comparison.js

'use strict';

var isOdd = require('is-odd');
var isEven = require('is-even');
var typeOf = require('kind-of');
var contains = require('./utils/contains');
var isObject = require('./object').isObject;
var isString = require('./string').isString;

/**
 * Expose `helpers`
 */

var helpers = module.exports;

/**
 * Block helper that renders the block if **both** of the given values
 * are truthy. If an inverse block is specified it will be rendered
 * when falsy.
 *
 * @param {any} `a`
 * @param {any} `b`
 * @param {Object} `options` Handlebars provided options object
 * @return {String}
 * @block
 * @api public
 */

helpers.and = function(a, b, options) {
  if (a && b) {
    return options.fn(this);
  }
  return options.inverse(this);
};

/**
 * Render a block when a comparison of the first and third
 * arguments returns true. The second argument is
 * the [arithemetic operator][operators] to use. You may also
 * optionally specify an inverse block to render when falsy.
 *
 * @param `a`
 * @param `operator` The operator to use. Operators must be enclosed in quotes: `">"`, `"="`, `"<="`, and so on.
 * @param `b`
 * @param {Object} `options` Handlebars provided options object
 * @return {String} Block, or if specified the inverse block is rendered if falsey.
 * @block
 * @api public
 */

helpers.compare = function(a, operator, b, options) {
  /*jshint eqeqeq: false*/

  if (arguments.length < 4) {
    throw new Error('handlebars Helper {{compare}} expects 2 arguments.');
  }

  var result;

  switch(operator) {
    case '==':
      result = a == b;
      break;
    case '===':
      result = a === b;
      break;
    case '!=':
      result = a != b;
      break;
    case '!==':
      result = a !== b;
      break;
    case '<':
      result = a < b;
      break;
    case '>':
      result = a > b;
      break;
    case '<=':
      result = a <= b;
      break;
    case '>=':
      result = a >= b;
      break;
    case 'typeof':
      result = typeof a === b;
     break;
     default: {
       throw new Error('helper {{compare}}: invalid operator: `' + operator + '`');
     }
  }

  if (result === false) {
    return options.inverse(this);
  }
  return options.fn(this);
};

/**
 * Block helper that renders the block if `collection` has the
 * given `value`, using strict equality (`===`) for comparison,
 * otherwise the inverse block is rendered (if specified). If a
 * `startIndex` is specified and is negative, it is used as the
 * offset from the end of the collection.
 *
 * Given the array `['a', 'b', 'c']`:
 *
 * ```handlebars
 * {{#contains array "d"}}
 *   This will not be rendered.
 * {{else}}
 *   This will be rendered.
 * {{/contains}}
 * ```
 * @param {Array|Object|String} `collection` The collection to iterate over.
 * @param {any} `value` The value to check for.
 * @param {Number} `[startIndex=0]` Optionally define the starting index.
 * @param {Object} `options` Handlebars provided options object.
 * @block
 * @api public
 */

helpers.contains = function(collection, value, startIndex, options) {
  if (typeof startIndex === 'object') {
    options = startIndex;
    startIndex = undefined;
  }
  if (contains(collection, value, startIndex)) {
    return options.fn(this);
  }
  return options.inverse(this);
};

/**
 * Block helper that renders a block if `a` is **greater than** `b`.
 *
 * If an inverse block is specified it will be rendered when falsy.
 * You may optionally use the `compare=""` hash argument for the
 * second value.
 *
 * @name .gt
 * @param {String} `a`
 * @param {String} `b`
 * @param {Object} `options` Handlebars provided options object
 * @return {String} Block, or inverse block if specified and falsey.
 * @block
 * @api public
 */

helpers.gt = function(a, b, options) {
  if (arguments.length === 2) {
    options = b;
    b = options.hash.compare;
  }
  if (a > b) {
    return options.fn(this);
  }
  return options.inverse(this);
};

/**
 * Block helper that renders a block if `a` is **greater than or
 * equal to** `b`.
 *
 * If an inverse block is specified it will be rendered when falsy.
 * You may optionally use the `compare=""` hash argument for the
 * second value.
 *
 * @name .gte
 * @param {String} `a`
 * @param {String} `b`
 * @param {Object} `options` Handlebars provided options object
 * @return {String} Block, or inverse block if specified and falsey.
 * @block
 * @api public
 */

helpers.gte = function(a, b, options) {
  if (arguments.length === 2) {
    options = b;
    b = options.hash.compare;
  }
  if (a >= b) {
    return options.fn(this);
  }
  return options.inverse(this);
};

