/**
 * Script for landing.ejs
 */
// Requirements
const cp                      = require('child_process')
const crypto                  = require('crypto')
const { URL }                 = require('url')
const {
    MojangRestAPI,
    getServerStatus
}                             = require('helios-core/mojang')
const {
    RestResponseStatus,
    isDisplayableError,
    mcVersionAtLeast
}                             = require('helios-core/common')
const {
    FullRepair,
    DistributionIndexProcessor,
    MojangIndexProcessor
}                             = require('helios-core/dl')
const {
    getDefaultSemverRange,
    validateSelectedJvm,
    ensureJavaDirIsRoot,
    javaExecFromRoot,
    discoverBestJvmInstallation
}                             = require('helios-core/java')

// Internal Requirements
const DiscordWrapper          = require('./assets/js/discordwrapper')
const ProcessBuilder          = require('./assets/js/processbuilder')

// Launch Elements
const launch_content          = document.getElementById('launch_content')
const launch_details          = document.getElementById('launch_details')
const launch_progress         = document.getElementById('launch_progress')
const launch_progress_label   = document.getElementById('launch_progress_label')
const launch_details_text     = document.getElementById('launch_details_text')
const server_selection_button = document.getElementById('server_selection_button')
const user_text               = document.getElementById('user_text')

const loggerLanding = LoggerUtil.getLogger('Landing')

/* Launch Progress Wrapper Functions */

/**
 * Show/hide the loading area.
 * 
 * @param {boolean} loading True if the loading area should be shown, otherwise false.
 */
function toggleLaunchArea(loading){
    if(loading){
        launch_details.style.display = 'flex'
        launch_content.style.display = 'none'
    } else {
        launch_details.style.display = 'none'
        launch_content.style.display = 'inline-flex'
    }
}

/**
 * Set the details text of the loading area.
 * 
 * @param {string} details The new text for the loading details.
 */
function setLaunchDetails(details){
    launch_details_text.innerHTML = details
}

/**
 * Set the value of the loading progress bar and display that value.
 * 
 * @param {number} percent Percentage (0-100)
 */
function setLaunchPercentage(percent){
    launch_progress.setAttribute('max', 100)
    launch_progress.setAttribute('value', percent)
    launch_progress_label.innerHTML = percent + '%'
}

/**
 * Set the value of the OS progress bar and display that on the UI.
 * 
 * @param {number} percent Percentage (0-100)
 */
function setDownloadPercentage(percent){
    remote.getCurrentWindow().setProgressBar(percent/100)
    setLaunchPercentage(percent)
}

/**
 * Enable or disable the launch button.
 * 
 * @param {boolean} val True to enable, false to disable.
 */
function setLaunchEnabled(val){
    document.getElementById('launch_button').disabled = !val
}

// Bind launch button
document.getElementById('launch_button').addEventListener('click', async (e) => {
    loggerLanding.info('Launching game..')
    const mcVersion = (await DistroAPI.getDistribution()).getServerById(ConfigManager.getSelectedServer()).rawServer.minecraftVersion
    const jExe = ConfigManager.getJavaExecutable(ConfigManager.getSelectedServer())
    if(jExe == null){
        await asyncSystemScan(mcVersion)
    } else {

        setLaunchDetails(Lang.queryJS('landing.launch.pleaseWait'))
        toggleLaunchArea(true)
        setLaunchPercentage(0, 100)

        // TODO Update to use semver range
        const details = await validateSelectedJvm(ensureJavaDirIsRoot(execPath), getDefaultSemverRange(mcVer))
        if(details != null){
            loggerLanding.info('Jvm Details', details)
            await dlAsync()
        } else {
            await asyncSystemScan(mcVersion)
        }
    }
})

// Bind settings button
document.getElementById('settingsMediaButton').onclick = async e => {
    await prepareSettings()
    switchView(getCurrentView(), VIEWS.settings)
}

// Bind avatar overlay button.
document.getElementById('avatarOverlay').onclick = async e => {
    await prepareSettings()
    switchView(getCurrentView(), VIEWS.settings, 500, 500, () => {
        settingsNavItemListener(document.getElementById('settingsNavAccount'), false)
    })
}

