For cases where additional logic is required to determine the URL for a rule, the Cake.Issue addin provides the BaseRuleDescription and BaseRuleUrlResolver classes for simplifying implementation of providing URLs linking to site providing information about issues.

Implementing RuleUrlResolver

In the issue provider a concrete class inheriting from BaseRuleDescription should be implemented containing all properties required to determine the URL to a rule. The following class adds two properties Category and RuleId to the description:

/// <summary>
/// Class describing rules for my issue provider.
/// </summary>
public class MyRuleDescription : BaseRuleDescription
{
    /// <summary>
    /// Gets or sets the category of the rule.
    /// </summary>
    public string Category { get; set; }

    /// <summary>
    /// Gets or sets the identifier of the rule.
    /// </summary>
    public int RuleId { get; set; }
}

Also a class inheriting from BaseRuleUrlResolver needs to be implemented containing an implementation of TryGetRuleDescription for parsing rule urls to the concrete BaseRuleDescription class.

/// <summary>
/// Class for retrieving an URL linking to a site describing a rule.
/// </summary>
internal class MyRuleUrlResolver : BaseUrlResolver<MyRuleDescription>
{
        /// <inheritdoc/>
        protected override bool TryGetRuleDescription(string rule, MyRuleDescription ruleDescription)
        {
            ruleDescription.RuleId = rule.Substring(3, rule.Length - 3);
            ruleDescription.Category = rule.Substring(0, 3);

            return true;
        }
    }

To use the URL resolver the ResolveRuleUrl method needs to be called:

var resolver = new MyRuleUrlResolver();
var url = resolver.ResolveRuleUrl(rule)

Afterwards different resolvers can be registered which return the actual URL based on the rule description:

/// <summary>
/// Class for retrieving an URL linking to a site describing a rule.
/// </summary>
internal class MyRuleUrlResolver : BaseUrlResolver<MyRuleDescription>
{
        /// <summary>
        /// Initializes a new instance of the <see cref="MyRuleUrlResolver"/> class.
        /// </summary>
        private MyRuleUrlResolver()
        {
            // Add resolver for different issue categories.
            this.AddUrlResolver(x =>
                x.Category.ToUpperInvariant() == "FOO" ?
                    new Uri("https://www.google.com/search?q=%22" + x.Rule) :
                    null);
            this.AddUrlResolver(x =>
                x.Category.ToUpperInvariant() == "BAR" ?
                    new Uri("https://www.bing.com/search?q=%22" + x.Rule) :
                    null);
        }
    }

Support custom URL resolvers

The AddUrlResolver method can also be called from an Cake alias to allow users of the addin to register custom resolvers. For this the URL resolver class needs to be implemented as a singleton:

/// <summary>
/// Class for retrieving an URL linking to a site describing a rule.
/// </summary>
internal class MyRuleUrlResolver : BaseUrlResolver<MyRuleDescription>
{
    private static readonly Lazy<MyRuleUrlResolver> InstanceValue =
        new Lazy<MyRuleUrlResolver>(() => new MyRuleUrlResolver());

    /// <summary>
    /// Gets the instance of the rule resolver.
    /// </summary>
    public static MyRuleUrlResolver Instance => InstanceValue.Value;
}

[CakeAliasCategory(IssuesAliasConstants.MainCakeAliasCategory)]
public static class MyIssueProviderAliases
{
    /// <summary>
    /// Registers a new URL resolver with default priority of 0.
    /// </summary>
    /// <param name="context">The context.</param>
    /// <param name="resolver">Resolver which returns an <see cref="Uri"/> linking to a site
    /// containing help for a specific <see cref="MyRuleDescription"/>.</param>
    [CakeMethodAlias]
    [CakeAliasCategory(IssuesAliasConstants.IssueProviderCakeAliasCategory)]
    public static void MyIssueProviderAddRuleUrlResolver(
        this ICakeContext context,
        Func<MyRuleDescription, Uri> resolver)
    {
        context.NotNull(nameof(context));
        resolver.NotNull(nameof(resolver));

        MyRuleUrlResolver.Instance.AddUrlResolver(resolver);
    }