prefab-page-detail/Prefab.Web/UrlPolicy/UrlPolicy.cs

using System.Collections.Generic;
using System.Globalization;
using System.Linq;
using Microsoft.AspNetCore.WebUtilities;
using Microsoft.Extensions.Primitives;

namespace Prefab.Web.UrlPolicy;

/// <summary>
/// Provides centralized helpers for building canonical catalog URLs used by the BFF.
/// </summary>
public static class UrlPolicy
{
    public const int DefaultPage = 1;
    public const int DefaultPageSize = 24;
    public const string DefaultSort = "name:asc";
    public const string DefaultView = "grid";

    private static readonly int[] AllowedPageSizes = [12, 24, 48];

    /// <summary>
    /// Builds a canonical catalog URL for navigating to a category landing page.
    /// </summary>
    /// <param name="slug">The category slug to embed in the query string.</param>
    public static string BrowseCategory(string slug)
    {
        ArgumentException.ThrowIfNullOrWhiteSpace(slug);
        return $"/catalog/category?category-slug={Uri.EscapeDataString(slug)}";
    }

    /// <summary>
    /// Builds a canonical catalog URL for navigating to the products grid for a category.
    /// </summary>
    /// <param name="categorySlug">The slug of the category whose products should be displayed.</param>
    public static string BrowseProducts(string categorySlug)
    {
        ArgumentException.ThrowIfNullOrWhiteSpace(categorySlug);
        return $"/catalog/products?category-slug={Uri.EscapeDataString(categorySlug)}";
    }

    /// <summary>
    /// Builds a canonical catalog URL for navigating to a specific product detail page.
    /// </summary>
    /// <param name="slug">The slug of the product.</param>
    public static string BrowseProduct(string slug)
    {
        ArgumentException.ThrowIfNullOrWhiteSpace(slug);
        return $"/browse/product?slug={Uri.EscapeDataString(slug)}";
    }

    /// <summary>
    /// Builds a canonical catalog URL for the category browsing experience including paging state.
    /// </summary>
    public static string Category(
        string slug,
        int page = DefaultPage,
        int pageSize = DefaultPageSize,
        string? sort = null,
        string? view = null)
    {
        ArgumentException.ThrowIfNullOrWhiteSpace(slug);

        var normalizedPage = NormalizePage(page);
        var normalizedPageSize = NormalizePageSize(pageSize);
        var normalizedSort = NormalizeSort(sort);
        var normalizedView = NormalizeView(view);

        var parameters = new Dictionary<string, string?>(StringComparer.OrdinalIgnoreCase)
        {
            ["slug"] = slug,
            ["page"] = normalizedPage.ToString(CultureInfo.InvariantCulture),
            ["pageSize"] = normalizedPageSize.ToString(CultureInfo.InvariantCulture),
            ["sort"] = normalizedSort,
            ["view"] = normalizedView
        };

        return QueryHelpers.AddQueryString("/catalog/category", parameters);
    }

    /// <summary>
    /// Attempts to parse the catalog category browse URL parameters.
    /// </summary>
    public static bool TryParseCategory(
        Uri uri,
        out string slug,
        out int page,
        out int pageSize,
        out string sort,
        out string view)
    {
        ArgumentNullException.ThrowIfNull(uri);

        slug = string.Empty;
        page = DefaultPage;
        pageSize = DefaultPageSize;
        sort = DefaultSort;
        view = DefaultView;

        var queryValues = ParseQuery(uri);
        if (!queryValues.TryGetValue("slug", out var slugValues))
        {
            return false;
        }

        var candidateSlug = slugValues.ToString();
        if (string.IsNullOrWhiteSpace(candidateSlug))
        {
            return false;
        }

        slug = candidateSlug;
        page = NormalizePage(ParseInt(queryValues, "page", DefaultPage));
        pageSize = NormalizePageSize(ParseInt(queryValues, "pageSize", DefaultPageSize));
        sort = NormalizeSort(queryValues.TryGetValue("sort", out var sortValues) ? sortValues.ToString() : null);
        view = NormalizeView(queryValues.TryGetValue("view", out var viewValues) ? viewValues.ToString() : null);

        return true;
    }

    /// <summary>
    /// Builds a canonical catalog URL for browsing products without a category context.
    /// </summary>
    public static string Products(
        int page = DefaultPage,
        int pageSize = DefaultPageSize,
        string? sort = null,
        string? view = null)
    {
        var normalizedPage = NormalizePage(page);
        var normalizedPageSize = NormalizePageSize(pageSize);
        var normalizedSort = NormalizeSort(sort);
        var normalizedView = NormalizeView(view);

        var parameters = new Dictionary<string, string?>(StringComparer.OrdinalIgnoreCase)
        {
            ["page"] = normalizedPage.ToString(CultureInfo.InvariantCulture),
            ["pageSize"] = normalizedPageSize.ToString(CultureInfo.InvariantCulture),
            ["sort"] = normalizedSort,
            ["view"] = normalizedView
        };

        return QueryHelpers.AddQueryString("/catalog/products", parameters);
    }

    /// <summary>
    /// Attempts to parse the products browse URL parameters.
    /// </summary>
    public static bool TryParseProducts(
        Uri uri,
        out int page,
        out int pageSize,
        out string sort,
        out string view)
    {
        ArgumentNullException.ThrowIfNull(uri);

        page = DefaultPage;
        pageSize = DefaultPageSize;
        sort = DefaultSort;
        view = DefaultView;

        var queryValues = ParseQuery(uri);

        page = NormalizePage(ParseInt(queryValues, "page", DefaultPage));
        pageSize = NormalizePageSize(ParseInt(queryValues, "pageSize", DefaultPageSize));
        sort = NormalizeSort(queryValues.TryGetValue("sort", out var sortValues) ? sortValues.ToString() : null);
        view = NormalizeView(queryValues.TryGetValue("view", out var viewValues) ? viewValues.ToString() : null);

        return true;
    }

    private static IDictionary<string, StringValues> ParseQuery(Uri uri)
    {
        var querySegment = uri.IsAbsoluteUri ? uri.Query : uri.OriginalString;
        if (string.IsNullOrEmpty(querySegment))
        {
            return new Dictionary<string, StringValues>(StringComparer.OrdinalIgnoreCase);
        }

        if (!uri.IsAbsoluteUri)
        {
            var questionIndex = querySegment.IndexOf('?', StringComparison.Ordinal);
            querySegment = questionIndex >= 0 ? querySegment[questionIndex..] : string.Empty;
        }

        if (string.IsNullOrEmpty(querySegment))
        {
            return new Dictionary<string, StringValues>(StringComparer.OrdinalIgnoreCase);
        }

        return QueryHelpers.ParseQuery(querySegment);
    }

    private static int ParseInt(IDictionary<string, StringValues> values, string key, int fallback)
    {
        if (values.TryGetValue(key, out var raw) &&
            int.TryParse(raw.ToString(), NumberStyles.Integer, CultureInfo.InvariantCulture, out var parsed))
        {
            return parsed;
        }

        return fallback;
    }

    private static int NormalizePage(int page) => page < 1 ? DefaultPage : page;

    private static int NormalizePageSize(int pageSize) =>
        AllowedPageSizes.Contains(pageSize) ? pageSize : DefaultPageSize;

    private static string NormalizeSort(string? sort) =>
        string.IsNullOrWhiteSpace(sort) ? DefaultSort : sort.Trim();

    private static string NormalizeView(string? view) =>
        string.IsNullOrWhiteSpace(view) ? DefaultView : view.Trim().ToLowerInvariant();
}