q: %w", name, err)
	}
	return version, nil
}

func (s *Store) isMigrationApplied(version int) (bool, error) {
	var count int
	err := s.db.QueryRow(
		`SELECT COUNT(*) FROM schema_migrations WHERE version = ?`,
		version,
	).Scan(&count)
	if err != nil {
		return false, err
	}
	return count > 0, nil
}