//
// This file manages the API security handling for the Device-style Swagger security
// definitions
//
'use strict';
/* eslint max-nested-callbacks: ["error", 7] import/max-dependencies: ["error", {"max": 11}] */

const config = require(global.configFile);
const debug = require('debug')('webconsole-api:security:device');
const _ = require('lodash');
const Ajv = require('ajv');
const Q = require('q');
const url = require('url');
const JsonRefs = require('json-refs');
const mongodb = require('mongodb');

const auth = require('../ComServe/auth-promises.js');
const references = require('../utils/references.js');
const mainDBP = require('../ComServe/mainDB-promises.js');

const featureFlags = require(global.pathPrefix + '../utils/feature-flags/feature-flags.js');
const utils = require(global.pathPrefix + 'utils.js');
const apiUtils = require('./api_utils.js');

module.exports = {
    deviceSession,
    deviceHmacNoSession
};

/**
 * Cache of the validation functions once we compile them from the swagger schema
 */
const VALIDATORS = {
    initialised: false,
    session: null,
    hmac: null,
    timestamp: null
};

/**
 * Create the ajv object with the settings we want to use
 */
const AJV_OPTIONS = {
    /* Return all errors, not just the first one */
    allErrors: false,

    /* Validate formats fully. Slower but more correct than 'fast' mode */
    format: 'full',

    /* Throw exceptions during schema compilation for unknown formats */
    unknownFormats: true,

    /* Don't remove additional properties, so that we can detect they exist and fail validation */
    /* If removeAdditional = true, they are removed before they can be detected as additional */
    removeAdditional: false,

    /* No defaults - all specified values must exist.*/
    useDefaults: false,

    /* Ensure all types are exactly as specified. E.g. this will not accept "1" as a number */
    coerceTypes: false
};
const ajv = new Ajv(AJV_OPTIONS);

/**
 * Validates the security against the "device"\ security model.  This requires 3 headers:
 * 1. `x-bridge-device-session`: `<device_token>:<session_token>`
 * 2. `x-bridge-hmac`: The hmac for the request as described in the wiki
 * 3. `x-bridge-timestamp`: The timestamp of the packet
 *
 * @param {Object} req      - the express request object
 * @param {Object} def      - the definition of the security definition we are validating
 * @param {Object} scopes   - the value of the header specified in the definition
 * @param {Function!} callback - the callback function for success or failure or the security validation
 */
function deviceSession(req, def, scopes, callback) {
    debug('DEVICE SESSION CALLED');

    //
    // Check we have valid tokens.
    //
    const detailsP = getSecurityValues(req, scopes).catch((error) => {
        debug('Failed to get security values', error);
        return Q.reject(utils.createError(30013, 'Missing or invalid security params'));
    });

    //
    // Validate the client and device details
    //
    const validP = detailsP.then((info) => {
        return validateDeviceSession(info);
    });

    //
    // Initialise the session info
    //
    const sessionP = validP.then((sessionInfo) => {
        return apiUtils.initSession(req, sessionInfo.client, sessionInfo.device);
    });

    //
    // Check all the requirements passed
    //
    Q.all([detailsP, validP, sessionP])
        .then(() => {
            //
            // Everything passed so continue
            //
            return callback();
        })
        .catch((error) => {
            //
            // Something failed.  Log the real error, then return a generic error (for security)
            //
            debug('Failed to authorise deviceSession', error);
            const authFail = new Error('Not authorised');
            authFail.statusCode = 401;
            return callback(authFail);
        });
}

/**
 * Validates the HMAC against the "device" security model in Login (and similar) where there is no
 * session yet.  This requires 2 headers:
 * 1. `x-bridge-hmac`: The hmac for the request as described in the wiki
 * 2. `x-bridge-timestamp`: The timestamp of the packet
 *
 * It also requires a path with the device specified as the objectId
 *
 * @param {Object} req      - the express request object
 * @param {Object} def      - the definition of the security definition we are validating
 * @param {Object} scopes   - the value of the header specified in the definition
 * @param {Function!} callback - the callback function for success or failure or the security validation
 */
function deviceHmacNoSession(req, def, scopes, callback) {
    debug('DEVICE HMAC NO SESSION CALLED');