// Bind selected account
function updateSelectedAccount(authUser){
    let username = 'No Account Selected'
    if(authUser != null){
        if(authUser.displayName != null){
            username = authUser.displayName
        }
        if(authUser.uuid != null){
            document.getElementById('avatarContainer').style.backgroundImage = `url('https://mc-heads.net/body/${authUser.uuid}/right')`
        }
    }
    user_text.innerHTML = username
}
updateSelectedAccount(ConfigManager.getSelectedAccount())

// Bind selected server
function updateSelectedServer(serv){
    if(getCurrentView() === VIEWS.settings){
        fullSettingsSave()
    }
    ConfigManager.setSelectedServer(serv != null ? serv.rawServer.id : null)
    ConfigManager.save()
    server_selection_button.innerHTML = '\u2022 ' + (serv != null ? serv.rawServer.name : 'No Server Selected')
    if(getCurrentView() === VIEWS.settings){
        animateSettingsTabRefresh()
    }
    setLaunchEnabled(serv != null)
}
// Real text is set in uibinder.js on distributionIndexDone.
server_selection_button.innerHTML = '\u2022 Loading..'
server_selection_button.onclick = async e => {
    e.target.blur()
    await toggleServerSelection(true)
}

// Update Mojang Status Color
const refreshMojangStatuses = async function(){
    loggerLanding.info('Refreshing Mojang Statuses..')

    let status = 'grey'
    let tooltipEssentialHTML = ''
    let tooltipNonEssentialHTML = ''

    const response = await MojangRestAPI.status()
    let statuses
    if(response.responseStatus === RestResponseStatus.SUCCESS) {
        statuses = response.data
    } else {
        loggerLanding.warn('Unable to refresh Mojang service status.')
        statuses = MojangRestAPI.getDefaultStatuses()
    }
    
    greenCount = 0
    greyCount = 0

    for(let i=0; i<statuses.length; i++){
        const service = statuses[i]

        if(service.essential){
            tooltipEssentialHTML += `<div class="mojangStatusContainer">
                <span class="mojangStatusIcon" style="color: ${MojangRestAPI.statusToHex(service.status)};">&#8226;</span>
                <span class="mojangStatusName">${service.name}</span>
            </div>`
        } else {
            tooltipNonEssentialHTML += `<div class="mojangStatusContainer">
                <span class="mojangStatusIcon" style="color: ${MojangRestAPI.statusToHex(service.status)};">&#8226;</span>
                <span class="mojangStatusName">${service.name}</span>
            </div>`
        }

        if(service.status === 'yellow' && status !== 'red'){
            status = 'yellow'
        } else if(service.status === 'red'){
            status = 'red'
        } else {
            if(service.status === 'grey'){
                ++greyCount
            }
            ++greenCount
        }

    }

    if(greenCount === statuses.length){
        if(greyCount === statuses.length){
            status = 'grey'
        } else {
            status = 'green'
        }
    }
    
    document.getElementById('mojangStatusEssentialContainer').innerHTML = tooltipEssentialHTML
    document.getElementById('mojangStatusNonEssentialContainer').innerHTML = tooltipNonEssentialHTML
    document.getElementById('mojang_status_icon').style.color = MojangRestAPI.statusToHex(status)
}

const refreshServerStatus = async (fade = false) => {
    loggerLanding.info('Refreshing Server Status')
    const serv = (await DistroAPI.getDistribution()).getServerById(ConfigManager.getSelectedServer())

    let pLabel = 'SERVER'
    let pVal = 'OFFLINE'

    try {

        const servStat = await getServerStatus(47, serv.hostname, serv.port)
        console.log(servStat)
        pLabel = 'PLAYERS'
        pVal = servStat.players.online + '/' + servStat.players.max

    } catch (err) {
        loggerLanding.warn('Unable to refresh server status, assuming offline.')
        loggerLanding.debug(err)
    }
    if(fade){
        $('#server_status_wrapper').fadeOut(250, () => {
            document.getElementById('landingPlayerLabel').innerHTML = pLabel
            document.getElementById('player_count').innerHTML = pVal
            $('#server_status_wrapper').fadeIn(500)
        })
    } else {
        document.getElementById('landingPlayerLabel').innerHTML = pLabel
        document.getElementById('player_count').innerHTML = pVal
    }
    
}

refreshMojangStatuses()
// Server Status is refreshed in uibinder.js on distributionIndexDone.