/**
 * Block helper that renders a block if `value` has `pattern`.
 * If an inverse block is specified it will be rendered when falsy.
 *
 * @param {any} `val` The value to check.
 * @param {any} `pattern` The pattern to check for.
 * @param {Object} `options` Handlebars provided options object
 * @return {String}
 * @block
 * @api public
 */

helpers.has = function(value, pattern, options) {
  if (arguments.length === 2) {
    return pattern.inverse(this);
  }

  if (arguments.length === 1) {
    return value.inverse(this);
  }

  if ((Array.isArray(value) || isString(value)) && isString(pattern)) {
    if (value.indexOf(pattern) > -1) {
      return options.fn(this);
    }
  }
  if (isObject(value) && isString(pattern) && pattern in value) {
    return options.fn(this);
  }
  return options.inverse(this);
};

/**
 * Block helper that renders a block if `a` is **equal to** `b`.
 * If an inverse block is specified it will be rendered when falsy.
 * You may optionally use the `compare=""` hash argument for the
 * second value.
 *
 * @name .eq
 * @param {String} `a`
 * @param {String} `b`
 * @param {Object} `options` Handlebars provided options object
 * @return {String} Block, or inverse block if specified and falsey.
 * @block
 * @api public
 */

helpers.eq = function(a, b, options) {
  if (arguments.length === 2) {
    options = b;
    b = options.hash.compare;
  }
  if (a === b) {
    return options.fn(this);
  }
  return options.inverse(this);
};

/**
 * Return true if the given vaue is an even number.
 *
 * ```handlebars
 * {{#ifEven value}}
 *   render A
 * {{else}}
 *   render B
 * {{/ifEven}}
 * ```
 * @param  {Number} `number`
 * @param {Object} `options` Handlebars provided options object
 * @return {String} Block, or inverse block if specified and falsey.
 * @block
 * @api public
 */

helpers.ifEven = function(num, options) {
  return isEven(num) ? options.fn(this) : options.inverse(this);
};

/**
 * Conditionally renders a block if the remainder is zero when
 * `a` operand is divided by `b`. If an inverse block is specified
 * it will be rendered when the remainder is **not zero**.
 *
 * @param {Number}
 * @param {Number}
 * @param {Object} `options` Handlebars provided options object
 * @return {String} Block, or inverse block if specified and falsey.
 * @block
 * @api public
 */

helpers.ifNth = function(a, b, options) {
  if (++b % a === 0) {
    return options.fn(this);
  }
  return options.inverse(this);
};

/**
 * Block helper that renders a block if `value` is **an odd number**.
 * If an inverse block is specified it will be rendered when falsy.
 *
 * ```handlebars
 * {{#ifOdd value}}
 *   render A
 * {{else}}
 *   render B
 * {{/ifOdd}}
 * ```
 * @param  {Object} `value`
 * @param {Object} `options` Handlebars provided options object
 * @return {String} Block, or inverse block if specified and falsey.
 * @block
 * @api public
 */

helpers.ifOdd = function(val, options) {
  return isOdd(val) ? options.fn(this) : options.inverse(this);
};

/**
 * Block helper that renders a block if `a` is **equal to** `b`.
 * If an inverse block is specified it will be rendered when falsy.
 *
 * @name .is
 * @param {any} `a`
 * @param {any} `b`
 * @param {Object} `options` Handlebars provided options object
 * @return {String}
 * @block
 * @api public
 */

helpers.is = function(a, b, options) {
  if (arguments.length === 2) {
    options = b;
    b = options.hash.compare;
  }
  if (a === b) {
    return options.fn(this);
  }
  return options.inverse(this);
};

/**
 * Block helper that renders a block if `a` is **not equal to** `b`.
 * If an inverse block is specified it will be rendered when falsy.
 *
 * @name .isnt
 * @param {String} `a`
 * @param {String} `b`
 * @param {Object} `options` Handlebars provided options object
 * @return {String}
 * @block
 * @api public
 */

helpers.isnt = function(a, b, options) {
  if (arguments.length === 2) {
    options = b;
    b = options.hash.compare;
  }
  if (a !== b) {
    return options.fn(this);
  }
  return options.inverse(this);
};

