LibWeb+WebDriver: Begin processing and matching WebDriver capabilities

Still some TODOs here:
* We don't handle all capabilities (e.g. proxy)
* We don't match the capabilities against the running browser

But this will parse the capabilities JSON object received from the
WebDriver client.

4 files changed, 321 insertions, 4 deletions

diff --git a/Userland/Libraries/LibWeb/CMakeLists.txt b/Userland/Libraries/LibWeb/CMakeLists.txt
index 03e44cf3a8..b0464ba9fa 100644
--- a/Userland/Libraries/LibWeb/CMakeLists.txt
+++ b/Userland/Libraries/LibWeb/CMakeLists.txt
@@ -439,6 +439,7 @@ set(SOURCES
     WebAssembly/WebAssemblyTableConstructor.cpp
     WebAssembly/WebAssemblyTableObject.cpp
     WebAssembly/WebAssemblyTablePrototype.cpp
+    WebDriver/Capabilities.cpp
     WebDriver/Client.cpp
     WebDriver/ElementLocationStrategies.cpp
     WebDriver/Error.cpp
diff --git a/Userland/Libraries/LibWeb/WebDriver/Capabilities.cpp b/Userland/Libraries/LibWeb/WebDriver/Capabilities.cpp
new file mode 100644
index 0000000000..38e0df66ed
--- /dev/null
+++ b/Userland/Libraries/LibWeb/WebDriver/Capabilities.cpp
@@ -0,0 +1,254 @@
+/*
+ * Copyright (c) 2022, Tim Flynn <trflynn89@serenityos.org>
+ *
+ * SPDX-License-Identifier: BSD-2-Clause
+ */
+
+#include <AK/JsonArray.h>
+#include <AK/JsonObject.h>
+#include <AK/JsonValue.h>
+#include <AK/Optional.h>
+#include <LibWeb/WebDriver/Capabilities.h>
+#include <LibWeb/WebDriver/TimeoutsConfiguration.h>
+
+namespace Web::WebDriver {
+
+// https://w3c.github.io/webdriver/#dfn-deserialize-as-a-page-load-strategy
+static Response deserialize_as_a_page_load_strategy(JsonValue value)
+{
+    // 1. If value is not a string return an error with error code invalid argument.
+    if (!value.is_string())
+        return Error::from_code(ErrorCode::InvalidArgument, "Capability pageLoadStrategy must be a string"sv);
+
+    // 2. If there is no entry in the table of page load strategies with keyword value return an error with error code invalid argument.
+    if (!value.as_string().is_one_of("none"sv, "eager"sv, "normal"sv))
+        return Error::from_code(ErrorCode::InvalidArgument, "Invalid pageLoadStrategy capability"sv);
+
+    // 3. Return success with data value.
+    return value;
+}
+
+// https://w3c.github.io/webdriver/#dfn-deserialize-as-an-unhandled-prompt-behavior
+static Response deserialize_as_an_unhandled_prompt_behavior(JsonValue value)
+{
+    // 1. If value is not a string return an error with error code invalid argument.
+    if (!value.is_string())
+        return Error::from_code(ErrorCode::InvalidArgument, "Capability unhandledPromptBehavior must be a string"sv);
+
+    // 2. If value is not present as a keyword in the known prompt handling approaches table return an error with error code invalid argument.
+    if (!value.as_string().is_one_of("dismiss"sv, "accept"sv, "dismiss and notify"sv, "accept and notify"sv, "ignore"sv))
+        return Error::from_code(ErrorCode::InvalidArgument, "Invalid pageLoadStrategy capability"sv);
+
+    // 3. Return success with data value.
+    return value;
+}
+
+// https://w3c.github.io/webdriver/#dfn-validate-capabilities
+static ErrorOr<JsonObject, Error> validate_capabilities(JsonValue const& capability)
+{
+    // 1. If capability is not a JSON Object return an error with error code invalid argument.
+    if (!capability.is_object())
+        return Error::from_code(ErrorCode::InvalidArgument, "Capability is not an Object"sv);
+
+    // 2. Let result be an empty JSON Object.
+    JsonObject result;
+
+    // 3. For each enumerable own property in capability, run the following substeps:
+    TRY(capability.as_object().try_for_each_member([&](auto const& name, auto const& value) -> ErrorOr<void, Error> {
+        // a. Let name be the name of the property.
+        // b. Let value be the result of getting a property named name from capability.
+
+        // c. Run the substeps of the first matching condition:
+        JsonValue deserialized;
+
+        // -> value is null
+        if (value.is_null()) {
+            // Let deserialized be set to null.
+        }
+
+        // -> name equals "acceptInsecureCerts"
+        else if (name == "acceptInsecureCerts"sv) {
+            // If value is not a boolean return an error with error code invalid argument. Otherwise, let deserialized be set to value
+            if (!value.is_bool())
+                return Error::from_code(ErrorCode::InvalidArgument, "Capability acceptInsecureCerts must be a boolean"sv);
+            deserialized = value;
+        }
+
+        // -> name equals "browserName"
+        // -> name equals "browserVersion"
+        // -> name equals "platformName"
+        else if (name.is_one_of("browserName"sv, "browser_version"sv, "platformName"sv)) {
+            // If value is not a string return an error with error code invalid argument. Otherwise, let deserialized be set to value.
+            if (!value.is_string())
+                return Error::from_code(ErrorCode::InvalidArgument, String::formatted("Capability {} must be a string", name));
+            deserialized = value;
+        }
+
+        // -> name equals "pageLoadStrategy"
+        else if (name == "pageLoadStrategy"sv) {
+            // Let deserialized be the result of trying to deserialize as a page load strategy with argument value.
+            deserialized = TRY(deserialize_as_a_page_load_strategy(value));
+        }