// Refresh statuses every hour. The status page itself refreshes every day so...
let mojangStatusListener = setInterval(() => refreshMojangStatuses(true), 60*60*1000)
// Set refresh rate to once every 5 minutes.
let serverStatusListener = setInterval(() => refreshServerStatus(true), 300000)

/**
 * Shows an error overlay, toggles off the launch area.
 * 
 * @param {string} title The overlay title.
 * @param {string} desc The overlay description.
 */
function showLaunchFailure(title, desc){
    setOverlayContent(
        title,
        desc,
        'Okay'
    )
    setOverlayHandler(null)
    toggleOverlay(true)
    toggleLaunchArea(false)
}

/* System (Java) Scan */

let extractListener

/**
 * Asynchronously scan the system for valid Java installations.
 * 
 * @param {string} mcVersion The Minecraft version we are scanning for.
 * @param {boolean} launchAfter Whether we should begin to launch after scanning. 
 */
async function asyncSystemScan(mcVersion, launchAfter = true){

    setLaunchDetails('Checking system info..')
    toggleLaunchArea(true)
    setLaunchPercentage(0, 100)

    const javaVer = mcVersionAtLeast('1.17', mcVersion) ? '17' : '8'

    const jvmDetails = await discoverBestJvmInstallation(
        ConfigManager.getDataDirectory(),
        getDefaultSemverRange(mcVersion)
    )

    if(jvmDetails == null) {
        // If the result is null, no valid Java installation was found.
        // Show this information to the user.
        setOverlayContent(
            'No Compatible<br>Java Installation Found',
            `In order to join WesterosCraft, you need a 64-bit installation of Java ${javaVer}. Would you like us to install a copy?`,
            'Install Java',
            'Install Manually'
        )
        setOverlayHandler(() => {
            setLaunchDetails('Preparing Java Download..')
            
            // TODO Kick off JDK download.

            toggleOverlay(false)
        })
        setDismissHandler(() => {
            $('#overlayContent').fadeOut(250, () => {
                //$('#overlayDismiss').toggle(false)
                setOverlayContent(
                    'Java is Required<br>to Launch',
                    `A valid x64 installation of Java ${javaVer} is required to launch.<br><br>Please refer to our <a href="https://github.com/dscalzi/HeliosLauncher/wiki/Java-Management#manually-installing-a-valid-version-of-java">Java Management Guide</a> for instructions on how to manually install Java.`,
                    'I Understand',
                    'Go Back'
                )
                setOverlayHandler(() => {
                    toggleLaunchArea(false)
                    toggleOverlay(false)
                })
                setDismissHandler(() => {
                    toggleOverlay(false, true)

                    // TODO Change this flow
                    // Should be a separate function probably.
                    asyncSystemScan()
                })
                $('#overlayContent').fadeIn(250)
            })
        })
        toggleOverlay(true, true)
    } else {
        // Java installation found, use this to launch the game.
        const javaExec = javaExecFromRoot(jvmDetails.path)
        ConfigManager.setJavaExecutable(ConfigManager.getSelectedServer(), javaExec)
        ConfigManager.save()

        // We need to make sure that the updated value is on the settings UI.
        // Just incase the settings UI is already open.
        settingsJavaExecVal.value = javaExec
        await populateJavaExecDetails(settingsJavaExecVal.value)

        // TODO Move this out, separate concerns.
        if(launchAfter){
            await dlAsync()
        }
    }
    
    // TODO Integrate into assetguard 2.
    // if(m.context === '_enqueueOpenJDK'){

    //     if(m.result === true){

    //         // Oracle JRE enqueued successfully, begin download.
    //         setLaunchDetails('Downloading Java..')
    //         sysAEx.send({task: 'execute', function: 'processDlQueues', argsArr: [[{id:'java', limit:1}]]})

