/**
 * Register the function `handler` to be called when the `Convert` button is
 * pressed.
 */
function setHandler() {
    let convertButton = document.getElementById('convertbutton')
    convertButton.addEventListener('click', handler, false)
}


/**
 * Read parameters and pass them to the `main` function. This function is
 * called when the `Convert` button is clicked.
 */
function handler() {
    let selectedFile = document.getElementById('inputopenvpn').files[0]
    let certificates = document.getElementById('inputcertificates').files
    let connName = document.getElementById('connname').value
    let output = document.getElementById('output')
    main(connName, selectedFile, certificates, output)
}


/**
 * Return a function that logs text to the log output.
 */
function getLogger() {
    let logOutput = document.getElementById('log')
    let logger = function (text) {
        logOutput.innerHTML += `<p>${text}</p>`
    }
    return logger
}


/**
 * Read, convert and print result. This function calls other functions
 * to first read everything, then convert it and finally print the result.
 *
 * The function is `async` because it uses `await` when reading files.
 *
 * @param {String} connName         Name of the connection
 * @param {File}   ovpnFile         File object for the ovpn file
 * @param {Array}  certificateFiles List of file objects for the certificates
 * @param {Object} output           HTML element where the output should go
 */
async function main(connName, ovpnFile, certificateFiles, output) {
    log = getLogger()
    if (connName === '') {
        log('connName is empty')
        alert('Please specify a name for the connection.')
        return
    }
    log(`Size of OVPN file: ${ovpnFile.size} bytes`)
    let ovpnContent = await readFile(ovpnFile)
    let ovpn
    let keys
    try {
        [ovpn, keys] = parseOvpn(ovpnContent)
    } catch (err) {
        log(err)
        return
    }
    log("Parsed config:")
    log(JSON.stringify(ovpn))
    for (const certificateFile of certificateFiles) {
        keys[certificateFile.name] = await readFile(certificateFile)
    }
    let onc
    try {
        onc = constructOnc(connName, ovpn, keys)
    } catch (err) {
        log(err)
        return
    }
    output.value = JSON.stringify(onc, null, 2)
    log('All done!')
}


/**
 * Return a promise to read a file as text.
 *
 * @param {File} file A file object
 *
 * @return {Promise} A promise with the contents of the file
 */
function readFile(file) {
    return new Promise(resolve => {
        let reader = new FileReader()
        reader.onload = e => {
            // callback and remove windows-style newlines
            resolve(e.target.result.replace(/\r/g, ''))
        }
        // start reading
        reader.readAsText(file)
    })
}


/**
 * Parse an OVPN file. Extract all the key-value pairs and keys
 * that are written inside XML tags.
 *
 * The key-value pairs are written into an object. The keys are also
 * written into an object with the the XML tag name as the key.
 *
 * @param {String} str The contents of the ovpn file as a string.
 *
 * @return {Array} An array that contains the key-value pairs and
 *                 the keys.
 */
function parseOvpn(str) {
    log = getLogger()
    let ovpn = {}
    let keys = {}
    // define regexes for properties, opening xml tag and closing xml tag
    const reProperty = /^([^ ]+)( (.*))?$/i
    const reXmlOpen = /^<([^\/].*)>$/i
    const reXmlClose = /^<\/(.*)>$/i

    // temporary variables for handling xml tags
    let xmlTag = ''
    let inXml = false
    let xmlContent = ''

    let lines = str.split(/[\r\n]+/g)

    for (let line of lines) {
        // skip line if it is empty or begins with '#' or ';'
        if (!line || line.match(/^\s*[;#]/)) {
            log(`Skipped line: "${line}"`)
            continue
        }
        if (inXml) {  // an XML tag was opened and hasn't been closed yet
            const xmlMatch = line.match(reXmlClose)
            if (!xmlMatch) {
                // no closing tag -> add content to `xmlContent`
                xmlContent += line + '\n'
                continue
            }
            const tag = xmlMatch[1]
            if (tag !== xmlTag) {
                alert('Cannot parse ovpn file.')
                throw 'bad xml tag'
            }
            // closing tag was found
            // make sure the tag name and the contents are safe
            const name = makeSafe(xmlTag)
            const value = xmlContent
            // store everything and reset the xml variables
            keys[name] = value
            ovpn[name] = name
            xmlContent = ''
            inXml = false
            continue
        }
        const xmlMatch = line.match(reXmlOpen)
        if (xmlMatch) {
            // an xml tag was opened
            inXml = true
            xmlTag = xmlMatch[1]
            log(`XML tag was opened: "${xmlTag}"`)
            continue
        }
        // check if the line contains a property
        const match = line.match(reProperty)
        if (!match) continue
        // make sure everything is safe and then store it
        const key = makeSafe(match[1])
        const value = match[2] ? (match[3] || '') : true
        ovpn[key] = value
        log(`Found: ${key} = ${value}`)
    }

    log('Finished parsing')
    return [ovpn, keys]
}


/**
 * Check if string is quoted
 */
function isQuoted(val) {
    return ((val.charAt(0) === '"' && val.slice(-1) === '"') ||
        (val.charAt(0) === "'" && val.slice(-1) === "'"))
}


