// roughly based on https://github.com/sindresorhus/exit-hook/blob/main/index.js, MIT license

let installed = false
let handled = false

const callbacks = new Set<() => void>()

const myHandlers = new Map<string, () => void>()

function register(shouldManuallyExit: boolean, signal: number, event: string) {
    function eventHandler() {
        if (handled) {
            return
        }

        handled = true

        for (const callback of callbacks) {
            callback()
        }

        for (const [event, handler] of myHandlers) {
            process.off(event, handler)
        }

        if (shouldManuallyExit) {
            // send the signal again and let node handle it
            process.kill(process.pid, signal)
        }
    }

    process.on(event, eventHandler)
    myHandlers.set(event, eventHandler)
}

export function beforeExit(fn: () => void): () => void {
    // unsupported platform
    if (typeof process === 'undefined') return () => {}

    if (!installed) {
        installed = true

        register(true, 0, 'beforeExit')
        register(true, 2, 'SIGINT')
        register(true, 15, 'SIGTERM')
        register(false, 15, 'exit')
    }

    callbacks.add(fn)

    return () => {
        callbacks.delete(fn)
    }
}