    //     } else {

    //         // Oracle JRE enqueue failed. Probably due to a change in their website format.
    //         // User will have to follow the guide to install Java.
    //         setOverlayContent(
    //             'Unexpected Issue:<br>Java Download Failed',
    //             'Unfortunately we\'ve encountered an issue while attempting to install Java. You will need to manually install a copy. Please check out our <a href="https://github.com/dscalzi/HeliosLauncher/wiki">Troubleshooting Guide</a> for more details and instructions.',
    //             'I Understand'
    //         )
    //         setOverlayHandler(() => {
    //             toggleOverlay(false)
    //             toggleLaunchArea(false)
    //         })
    //         toggleOverlay(true)
    //         sysAEx.disconnect()

    //     }

    // } else if(m.context === 'progress'){

    //     switch(m.data){
    //         case 'download':
    //             // Downloading..
    //             setDownloadPercentage(m.value, m.total, m.percent)
    //             break
    //     }

    // } else if(m.context === 'complete'){

    //     switch(m.data){
    //         case 'download': {
    //             // Show installing progress bar.
    //             remote.getCurrentWindow().setProgressBar(2)

    //             // Wait for extration to complete.
    //             const eLStr = 'Extracting'
    //             let dotStr = ''
    //             setLaunchDetails(eLStr)
    //             extractListener = setInterval(() => {
    //                 if(dotStr.length >= 3){
    //                     dotStr = ''
    //                 } else {
    //                     dotStr += '.'
    //                 }
    //                 setLaunchDetails(eLStr + dotStr)
    //             }, 750)
    //             break
    //         }
    //         case 'java':
    //         // Download & extraction complete, remove the loading from the OS progress bar.
    //             remote.getCurrentWindow().setProgressBar(-1)

    //             // Extraction completed successfully.
    //             ConfigManager.setJavaExecutable(ConfigManager.getSelectedServer(), m.args[0])
    //             ConfigManager.save()

    //             if(extractListener != null){
    //                 clearInterval(extractListener)
    //                 extractListener = null
    //             }

    //             setLaunchDetails('Java Installed!')

    //             if(launchAfter){
    //                 await dlAsync()
    //             }

    //             sysAEx.disconnect()
    //             break
    //     }

    // } else if(m.context === 'error'){
    //     console.log(m.error)
    // }

}

// Keep reference to Minecraft Process
let proc
// Is DiscordRPC enabled
let hasRPC = false
// Joined server regex
// Change this if your server uses something different.
const GAME_JOINED_REGEX = /\[.+\]: Sound engine started/
const GAME_LAUNCH_REGEX = /^\[.+\]: (?:MinecraftForge .+ Initialized|ModLauncher .+ starting: .+)$/
const MIN_LINGER = 5000

async function dlAsync(login = true) {

    // Login parameter is temporary for debug purposes. Allows testing the validation/downloads without
    // launching the game.

    const loggerLaunchSuite = LoggerUtil.getLogger('LaunchSuite')

    setLaunchDetails('Loading server information..')

    let distro

    try {
        distro = await DistroAPI.refreshDistributionOrFallback()
        onDistroRefresh(distro)
    } catch(err) {
        loggerLaunchSuite.error('Unable to refresh distribution index.', err)
        showLaunchFailure('Fatal Error', 'Could not load a copy of the distribution index. See the console (CTRL + Shift + i) for more details.')
        return
    }

    const serv = distro.getServerById(ConfigManager.getSelectedServer())

    if(login) {
        if(ConfigManager.getSelectedAccount() == null){
            loggerLanding.error('You must be logged into an account.')
            return
        }
    }

    setLaunchDetails('Please wait..')
    toggleLaunchArea(true)
    setLaunchPercentage(0, 100)

    const fullRepairModule = new FullRepair(
        ConfigManager.getCommonDirectory(),
        ConfigManager.getInstanceDirectory(),
        ConfigManager.getLauncherDirectory(),
        ConfigManager.getSelectedServer(),
        DistroAPI.isDevMode()
    )

    fullRepairModule.spawnReceiver()

    fullRepairModule.childProcess.on('error', (err) => {
        loggerLaunchSuite.error('Error during launch', err)
        showLaunchFailure('Error During Launch', err.message || 'See console (CTRL + Shift + i) for more details.')
    })
    fullRepairModule.childProcess.on('close', (code, _signal) => {
        if(code !== 0){
            loggerLaunchSuite.error(`AssetExec exited with code ${code}, assuming error.`)
            showLaunchFailure('Error During Launch', 'See console (CTRL + Shift + i) for more details.')
        }
    })