/**
 * This function is supposed to prevent any exploits via the object keys
 *
 * It's probably complete overkill.
 */
function makeSafe(val, doUnesc) {
    val = (val || '').trim()
    if (isQuoted(val)) {
        // remove the single quotes before calling JSON.parse
        if (val.charAt(0) === "'") {
            val = val.substr(1, val.length - 2)
        }
        try { val = JSON.parse(val) } catch (_) { }
    } else {
        // walk the val to find the first not-escaped ; character
        var esc = false
        var unesc = ''
        for (var i = 0, l = val.length; i < l; i++) {
            var c = val.charAt(i)
            if (esc) {
                if ('\\;#'.indexOf(c) !== -1) {
                    unesc += c
                } else {
                    unesc += '\\' + c
                }
                esc = false
            } else if (';#'.indexOf(c) !== -1) {
                break
            } else if (c === '\\') {
                esc = true
            } else {
                unesc += c
            }
        }
        if (esc) {
            unesc += '\\'
        }
        return unesc
    }
    return val
}


/**
 * Convert the keys from the parsed OVPN file into ONC keys
 *
 * @param {Object} keys     Strings with keys, indexed by key name
 * @param {Object} keynames Object with the key names
 * @return {Object} ONC parameters and a list of converted certificates
 */
function convertKeys(keys, keyNames) {
    let params = {}

    // Add certificates
    let certs = []

    // Server certificate
    // TODO: confirm that the type should be 'Authority'
    let [cas, caGuids] = constructCerts(keys, keyNames.certificateAuthorities,
        'Authority')
    params['ServerCARefs'] = caGuids
    certs = certs.concat(cas)

    // Client certificate
    if (keyNames.clientCertificates) {
        // TODO: handle other types of client certificates
        let [clientCerts, clientCertGuids] = constructCerts(
            keys, keyNames.clientCertificates, 'Authority')
        params['ClientCertType'] = 'Pattern'
        params['ClientCertPattern'] = {
            'IssuerCARef': clientCertGuids
        }
        certs = certs.concat(clientCerts)
    } else {
        params['ClientCertType'] = 'None'
    }

    // TLS auth
    if (keyNames.tlsAuth) {
        let authKey = keyNames.tlsAuth.split(' ')
        let keyString = keys[authKey[0]]
        if (!keyString) {
            alert(`Please provide the file '${authKey[0]}' in 'Certificates and keys'`)
            throw `Couldn't find the key for ${authKey[0]}`
        }
        params['TLSAuthContents'] = convertKey(keyString)
        if (authKey[1]) params['KeyDirection'] = authKey[1]
    }
    return [params, certs]
}


/**
 * Convert the parsed ovpn file into the ONC structure
 *
 * @param {Object} ovpn The parsed OVPN file
 * @return {Array} An array with the host and an object with the parameters
 */
function convertToOnc(ovpn) {
    if (!ovpn.client) {
        console.warn('Is this a server file?')
    }
    let params = {}

    // Add parameters
    let remote = ovpn.remote.split(' ')
    const host = remote[0]
    if (remote[1]) params['Port'] = Number(remote[1])
    if (ovpn['auth-user-pass']) params['UserAuthenticationType'] = 'Password'
    if (ovpn['comp-lzo'] && ovpn['comp-lzo'] !== 'no') {
        params['CompLZO'] = 'true'
    } else {
        params['CompLZO'] = 'false'
    }
    if (ovpn['persist-key']) params['SaveCredentials'] = true
    if (ovpn['verify-x509-name']) {
        const x509String = ovpn['verify-x509-name']
        let x509 = {}
        if (x509String.includes("'")) {
            // the name is quoted with '
            const parts = x509String.split("'")
            x509['Name'] = parts[1]
            if (parts[2]) {
                x509['Type'] = parts[2].trim()
            }
        } else {
            const parts = x509String.split(' ')
            x509['Name'] = parts[0]
            if (parts[1]) {
                x509['Type'] = parts[1]
            }
        }
        params['VerifyX509'] = x509
    }

