/**
 * This is not the set of all possible signals.
 *
 * It IS, however, the set of all signals that trigger
 * an exit on either Linux or BSD systems.  Linux is a
 * superset of the signal names supported on BSD, and
 * the unknown signals just fail to register, so we can
 * catch that easily enough.
 *
 * Windows signals are a different set, since there are
 * signals that terminate Windows processes, but don't
 * terminate (or don't even exist) on Posix systems.
 *
 * Don't bother with SIGKILL.  It's uncatchable, which
 * means that we can't fire any callbacks anyway.
 *
 * If a user does happen to register a handler on a non-
 * fatal signal like SIGWINCH or something, and then
 * exit, it'll end up firing `process.emit('exit')`, so
 * the handler will be fired anyway.
 *
 * SIGBUS, SIGFPE, SIGSEGV and SIGILL, when not raised
 * artificially, inherently leave the process in a
 * state from which it is not safe to try and enter JS
 * listeners.
 */
const signals = [];
signals.push('SIGHUP', 'SIGINT', 'SIGTERM');
if (process.platform !== 'win32') {
    signals.push('SIGALRM', 'SIGABRT', 'SIGVTALRM', 'SIGXCPU', 'SIGXFSZ', 'SIGUSR2', 'SIGTRAP', 'SIGSYS', 'SIGQUIT', 'SIGIOT'
    // should detect profiler and enable/disable accordingly.
    // see #21
    // 'SIGPROF'
    );
}
if (process.platform === 'linux') {
    signals.push('SIGIO', 'SIGPOLL', 'SIGPWR', 'SIGSTKFLT');
}

// Note: since nyc uses this module to output coverage, any lines
// that are in the direct sync flow of nyc's outputCoverage are
// ignored, since we can never get coverage for them.
// grab a reference to node's real process object right away
const processOk = (process) => !!process &&
    typeof process === 'object' &&
    typeof process.removeListener === 'function' &&
    typeof process.emit === 'function' &&
    typeof process.reallyExit === 'function' &&
    typeof process.listeners === 'function' &&
    typeof process.kill === 'function' &&
    typeof process.pid === 'number' &&
    typeof process.on === 'function';
const kExitEmitter = Symbol.for('signal-exit emitter');
const global = globalThis;
const ObjectDefineProperty = Object.defineProperty.bind(Object);
// teeny special purpose ee
class Emitter {
    emitted = {
        afterExit: false,
        exit: false,
    };
    listeners = {
        afterExit: [],
        exit: [],
    };
    count = 0;
    id = Math.random();
    constructor() {
        if (global[kExitEmitter]) {
            return global[kExitEmitter];
        }
        ObjectDefineProperty(global, kExitEmitter, {
            value: this,
            writable: false,
            enumerable: false,
            configurable: false,
        });
    }
    on(ev, fn) {
        this.listeners[ev].push(fn);
    }
    removeListener(ev, fn) {
        const list = this.listeners[ev];
        const i = list.indexOf(fn);
        /* c8 ignore start */
        if (i === -1) {
            return;
        }
        /* c8 ignore stop */
        if (i === 0 && list.length === 1) {
            list.length = 0;
        }
        else {
            list.splice(i, 1);
        }
    }
    emit(ev, code, signal) {
        if (this.emitted[ev]) {
            return false;
        }
        this.emitted[ev] = true;
        let ret = false;
        for (const fn of this.listeners[ev]) {
            ret = fn(code, signal) === true || ret;
        }
        if (ev === 'exit') {
            ret = this.emit('afterExit', code, signal) || ret;
        }
        return ret;
    }
}
class SignalExitBase {
}
const signalExitWrap = (handler) => {
    return {
        onExit(cb, opts) {
            return handler.onExit(cb, opts);
        },
        load() {
            return handler.load();
        },
        unload() {
            return handler.unload();
        },
    };
};
class SignalExitFallback extends SignalExitBase {
    onExit() {
        return () => { };
    }
    load() { }
    unload() { }
}
class SignalExit extends SignalExitBase {
    // "SIGHUP" throws an `ENOSYS` error on Windows,
    // so use a supported signal instead
    /* c8 ignore start */
    #hupSig = process$1.platform === 'win32' ? 'SIGINT' : 'SIGHUP';
    /* c8 ignore stop */
    #emitter = new Emitter();
    #process;
    #originalProcessEmit;
    #originalProcessReallyExit;
    #sigListeners = {};
    #loaded = false;
    constructor(process) {
        super();
        this.#process = process;
        // { <signal>: <listener fn>, ... }
        this.#sigListeners = {};
        for (const sig of signals) {
            this.#sigListeners[sig] = () => {
                // If there are no other listeners, an exit is coming!
