// Copyright 2024 The Dawn & Tint Authors
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#include <cstddef>
#include <span>

#include "src/tint/cmd/fuzz/ir/fuzz.h"
#include "src/tint/lang/core/ir/module.h"
#include "src/tint/lang/core/ir/validator.h"

#if TINT_BUILD_IR_BINARY

#include "src/tint/lang/core/ir/binary/decode.h"
#include "src/tint/utils/command/cli.h"
#include "src/tint/utils/containers/vector.h"
#include "src/tint/utils/macros/defer.h"

TINT_BEGIN_DISABLE_PROTOBUF_WARNINGS();
#include "src/libfuzzer/libfuzzer_macro.h"
#include "src/tint/utils/protos/ir_fuzz/ir_fuzz.pb.h"
#include "testing/libfuzzer/proto/lpm_interface.h"
TINT_END_DISABLE_PROTOBUF_WARNINGS();

namespace {

tint::fuzz::ir::Options options;

}

DEFINE_BINARY_PROTO_FUZZER(const tint::cmd::fuzz::ir::pb::Root& pb) {
    /// As the fuzzers are free to mutate the module, we need to deserialize a new module for each
    /// sub-fuzzer. Because the protobuf may error when deserializing and the module may be invalid,
    /// we early deserialize. If this fails, then we do not call Run().
    thread_local std::optional<tint::core::ir::Module> module;
    {
        auto decoded = tint::core::ir::binary::Decode(pb.module());
        if (decoded != tint::Success) {
            return;  // Failed to decode
        }
        module = std::move(decoded.Move());
    }
    auto acquire_module = [&] {
        if (!module) {
            auto decoded = tint::core::ir::binary::Decode(pb.module());
            TINT_ASSERT(decoded == tint::Success)
                << "module successfully decoded once, then failed a subsequent time\n"
                << decoded.Failure();

            module = std::move(decoded.Move());
        }

        auto out = std::move(module.value());
        module.reset();
        return out;
    };

    std::span<const std::byte> data(reinterpret_cast<const std::byte*>(pb.data().data()),
                                    pb.data().length());
    tint::fuzz::ir::Run(acquire_module, options, data);
}

// Explicitly specify the visibility to prevent the linker from stripping the function on macOS, as
// the LibFuzzer runtime uses dlsym() instead of calling the function directly.
extern "C" __attribute__((visibility("default"))) int LLVMFuzzerInitialize(int* argc,
                                                                           char*** argv) {
    tint::cli::OptionSet opts;

    tint::Vector<std::string_view, 8> arguments;
    for (int i = 1; i < *argc; i++) {
        std::string_view arg((*argv)[i]);
        if (!arg.empty()) {
            arguments.Push(arg);
        }
    }

    auto show_help = [&] {
        std::cerr << "Custom fuzzer options:" << '\n';
        opts.ShowHelp(std::cerr);
        std::cerr << '\n';
        // Change args to show libfuzzer help
        std::cerr << "Standard libfuzzer ";  // libfuzzer will print 'Usage:'
        static char help[] = "-help=1";
        *argc = 2;
        (*argv)[1] = help;
    };

    auto& opt_help = opts.Add<tint::cli::BoolOption>("help", "shows the usage");
    auto& opt_filter = opts.Add<tint::cli::StringOption>(
        "filter", "runs only the fuzzers with the given substring");
    auto& opt_concurrent =
        opts.Add<tint::cli::BoolOption>("concurrent", "runs the fuzzers concurrently");
    auto& opt_verbose =
        opts.Add<tint::cli::BoolOption>("verbose", "prints the name of each fuzzer before running");
#if TINT_BUILD_FUZZER_VULKAN_SUPPORT
    auto& opt_vk_icd = opts.Add<tint::cli::StringOption>("vk_icd", "path to Vulkan ICD JSON");
#endif
    auto& opt_dump_ir =
        opts.Add<tint::cli::BoolOption>("dump-ir", "Dump IR at each stage of the compilation flow");

    tint::cli::ParseOptions parse_opts;
    parse_opts.ignore_unknown = true;
    if (auto res = opts.Parse(arguments, parse_opts); res != tint::Success) {
        show_help();
        std::cerr << res.Failure();
        return 0;
    }

    if (opt_help.value.value_or(false)) {
        show_help();
        return 0;
    }

    options.filter = opt_filter.value.value_or("");
    options.run_concurrently = opt_concurrent.value.value_or(false);
    options.verbose = opt_verbose.value.value_or(false);
#if TINT_BUILD_FUZZER_VULKAN_SUPPORT
    options.vk_icd = opt_vk_icd.value.value_or("");
#endif
    options.dump_ir_when_validating = opt_dump_ir.value.value_or(false);

    return 0;
}

#endif