+
+        // FIXME: -> name equals "proxy"
+        // FIXME:     Let deserialized be the result of trying to deserialize as a proxy with argument value.
+
+        // -> name equals "strictFileInteractability"
+        else if (name == "strictFileInteractability"sv) {
+            // If value is not a boolean return an error with error code invalid argument. Otherwise, let deserialized be set to value
+            if (!value.is_bool())
+                return Error::from_code(ErrorCode::InvalidArgument, "Capability strictFileInteractability must be a boolean"sv);
+            deserialized = value;
+        }
+
+        // -> name equals "timeouts"
+        else if (name == "timeouts"sv) {
+            // Let deserialized be the result of trying to JSON deserialize as a timeouts configuration the value.
+            auto timeouts = TRY(json_deserialize_as_a_timeouts_configuration(value));
+            deserialized = JsonValue { timeouts_object(timeouts) };
+        }
+
+        // -> name equals "unhandledPromptBehavior"
+        else if (name == "unhandledPromptBehavior"sv) {
+            // Let deserialized be the result of trying to deserialize as an unhandled prompt behavior with argument value.
+            deserialized = TRY(deserialize_as_an_unhandled_prompt_behavior(value));
+        }
+
+        // FIXME: -> name is the name of an additional WebDriver capability
+        // FIXME:     Let deserialized be the result of trying to run the additional capability deserialization algorithm for the extension capability corresponding to name, with argument value.
+        // FIXME: -> name is the key of an extension capability
+        // FIXME:     If name is known to the implementation, let deserialized be the result of trying to deserialize value in an implementation-specific way. Otherwise, let deserialized be set to value.
+
+        // -> The remote end is an endpoint node
+        else {
+            // Return an error with error code invalid argument.
+            return Error::from_code(ErrorCode::InvalidArgument, String::formatted("Unrecognized capability: {}", name));
+        }
+
+        // d. If deserialized is not null, set a property on result with name name and value deserialized.
+        if (!deserialized.is_null())
+            result.set(name, move(deserialized));
+
+        return {};
+    }));
+
+    // 4. Return success with data result.
+    return result;
+}
+
+// https://w3c.github.io/webdriver/#dfn-merging-capabilities
+static ErrorOr<JsonObject, Error> merge_capabilities(JsonObject const& primary, Optional<JsonObject const&> const& secondary)
+{
+    // 1. Let result be a new JSON Object.
+    JsonObject result;
+
+    // 2. For each enumerable own property in primary, run the following substeps:
+    primary.for_each_member([&](auto const& name, auto const& value) {
+        // a. Let name be the name of the property.
+        // b. Let value be the result of getting a property named name from primary.
+
+        // c. Set a property on result with name name and value value.
+        result.set(name, value);
+    });
+
+    // 3. If secondary is undefined, return result.
+    if (!secondary.has_value())
+        return result;
+
+    // 4. For each enumerable own property in secondary, run the following substeps:
+    TRY(secondary->try_for_each_member([&](auto const& name, auto const& value) -> ErrorOr<void, Error> {
+        // a. Let name be the name of the property.
+        // b. Let value be the result of getting a property named name from secondary.
+
+        // c. Let primary value be the result of getting the property name from primary.
+        auto const* primary_value = primary.get_ptr(name);
+
+        // d. If primary value is not undefined, return an error with error code invalid argument.
+        if (primary_value != nullptr)
+            return Error::from_code(ErrorCode::InvalidArgument, String::formatted("Unable to merge capability {}", name));
+
+        // e. Set a property on result with name name and value value.
+        result.set(name, value);
+        return {};
+    }));
+
+    // 5. Return result.
+    return result;
+}
+
+// https://w3c.github.io/webdriver/#dfn-capabilities-processing
+Response process_capabilities(JsonValue const& parameters)
+{
+    if (!parameters.is_object())
+        return Error::from_code(ErrorCode::InvalidArgument, "Session parameters is not an object"sv);
+
+    // 1. Let capabilities request be the result of getting the property "capabilities" from parameters.
+    //     a. If capabilities request is not a JSON Object, return error with error code invalid argument.
+    auto const* capabilities_request_ptr = parameters.as_object().get_ptr("capabilities"sv);
+    if (!capabilities_request_ptr || !capabilities_request_ptr->is_object())
+        return Error::from_code(ErrorCode::InvalidArgument, "Capabilities is not an object"sv);
+
+    auto const& capabilities_request = capabilities_request_ptr->as_object();
+
+    // 2. Let required capabilities be the result of getting the property "alwaysMatch" from capabilities request.
+    //     a. If required capabilities is undefined, set the value to an empty JSON Object.
+    JsonObject required_capabilities;
+
+    if (auto const* capability = capabilities_request.get_ptr("alwaysMatch"sv)) {
+        // b. Let required capabilities be the result of trying to validate capabilities with argument required capabilities.
