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#include "c-calls.hh"
#include "lix/libutil/config-impl.hh"
#include "lix/libutil/environment-variables.hh"
#include "lix/libutil/file-descriptor.hh"
#include "lix/libutil/logging.hh"
#include "lix/libutil/config.hh"
#include "lix/libutil/json.hh"
#include "lix/libutil/position.hh"
#include "lix/libutil/terminal.hh"
#include "manually-drop.hh"

#include <algorithm>
#include <atomic>
#include <mutex>
#include <optional>
#include <sstream>
#include <syslog.h>

namespace nix {

LoggerSettings loggerSettings;

Logger * logger = makeSimpleLogger(true);

Activity Logger::startActivity(
    Verbosity lvl,
    ActivityType type,
    const std::string & s,
    const Fields & fields,
    const Activity * parent
)
{
    Activity result{*this};
    // NOTE we assume that activities aren't started in monstrous numbers, so the inevitable
    // state updates (via progress, result, or setExpected) should be enough to flush stuff.
    (void) startActivityImpl(result.id, lvl, type, s, fields, parent ? parent->id : 0);
    return result;
}

Activity Logger::startActivity(ActivityType type, const Fields & fields, const Activity * parent)
{
    return startActivity(lvlError, type, "", fields, parent);
}

void Logger::writeToStdout(std::string_view s)
{
    writeFull(
        STDOUT_FILENO,
        filterANSIEscapes(
            s,
            !shouldANSI(StandardOutputStream::Stdout),
            std::numeric_limits<unsigned int>::max(),
            false
        )
    );
    writeFull(STDOUT_FILENO, "\n");
}

class SimpleLogger : public Logger
{
public:

    bool systemd, tty;
    bool printBuildLogs;

    SimpleLogger(bool printBuildLogs)
        : printBuildLogs(printBuildLogs)
    {
        systemd = getEnv("IN_SYSTEMD") == "1";
        tty = shouldANSI();
    }

    bool isVerbose() override {
        return printBuildLogs;
    }

    BufferState log(Verbosity lvl, std::string_view s) override
    {
        if (lvl > verbosity) {
            return BufferState::HasSpace;
        }

        std::string prefix;

        if (systemd) {
            char c;
            switch (lvl) {
            case lvlError: c = '3'; break;
            case lvlWarn: c = '4'; break;
            case lvlNotice: case lvlInfo: c = '5'; break;
            case lvlTalkative: case lvlChatty: c = '6'; break;
            case lvlDebug: case lvlVomit:
            default: c = '7'; break; // default case should not happen, and missing enum case is reported by -Werror=switch-enum
            }
            prefix = std::string("<") + c + ">";
        }

        writeLogsToStderr(prefix + filterANSIEscapes(s, !tty) + "\n");
        return BufferState::HasSpace;
    }

    BufferState logEI(const ErrorInfo & ei) override
    {
        std::stringstream oss;
        showErrorInfo(oss, ei, loggerSettings.showTrace.get());

        return log(ei.level, oss.str());
    }

    BufferState startActivityImpl(
        ActivityId act,
        Verbosity lvl,
        ActivityType type,
        const std::string & s,
        const Fields & fields,
        ActivityId parent
    ) override
    {
        if (lvl <= verbosity && !s.empty()) {
            return log(lvl, s + "...");
        }
        return BufferState::HasSpace;
    }

    BufferState resultImpl(ActivityId act, ResultType type, const Fields & fields) override
    {
        if (type == resBuildLogLine && printBuildLogs) {
            auto lastLine = fields[0].s;
            printError("%1%", Uncolored(lastLine));
        }
        else if (type == resPostBuildLogLine) {
            auto lastLine = fields[0].s;
            printError("post-build-hook: %1%", Uncolored(lastLine));
        }
        return BufferState::HasSpace;
    }
};

Verbosity verbosity = lvlInfo;

Verbosity verbosityFromIntClamped(int val)
{
    int clamped = std::clamp(val, int(lvlError), int(lvlVomit));
    return static_cast<Verbosity>(clamped);
}

Logger * makeSimpleLogger(bool printBuildLogs)
{
    return new SimpleLogger(printBuildLogs);
}

std::atomic<uint64_t> nextId{0};