    // set parameters if they exist in the ovpn config
    let conditionalSet = (ovpnName, oncName, type = 'str') => {
        if (ovpn[ovpnName]) {
            const raw = ovpn[ovpnName]
            let value
            switch (type) {
                case 'int':
                    value = Number(raw)
                    break
                default:
                    value = raw
            }
            params[oncName] = value
        } else {
            log(`Value for '${ovpnName}' not specified.`)
        }
    }
    conditionalSet('port', 'Port', 'int')
    conditionalSet('proto', 'Proto')
    conditionalSet('key-direction', 'KeyDirection')
    conditionalSet('remote-cert-tls', 'RemoteCertTLS')
    conditionalSet('cipher', 'Cipher')
    conditionalSet('auth', 'Auth')
    conditionalSet('auth-retry', 'AuthRetry')
    conditionalSet('reneg-sec', 'RenegSec', 'int')

    const keyNames = {
        'certificateAuthorities': ovpn['ca'],
        'clientCertificates': ovpn['cert'],
        'tlsAuth': ovpn['tls-auth'],
    }

    return [host, params, keyNames]
}


/**
 * Construct the ONC structure from the name, the parsed ovpn file and the keys
 *
 * @param {string} name Name of the connection
 * @param {Object} ovpn The parsed OVPN file
 * @param {Object} keys Strings with keys, indexed by key name
 * @return {Object} The converted ONC structure
 */
function constructOnc(name, ovpn, keys) {
    let [host, params, keyNames] = convertToOnc(ovpn)
    let [certParams, certificates] = convertKeys(keys, keyNames)
    // merge parameters
    params = Object.assign({}, params, certParams)

    // Put together network configuration
    let networkConfiguration = {
        'GUID': `{${uuidv4()}}`,
        'Name': name,
        'Type': 'VPN',
        'VPN': {
            'Type': 'OpenVPN',
            'Host': host,
            'OpenVPN': params
        }
    }

    // Put everything together
    return {
        'Type': 'UnencryptedConfiguration',
        'Certificates': certificates,
        'NetworkConfigurations': [networkConfiguration]
    }
}


/**
 * Create UUID (from Stackoverflow).
 */
function uuidv4() {
    return ([1e7] + -1e3 + -4e3 + -8e3 + -1e11).replace(/[018]/g, c =>
        (c ^ crypto.getRandomValues(new Uint8Array(1))[0] & 15 >> c / 4).toString(16)
    )
}


/**
 * Replace newlines with explicit `\n` and filter out comments
 */
function convertKey(key) {
    let lines = key.split(/\n/g)
    let out = ''
    for (let line of lines) {
        // filter out empty lines and lines with comments
        if (!line || line.match(/^\s*[;#]/)) continue
        out += line + '\n'
    }
    return out
}


/**
 * Find all certificates in a string and extract them
 */
function extractCas(str) {
    log = getLogger()
    let splits = str.replace(/\n/g, '').split('-----BEGIN CERTIFICATE-----')
    let cas = []
    for (const s of splits) {
        if (s.includes('-----END CERTIFICATE-----')) {
            let extractedCa = s.split('-----END CERTIFICATE-----')[0]
            log("Extracted CA:")
            log(extractedCa)
            cas.push(extractedCa)
        }
    }
    return cas
}


/**
 * Construct certificates in the ONC format
 *
 * @param {Object} keys     Strings with keys, indexed by key name
 * @param {string} certName The index for the keys object
 * @param {string} certType Type of the certificate: 'Authority', 'Client' or
 *                          'Server'
 * @return {Array} An array of certificates and an array of corresponding IDs
 */
function constructCerts(keys, certName, certType) {
    let certs = []
    let certGuids = []
    if (certName) {
        let cert = keys[certName]
        if (!cert) {
            alert(`Please provide the file '${certName}' in 'Certificates and keys'`)
            throw `Couldn't find a certificate for ${certName}`
        }
        let rawCerts = extractCas(cert)
        const format = (certType === 'Authority') ? 'X509' : 'PKCS12'
        for (const cert of rawCerts) {
            const guid = `{${uuidv4()}}`
            certGuids.push(guid)
            let oncCert = {
                'GUID': guid,
                'Type': certType
            }
            oncCert[format] = cert
            certs.push(oncCert)
        }
    }
    return [certs, certGuids]
}