/*
 * Copyright (c) 2021, Idan Horowitz <idan.horowitz@serenityos.org>
 * Copyright (c) 2022, stelar7 <dudedbz@gmail.com>
 *
 * SPDX-License-Identifier: BSD-2-Clause
 */

#include <AK/Random.h>
#include <AK/StringBuilder.h>
#include <LibCrypto/SecureRandom.h>
#include <LibJS/Runtime/TypedArray.h>
#include <LibWeb/Bindings/CryptoPrototype.h>
#include <LibWeb/Bindings/ExceptionOrUtils.h>
#include <LibWeb/Bindings/Intrinsics.h>
#include <LibWeb/Crypto/Crypto.h>
#include <LibWeb/Crypto/SubtleCrypto.h>
#include <LibWeb/WebIDL/Buffers.h>

namespace Web::Crypto {

GC_DEFINE_ALLOCATOR(Crypto);

GC::Ref<Crypto> Crypto::create(JS::Realm& realm)
{
    return realm.create<Crypto>(realm);
}

Crypto::Crypto(JS::Realm& realm)
    : PlatformObject(realm)
{
}

Crypto::~Crypto() = default;

void Crypto::initialize(JS::Realm& realm)
{
    Base::initialize(realm);
    WEB_SET_PROTOTYPE_FOR_INTERFACE(Crypto);
    m_subtle = SubtleCrypto::create(realm);
}

GC::Ref<SubtleCrypto> Crypto::subtle() const
{
    return *m_subtle;
}

// https://w3c.github.io/webcrypto/#dfn-Crypto-method-getRandomValues
WebIDL::ExceptionOr<GC::Root<WebIDL::ArrayBufferView>> Crypto::get_random_values(GC::Root<WebIDL::ArrayBufferView> array) const
{
    // 1. If array is not an Int8Array, Uint8Array, Uint8ClampedArray, Int16Array, Uint16Array, Int32Array, Uint32Array, BigInt64Array, or BigUint64Array, then throw a TypeMismatchError and terminate the algorithm.
    if (!array->is_typed_array_base())
        return WebIDL::TypeMismatchError::create(realm(), "array must be one of Int8Array, Uint8Array, Uint8ClampedArray, Int16Array, Uint16Array, Int32Array, Uint32Array, BigInt64Array, or BigUint64Array"_string);

    auto const& typed_array = *array->bufferable_object().get<GC::Ref<JS::TypedArrayBase>>();
    if (!typed_array.element_name().is_one_of("Int8Array", "Uint8Array", "Uint8ClampedArray", "Int16Array", "Uint16Array", "Int32Array", "Uint32Array", "BigInt64Array", "BigUint64Array"))
        return WebIDL::TypeMismatchError::create(realm(), "array must be one of Int8Array, Uint8Array, Uint8ClampedArray, Int16Array, Uint16Array, Int32Array, Uint32Array, BigInt64Array, or BigUint64Array"_string);

    auto typed_array_record = JS::make_typed_array_with_buffer_witness_record(typed_array, JS::ArrayBuffer::Order::SeqCst);

    // IMPLEMENTATION DEFINED: If the viewed array buffer is out-of-bounds, throw a InvalidStateError and terminate the algorithm.
    if (JS::is_typed_array_out_of_bounds(typed_array_record))
        return WebIDL::InvalidStateError::create(realm(), MUST(String::formatted(JS::ErrorType::BufferOutOfBounds.message(), "TypedArray"sv)));

    // 2. If the byteLength of array is greater than 65536, throw a QuotaExceededError and terminate the algorithm.
    if (JS::typed_array_byte_length(typed_array_record) > 65536)
        return WebIDL::QuotaExceededError::create(realm(), "array's byteLength may not be greater than 65536"_string);

    // FIXME: Handle SharedArrayBuffers

    // 3. Overwrite all elements of array with cryptographically strong random values of the appropriate type.
    ::Crypto::fill_with_secure_random(array->viewed_array_buffer()->buffer().bytes().slice(array->byte_offset(), array->byte_length()));

    // 4. Return array.
    return array;
}

// https://w3c.github.io/webcrypto/#dfn-Crypto-method-randomUUID
WebIDL::ExceptionOr<String> Crypto::random_uuid() const
{
    auto& vm = realm().vm();

    return TRY_OR_THROW_OOM(vm, generate_random_uuid());
}

void Crypto::visit_edges(Cell::Visitor& visitor)
{
    Base::visit_edges(visitor);
    visitor.visit(m_subtle);
}

// https://w3c.github.io/webcrypto/#dfn-generate-a-random-uuid
ErrorOr<String> generate_random_uuid()
{
    // 1. Let bytes be a byte sequence of length 16.
    u8 bytes[16];

    // 2. Fill bytes with cryptographically secure random bytes.
    ::Crypto::fill_with_secure_random(bytes);

    // 3. Set the 4 most significant bits of bytes[6], which represent the UUID version, to 0100.
    bytes[6] &= ~(1 << 7);
    bytes[6] |= 1 << 6;
    bytes[6] &= ~(1 << 5);
    bytes[6] &= ~(1 << 4);

    // 4. Set the 2 most significant bits of bytes[8], which represent the UUID variant, to 10.
    bytes[8] |= 1 << 7;
    bytes[8] &= ~(1 << 6);

    /* 5. Return the string concatenation of
        «
        hexadecimal representation of bytes[0],
        hexadecimal representation of bytes[1],
        hexadecimal representation of bytes[2],
        hexadecimal representation of bytes[3],
        "-",
        hexadecimal representation of bytes[4],
        hexadecimal representation of bytes[5],
        "-",
        hexadecimal representation of bytes[6],
        hexadecimal representation of bytes[7],
        "-",
        hexadecimal representation of bytes[8],
        hexadecimal representation of bytes[9],
        "-",
        hexadecimal representation of bytes[10],
        hexadecimal representation of bytes[11],
        hexadecimal representation of bytes[12],
        hexadecimal representation of bytes[13],
        hexadecimal representation of bytes[14],
        hexadecimal representation of bytes[15]
        ».
        */
    StringBuilder builder;
    TRY(builder.try_appendff("{:02x}{:02x}{:02x}{:02x}-", bytes[0], bytes[1], bytes[2], bytes[3]));
    TRY(builder.try_appendff("{:02x}{:02x}-", bytes[4], bytes[5]));
    TRY(builder.try_appendff("{:02x}{:02x}-", bytes[6], bytes[7]));
    TRY(builder.try_appendff("{:02x}{:02x}-", bytes[8], bytes[9]));
    TRY(builder.try_appendff("{:02x}{:02x}{:02x}{:02x}{:02x}{:02x}", bytes[10], bytes[11], bytes[12], bytes[13], bytes[14], bytes[15]));

    return builder.to_string();
}

}
