/*

 * Copyright (c) 2021-2022, Linus Groh <linusg@serenityos.org>

 *

 * SPDX-License-Identifier: BSD-2-Clause

 */

#include <LibJS/Runtime/TypedArray.h>

#include <LibWeb/Bindings/Intrinsics.h>

#include <LibWeb/Bindings/TextEncoderPrototype.h>

#include <LibWeb/Encoding/TextEncoder.h>

#include <LibWeb/WebIDL/ExceptionOr.h>

namespace Web::Encoding {

JS_DEFINE_ALLOCATOR(TextEncoder);

WebIDL::ExceptionOr<JS::NonnullGCPtr<TextEncoder>> TextEncoder::construct_impl(JS::Realm& realm)

{

    return realm.heap().allocate<TextEncoder>(realm, realm);

}

TextEncoder::TextEncoder(JS::Realm& realm)

    : PlatformObject(realm)

{

}

TextEncoder::~TextEncoder() = default;

void TextEncoder::initialize(JS::Realm& realm)

{

    Base::initialize(realm);

    WEB_SET_PROTOTYPE_FOR_INTERFACE(TextEncoder);

}

// https://encoding.spec.whatwg.org/#dom-textencoder-encode

JS::NonnullGCPtr<JS::Uint8Array> TextEncoder::encode(String const& input) const

{

    // NOTE: The AK::String is always UTF-8, so most of these steps are no-ops.

    // 1. Convert input to an I/O queue of scalar values.

    // 2. Let output be the I/O queue of bytes « end-of-queue ».

    // 3. While true:

    //     1. Let item be the result of reading from input.

    //     2. Let result be the result of processing an item with item, an instance of the UTF-8 encoder, input, output, and "fatal".

    //     3. Assert: result is not an error.

    //     4. If result is finished, then convert output into a byte sequence and return a Uint8Array object wrapping an ArrayBuffer containing output.

    auto byte_buffer = MUST(ByteBuffer::copy(input.bytes()));

    auto array_length = byte_buffer.size();

    auto array_buffer = JS::ArrayBuffer::create(realm(), move(byte_buffer));

    return JS::Uint8Array::create(realm(), array_length, *array_buffer);

}

// https://encoding.spec.whatwg.org/#dom-textencoder-encodeinto

TextEncoderEncodeIntoResult TextEncoder::encode_into(String const& source, JS::Handle<WebIDL::BufferSource> const& destination) const

{

    auto& data = destination->viewed_array_buffer()->buffer();

    // 1. Let read be 0.

    WebIDL::UnsignedLongLong read = 0;

    // 2. Let written be 0.

    WebIDL::UnsignedLongLong written = 0;

    // NOTE: The AK::String is always UTF-8, so most of these steps are no-ops.

    // 3. Let encoder be an instance of the UTF-8 encoder.

    // 4. Let unused be the I/O queue of scalar values « end-of-queue ».

    // 5. Convert source to an I/O queue of scalar values.

    auto code_points = source.code_points();

    auto it = code_points.begin();

    // 6. While true:

    while (true) {

        // 6.1. Let item be the result of reading from source.

        // 6.2. Let result be the result of running encoder’s handler on unused and item.

        // 6.3. If result is finished, then break.

        if (it.done())

            break;

        auto item = *it;

        auto result = it.underlying_code_point_bytes();

        // 6.4. Otherwise:

        // 6.4.1. If destination’s byte length − written is greater than or equal to the number of bytes in result, then:

        if (data.size() - written >= result.size()) {

            // 6.4.1.1. If item is greater than U+FFFF, then increment read by 2.

            if (item > 0xffff) {

                read += 2;

            }

            // 6.4.1.2. Otherwise, increment read by 1.

            else {

                read++;

            }

            // 6.4.1.3. Write the bytes in result into destination, with startingOffset set to written.

            // 6.4.1.4. Increment written by the number of bytes in result.

            for (auto byte : result)

                data[written++] = byte;

        }

        // 6.4.2. Otherwise, break.

        else {

            break;

        }

        ++it;

    }

    // 7. Return «[ "read" → read, "written" → written ]».

    return { read, written };

}

// https://encoding.spec.whatwg.org/#dom-textencoder-encoding

FlyString const& TextEncoder::encoding()

{

    static FlyString const encoding = "utf-8"_fly_string;

    return encoding;

}

}