namespace fs = std::filesystem;

const auto home = mcpp::home::root();

std::error_code ec;

const auto registry = home / "registry";

const auto config = home / "config.toml";

const bool initialized = fs::exists(config, ec);

auto s = [](const fs::path& p) { return p.string(); };

return nlohmann::json{

{"initialized", initialized},

{"mcppHome", s(home)},

{"registry", s(registry)},

{"xlingsHome", s(registry)}, // registryDir unless overridden

{"xlingsBinary", s(registry / "bin" /

("xlings" + std::string(mcpp::platform::exe_suffix)))},

{"config", s(config)},

{"buildCache", s(mcpp::home::cache_root())},

{"mcppVersion", std::string(mcpp::toolchain::MCPP_VERSION)},

};

if (auto f = parsed.value("format")) {

auto fmt = mcpp::wire::parse_format(*f);

if (!fmt) {

std::println(stderr, "error: {}",

mcpp::wire::unsupported_format(*f));

return 2;

}

mcpp::wire::emit({

.kind = "mcpp.env",

.effects = {}, // this path creates nothing; see above

.data = env_data_readonly(),

});

return 0;

}

return mcpp::doctor::env_report();

// ⚠️ `--format` IS ONLY DEFINED FOR THE `toolchain` TOPIC, and saying so

// beats emitting an envelope whose `data` silently omits what was asked

// for. `runtime` and `deps` have their own shapes and no consumer yet;

// inventing one here would publish a contract nobody has read.

if (auto f = parsed.value("format")) {

auto fmt = mcpp::wire::parse_format(*f);

if (!fmt) {

std::println(stderr, "error: {}",

mcpp::wire::unsupported_format(*f));

return 2;

}

const std::string topic = parsed.positional(0);

if (!topic.empty() && topic != "toolchain") {

std::println(stderr,

"error: --format json is defined for `mcpp why toolchain`; "

"'{}' has no machine-readable shape yet", topic);

return 2;

}

return mcpp::doctor::why_toolchain_json(

parsed.option_or_empty("target").value(),

parsed.option_or_empty("toolchain").value());

}

return mcpp::doctor::why_report(parsed.positional(0));

std::string code = parsed.positional(0);

if (code.empty()) {

std::println(stderr, "error: explain requires an error code (e.g. E0001)");

return 2;

}

return cmd_explain(code);