    //
    // Check we have valid values.
    //
    const detailsP = getSecurityValues(req, scopes, true).catch((error) => {
        debug('Failed to get security values', error);
        return Q.reject(utils.createError(30013, 'Missing or invalid security params'));
    });

    //
    // Validate the client and device details
    //
    const validP = detailsP.then((info) => {
        return validateDeviceNoSession(req, info);
    });

    //
    // Initialise the session info
    //
    const sessionP = validP.then((sessionInfo) => {
        return apiUtils.initSession(req, sessionInfo.client, sessionInfo.device);
    });

    //
    // Check all the requirements passed
    //
    Q.all([detailsP, validP, sessionP])
        .then(() => {
            //
            // Everything passed so continue
            //
            return callback();
        })
        .catch((error) => {
            //
            // Something failed.  Log the real error, then return a generic error (for security)
            //
            debug('Failed to authorise deviceHmacNoSession', error);
            const authFail = new Error('Not authorised');
            authFail.statusCode = 401;
            return callback(authFail);
        });
}

/**
 * Gets the values we need to check the security from the appropriate headers.
 * This also validates that they are in the correct format, splits the session
 * tokens, etc.
 *
 * @param {Object} req              - the request object
 * @param {string} session          - the session header value
 * @param {boolean} ignoreSession   - true to not expect any session values
 *
 * @returns {Object}        - Object containing the information we need for the security testing
 */
async function getSecurityValues(req, session, ignoreSession) {
    if (!VALIDATORS.initialised) {
        debug('Validators not initialised!');
        await initialiseValidators();
    }

    //
    // Get tokens from the headers we expect
    //
    let deviceToken;
    let sessionToken;
    let sessionOk = false;

    if (ignoreSession) {
        sessionOk = true;
    } else {
        sessionOk = VALIDATORS.session(session);
        if (sessionOk === false) {
            debug('Session header failed validation:', VALIDATORS.session.errors);
        } else {
            //
            // Need to split the token into the two parts.
            // NOTE: the JSON Schema validation has ensured that it is in the right format
            //       so we don't need to check for errors
            //
            [deviceToken, sessionToken] = session.split(':');
        }
    }

    const hmac = req.headers['x-bridge-hmac'];
    const hmacOk = VALIDATORS.hmac(hmac);
    if (!hmacOk) {
        debug('HMAC header failed validation:', VALIDATORS.hmac.errors);
    }

    const timestamp = req.headers['x-bridge-timestamp'];
    const timestampOk = VALIDATORS.timestamp(timestamp);
    if (!timestampOk) {
        debug('HMAC timestamp header failed validation:', VALIDATORS.timestamp.errors);
    }

    //
    // Check we got all 3 headers and they are formatted correctly
    //
    if (!sessionOk || !hmacOk || !timestampOk) {
        throw new Error('Invalid headers');
    }

    //
    // Get the full request address.  This is a little tricky because there is no one place to get it:
    // 1. The hostname comes in a header which is controlled by the caller, and is thus untrusted.
    //    e.g. see http://www.skeletonscribe.net/2013/05/practical-http-host-header-attacks.html
    //    - We use our configuration value instead, which is set by us and thus trusted
    // 2. The port is only included in the URL if using a non-standard port, and more importantly
    //    we care about the external port (at the gateway), not the internal one we are running on.
    //    - Again, we rely on the configuration value to include the port if neccessary
    // 3. The other parts of the URL are split across multiple params in the request
    //    - We recombine everything in a safe way using the nodejs URL lib
    //
    const baseUrl = url.format({
        host: config.CCWebsiteAddress,
        protocol: req.protocol,
        slashes: true
    });
    const fullUrl = new url.URL(
        req.originalUrl,
        baseUrl
    );
    const address = fullUrl.toString();

