var types = require("../lib/types");
var Type = types.Type;
var builtin = types.builtInTypes;
var isNumber = builtin.number;

// An example of constructing a new type with arbitrary constraints from
// an existing type.
exports.geq = function(than) {
    return new Type(function(value) {
        return isNumber.check(value) && value >= than;
    }, isNumber + " >= " + than);
};

// Default value-returning functions that may optionally be passed as a
// third argument to Def.prototype.field.
exports.defaults = {
    // Functions were used because (among other reasons) that's the most
    // elegant way to allow for the emptyArray one always to give a new
    // array instance.
    "null": function() { return null },
    "emptyArray": function() { return [] },
    "false": function() { return false },
    "true": function() { return true },
    "undefined": function() {}
};

var naiveIsPrimitive = Type.or(
    builtin.string,
    builtin.number,
    builtin.boolean,
    builtin.null,
    builtin.undefined
);

exports.isPrimitive = new Type(function(value) {
    if (value === null)
        return true;
    var type = typeof value;
    return !(type === "object" ||
             type === "function");
}, naiveIsPrimitive.toString());