package routing

import (
	"fmt"
	"regexp"
	"strings"
)

// validateCronExpression validates a cron expression (simplified)
// Supports standard 5-field cron: minute hour day month weekday
// Does NOT validate all possible edge cases - just basic format
func validateCronExpression(expr string) error {
	fields := strings.Fields(expr)
	if len(fields) != 5 {
		return fmt.Errorf("cron expression must have 5 fields (minute hour day month weekday), got %d", len(fields))
	}

	// Validate field ranges
	ranges := []struct {
		name string
		min  int
		max  int
	}{
		{"minute", 0, 59},
		{"hour", 0, 23},
		{"day", 1, 31},
		{"month", 1, 12},
		{"weekday", 0, 6},
	}

	// Basic pattern: * or */n or n or n-m or n,m or n-m/p
	// This is simplified and doesn't validate all edge cases
	fieldRegex := regexp.MustCompile(`^(\*|(\d+)(,(\d+))*(\/\d+)?|(\d+)-(\d+)(\/\d+)?|\*\/\d+)$`)

	for i, field := range fields {
		if field == "*" {
			continue
		}

		// Check basic format
		if !fieldRegex.MatchString(field) {
			return fmt.Errorf("invalid %s field: %s", ranges[i].name, field)
		}

		// Validate simple number values
		if !strings.ContainsAny(field, "*,-/") {
			var val int
			_, _ = fmt.Sscanf(field, "%d", &val)
			if val < ranges[i].min || val > ranges[i].max {
				return fmt.Errorf("invalid %s value %d (range %d-%d)", ranges[i].name, val, ranges[i].min, ranges[i].max)
			}
		}
	}

	return nil
}