    //
    // Get the raw body so we can use that as part of validating the hmac.
    // This is stored in the req object by the api_body_middleware.js, and only
    // exists if there was a body (and it was readable according to the given encoding).
    //
    const body = _.isUndefined(req.bodyRaw) ? '' : req.bodyRaw;

    //
    // Get other basic values from the request
    //
    const method = req.method;
    const featureFlag = req.swagger.operation['x-feature-flag'];

    return {
        deviceToken,
        sessionToken,
        hmac,
        timestamp,
        address,
        method,
        body,
        featureFlag
    };
}

/**
 * Initialises the validator object with compiled versions of the schemas we will
 * use to validate our incoming header parameters. These schemas are held within
 * the definitions section of the swagger definition.
 *
 * @throws {Error}                  - throws an error if the schema is invalid
 */
async function initialiseValidators() {
    const swaggerDefs = await JsonRefs.resolveRefsAt(require.resolve('./api_definitions.json'));
    const definitions = swaggerDefs.resolved.definitions;

    const sessionSchema = definitions['security.Device.sessionHeader'];
    const hmacSchema = definitions['security.Device.hmacHeader'];
    const timestampSchema = definitions['security.Device.hmacTimestamp'];

    const emailSchema = definitions.email;
    const objectIdSchema = definitions.uuid;

    VALIDATORS.session = ajv.compile(sessionSchema);
    VALIDATORS.hmac = ajv.compile(hmacSchema);
    VALIDATORS.timestamp = ajv.compile(timestampSchema);
    VALIDATORS.email = ajv.compile(emailSchema);
    VALIDATORS.objectId = ajv.compile(objectIdSchema);
    VALIDATORS.initialised = true;
}

/**
 * Function to do the validation of the session and HMAC based on the info we extracted from
 * the headers.
 *
 * @param {Object} sessionInfo      - The validated info from the request headers etc.
 * @param {string} sessionInfo.deviceToken  - The device token from the header
 * @param {string} sessionInfo.sessionToken - The session token from the header
 * @param {string} sessionInfo.hmac         - The value of the HMAC header (expected HMAC)
 * @param {string} sessionInfo.timestamp    - The value of the HMAC timestamp header
 * @param {string} sessionInfo.address      - The full request url: https://example.com/p/a/t/h/?a=123
 * @param {string} sessionInfo.method       - The HTTP method used for the request
 * @param {string?} sessionInfo.body        - The request body (if any)
 * @param {string?} sessionInfo.featureFlag - The feature flag required for this feature (if any)
 *
 * @returns {Promise}               - Promise for the successful validation (or rejected with error)
 */
async function validateDeviceSession(sessionInfo) {
    /**
     * Get the client details (client and device objects)
     */
    const clientDetails = await auth.validateCurrentSession(
        sessionInfo.deviceToken,
        sessionInfo.sessionToken
    );

    /**
     * Build the data in the format the legacy checkHMAC() function expects it.
     * NOTE: the device and session tokens used to be implicitly included in the hmac calculation
     *       as they were passed in the body itself.  As they are now passed as a header, we
     *       manually append them to the body to have the same effect of verifying that this
     *       request is tied to this device and session.
     */
    const device = clientDetails[0];
    const client = clientDetails[1];

    const hmacData = {
        address: sessionInfo.address,
        method: sessionInfo.method,
        body: sessionInfo.body + sessionInfo.deviceToken + ':' + sessionInfo.sessionToken,
        ClientName: client.ClientName,
        timestamp: sessionInfo.timestamp,
        hmac: sessionInfo.hmac
    };

    /**
     * Validate the HMAC based on all the details
     */
    await auth.checkHMAC(
        device,
        hmacData,
        'validateDeviceSession',
    );