Activity::Activity(Logger & logger) : logger(&logger), id(nextId++ + (((uint64_t) getpid()) << 32))
{
}

void to_json(JSON & json, std::shared_ptr<Pos> pos)
{
    if (pos) {
        json["line"] = pos->line;
        json["column"] = pos->column;
        std::ostringstream str;
        pos->print(str, true);
        json["file"] = str.str();
    } else {
        json["line"] = nullptr;
        json["column"] = nullptr;
        json["file"] = nullptr;
    }
}

struct JSONLogger : Logger {
    Logger & prevLogger;

    JSONLogger(Logger & prevLogger) : prevLogger(prevLogger) { }

    bool isVerbose() override {
        return true;
    }

    void addFields(JSON & json, const Fields & fields)
    {
        if (fields.empty()) return;
        auto & arr = json["fields"] = JSON::array();
        for (auto & f : fields)
            if (f.type == Logger::Field::tInt)
                arr.push_back(f.i);
            else if (f.type == Logger::Field::tString)
                arr.push_back(f.s);
            else
                abort();
    }

    BufferState write(const JSON & json)
    {
        return prevLogger.log(
            lvlError, "@nix " + json.dump(-1, ' ', false, JSON::error_handler_t::replace)
        );
    }

    BufferState log(Verbosity lvl, std::string_view s) override
    {
        JSON json;
        json["action"] = "msg";
        json["level"] = lvl;
        json["msg"] = s;
        return write(json);
    }

    BufferState logEI(const ErrorInfo & ei) override
    {
        std::ostringstream oss;
        showErrorInfo(oss, ei, loggerSettings.showTrace.get());

        JSON json;
        json["action"] = "msg";
        json["level"] = ei.level;
        json["msg"] = oss.str();
        json["raw_msg"] = ei.msg.str();
        to_json(json, ei.pos);

        if (loggerSettings.showTrace.get() && !ei.traces.empty()) {
            JSON traces = JSON::array();
            for (auto iter = ei.traces.rbegin(); iter != ei.traces.rend(); ++iter) {
                JSON stackFrame;
                stackFrame["raw_msg"] = iter->hint.str();
                to_json(stackFrame, iter->pos);
                traces.push_back(stackFrame);
            }

            json["trace"] = traces;
        }

        return write(json);
    }

    BufferState startActivityImpl(
        ActivityId act,
        Verbosity lvl,
        ActivityType type,
        const std::string & s,
        const Fields & fields,
        ActivityId parent
    ) override
    {
        JSON json;
        json["action"] = "start";
        json["id"] = act;
        json["level"] = lvl;
        json["type"] = type;
        json["text"] = s;
        json["parent"] = parent;
        addFields(json, fields);
        return write(json);
    }

    BufferState stopActivityImpl(ActivityId act) override
    {
        JSON json;
        json["action"] = "stop";
        json["id"] = act;
        return write(json);
    }

    BufferState resultImpl(ActivityId act, ResultType type, const Fields & fields) override
    {
        JSON json;
        json["action"] = "result";
        json["id"] = act;
        json["type"] = type;
        addFields(json, fields);
        return write(json);
    }
};

Logger * makeJSONLogger(Logger & prevLogger)
{
    return new JSONLogger(prevLogger);
}

MakeError(StructuredLogError, Error);

static Logger::Fields getFields(JSON & json)
{
    Logger::Fields fields;
    for (auto & f : json) {
        if (f.type() == JSON::value_t::number_unsigned)
            fields.emplace_back(Logger::Field(f.get<uint64_t>()));
        else if (f.type() == JSON::value_t::string)
            fields.emplace_back(Logger::Field(f.get<std::string>()));
        else throw StructuredLogError("unsupported log field type '%s'", f.type_name());
    }
    return fields;
}

std::optional<JSON> parseJSONMessage(const std::string & msg, std::string_view source)
{
    if (!msg.starts_with("@nix ")) return std::nullopt;
    try {
        return json::parse(std::string(msg, 5));
    } catch (std::exception & e) { // NOLINT(lix-foreign-exceptions)
        printError("bad JSON log message from %s: %s",
            Uncolored(source),
            e.what());
    }
    return std::nullopt;
}

