import * as Curve from 'curve25519-js'
import * as Utils from './Utils'
import {WAConnection as Base} from './0.Base'
import { MessageLogLevel, WAMetric, WAFlag, BaileysError, Presence } from './Constants'

export class WAConnection extends Base {
    
    /** Authenticate the connection */
    protected async authenticate (reconnect?: string) {
        // if no auth info is present, that is, a new session has to be established
        // generate a client ID
        if (!this.authInfo?.clientID) {
            this.authInfo = { clientID: Utils.generateClientID() } as any
        }
        
        this.referenceDate = new Date () // refresh reference date
        const json = ['admin', 'init', this.version, this.browserDescription, this.authInfo?.clientID, true]

        return this.query({json, expect200: true, waitForOpen: false})
            .then(json => {
                // we're trying to establish a new connection or are trying to log in
                if (this.authInfo?.encKey && this.authInfo?.macKey) {
                    // if we have the info to restore a closed session
                    const json = [
                        'admin',
                        'login',
                        this.authInfo?.clientToken,
                        this.authInfo?.serverToken,
                        this.authInfo?.clientID,
                    ]
                    if (reconnect) json.push(...['reconnect', reconnect.replace('@s.whatsapp.net', '@c.us')])
                    else json.push ('takeover')
                    return this.query({ json, tag: 's1', waitForOpen: false }) // wait for response with tag "s1"
                }
                return this.generateKeysForAuth(json.ref) // generate keys which will in turn be the QR
            })
            .then(async json => {
                if ('status' in json) { 
                    switch (json.status) {
                        case 401: // if the phone was unpaired
                            throw new BaileysError ('unpaired from phone', json)
                        case 429: // request to login was denied, don't know why it happens
                            throw new BaileysError ('request denied', json)
                        default:
                            throw new BaileysError ('unexpected status ' + json.status, json)
                    }
                }
                // if its a challenge request (we get it when logging in)
                if (json[1]?.challenge) {
                    await this.respondToChallenge(json[1].challenge)
                    return this.waitForMessage('s2', [])
                }
                // otherwise just chain the promise further
                return json
            })
            .then(async json => {
                this.validateNewConnection(json[1]) // validate the connection
                this.log('validated connection successfully', MessageLogLevel.info)

                this.sendPostConnectQueries ()
                
                this.lastSeen = new Date() // set last seen to right now
            })
    }
    /**
     * Send the same queries WA Web sends after connect
     */
    sendPostConnectQueries () {
        this.sendBinary (['query', {type: 'contacts', epoch: '1'}, null], [ WAMetric.queryContact, WAFlag.ignore ])
        this.sendBinary (['query', {type: 'chat', epoch: '1'}, null], [ WAMetric.queryChat, WAFlag.ignore ])
        this.sendBinary (['query', {type: 'status', epoch: '1'}, null], [ WAMetric.queryStatus, WAFlag.ignore ])
        this.sendBinary (['query', {type: 'quick_reply', epoch: '1'}, null], [ WAMetric.queryQuickReply, WAFlag.ignore ])
        this.sendBinary (['query', {type: 'label', epoch: '1'}, null], [ WAMetric.queryLabel, WAFlag.ignore ])
        this.sendBinary (['query', {type: 'emoji', epoch: '1'}, null], [ WAMetric.queryEmoji, WAFlag.ignore ])
        this.sendBinary (['action', {type: 'set', epoch: '1'}, [['presence', {type: Presence.available}, null]] ], [ WAMetric.presence, 160 ])
    }
    /** 
     * Refresh QR Code 
     * @returns the new ref
     */
    async generateNewQRCodeRef() {
        const response = await this.query({json: ['admin', 'Conn', 'reref'], expect200: true, waitForOpen: false})
        return response.ref as string
    }
    /**
     * Once the QR code is scanned and we can validate our connection, or we resolved the challenge when logging back in
     * @private
     * @param {object} json
     */
    private validateNewConnection(json) {
        const onValidationSuccess = () => {
            // set metadata: one's WhatsApp ID [cc][number]@s.whatsapp.net, name on WhatsApp, info about the phone
            this.user = {
                id: Utils.whatsappID(json.wid),
                name: json.pushname,
                phone: json.phone,
                imgUrl: null
            }
            return this.user
        }