    loggerLaunchSuite.info('Validating files.')
    setLaunchDetails('Validating file integrity..')
    const invalidFileCount = await fullRepairModule.verifyFiles(percent => {
        setLaunchPercentage(percent)
    })
    setLaunchPercentage(100)

    if(invalidFileCount > 0) {
        loggerLaunchSuite.info('Downloading files.')
        setLaunchDetails('Downloading files..')
        await fullRepairModule.download(percent => {
            setDownloadPercentage(percent)
        })
        setDownloadPercentage(100)
    } else {
        loggerLaunchSuite.info('No invalid files, skipping download.')
    }

    // Remove download bar.
    remote.getCurrentWindow().setProgressBar(-1)

    fullRepairModule.destroyReceiver()

    setLaunchDetails('Preparing to launch..')

    const mojangIndexProcessor = new MojangIndexProcessor(
        ConfigManager.getCommonDirectory(),
        serv.rawServer.minecraftVersion)
    const distributionIndexProcessor = new DistributionIndexProcessor(
        ConfigManager.getCommonDirectory(),
        distro,
        serv.rawServer.id
    )

    const forgeData = await distributionIndexProcessor.loadForgeVersionJson(serv)
    const versionData = await mojangIndexProcessor.getVersionJson()

    if(login) {
        const authUser = ConfigManager.getSelectedAccount()
        loggerLaunchSuite.info(`Sending selected account (${authUser.displayName}) to ProcessBuilder.`)
        let pb = new ProcessBuilder(serv, versionData, forgeData, authUser, remote.app.getVersion())
        setLaunchDetails('Launching game..')

        // const SERVER_JOINED_REGEX = /\[.+\]: \[CHAT\] [a-zA-Z0-9_]{1,16} joined the game/
        const SERVER_JOINED_REGEX = new RegExp(`\\[.+\\]: \\[CHAT\\] ${authUser.displayName} joined the game`)

        const onLoadComplete = () => {
            toggleLaunchArea(false)
            if(hasRPC){
                DiscordWrapper.updateDetails('Loading game..')
            }
            proc.stdout.on('data', gameStateChange)
            proc.stdout.removeListener('data', tempListener)
            proc.stderr.removeListener('data', gameErrorListener)
        }
        const start = Date.now()

        // Attach a temporary listener to the client output.
        // Will wait for a certain bit of text meaning that
        // the client application has started, and we can hide
        // the progress bar stuff.
        const tempListener = function(data){
            if(GAME_LAUNCH_REGEX.test(data.trim())){
                const diff = Date.now()-start
                if(diff < MIN_LINGER) {
                    setTimeout(onLoadComplete, MIN_LINGER-diff)
                } else {
                    onLoadComplete()
                }
            }
        }

        // Listener for Discord RPC.
        const gameStateChange = function(data){
            data = data.trim()
            if(SERVER_JOINED_REGEX.test(data)){
                DiscordWrapper.updateDetails('Exploring the Realm!')
            } else if(GAME_JOINED_REGEX.test(data)){
                DiscordWrapper.updateDetails('Sailing to Westeros!')
            }
        }

        const gameErrorListener = function(data){
            data = data.trim()
            if(data.indexOf('Could not find or load main class net.minecraft.launchwrapper.Launch') > -1){
                loggerLaunchSuite.error('Game launch failed, LaunchWrapper was not downloaded properly.')
                showLaunchFailure('Error During Launch', 'The main file, LaunchWrapper, failed to download properly. As a result, the game cannot launch.<br><br>To fix this issue, temporarily turn off your antivirus software and launch the game again.<br><br>If you have time, please <a href="https://github.com/dscalzi/HeliosLauncher/issues">submit an issue</a> and let us know what antivirus software you use. We\'ll contact them and try to straighten things out.')
            }
        }

        try {
            // Build Minecraft process.
            proc = pb.build()

            // Bind listeners to stdout.
            proc.stdout.on('data', tempListener)
            proc.stderr.on('data', gameErrorListener)

            setLaunchDetails('Done. Enjoy the server!')