+        required_capabilities = TRY(validate_capabilities(*capability));
+    }
+
+    // 3. Let all first match capabilities be the result of getting the property "firstMatch" from capabilities request.
+    JsonArray all_first_match_capabilities;
+
+    if (auto const* capabilities = capabilities_request.get_ptr("firstMatch"sv)) {
+        // b. If all first match capabilities is not a JSON List with one or more entries, return error with error code invalid argument.
+        if (!capabilities->is_array() || capabilities->as_array().is_empty())
+            return Error::from_code(ErrorCode::InvalidArgument, "Capability firstMatch must be an array with at least one entry"sv);
+
+        all_first_match_capabilities = capabilities->as_array();
+    } else {
+        // a. If all first match capabilities is undefined, set the value to a JSON List with a single entry of an empty JSON Object.
+        all_first_match_capabilities.append(JsonObject {});
+    }
+
+    // 4. Let validated first match capabilities be an empty JSON List.
+    JsonArray validated_first_match_capabilities;
+    validated_first_match_capabilities.ensure_capacity(all_first_match_capabilities.size());
+
+    // 5. For each first match capabilities corresponding to an indexed property in all first match capabilities:
+    TRY(all_first_match_capabilities.try_for_each([&](auto const& first_match_capabilities) -> ErrorOr<void, Error> {
+        // a. Let validated capabilities be the result of trying to validate capabilities with argument first match capabilities.
+        auto validated_capabilities = TRY(validate_capabilities(first_match_capabilities));
+
+        // b. Append validated capabilities to validated first match capabilities.
+        validated_first_match_capabilities.append(move(validated_capabilities));
+        return {};
+    }));
+
+    // 6. Let merged capabilities be an empty List.
+    JsonArray merged_capabilities;
+    merged_capabilities.ensure_capacity(validated_first_match_capabilities.size());
+
+    // 7. For each first match capabilities corresponding to an indexed property in validated first match capabilities:
+    TRY(validated_first_match_capabilities.try_for_each([&](auto const& first_match_capabilities) -> ErrorOr<void, Error> {
+        // a. Let merged be the result of trying to merge capabilities with required capabilities and first match capabilities as arguments.
+        auto merged = TRY(merge_capabilities(required_capabilities, first_match_capabilities.as_object()));
+
+        // b. Append merged to merged capabilities.
+        merged_capabilities.append(move(merged));
+        return {};
+    }));
+
+    // FIXME: 8. For each capabilities corresponding to an indexed property in merged capabilities:
+    // FIXME:    a. Let matched capabilities be the result of trying to match capabilities with capabilities as an argument.
+    // FIXME:    b. If matched capabilities is not null, return success with data matched capabilities.
+
+    // For now, we just assume the first validated capabilties object is a match.
+    return merged_capabilities.take(0);
+
+    // 9. Return success with data null.
+}
+
+}
diff --git a/Userland/Libraries/LibWeb/WebDriver/Capabilities.h b/Userland/Libraries/LibWeb/WebDriver/Capabilities.h
new file mode 100644
index 0000000000..72153f688b
--- /dev/null
+++ b/Userland/Libraries/LibWeb/WebDriver/Capabilities.h
@@ -0,0 +1,59 @@
+/*
+ * Copyright (c) 2022, Tim Flynn <trflynn89@serenityos.org>
+ *
+ * SPDX-License-Identifier: BSD-2-Clause
+ */
+
+#pragma once
+
+#include <AK/Forward.h>
+#include <AK/StringView.h>
+#include <LibWeb/WebDriver/Response.h>
+
+namespace Web::WebDriver {
+
+// https://w3c.github.io/webdriver/#dfn-page-load-strategy
+enum class PageLoadStrategy {
+    None,
+    Eager,
+    Normal,
+};
+
+constexpr PageLoadStrategy page_load_strategy_from_string(StringView strategy)
+{
+    if (strategy == "none"sv)
+        return PageLoadStrategy::None;
+    if (strategy == "eager"sv)
+        return PageLoadStrategy::Eager;
+    if (strategy == "normal"sv)
+        return PageLoadStrategy::Normal;
+    VERIFY_NOT_REACHED();
+}
+
+// https://w3c.github.io/webdriver/#dfn-unhandled-prompt-behavior
+enum class UnhandledPromptBehavior {
+    Dismiss,
+    Accept,
+    DismissAndNotify,
+    AcceptAndNotify,
+    Ignore,
+};
+
+constexpr UnhandledPromptBehavior unhandled_prompt_behavior_from_string(StringView behavior)
+{
+    if (behavior == "dismiss"sv)
+        return UnhandledPromptBehavior::Dismiss;
+    if (behavior == "accept"sv)
+        return UnhandledPromptBehavior::Accept;
+    if (behavior == "dismiss and notify"sv)
+        return UnhandledPromptBehavior::DismissAndNotify;
+    if (behavior == "accept and notify"sv)
+        return UnhandledPromptBehavior::AcceptAndNotify;
+    if (behavior == "ignore"sv)
+        return UnhandledPromptBehavior::Ignore;
+    VERIFY_NOT_REACHED();
+}
+
+Response process_capabilities(JsonValue const& parameters);
+
+}
diff --git a/Userland/Services/WebDriver/Client.cpp b/Userland/Services/WebDriver/Client.cpp
index fa099e5048..24a777e3fb 100644
--- a/Userland/Services/WebDriver/Client.cpp
+++ b/Userland/Services/WebDriver/Client.cpp
@@ -11,6 +11,7 @@
 #include <AK/Debug.h>
 #include <AK/JsonObject.h>
 #include <AK/JsonValue.h>
+#include <LibWeb/WebDriver/Capabilities.h>
 #include <WebDriver/Client.h>
 