    /**
     * Validate the featureFlags exist if required
     */
    const requiredFlag = sessionInfo.featureFlag;
    if (requiredFlag && !featureFlags.isEnabled(requiredFlag, client)) {
        debug('Required feature flag not present', requiredFlag);
        throw utils.createError(30012, 'Feature unavailable');
    }

    /**
     * Return the client and device for setting up the session
     */
    return {
        client,
        device
    };
}

/**
 * Function to do the validation of the provided values and HMAC based on the
 * info provided in the path, the headers, and the body.  This requires:
 * - hmac and timestamp from the headers
 * - objectId from the path
 * - ClientName from the body
 *
 * @param {Object} req              - The express request object
 * @param {Object} sessionInfo      - The validated info from the request headers etc.
 * @param {string} sessionInfo.hmac         - The value of the HMAC header (expected HMAC)
 * @param {string} sessionInfo.timestamp    - The value of the HMAC timestamp header
 * @param {string} sessionInfo.address      - The full request url: https://example.com/p/a/t/h/?a=123
 * @param {string} sessionInfo.method       - The HTTP method used for the request
 * @param {string?} sessionInfo.body        - The request body (if any)
 * @param {string?} sessionInfo.featureFlag - The feature flag required for this feature (if any)
 *
 * @returns {Promise}               - Promise for the successful validation (or rejected with error)
 */
async function validateDeviceNoSession(req, sessionInfo) {
    /**
     * Get the client details (client and device objects)
     * As this is run before the main validation we have to manually validate it ourselves
     */
    const deviceID = _.get(req, 'swagger.params.objectId.value');
    const deviceIDOk = VALIDATORS.objectId(deviceID);
    const clientEmail = _.get(req, 'swagger.params.body.value.ClientName');
    const clientEmailOk = VALIDATORS.email(clientEmail);

    if (!deviceIDOk || !clientEmailOk) {
        throw new Error('Invalid parameters');
    }

    /**
     * Get the client
     */
    const client = await references.getClientByEmail(clientEmail);

    /**
     * Get the device (checking it belongs to our client)
     */
    const device = await mainDBP.findOneObject(
        mainDBP.mainDB.collectionDevice,
        {
            _id: mongodb.ObjectID(deviceID),
            ClientID: client.ClientID
        },
        undefined,  // No options
        true        // Suppress errors (i.e. failing to find an object isn't a db connection issue)
    );

    /**
     * Verify that both client and device are in a good state (validated, & not banned or blocked)
     */
    const clientStatus = auth.checkClientStatus(client.ClientStatus);
    const deviceStatus = auth.checkDeviceStatus(device.DeviceStatus);

    if (clientStatus !== null) {
        throw clientStatus;
    }
    if (deviceStatus !== null) {
        throw deviceStatus;
    }

    /**
     * Need to convert the request name to the one expected by the legacy auth functions
     */
    const swaggerFunction = _.get(req, 'swagger.operation.operationId');
    let authFunctionName = swaggerFunction;
    if (swaggerFunction === 'deviceLogin') {
        authFunctionName = 'Login1.process';
    }

    /**
     * Build the data in the format the legacy checkHMAC() function expects it.
     */
    const hmacData = {
        address: sessionInfo.address,
        method: sessionInfo.method,
        body: sessionInfo.body,
        ClientName: client.ClientName,
        timestamp: sessionInfo.timestamp,
        hmac: sessionInfo.hmac
    };

    /**
     * Validate the HMAC based on all the details
     */
    await auth.checkHMAC(
        device,
        hmacData,
        authFunctionName,
    );

    /**
     * Validate the featureFlags exist if required
     */
    const requiredFlag = sessionInfo.featureFlag;
    if (requiredFlag && !featureFlags.isEnabled(requiredFlag, client)) {
        debug('Required feature flag not present', requiredFlag);
        throw utils.createError(30012, 'Feature unavailable');
    }

    /**
     * Return the client and device for setting up the session
     */
    return {
        client,
        device
    };
}