            // Init Discord Hook
            if(distro.rawDistribution.discord != null && serv.rawServerdiscord != null){
                DiscordWrapper.initRPC(distro.rawDistribution.discord, serv.rawServer.discord)
                hasRPC = true
                proc.on('close', (code, signal) => {
                    loggerLaunchSuite.info('Shutting down Discord Rich Presence..')
                    DiscordWrapper.shutdownRPC()
                    hasRPC = false
                    proc = null
                })
            }

        } catch(err) {

            loggerLaunchSuite.error('Error during launch', err)
            showLaunchFailure('Error During Launch', 'Please check the console (CTRL + Shift + i) for more details.')

        }
    }

}

/**
 * News Loading Functions
 */

// DOM Cache
const newsContent                   = document.getElementById('newsContent')
const newsArticleTitle              = document.getElementById('newsArticleTitle')
const newsArticleDate               = document.getElementById('newsArticleDate')
const newsArticleAuthor             = document.getElementById('newsArticleAuthor')
const newsArticleComments           = document.getElementById('newsArticleComments')
const newsNavigationStatus          = document.getElementById('newsNavigationStatus')
const newsArticleContentScrollable  = document.getElementById('newsArticleContentScrollable')
const nELoadSpan                    = document.getElementById('nELoadSpan')

// News slide caches.
let newsActive = false
let newsGlideCount = 0

/**
 * Show the news UI via a slide animation.
 * 
 * @param {boolean} up True to slide up, otherwise false. 
 */
function slide_(up){
    const lCUpper = document.querySelector('#landingContainer > #upper')
    const lCLLeft = document.querySelector('#landingContainer > #lower > #left')
    const lCLCenter = document.querySelector('#landingContainer > #lower > #center')
    const lCLRight = document.querySelector('#landingContainer > #lower > #right')
    const newsBtn = document.querySelector('#landingContainer > #lower > #center #content')
    const landingContainer = document.getElementById('landingContainer')
    const newsContainer = document.querySelector('#landingContainer > #newsContainer')

    newsGlideCount++

    if(up){
        lCUpper.style.top = '-200vh'
        lCLLeft.style.top = '-200vh'
        lCLCenter.style.top = '-200vh'
        lCLRight.style.top = '-200vh'
        newsBtn.style.top = '130vh'
        newsContainer.style.top = '0px'
        //date.toLocaleDateString('en-US', {month: 'short', day: 'numeric', year: 'numeric', hour: 'numeric', minute: 'numeric'})
        //landingContainer.style.background = 'rgba(29, 29, 29, 0.55)'
        landingContainer.style.background = 'rgba(0, 0, 0, 0.50)'
        setTimeout(() => {
            if(newsGlideCount === 1){
                lCLCenter.style.transition = 'none'
                newsBtn.style.transition = 'none'
            }
            newsGlideCount--
        }, 2000)
    } else {
        setTimeout(() => {
            newsGlideCount--
        }, 2000)
        landingContainer.style.background = null
        lCLCenter.style.transition = null
        newsBtn.style.transition = null
        newsContainer.style.top = '100%'
        lCUpper.style.top = '0px'
        lCLLeft.style.top = '0px'
        lCLCenter.style.top = '0px'
        lCLRight.style.top = '0px'
        newsBtn.style.top = '10px'
    }
}

// Bind news button.
document.getElementById('newsButton').onclick = () => {
    // Toggle tabbing.
    if(newsActive){
        $('#landingContainer *').removeAttr('tabindex')
        $('#newsContainer *').attr('tabindex', '-1')
    } else {
        $('#landingContainer *').attr('tabindex', '-1')
        $('#newsContainer, #newsContainer *, #lower, #lower #center *').removeAttr('tabindex')
        if(newsAlertShown){
            $('#newsButtonAlert').fadeOut(2000)
            newsAlertShown = false
            ConfigManager.setNewsCacheDismissed(true)
            ConfigManager.save()
        }
    }
    slide_(!newsActive)
    newsActive = !newsActive
}

