agson/lib/agson/lenses.js

Querying and manipulating JSON graphs

(function() {
  var Just, Nothing, constant, fromNullable, identity, lens, nothing, property, withProperty, _ref,
    __hasProp = {}.hasOwnProperty;

  _ref = require('data.maybe'), Just = _ref.Just, Nothing = _ref.Nothing, fromNullable = _ref.fromNullable;

  lens = require('./Lens').of;

  nothing = lens("nothing", function() {
    return {
      modify: Nothing,
      get: Nothing
    };
  });

  identity = lens("identity", function(ma) {
    return {
      modify: function(f) {
        return f(ma);
      },
      get: function() {
        return ma;
      }
    };
  });

  constant = function(value) {
    return lens("constant(" + value + ")", function() {
      return {
        modify: function() {
          return fromNullable(value);
        },
        get: function() {
          return fromNullable(value);
        }
      };
    });
  };

  property = function(key) {
    return lens("property(" + key + ")", function(mo) {
      var setProperty;
      setProperty = withProperty(key);
      return {
        modify: function(f) {
          return mo.chain(function(object) {
            var mv;
            mv = fromNullable(object[key]);
            return f(mv).chain(function(value) {
              return Just(setProperty(object, value));
            });
          });
        },
        get: function() {
          return mo.chain(function(object) {
            return fromNullable(object[key]);
          });
        }
      };
    });
  };

  withProperty = function(key) {
    return function(object, value) {
      var k, result, v;
      result = {};
      for (k in object) {
        if (!__hasProp.call(object, k)) continue;
        v = object[k];
        result[k] = v;
      }
      result[key] = value;
      return result;
    };
  };

  module.exports = {
    nothing: nothing,
    identity: identity,
    constant: constant,
    property: property
  };

}).call(this);