LibWeb: Introduce CredentialInterface to handle credentials metadata

The introduction of the abstract `CredentialInterface` class serves to
implement what is mentioned in the spec as "interface objects". It is
not possible to implement this perfectly to spec in Ladybird so let's
make use of a custom abstraction.

Libraries/LibWeb/CredentialManagement/Credential.h

@@ -13,6 +13,74 @@
 
 namespace Web::CredentialManagement {
 
+typedef GC::Function<JS::ThrowCompletionOr<GC::Ref<Credential>>(JS::Object const&)> CreateCredentialAlgorithm;
+
+#define CREDENTIAL_INTERFACE(class_name)       \
+public:                                        \
+    static class_name const* the()             \
+    {                                          \
+        static class_name* instance = nullptr; \
+        if (!instance)                         \
+            instance = new class_name();       \
+        return instance;                       \
+    }
+
+class CredentialInterface {
+    AK_MAKE_NONCOPYABLE(CredentialInterface);
+
+protected:
+    CredentialInterface() { }
+
+public:
+    virtual ~CredentialInterface() = default;
+
+    // https://w3c.github.io/webappsec-credential-management/#credential-type-registry-credential-type
+    virtual String type() const = 0;
+
+    // https://w3c.github.io/webappsec-credential-management/#credential-type-registry-options-member-identifier
+    virtual String options_member_identifier() const = 0;
+
+    // https://w3c.github.io/webappsec-credential-management/#credential-type-registry-get-permissions-policy
+    virtual Optional<String> get_permission_policy() const = 0;
+
+    // https://w3c.github.io/webappsec-credential-management/#credential-type-registry-create-permissions-policy
+    virtual Optional<String> create_permission_policy() const = 0;
+
+    // https://w3c.github.io/webappsec-credential-management/#dom-credential-discovery-slot
+    virtual String discovery() const = 0;
+
+    // NOTE: This is not explicitly present in the spec, it is inferred.
+    virtual bool supports_conditional_user_mediation() const = 0;
+
+    // https://w3c.github.io/webappsec-credential-management/#algorithm-create-cred
+    virtual JS::ThrowCompletionOr<Variant<Empty, GC::Ref<Credential>, GC::Ref<CreateCredentialAlgorithm>>> create(JS::Realm&, URL::Origin const&, CredentialCreationOptions const&, bool) const
+    {
+        // 1. Return null.
+        return Empty {};
+    }
+
+    // https://w3c.github.io/webappsec-credential-management/#algorithm-store-cred
+    virtual JS::ThrowCompletionOr<void> store(JS::Realm& realm, bool) const
+    {
+        // 1. Throw a NotSupportedError.
+        return throw_completion(WebIDL::NotSupportedError::create(realm, "store"_string));
+    }
+
+    // https://w3c.github.io/webappsec-credential-management/#algorithm-discover-creds
+    virtual JS::ThrowCompletionOr<Variant<Empty, GC::Ref<Credential>>> discover_from_external_source(JS::Realm&, URL::Origin const&, CredentialRequestOptions const&, bool) const
+    {
+        // 1. Return null.
+        return Empty {};
+    }
+
+    // https://w3c.github.io/webappsec-credential-management/#algorithm-collect-creds
+    virtual JS::ThrowCompletionOr<Vector<Credential>> collect_from_credential_store(JS::Realm&, URL::Origin const&, CredentialRequestOptions const&, bool) const
+    {
+        // 1. Return an empty set.
+        return Vector<Credential> {};
+    }
+};
+
 class Credential : public Bindings::PlatformObject {
     WEB_PLATFORM_OBJECT(Credential, Bindings::PlatformObject);
     GC_DECLARE_ALLOCATOR(Credential);
@@ -30,6 +98,7 @@ public:
     String const& icon_url() const { return m_icon_url; }
 
     virtual String type() const = 0;
+    virtual CredentialInterface const* interface() const = 0;
 
 protected:
     explicit Credential(JS::Realm&);

Libraries/LibWeb/CredentialManagement/FederatedCredential.h

@@ -13,6 +13,24 @@
 
 namespace Web::CredentialManagement {
 
+class FederatedCredentialInterface final : public CredentialInterface {
+    CREDENTIAL_INTERFACE(FederatedCredentialInterface);
+
+public:
+    virtual String type() const override { return "federated"_string; }
+    virtual String options_member_identifier() const override { return "federated"_string; }
+    virtual Optional<String> get_permission_policy() const override { return {}; }
+    virtual Optional<String> create_permission_policy() const override { return {}; }
+
+    virtual String discovery() const override { return "credential store"_string; }
+    virtual bool supports_conditional_user_mediation() const override
+    {
+        // NOTE: FederatedCredential does not override is_conditional_mediation_available(),
+        //       therefore conditional mediation is not supported.
+        return false;
+    }
+};
+
 class FederatedCredential final : public Credential {
     WEB_PLATFORM_OBJECT(FederatedCredential, Credential);
     GC_DECLARE_ALLOCATOR(FederatedCredential);
@@ -27,6 +45,10 @@ public:
     Optional<String> const& protocol() const { return m_protocol; }
 
     String type() const override { return "federated"_string; }
+    virtual CredentialInterface const* interface() const override
+    {
+        return FederatedCredentialInterface::the();
+    }
 
 private:
     explicit FederatedCredential(JS::Realm&);

Libraries/LibWeb/CredentialManagement/PasswordCredential.h

@@ -14,6 +14,24 @@
 
 namespace Web::CredentialManagement {
 
+class PasswordCredentialInterface final : public CredentialInterface {
+    CREDENTIAL_INTERFACE(PasswordCredentialInterface);
+
+public:
+    virtual String type() const override { return "password"_string; }
+    virtual String options_member_identifier() const override { return "password"_string; }
+    virtual Optional<String> get_permission_policy() const override { return {}; }
+    virtual Optional<String> create_permission_policy() const override { return {}; }
+
+    virtual String discovery() const override { return "credential store"_string; }
+    virtual bool supports_conditional_user_mediation() const override
+    {
+        // NOTE: PasswordCredential does not override is_conditional_mediation_available(),
+        //       therefore conditional mediation is not supported.
+        return false;
+    }
+};
+
 class PasswordCredential final : public Credential {
     WEB_PLATFORM_OBJECT(PasswordCredential, Credential);
     GC_DECLARE_ALLOCATOR(PasswordCredential);
@@ -28,6 +46,10 @@ public:
     String const& password() const { return m_password; }
 
     String type() const override { return "password"_string; }
+    virtual CredentialInterface const* interface() const override
+    {
+        return PasswordCredentialInterface::the();
+    }
 
 private:
     explicit PasswordCredential(JS::Realm&);