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var assert = require('assert');var jsv = require('jsverify');
var R = require('../source');var eq = require('./shared/eq');

describe('compose', function() {
  it('is a variadic function', function() {    eq(typeof R.compose, 'function');    eq(R.compose.length, 0);  });
  it('performs right-to-left function composition', function() {    //  f :: (String, Number?) -> ([Number] -> [Number])    var f = R.compose(R.map, R.multiply, parseInt);
    eq(f.length, 2);    eq(f('10')([1, 2, 3]), [10, 20, 30]);    eq(f('10', 2)([1, 2, 3]), [2, 4, 6]);  });
  it('passes context to functions', function() {    function x(val) {      return this.x * val;    }    function y(val) {      return this.y * val;    }    function z(val) {      return this.z * val;    }    var context = {      a: R.compose(x, y, z),      x: 4,      y: 2,      z: 1    };    eq(context.a(5), 40);  });
  it('throws if given no arguments', function() {    assert.throws(      function() { R.compose(); },      function(err) {        return err.constructor === Error &&               err.message === 'compose requires at least one argument';      }    );  });
  it('can be applied to one argument', function() {    var f = function(a, b, c) { return [a, b, c]; };    var g = R.compose(f);    eq(g.length, 3);    eq(g(1, 2, 3), [1, 2, 3]);  });
});

describe('compose properties', function() {
  jsv.property('composes two functions', jsv.fn(), jsv.fn(), jsv.nat, function(f, g, x) {    return R.equals(R.compose(f, g)(x), f(g(x)));  });
  jsv.property('associative',  jsv.fn(), jsv.fn(), jsv.fn(), jsv.nat, function(f, g, h, x) {    var result = f(g(h(x)));    return R.all(R.equals(result), [      R.compose(f, g, h)(x),      R.compose(f, R.compose(g, h))(x),      R.compose(R.compose(f, g), h)(x)    ]);  });});