acl2/lib/contract.js

An Access Control List module based on memory, Redis, or MongoDB with Express middleware support

/*
  Design by Contract module (c) OptimalBits 2011.

  Roadmap:
    - Optional parameters. ['(string)', 'array']
    - Variable number of parameters.['number','...']

  api?:

  contract(arguments)
    .params('string', 'array', '...')
    .params('number')
    .end()

*/

const noop = {};
const _ = require("lodash");

noop.params = function () {
    return this;
};
noop.end = function () {};

const contract = function (args) {
    if (contract.debug === true) {
        contract.fulfilled = false;
        contract.args = _.toArray(args);
        contract.checkedParams = [];
        return contract;
    } else {
        return noop;
    }
};

contract.params = function () {
    this.fulfilled |= checkParams(this.args, _.toArray(arguments));
    if (this.fulfilled) {
        return noop;
    } else {
        this.checkedParams.push(arguments);
        return this;
    }
};
contract.end = function () {
    if (!this.fulfilled) {
        printParamsError(this.args, this.checkedParams);
        throw new Error("Broke parameter contract");
    }
};

const typeOf = function (obj) {
    return Array.isArray(obj) ? "array" : typeof obj;
};

const checkParams = function (args, contract) {
    let fulfilled, types, type, i, j;

    if (args.length !== contract.length) {
        return false;
    } else {
        for (i = 0; i < args.length; i++) {
            try {
                types = contract[i].split("|");
            } catch (e) {
                console.log(e, args);
            }
            if (args[i]) {
                type = typeOf(args[i]);
                fulfilled = false;
                for (j = 0; j < types.length; j++) {
                    if (type === types[j]) {
                        fulfilled = true;
                        break;
                    }
                }
            }
            if (fulfilled === false) {
                return false;
            }
        }
        return true;
    }
};

const printParamsError = function (args, checkedParams) {
    let msg = "Parameter mismatch.\nInput:\n( ",
        type,
        i;
    _.each(args, function (input, key) {
        type = typeOf(input);
        if (key !== 0) {
            msg += ", ";
        }
        msg += input + ": " + type;
    });

    msg += ")\nAccepted:\n";

    for (i = 0; i < checkedParams.length; i++) {
        msg += "(" + argsToString(checkedParams[i]) + ")\n";
    }

    console.log(msg);
};

const argsToString = function (args) {
    let res = "";
    _.each(args, function (arg, key) {
        if (key !== 0) {
            res += ", ";
        }
        res += arg;
    });
    return res;
};

exports = module.exports = contract;