        if (!json.secret) {
            // if we didn't get a secret, we don't need it, we're validated
            return onValidationSuccess()
        }
        const secret = Buffer.from(json.secret, 'base64')
        if (secret.length !== 144) {
            throw new Error ('incorrect secret length received: ' + secret.length)
        }
        // generate shared key from our private key & the secret shared by the server
        const sharedKey = Curve.sharedKey(this.curveKeys.private, secret.slice(0, 32))
        // expand the key to 80 bytes using HKDF
        const expandedKey = Utils.hkdf(sharedKey as Buffer, 80)

        // perform HMAC validation.
        const hmacValidationKey = expandedKey.slice(32, 64)
        const hmacValidationMessage = Buffer.concat([secret.slice(0, 32), secret.slice(64, secret.length)])

        const hmac = Utils.hmacSign(hmacValidationMessage, hmacValidationKey)

        if (hmac.equals(secret.slice(32, 64))) {
            // computed HMAC should equal secret[32:64]
            // expandedKey[64:] + secret[64:] are the keys, encrypted using AES, that are used to encrypt/decrypt the messages recieved from WhatsApp
            // they are encrypted using key: expandedKey[0:32]
            const encryptedAESKeys = Buffer.concat([
                expandedKey.slice(64, expandedKey.length),
                secret.slice(64, secret.length),
            ])
            const decryptedKeys = Utils.aesDecrypt(encryptedAESKeys, expandedKey.slice(0, 32))
            // set the credentials
            this.authInfo = {
                encKey: decryptedKeys.slice(0, 32), // first 32 bytes form the key to encrypt/decrypt messages
                macKey: decryptedKeys.slice(32, 64), // last 32 bytes from the key to sign messages
                clientToken: json.clientToken,
                serverToken: json.serverToken,
                clientID: this.authInfo.clientID,
            }
            return onValidationSuccess()
        } else {
            // if the checksums didn't match
            throw new BaileysError ('HMAC validation failed', json)
        }
    }
    /**
     * When logging back in (restoring a previously closed session), WhatsApp may challenge one to check if one still has the encryption keys
     * WhatsApp does that by asking for us to sign a string it sends with our macKey
     */
    protected respondToChallenge(challenge: string) {
        const bytes = Buffer.from(challenge, 'base64') // decode the base64 encoded challenge string
        const signed = Utils.hmacSign(bytes, this.authInfo.macKey).toString('base64') // sign the challenge string with our macKey
        const json = ['admin', 'challenge', signed, this.authInfo.serverToken, this.authInfo.clientID] // prepare to send this signed string with the serverToken & clientID
        this.log('resolving login challenge', MessageLogLevel.info)
        return this.query({json, expect200: true, waitForOpen: false})
    }
    /** When starting a new session, generate a QR code by generating a private/public key pair & the keys the server sends */
    protected async generateKeysForAuth(ref: string) {
        this.curveKeys = Curve.generateKeyPair(Utils.randomBytes(32))
        const publicKey = Buffer.from(this.curveKeys.public).toString('base64')

        const emitQR = () => {
            const qr = [ref, publicKey, this.authInfo.clientID].join(',')
            this.emit ('qr', qr)
        }

        const regenQR = () => {
            this.qrTimeout = setTimeout (() => {
                if (this.state === 'open') return

                this.log ('regenerated QR', MessageLogLevel.info)
                
                this.generateNewQRCodeRef ()
                .then (newRef => ref = newRef)
                .then (emitQR)
                .then (regenQR)
                .catch (err => this.log (`error in QR gen: ${err}`, MessageLogLevel.info))
            }, this.regenerateQRIntervalMs)
        }

        emitQR ()
        if (this.regenerateQRIntervalMs) regenQR ()

        const json = await this.waitForMessage('s1', [])
        this.qrTimeout && clearTimeout (this.qrTimeout)
        this.qrTimeout = null
        
        return json
    }
}