// Array to store article meta.
let newsArr = null

// News load animation listener.
let newsLoadingListener = null

/**
 * Set the news loading animation.
 * 
 * @param {boolean} val True to set loading animation, otherwise false.
 */
function setNewsLoading(val){
    if(val){
        const nLStr = 'Checking for News'
        let dotStr = '..'
        nELoadSpan.innerHTML = nLStr + dotStr
        newsLoadingListener = setInterval(() => {
            if(dotStr.length >= 3){
                dotStr = ''
            } else {
                dotStr += '.'
            }
            nELoadSpan.innerHTML = nLStr + dotStr
        }, 750)
    } else {
        if(newsLoadingListener != null){
            clearInterval(newsLoadingListener)
            newsLoadingListener = null
        }
    }
}

// Bind retry button.
newsErrorRetry.onclick = () => {
    $('#newsErrorFailed').fadeOut(250, () => {
        initNews()
        $('#newsErrorLoading').fadeIn(250)
    })
}

newsArticleContentScrollable.onscroll = (e) => {
    if(e.target.scrollTop > Number.parseFloat($('.newsArticleSpacerTop').css('height'))){
        newsContent.setAttribute('scrolled', '')
    } else {
        newsContent.removeAttribute('scrolled')
    }
}

/**
 * Reload the news without restarting.
 * 
 * @returns {Promise.<void>} A promise which resolves when the news
 * content has finished loading and transitioning.
 */
function reloadNews(){
    return new Promise((resolve, reject) => {
        $('#newsContent').fadeOut(250, () => {
            $('#newsErrorLoading').fadeIn(250)
            initNews().then(() => {
                resolve()
            })
        })
    })
}

let newsAlertShown = false

/**
 * Show the news alert indicating there is new news.
 */
function showNewsAlert(){
    newsAlertShown = true
    $(newsButtonAlert).fadeIn(250)
}

/**
 * Initialize News UI. This will load the news and prepare
 * the UI accordingly.
 * 
 * @returns {Promise.<void>} A promise which resolves when the news
 * content has finished loading and transitioning.
 */
function initNews(){

    return new Promise((resolve, reject) => {
        setNewsLoading(true)

        let news = {}
        loadNews().then(news => {

            newsArr = news.articles || null

            if(newsArr == null){
                // News Loading Failed
                setNewsLoading(false)

                $('#newsErrorLoading').fadeOut(250, () => {
                    $('#newsErrorFailed').fadeIn(250, () => {
                        resolve()
                    })
                })
            } else if(newsArr.length === 0) {
                // No News Articles
                setNewsLoading(false)

                ConfigManager.setNewsCache({
                    date: null,
                    content: null,
                    dismissed: false
                })
                ConfigManager.save()

                $('#newsErrorLoading').fadeOut(250, () => {
                    $('#newsErrorNone').fadeIn(250, () => {
                        resolve()
                    })
                })
            } else {
                // Success
                setNewsLoading(false)

                const lN = newsArr[0]
                const cached = ConfigManager.getNewsCache()
                let newHash = crypto.createHash('sha1').update(lN.content).digest('hex')
                let newDate = new Date(lN.date)
                let isNew = false

                if(cached.date != null && cached.content != null){

                    if(new Date(cached.date) >= newDate){

                        // Compare Content
                        if(cached.content !== newHash){
                            isNew = true
                            showNewsAlert()
                        } else {
                            if(!cached.dismissed){
                                isNew = true
                                showNewsAlert()
                            }
                        }

                    } else {
                        isNew = true
                        showNewsAlert()
                    }

                } else {
                    isNew = true
                    showNewsAlert()
                }

                if(isNew){
                    ConfigManager.setNewsCache({
                        date: newDate.getTime(),
                        content: newHash,
                        dismissed: false
                    })
                    ConfigManager.save()
                }

                const switchHandler = (forward) => {
                    let cArt = parseInt(newsContent.getAttribute('article'))
                    let nxtArt = forward ? (cArt >= newsArr.length-1 ? 0 : cArt + 1) : (cArt <= 0 ? newsArr.length-1 : cArt - 1)
            
                    displayArticle(newsArr[nxtArt], nxtArt+1)
                }

                document.getElementById('newsNavigateRight').onclick = () => { switchHandler(true) }
                document.getElementById('newsNavigateLeft').onclick = () => { switchHandler(false) }

