LibWeb: Add the URLSearchParams built-in

This is a very partial implementation, as some features (like 2 of the
possible constructor types, iteration and the getAll method) are
missing, and other's are not implemented due to the currently missing
URL built-in.

Userland/Libraries/LibWeb/URL/URLSearchParams.cpp

@@ -0,0 +1,137 @@
+/*
+ * Copyright (c) 2021, Idan Horowitz <idan.horowitz@serenityos.org>
+ *
+ * SPDX-License-Identifier: BSD-2-Clause
+ */
+
+#include <AK/QuickSort.h>
+#include <AK/Utf8View.h>
+#include <LibWeb/URL/URLSearchParams.h>
+
+namespace Web::URL {
+
+DOM::ExceptionOr<NonnullRefPtr<URLSearchParams>> URLSearchParams::create_with_global_object(Bindings::WindowObject&, String const& init)
+{
+    // 1. If init is a string and starts with U+003F (?), then remove the first code point from init.
+    StringView stripped_init = init.substring_view(init.starts_with('?'));
+    // 2. Initialize this with init.
+
+    // URLSearchParams init from this point forward
+
+    // TODO
+    // 1. If init is a sequence, then for each pair in init:
+    // a. If pair does not contain exactly two items, then throw a TypeError.
+    // b. Append a new name-value pair whose name is pair’s first item, and value is pair’s second item, to query’s list.
+
+    // TODO
+    // 2. Otherwise, if init is a record, then for each name → value of init, append a new name-value pair whose name is name and value is value, to query’s list.
+
+    // 3. Otherwise:
+    // a. Assert: init is a string.
+    // b. Set query’s list to the result of parsing init.
+    return URLSearchParams::create(url_decode(stripped_init));
+}
+
+void URLSearchParams::append(String const& name, String const& value)
+{
+    // 1. Append a new name-value pair whose name is name and value is value, to list.
+    m_list.empend(name, value);
+    // 2. Update this.
+    update();
+}
+
+void URLSearchParams::update()
+{
+    // TODO
+    // 1. If query’s URL object is null, then return.
+    // 2. Let serializedQuery be the serialization of query’s list.
+    // 3. If serializedQuery is the empty string, then set serializedQuery to null.
+    // 4. Set query’s URL object’s URL’s query to serializedQuery.
+}
+
+void URLSearchParams::delete_(String const& name)
+{
+    // 1. Remove all name-value pairs whose name is name from list.
+    m_list.remove_all_matching([&name](auto& entry) {
+        return entry.name == name;
+    });
+    // 2. Update this.
+    update();
+}
+
+String URLSearchParams::get(String const& name)
+{
+    // return the value of the first name-value pair whose name is name in this’s list, if there is such a pair, and null otherwise.
+    auto result = m_list.find_if([&name](auto& entry) {
+        return entry.name == name;
+    });
+    if (result.is_end())
+        return {};
+    return result->value;
+}
+
+bool URLSearchParams::has(String const& name)
+{
+    // return true if there is a name-value pair whose name is name in this’s list, and false otherwise.
+    return !m_list.find_if([&name](auto& entry) {
+                      return entry.name == name;
+                  })
+                .is_end();
+}
+
+void URLSearchParams::set(const String& name, const String& value)
+{
+    // 1. If this’s list contains any name-value pairs whose name is name, then set the value of the first such name-value pair to value and remove the others.
+    auto existing = m_list.find_if([&name](auto& entry) {
+        return entry.name == name;
+    });
+    if (!existing.is_end()) {
+        existing->value = value;
+        m_list.remove_all_matching([&name, &existing](auto& entry) {
+            return &entry != &*existing && name == name;
+        });
+    }
+    // 2. Otherwise, append a new name-value pair whose name is name and value is value, to this’s list.
+    else {
+        m_list.empend(name, value);
+    }
+    // 3. Update this.
+    update();
+}
+
+void URLSearchParams::sort()
+{
+    // 1. Sort all name-value pairs, if any, by their names. Sorting must be done by comparison of code units. The relative order between name-value pairs with equal names must be preserved.
+    quick_sort(m_list.begin(), m_list.end(), [](auto& a, auto& b) {
+        Utf8View a_code_points { a.name };
+        Utf8View b_code_points { b.name };
+
+        if (a_code_points.starts_with(b_code_points))
+            return false;
+        if (b_code_points.starts_with(a_code_points))
+            return true;
+
+        for (auto k = a_code_points.begin(), l = b_code_points.begin();
+             k != a_code_points.end() && l != b_code_points.end();
+             ++k, ++l) {
+            if (*k != *l) {
+                if (*k < *l) {
+                    return true;
+                } else {
+                    return false;
+                }
+            }
+        }
+        VERIFY_NOT_REACHED();
+    });
+    // 2. Update this.
+    update();
+}
+
+String URLSearchParams::to_string()
+{
+    // return the serialization of this’s list.
+    return url_encode(m_list, AK::URL::PercentEncodeSet::ApplicationXWWWFormUrlencoded);
+}
+
+}