error_handler.js

const errors = Object.freeze({
    UNKNOWN_ERROR: 'Unknown Error',
    MISSING_EMPLOYEE: 'Missing Employee',
    DUPLICATE_EMPLOYEE: 'Duplicate Employee',
    PARSE_ISSUE: 'Parse Issue',
    DISCONNECTED: 'Disconnected'
})

const errorHandler = (function() {
    let erroring = false
    
    const errorWindow = document.createElement('div')
    errorWindow.className = 'window errorWindow'

    const windowHeader = document.createElement('p')
    windowHeader.textContent = 'Application Error'
    windowHeader.className = 'error'
    errorWindow.appendChild(windowHeader)

    const textSpace = document.createElement('div')
    textSpace.className = 'textSpace'
    errorWindow.appendChild(textSpace)

    const confirmationButton = document.createElement('div')
    confirmationButton.className = 'windowButton'
    confirmationButton.textContent = String.fromCharCode(10003)
    errorWindow.appendChild(confirmationButton)

    confirmationButton.addEventListener('click', event => {
        errorQueue.shift()
        if(errorQueue.length >= 1) resolveError(errorQueue[0])
        else {
            document.body.removeChild(errorWindow)
            screen.enable()
            erroring = false
        }
    })

    function wrapper(func) {
        function onClick() {
            func()
            confirmationButton.removeEventListener('click', onClick)
        }
        confirmationButton.addEventListener('click', onClick)
    }

    function resolveError(error) {
        erroring = true
        // document.body.removeChild(errorWindow)

        let message = 'Unknown Error'
        if(error.type === errors.MISSING_EMPLOYEE) {
            message = `During loading, the project '${error.details.host.name}' requested the employee '${error.details.slot.employeeName}' (${error.details.slot.type}). This employee does not exist in the application.
            References to employee '${error.details.slot.employeeName}' will be removed from the application to fix conflicts. This can be reverted manually by re-adding the employee.
            Press the button below to confirm.`
            wrapper(() => save.all())
        }
        else if(error.type === errors.DUPLICATE_EMPLOYEE) {
            message = `During loading, the application detected duplicate copies of employee ${error.employee}; e.g. employees with the same name, in the same sheet, with the same job & details. Duplicate employees will be removed from the application to fix conflicts (Note: it is not possible to manually add duplicate employees and therefore this error-cleanup should not result in the loss of legitimate information).
            Press the button below to confirm.`

        }
        else if(error.type === errors.PARSE_ISSUE) {
            message = `During loading, a parsing issue was encountered. This means that there was likely an issue in the saving of the file you are attempting to open. Other files should still be accessible. Press the button below to confirm, and select another file.`
            wrapper(() => {
                openDirectorySelect(true)
                screen.disable(false)
            })
        }
        else if(error.type === errors.DISCONNECTED) {
            message = `Disconnected from server. This could be due to a server crash, or because of an unstable internet connection. Ensure that you have a stable internet connection. Be aware that continuing without a stable connection may lead to data loss. Press the button below to continue.`
        }
        else if(error.type === errors.UNKNOWN_ERROR) {
            message = `An unknown error has occurred. Restarting the application is most likely to avoid further issue. Press the button below to continue.`
        }
        windowHeader.textContent = `Error: ${error.type} (1 of ${errorQueue.length})`
        textSpace.textContent = message

        if(errorWindow.parentNode !== document.body) document.body.appendChild(errorWindow)
        screen.disable(false)
    }

    const errorQueue = []
    function registerError(error) {
        if(errorQueue.length < 1) resolveError(error)
        errorQueue.push(error)

        const errorHeading = document.querySelector('.error')
        if(errorHeading) {
            errorHeading.textContent = errorHeading.textContent.slice(0, -2) + errorQueue.length + ')'
        }
    }

    window.onerror = function(message, url, lineNumber) {
        console.log('error')
        // makeSaveRequest(JSON.stringify({data: {message, url, lineNumber}, type: 'log'}))
    }
    
    return {
        register: registerError, get erroring() { return erroring }
    }
})()