/**
 * Block helper that renders a block if `a` is **less than** `b`.
 *
 * If an inverse block is specified it will be rendered when falsy.
 * You may optionally use the `compare=""` hash argument for the
 * second value.
 *
 * @name .lt
 * @param {Object} `context`
 * @param {Object} `options` Handlebars provided options object
 * @return {String} Block, or inverse block if specified and falsey.
 * @block
 * @api public
 */

helpers.lt = function(a, b, options) {
  if (arguments.length === 2) {
    options = b;
    b = options.hash.compare;
  }
  if (a < b) {
    return options.fn(this);
  }
  return options.inverse(this);
};

/**
 * Block helper that renders a block if `a` is **less than or
 * equal to** `b`.
 *
 * If an inverse block is specified it will be rendered when falsy.
 * You may optionally use the `compare=""` hash argument for the
 * second value.
 *
 * @name .lte
 * @param {Sring} `a`
 * @param {Sring} `b`
 * @param {Object} `options` Handlebars provided options object
 * @return {String} Block, or inverse block if specified and falsey.
 * @block
 * @api public
 */

helpers.lte = function(a, b, options) {
  if (arguments.length === 2) {
    options = b;
    b = options.hash.compare;
  }
  if (a <= b) {
    return options.fn(this);
  }
  return options.inverse(this);
};

/**
 * Block helper that renders a block if **neither of** the given values
 * are truthy. If an inverse block is specified it will be rendered
 * when falsy.
 *
 * @name .neither
 * @param {any} `a`
 * @param {any} `b`
 * @param `options` Handlebars options object
 * @return {String} Block, or inverse block if specified and falsey.
 * @block
 * @api public
 */

helpers.neither = function(a, b, options) {
  if (!a && !b) {
    return options.fn(this);
  }
  return options.inverse(this);
};

/**
 * Block helper that renders a block if **either of** the given values
 * is truthy. If an inverse block is specified it will be rendered
 * when falsy.
 *
 * @name .or
 * @param {any} `a`
 * @param {any} `b`
 * @param `options` Handlebars options object
 * @return {String} Block, or inverse block if specified and falsey.
 * @block
 * @api public
 */

helpers.or = function(a, b, options) {
  if (a || b) {
    return options.fn(this);
  }
  return options.inverse(this);
};

/**
 * Block helper that always renders the inverse block **unless `a` is
 * is equal to `b`**.
 *
 * @name .unlessEq
 * @param {String} `a`
 * @param {String} `b`
 * @param {Object} `options` Handlebars provided options object
 * @return {String} Inverse block by default, or block if falsey.
 * @block
 * @api public
 */

helpers.unlessEq = function(context, options) {
  if (context === options.hash.compare) {
    return options.inverse(this);
  }
  return options.fn(this);
};

/**
 * Block helper that always renders the inverse block **unless `a` is
 * is greater than `b`**.
 *
 * @name .unlessGt
 * @param {Object} `context`
 * @param {Object} `options` Handlebars provided options object
 * @return {String} Inverse block by default, or block if falsey.
 * @block
 * @api public
 */

helpers.unlessGt = function(context, options) {
  if (context > options.hash.compare) {
    return options.inverse(this);
  }
  return options.fn(this);
};

/**
 * Block helper that always renders the inverse block **unless `a` is
 * is less than `b`**.
 *
 * @name .unlessLt
 * @param {Object} `context`
 * @param {Object} `options` Handlebars provided options object
 * @return {String} Block, or inverse block if specified and falsey.
 * @block
 * @api public
 */

helpers.unlessLt = function(context, options) {
  if (context < options.hash.compare) {
    return options.inverse(this);
  }
  return options.fn(this);
};

/**
 * Block helper that always renders the inverse block **unless `a` is
 * is greater than or equal to `b`**.
 *
 * @name .unlessGteq
 * @param {Object} `context`
 * @param {Object} `options` Handlebars provided options object
 * @return {String} Block, or inverse block if specified and falsey.
 * @block
 * @api public
 */

helpers.unlessGteq = function(context, options) {
  if (context >= options.hash.compare) {
    return options.inverse(this);
  }
  return options.fn(this);
};

/**
 * Block helper that always renders the inverse block **unless `a` is
 * is less than or equal to `b`**.
 *
 * @name .unlessLteq
 * @param {Object} `context`
 * @param {Object} `options` Handlebars provided options object
 * @return {String} Block, or inverse block if specified and falsey.
 * @block
 * @api public
 */

helpers.unlessLteq = function(context, options) {
  if (context <= options.hash.compare) {
    return options.inverse(this);
  }
  return options.fn(this);
};