std::optional<Logger::BufferState> handleJSONLogMessage(
    JSON & json,
    const Activity & act,
    std::map<ActivityId, Activity> & activities,
    std::string_view source
)
{
    try {
        std::string action = json["action"];

        if (action == "start") {
            auto type = (ActivityType) json["type"];
            activities.emplace(
                json["id"],
                act.addChild(
                    (Verbosity) json["level"], type, json["text"], getFields(json["fields"])
                )
            );
        }

        else if (action == "stop")
            activities.erase((ActivityId) json["id"]);

        else if (action == "result") {
            auto i = activities.find((ActivityId) json["id"]);
            if (i != activities.end())
                return i->second.result((ResultType) json["type"], getFields(json["fields"]));
        }

        else if (action == "setPhase") {
            std::string phase = json["phase"];
            return act.result(resSetPhase, phase);
        }

        else if (action == "msg") {
            std::string msg = json["msg"];
            return logger->log((Verbosity) json["level"], msg);
        }

        return Logger::BufferState::HasSpace;
    } catch (json::JSONError & e) {
        printTaggedWarning(
            "Unable to handle a JSON message from %s: %s", Uncolored(source), e.what()
        );
        return std::nullopt;
    } catch (StructuredLogError & e) {
        printTaggedWarning(
            "Unable to handle a JSON message from %s: %s", Uncolored(source), e.what()
        );
        return std::nullopt;
    }
}

std::optional<Logger::BufferState> handleJSONLogMessage(
    const std::string & msg,
    const Activity & act,
    std::map<ActivityId, Activity> & activities,
    std::string_view source
)
{
    auto json = parseJSONMessage(msg, source);
    if (!json) {
        return std::nullopt;
    }

    return handleJSONLogMessage(*json, act, activities, source);
}

Activity::~Activity()
{
    if (!logger) {
        return;
    }
    try {
        // NOTE we can't flush here, and async destruction of activities is bound to fail
        // at some point. eventually something will flush the buffer for us (see also the
        // startActivity comment, we also don't flush buffers there even when they fill.)
        (void) logger->stopActivityImpl(id);
    } catch (...) {
        ignoreExceptionInDestructor();
    }
}

void writeLogsToStderr(std::string_view s)
{
    // NOTE: If this lock is a regular static item (and not something
    // indestructible), then it will be destructed when Nix shuts down. When
    // other threads are running, it becomes possible for a static to be
    // destructed before Nix ends, leading to errors.
    //
    // Therefore, we use a wrapper type to block it ever getting destroyed.
    //
    // TODO: Audit other statics for this issue?
    //
    // See: https://git.lix.systems/lix-project/lix/issues/702
    // See: https://stackoverflow.com/a/27671727/5719760
    static ManuallyDrop<std::mutex> lock {std::in_place_t{}};

    // make sure only one thread uses this function at any given time.
    // multiple concurrent threads can have deleterious effects on log
    // output, especially when layering structured formats (like JSON)
    // on top of a SimpleLogger which is itself not thread-safe. every
    // Logger instance should be thread-safe in an ideal world, but we
    // cannot really enforce that on a per-logger level at this point.
    std::unique_lock _lock(*lock);
    try {
        writeFull(STDERR_FILENO, s, false);
    } catch (SysError & e) {
        /* Ignore failing writes to stderr.  We need to ignore write
           errors to ensure that cleanup code that logs to stderr runs
           to completion if the other side of stderr has been closed
           unexpectedly. */
    }
}

void logFatal(std::string const & s)
{
    writeLogsToStderr(s + "\n");
    // std::string for guaranteed null termination
    syslog(LOG_CRIT, "%s", requireCString(s).asCStr());
}

std::optional<std::string> LogLineSplitter::feed(std::string_view & input)
{
    for (auto [idx, c] : enumerate(input)) {
        if (c == '\r') {
            pos = 0;
        } else if (c == '\n') {
            input = input.substr(idx + 1);
            return finish();
        } else {
            if (pos >= line.size()) {
                line.resize(pos + 1);
            }
            line[pos++] = c;
        }
    }
    input = {};
    return std::nullopt;
}

std::string LogLineSplitter::finish()
{
    pos = 0;
    return std::move(line);
}
}