// Copyright 2021 The Tint Authors.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//     http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

#include "src/tint/fuzzers/tint_ast_fuzzer/cli.h"

#include <cstring>
#include <iostream>
#include <limits>
#include <sstream>
#include <string>
#include <utility>

namespace tint::fuzzers::ast_fuzzer {
namespace {

const char* const kHelpMessage = R"(
This is a fuzzer for the Tint compiler that works by mutating the AST.

Below is a list of all supported parameters for this fuzzer. You may want to
run it with -help=1 to check out libfuzzer parameters.

  -tint_enable_all_mutations=
                       If `false`, the fuzzer will only apply mutations from a
                       randomly selected subset of mutation types. Otherwise,
                       all mutation types will be considered. This must be one
                       of `true` or `false` (without `). By default it's `false`.

  -tint_fuzzing_target=
                       Specifies the shading language to target during fuzzing.
                       This must be one or a combination of `wgsl`, `spv`, `hlsl`,
                       `msl` (without `) separated by commas. By default it's
                       `wgsl,msl,hlsl,spv`.

  -tint_help
                       Show this message. Note that there is also a -help=1
                       parameter that will display libfuzzer's help message.

  -tint_mutation_batch_size=
                       The number of mutations to apply in a single libfuzzer
                       mutation session. This must be a numeric value that fits
                       in type `uint32_t`. By default it's 5.
)";

bool HasPrefix(const char* str, const char* prefix) {
    return strncmp(str, prefix, strlen(prefix)) == 0;
}

[[noreturn]] void InvalidParam(const char* param) {
    std::cout << "Invalid value for " << param << std::endl;
    std::cout << kHelpMessage << std::endl;
    exit(1);
}

bool ParseBool(const char* value, bool* out) {
    if (!strcmp(value, "true")) {
        *out = true;
    } else if (!strcmp(value, "false")) {
        *out = false;
    } else {
        return false;
    }
    return true;
}

bool ParseUint32(const char* value, uint32_t* out) {
    auto parsed = strtoul(value, nullptr, 10);
    if (parsed > std::numeric_limits<uint32_t>::max()) {
        return false;
    }
    *out = static_cast<uint32_t>(parsed);
    return true;
}

bool ParseFuzzingTarget(const char* value, FuzzingTarget* out) {
    if (!strcmp(value, "wgsl")) {
        *out = FuzzingTarget::kWgsl;
    } else if (!strcmp(value, "spv")) {
        *out = FuzzingTarget::kSpv;
    } else if (!strcmp(value, "msl")) {
        *out = FuzzingTarget::kMsl;
    } else if (!strcmp(value, "hlsl")) {
        *out = FuzzingTarget::kHlsl;
    } else {
        return false;
    }
    return true;
}

}  // namespace

CliParams ParseCliParams(int* argc, char** argv) {
    CliParams cli_params;
    auto help = false;

    for (int i = *argc - 1; i > 0; --i) {
        auto param = argv[i];
        auto recognized_parameter = true;

        if (HasPrefix(param, "-tint_enable_all_mutations=")) {
            if (!ParseBool(param + sizeof("-tint_enable_all_mutations=") - 1,
                           &cli_params.enable_all_mutations)) {
                InvalidParam(param);
            }
        } else if (HasPrefix(param, "-tint_mutation_batch_size=")) {
            if (!ParseUint32(param + sizeof("-tint_mutation_batch_size=") - 1,
                             &cli_params.mutation_batch_size)) {
                InvalidParam(param);
            }
        } else if (HasPrefix(param, "-tint_fuzzing_target=")) {
            auto result = FuzzingTarget::kNone;

            std::stringstream ss(param + sizeof("-tint_fuzzing_target=") - 1);
            for (std::string value; std::getline(ss, value, ',');) {
                auto tmp = FuzzingTarget::kNone;
                if (!ParseFuzzingTarget(value.c_str(), &tmp)) {
                    InvalidParam(param);
                }
                result = result | tmp;
            }

            if (result == FuzzingTarget::kNone) {
                InvalidParam(param);
            }

            cli_params.fuzzing_target = result;
        } else if (!strcmp(param, "-tint_help")) {
            help = true;
        } else {
            recognized_parameter = false;
        }

        if (recognized_parameter) {
            // Remove the recognized parameter from the list of all parameters by
            // swapping it with the last one. This will suppress warnings in the
            // libFuzzer about unrecognized parameters. By default, libFuzzer thinks
            // that all user-defined parameters start with two dashes. However, we are
            // forced to use a single one to make the fuzzer compatible with the
            // ClusterFuzz.
            std::swap(argv[i], argv[*argc - 1]);
            *argc -= 1;
        }
    }

    if (help) {
        std::cout << kHelpMessage << std::endl;
        exit(0);
    }

    return cli_params;
}

}  // namespace tint::fuzzers::ast_fuzzer