/**
 * Copyright 2013-2016  Zaid Abdulla
 *
 * GenieACS is free software: you can redistribute it and/or modify
 * it under the terms of the GNU Affero General Public License as
 * published by the Free Software Foundation, either version 3 of the
 * License, or (at your option) any later version.
 *
 * GenieACS is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU Affero General Public License for more details.
 *
 * You should have received a copy of the GNU Affero General Public License
 * along with GenieACS.  If not, see <http://www.gnu.org/licenses/>.
 */
"use strict";

const vm = require("vm");

const seedrandom = require("seedrandom");

const common = require("./common");
const device = require("./device");
const extensions = require("./extensions");


// Used for throwing to exit user script and commit
const COMMIT = Symbol();

// Used to execute extensions and restart
const EXT = Symbol();

const sandbox = {
  timestamp: null,
  deviceData: null,
  revision: null,
  maxRevision: null,
  uncommitted: false,
  declarations: null,
  extensionsCache: null,
  extensions: null,
  clear: null,
  rng: null,
  context: vm.createContext()
}

class SandboxDate {
  constructor(arg) {
    if (arguments.length)
      return new (Function.prototype.bind.apply(Date, arguments));

    return new Date(sandbox.timestamp);
  }

  static now() {
    return sandbox.timestamp;
  }
};

function random() {
  if (!sandbox.rng)
    sandbox.rng = seedrandom(sandbox.timestamp);

  return sandbox.rng();
}


class ParameterWrapper {
  constructor(path, attributes, unpacked, unpackedRevision) {
    for (let attrName of attributes) {
      Object.defineProperty(this, attrName, {get: function() {
        if (sandbox.uncommitted)
          commit();

        if (sandbox.revision !== unpackedRevision) {
          unpackedRevision = sandbox.revision;
          unpacked = device.unpack(sandbox.deviceData, path, sandbox.revision + 1);
        }

        if (!unpacked.length)
          return undefined;

        let attr = sandbox.deviceData.attributes.get(unpacked[0], sandbox.revision + 1)[attrName];

        if (!attr)
          return undefined;

        return attr[1];
      }});
    }

    Object.defineProperty(this, "path", {get: function() {
      if (sandbox.uncommitted)
        commit();

      if (sandbox.revision !== unpackedRevision) {
        unpackedRevision = sandbox.revision;
        unpacked = device.unpack(sandbox.deviceData, path, sandbox.revision + 1);
      }

      if (!unpacked.length)
        return undefined;

      return unpacked[0].join('.');
    }});

    Object.defineProperty(this, "size", {get: function() {
      if (sandbox.uncommitted)
        commit();

      if (sandbox.revision !== unpackedRevision) {
        unpackedRevision = sandbox.revision;
        unpacked = device.unpack(sandbox.deviceData, path, sandbox.revision + 1);
      }

      if (!unpacked.length)
        return undefined;

      return unpacked.length;
    }});

    this[Symbol.iterator] = function*() {
      if (sandbox.uncommitted)
        commit();

      if (sandbox.revision !== unpackedRevision) {
        unpackedRevision = sandbox.revision;
        unpacked = device.unpack(sandbox.deviceData, path, sandbox.revision + 1);
      }

      for (let p of unpacked)
        yield new ParameterWrapper(p, attributes, [p], sandbox.revision);
    }
  }
}


function declare(path, timestamps, values) {
  sandbox.uncommitted = true;
  if (!timestamps)
    timestamps = {};

  let parsedPath = common.parsePath(path);

  let declaration = [parsedPath, 1];

  let attrs = {};
  if (timestamps)
    for (let attrName in timestamps)
      if (attrName === "path")
        declaration[1] = timestamps.path;
      else {
        attrs[attrName] = 1;
        declaration[2] = declaration[2] || {};
        declaration[2][attrName] = timestamps[attrName];
      }

  if (values)
    for (let attrName in values)
      if (attrName === "path")
        declaration[3] = values.path;
      else {
        attrs[attrName] = 1;
        declaration[4] = declaration[4] || {};
        if (attrName === "value" && !Array.isArray(values.value))
          declaration[4].value = [values.value];
        else
          declaration[4][attrName] = values[attrName];
      }

  sandbox.declarations.push(declaration);

  return new ParameterWrapper(parsedPath, Object.keys(attrs));
}


function clear(path, timestamp, attributes) {
  sandbox.uncommitted = true;

  if (sandbox.revision === sandbox.maxRevision) {
    sandbox.clear = sandbox.clear || [];
    sandbox.clear.push([common.parsePath(path), timestamp, attributes]);
  }
}


function commit() {
  ++ sandbox.revision;
  sandbox.uncommitted = false;

  if (sandbox.revision === sandbox.maxRevision + 1)
    throw COMMIT;
  else if (sandbox.revision > sandbox.maxRevision + 1)
    throw new Error("Declare function should not be called from within a try/catch block");
}


function ext() {
  let extCall = Array.from(arguments).map(String);
  let key = `${sandbox.revision}: ${JSON.stringify(extCall)}`;

  if (key in sandbox.extensionsCache)
    return sandbox.extensionsCache[key];

  sandbox.extensions[key] = extCall;
  throw EXT;
}


Object.defineProperty(sandbox.context, 'Date', {value: SandboxDate});
Object.defineProperty(sandbox.context, 'declare', {value: declare});
Object.defineProperty(sandbox.context, 'clear', {value: clear});
Object.defineProperty(sandbox.context, 'commit', {value: commit});
Object.defineProperty(sandbox.context, 'ext', {value: ext});

// Monkey-patch Math.random() to make it deterministic
sandbox.context.random = random;
vm.runInContext("Math.random = random;", sandbox.context);
delete sandbox.random;


function errorToFault(err) {
  if (!err)
    return null;

  return {
    code: `script.${err.name}`,
    message: err.message,
    detail: {
      name: err.name,
      message: err.message,
      stack: err.stack
    }
  }
}


function run(script, globals, timestamp, deviceData, extensionsCache, startRevision, maxRevision, callback) {
  sandbox.timestamp = timestamp;
  sandbox.deviceData = deviceData;
  sandbox.extensionsCache = extensionsCache;
  sandbox.revision = startRevision;
  sandbox.maxRevision = maxRevision;
  sandbox.uncommitted = false;
  sandbox.declarations = [];
  sandbox.extensions = {};
  sandbox.clear = null;
  sandbox.rng = null;

  for (let n in sandbox.context)
    delete sandbox.context[n];

  for (let n in globals)
    sandbox.context[n] = globals[n];

  let ret, status;

  try {
    ret = script.runInContext(sandbox.context, {displayErrors: false});
    status = 0;
  }
  catch (err) {
    if (err === COMMIT)
      status = 1;
    else if (err === EXT)
      status = 2;
    else
      return callback(null, errorToFault(err));
  }

  let ext = sandbox.extensions;
  let decs = sandbox.declarations;
  let clr = sandbox.clear;
  let extCache = sandbox.extensionsCache;
  let args = arguments;

  let counter = 3;
  for (let key in sandbox.extensions) {
    counter += 2;
    extensions.run(sandbox.extensions[key], function(err, fault, res) {
      if (err || fault) {
        if (counter & 1)
          callback(err, fault);
        return counter = 0;
      }
      extCache[key] = res;
      if ((counter -= 2) === 1)
        if (status === 2)
          return run.apply(null, args);
        else
          return callback(null, null, clr, decs, status === 0, ret);
    });
  }

  if ((counter -= 2) === 1)
    if (status === 2)
      return run.apply(null, args);
    else
      return callback(null, null, clr, decs, status === 0, ret);
}


exports.run = run;