 namespace WebDriver {
@@ -73,7 +74,7 @@ void Client::close_session(unsigned session_id)
 
 // 8.1 New Session, https://w3c.github.io/webdriver/#dfn-new-sessions
 // POST /session
-Web::WebDriver::Response Client::new_session(Web::WebDriver::Parameters, JsonValue)
+Web::WebDriver::Response Client::new_session(Web::WebDriver::Parameters, JsonValue payload)
 {
     dbgln_if(WEBDRIVER_DEBUG, "Handling POST /session");
 
@@ -90,10 +91,12 @@ Web::WebDriver::Response Client::new_session(Web::WebDriver::Parameters, JsonVal
     // FIXME: 3. If the maximum active sessions is equal to the length of the list of active sessions,
     //           return error with error code session not created.
 
-    // FIXME: 4. Let capabilities be the result of trying to process capabilities with parameters as an argument.
-    auto capabilities = JsonObject {};
+    // 4. Let capabilities be the result of trying to process capabilities with parameters as an argument.
+    auto capabilities = TRY(Web::WebDriver::process_capabilities(payload));
 
-    // FIXME: 5. If capabilities’s is null, return error with error code session not created.
+    // 5. If capabilities’s is null, return error with error code session not created.
+    if (capabilities.is_null())
+        return Web::WebDriver::Error::from_code(Web::WebDriver::ErrorCode::SessionNotCreated, "Could not match capabilities"sv);
 
     // 6. Let session id be the result of generating a UUID.
     // FIXME: Actually create a UUID.