From 0bdb29326234a4cc89b2e14e3a2f83eb63ffb321 Mon Sep 17 00:00:00 2001
From: Idan Horowitz <idan.horowitz@gmail.com>
Date: Sun, 20 Feb 2022 19:53:50 +0200
Subject: [PATCH] LibJS: Add an initial implementation of Collator Compare
 Functions

This commit adds an initial implementation (without any real locale
support) of Collator Compare Functions, as well as the matching
CompareStrings AO. These two are used to implement the ECMA402 version
of String.localeCompare() and Int.Collator.compare().
---
 Userland/Libraries/LibJS/CMakeLists.txt       |  1 +
 .../Runtime/Intl/CollatorCompareFunction.cpp  | 75 +++++++++++++++++++
 .../Runtime/Intl/CollatorCompareFunction.h    | 33 ++++++++
 3 files changed, 109 insertions(+)
 create mode 100644 Userland/Libraries/LibJS/Runtime/Intl/CollatorCompareFunction.cpp
 create mode 100644 Userland/Libraries/LibJS/Runtime/Intl/CollatorCompareFunction.h

diff --git a/Userland/Libraries/LibJS/CMakeLists.txt b/Userland/Libraries/LibJS/CMakeLists.txt
index 9e92ef1343..c90d83b957 100644
--- a/Userland/Libraries/LibJS/CMakeLists.txt
+++ b/Userland/Libraries/LibJS/CMakeLists.txt
@@ -88,6 +88,7 @@ set(SOURCES
     Runtime/IndexedProperties.cpp
     Runtime/Intl/AbstractOperations.cpp
     Runtime/Intl/Collator.cpp
+    Runtime/Intl/CollatorCompareFunction.cpp
     Runtime/Intl/CollatorConstructor.cpp
     Runtime/Intl/CollatorPrototype.cpp
     Runtime/Intl/DateTimeFormat.cpp
diff --git a/Userland/Libraries/LibJS/Runtime/Intl/CollatorCompareFunction.cpp b/Userland/Libraries/LibJS/Runtime/Intl/CollatorCompareFunction.cpp
new file mode 100644
index 0000000000..6c8240470d
--- /dev/null
+++ b/Userland/Libraries/LibJS/Runtime/Intl/CollatorCompareFunction.cpp
@@ -0,0 +1,75 @@
+/*
+ * Copyright (c) 2022, Idan Horowitz <idan.horowitz@serenityos.org>
+ *
+ * SPDX-License-Identifier: BSD-2-Clause
+ */
+
+#include <AK/Utf8View.h>
+#include <LibJS/Runtime/GlobalObject.h>
+#include <LibJS/Runtime/Intl/Collator.h>
+#include <LibJS/Runtime/Intl/CollatorCompareFunction.h>
+
+namespace JS::Intl {
+
+CollatorCompareFunction* CollatorCompareFunction::create(GlobalObject& global_object, Collator& collator)
+{
+    return global_object.heap().allocate<CollatorCompareFunction>(global_object, global_object, collator);
+}
+
+CollatorCompareFunction::CollatorCompareFunction(GlobalObject& global_object, Collator& collator)
+    : NativeFunction(*global_object.function_prototype())
+    , m_collator(collator)
+{
+}
+
+void CollatorCompareFunction::initialize(GlobalObject& global_object)
+{
+    auto& vm = global_object.vm();
+    define_direct_property(vm.names.length, Value(2), Attribute::Configurable);
+}
+
+// 10.3.3.2 CompareStrings ( collator, x, y ), https://tc39.es/ecma402/#sec-collator-comparestrings
+double compare_strings(Collator& collator, Utf8View const& x, Utf8View const& y)
+{
+    // FIXME: Implement https://unicode.org/reports/tr10
+    (void)collator;
+    auto x_iterator = x.begin();
+    auto y_iterator = y.begin();
+    for (; x_iterator != x.end() && y_iterator != y.end(); ++x_iterator, ++y_iterator) {
+        if (*x_iterator != *y_iterator)
+            return static_cast<double>(*x_iterator) - static_cast<double>(*y_iterator);
+    }
+    if (x_iterator != x.end())
+        return 1.0;
+    if (y_iterator != y.end())
+        return -1.0;
+    return 0.0;
+}
+
+// 10.3.3.1 Collator Compare Functions, https://tc39.es/ecma402/#sec-collator-compare-functions
+ThrowCompletionOr<Value> CollatorCompareFunction::call()
+{
+    auto& vm = this->vm();
+    auto& global_object = this->global_object();
+
+    // 1. Let collator be F.[[Collator]].
+    // 2. Assert: Type(collator) is Object and collator has an [[InitializedCollator]] internal slot.
+    // 3. If x is not provided, let x be undefined.
+    // 4. If y is not provided, let y be undefined.
+
+    // 5. Let X be ? ToString(x).
+    auto x = TRY(vm.argument(0).to_string(global_object));
+    // 6. Let Y be ? ToString(y).
+    auto y = TRY(vm.argument(1).to_string(global_object));
+
+    // 7. Return CompareStrings(collator, X, Y).
+    return compare_strings(m_collator, Utf8View(x), Utf8View(y));
+}
+
+void CollatorCompareFunction::visit_edges(Visitor& visitor)
+{
+    Base::visit_edges(visitor);
+    visitor.visit(&m_collator);
+}
+
+}
diff --git a/Userland/Libraries/LibJS/Runtime/Intl/CollatorCompareFunction.h b/Userland/Libraries/LibJS/Runtime/Intl/CollatorCompareFunction.h
new file mode 100644
index 0000000000..a1540bc92b
--- /dev/null
+++ b/Userland/Libraries/LibJS/Runtime/Intl/CollatorCompareFunction.h
@@ -0,0 +1,33 @@
+/*
+ * Copyright (c) 2022, Idan Horowitz <idan.horowitz@serenityos.org>
+ *
+ * SPDX-License-Identifier: BSD-2-Clause
+ */
+
+#pragma once
+
+#include <LibJS/Runtime/NativeFunction.h>
+
+namespace JS::Intl {
+
+class CollatorCompareFunction : public NativeFunction {
+    JS_OBJECT(CollatorCompareFunction, NativeFunction);
+
+public:
+    static CollatorCompareFunction* create(GlobalObject&, Collator&);
+
+    explicit CollatorCompareFunction(GlobalObject&, Collator&);
+    virtual void initialize(GlobalObject&) override;
+    virtual ~CollatorCompareFunction() override = default;
+
+    virtual ThrowCompletionOr<Value> call() override;
+
+private:
+    virtual void visit_edges(Visitor&) override;
+
+    Collator& m_collator; // [[Collator]]
+};
+
+double compare_strings(Collator&, Utf8View const& x, Utf8View const& y);
+
+}