                // Simplest way: remove us and then re-send the signal.
                // We know that this will kill the process, so we can
                // safely emit now.
                const listeners = this.#process.listeners(sig);
                let { count } = this.#emitter;
                // This is a workaround for the fact that signal-exit v3 and signal
                // exit v4 are not aware of each other, and each will attempt to let
                // the other handle it, so neither of them do. To correct this, we
                // detect if we're the only handler *except* for previous versions
                // of signal-exit, and increment by the count of listeners it has
                // created.
                /* c8 ignore start */
                const p = process;
                if (typeof p.__signal_exit_emitter__ === 'object' &&
                    typeof p.__signal_exit_emitter__.count === 'number') {
                    count += p.__signal_exit_emitter__.count;
                }
                /* c8 ignore stop */
                if (listeners.length === count) {
                    this.unload();
                    const ret = this.#emitter.emit('exit', null, sig);
                    /* c8 ignore start */
                    const s = sig === 'SIGHUP' ? this.#hupSig : sig;
                    if (!ret)
                        process.kill(process.pid, s);
                    /* c8 ignore stop */
                }
            };
        }
        this.#originalProcessReallyExit = process.reallyExit;
        this.#originalProcessEmit = process.emit;
    }
    onExit(cb, opts) {
        /* c8 ignore start */
        if (!processOk(this.#process)) {
            return () => { };
        }
        /* c8 ignore stop */
        if (this.#loaded === false) {
            this.load();
        }
        const ev = opts?.alwaysLast ? 'afterExit' : 'exit';
        this.#emitter.on(ev, cb);
        return () => {
            this.#emitter.removeListener(ev, cb);
            if (this.#emitter.listeners['exit'].length === 0 &&
                this.#emitter.listeners['afterExit'].length === 0) {
                this.unload();
            }
        };
    }
    load() {
        if (this.#loaded) {
            return;
        }
        this.#loaded = true;
        // This is the number of onSignalExit's that are in play.
        // It's important so that we can count the correct number of
        // listeners on signals, and don't wait for the other one to
        // handle it instead of us.
        this.#emitter.count += 1;
        for (const sig of signals) {
            try {
                const fn = this.#sigListeners[sig];
                if (fn)
                    this.#process.on(sig, fn);
            }
            catch (_) { }
        }
        this.#process.emit = (ev, ...a) => {
            return this.#processEmit(ev, ...a);
        };
        this.#process.reallyExit = (code) => {
            return this.#processReallyExit(code);
        };
    }
    unload() {
        if (!this.#loaded) {
            return;
        }
        this.#loaded = false;
        signals.forEach(sig => {
            const listener = this.#sigListeners[sig];
            /* c8 ignore start */
            if (!listener) {
                throw new Error('Listener not defined for signal: ' + sig);
            }
            /* c8 ignore stop */
            try {
                this.#process.removeListener(sig, listener);
                /* c8 ignore start */
            }
            catch (_) { }
            /* c8 ignore stop */
        });
        this.#process.emit = this.#originalProcessEmit;
        this.#process.reallyExit = this.#originalProcessReallyExit;
        this.#emitter.count -= 1;
    }
    #processReallyExit(code) {
        /* c8 ignore start */
        if (!processOk(this.#process)) {
            return 0;
        }
        this.#process.exitCode = code || 0;
        /* c8 ignore stop */
        this.#emitter.emit('exit', this.#process.exitCode, null);
        return this.#originalProcessReallyExit.call(this.#process, this.#process.exitCode);
    }
    #processEmit(ev, ...args) {
        const og = this.#originalProcessEmit;
        if (ev === 'exit' && processOk(this.#process)) {
            if (typeof args[0] === 'number') {
                this.#process.exitCode = args[0];
                /* c8 ignore start */
            }
            /* c8 ignore start */
            const ret = og.call(this.#process, ev, ...args);
            /* c8 ignore start */
            this.#emitter.emit('exit', this.#process.exitCode, null);
            /* c8 ignore stop */
            return ret;
        }
        else {
            return og.call(this.#process, ev, ...args);
        }
    }
}
const process$1 = globalThis.process;
// wrap so that we call the method on the actual handler, without
// exporting it directly.
const { 
/**
 * Called when the process is exiting, whether via signal, explicit
 * exit, or running out of stuff to do.
 *
 * If the global process object is not suitable for instrumentation,
 * then this will be a no-op.
 *
 * Returns a function that may be used to unload signal-exit.
 */
onExit} = signalExitWrap(processOk(process$1) ? new SignalExit(process$1) : new SignalExitFallback());

export { onExit as o };