                $('#newsErrorContainer').fadeOut(250, () => {
                    displayArticle(newsArr[0], 1)
                    $('#newsContent').fadeIn(250, () => {
                        resolve()
                    })
                })
            }

        })
        
    })
}

/**
 * Add keyboard controls to the news UI. Left and right arrows toggle
 * between articles. If you are on the landing page, the up arrow will
 * open the news UI.
 */
document.addEventListener('keydown', (e) => {
    if(newsActive){
        if(e.key === 'ArrowRight' || e.key === 'ArrowLeft'){
            document.getElementById(e.key === 'ArrowRight' ? 'newsNavigateRight' : 'newsNavigateLeft').click()
        }
        // Interferes with scrolling an article using the down arrow.
        // Not sure of a straight forward solution at this point.
        // if(e.key === 'ArrowDown'){
        //     document.getElementById('newsButton').click()
        // }
    } else {
        if(getCurrentView() === VIEWS.landing){
            if(e.key === 'ArrowUp'){
                document.getElementById('newsButton').click()
            }
        }
    }
})

/**
 * Display a news article on the UI.
 * 
 * @param {Object} articleObject The article meta object.
 * @param {number} index The article index.
 */
function displayArticle(articleObject, index){
    newsArticleTitle.innerHTML = articleObject.title
    newsArticleTitle.href = articleObject.link
    newsArticleAuthor.innerHTML = 'by ' + articleObject.author
    newsArticleDate.innerHTML = articleObject.date
    newsArticleComments.innerHTML = articleObject.comments
    newsArticleComments.href = articleObject.commentsLink
    newsArticleContentScrollable.innerHTML = '<div id="newsArticleContentWrapper"><div class="newsArticleSpacerTop"></div>' + articleObject.content + '<div class="newsArticleSpacerBot"></div></div>'
    Array.from(newsArticleContentScrollable.getElementsByClassName('bbCodeSpoilerButton')).forEach(v => {
        v.onclick = () => {
            const text = v.parentElement.getElementsByClassName('bbCodeSpoilerText')[0]
            text.style.display = text.style.display === 'block' ? 'none' : 'block'
        }
    })
    newsNavigationStatus.innerHTML = index + ' of ' + newsArr.length
    newsContent.setAttribute('article', index-1)
}

/**
 * Load news information from the RSS feed specified in the
 * distribution index.
 */
async function loadNews(){

    const distroData = await DistroAPI.getDistribution()

    const promise = new Promise((resolve, reject) => {
        
        const newsFeed = distroData.rawDistribution.rss
        const newsHost = new URL(newsFeed).origin + '/'
        $.ajax({
            url: newsFeed,
            success: (data) => {
                const items = $(data).find('item')
                const articles = []

                for(let i=0; i<items.length; i++){
                // JQuery Element
                    const el = $(items[i])

                    // Resolve date.
                    const date = new Date(el.find('pubDate').text()).toLocaleDateString('en-US', {month: 'short', day: 'numeric', year: 'numeric', hour: 'numeric', minute: 'numeric'})

                    // Resolve comments.
                    let comments = el.find('slash\\:comments').text() || '0'
                    comments = comments + ' Comment' + (comments === '1' ? '' : 's')

                    // Fix relative links in content.
                    let content = el.find('content\\:encoded').text()
                    let regex = /src="(?!http:\/\/|https:\/\/)(.+?)"/g
                    let matches
                    while((matches = regex.exec(content))){
                        content = content.replace(`"${matches[1]}"`, `"${newsHost + matches[1]}"`)
                    }

                    let link   = el.find('link').text()
                    let title  = el.find('title').text()
                    let author = el.find('dc\\:creator').text()

                    // Generate article.
                    articles.push(
                        {
                            link,
                            title,
                            date,
                            author,
                            content,
                            comments,
                            commentsLink: link + '#comments'
                        }
                    )
                }
                resolve({
                    articles
                })
            },
            timeout: 2500
        }).catch(err => {
            resolve({
                articles: null
            })
        })
    })

    return await promise
}