var assert = require("assert"),
	SubstrExpression = require("../../../../lib/pipeline/expressions/SubstrExpression"),
	Expression = require("../../../../lib/pipeline/expressions/Expression");

module.exports = {

	"SubstrExpression": {

		"constructor()": {

			"should not throw Error when constructing without args": function testConstructor(){
				assert.doesNotThrow(function(){
					new SubstrExpression();
				});
			}

		},

		"#getOpName()": {

			"should return the correct op name; $substr": function testOpName(){
				assert.equal(new SubstrExpression().getOpName(), "$substr");
			}

		},

		"#evaluate()": {

			"Should fail if no end argument is given": function testMissing3rdArg(){
				var s = "mystring",
				start = 0,
				end = s.length;
				assert.throws(function(){Expression.parseOperand({$substr:["$s", "$start"]}).evaluate({s:s, start:start});});
			},

			"Should return entire string when called with 0 and length": function testWholeString(){
				var s = "mystring",
				start = 0,
				end = s.length;
				assert.strictEqual(Expression.parseOperand({$substr:["$s", "$start", "$end"]}).evaluate({s:s, start:start, end:end}), "mystring");
			},

			"Should return entire string less the last character when called with 0 and length-1": function testLastCharacter(){
				var s = "mystring",
				start = 0,
				end = s.length;
				assert.strictEqual(Expression.parseOperand({$substr:["$s", "$start", "$end"]}).evaluate({s:s, start:start, end:end-1}), "mystrin");
			},

			"Should return empty string when 0 and 0 are given as indexes": function test00Indexes(){
				var s = "mystring",
				start = 0,
				end = 0;
				assert.strictEqual(Expression.parseOperand({$substr:["$s", "$start", "$end"]}).evaluate({s:s, start:start, end:end}), "");
			},

			"Should first character when 0 and 1 are given as indexes": function testFirstCharacter(){
				var s = "mystring",
				start = 0,
				end = 1;
				assert.strictEqual(Expression.parseOperand({$substr:["$s", "$start", "$end"]}).evaluate({s:s, start:start, end:end}), "m");
			},

			"Should return empty string when empty string is given": function testEmptyString(){
				var s = "",
				start = 0,
				end = 0;
				assert.strictEqual(Expression.parseOperand({$substr:["$s", "$start", "$end"]}).evaluate({s:s, start:start, end:end}), "");
			},

			"Should fail if end is before begin": function testUnorderedIndexes(){
				var s = "mystring",
				start = s.length,
				end = 0;
				assert.throws(function(){Expression.parseOperand({$substr:["$s", "$start"]}).evaluate({s:s, start:start, end:end});});
			},

			"Should fail if end is greater than length": function testIndexTooLarge(){
				var s = "mystring",
				start = 0,
				end = s.length+1;
				assert.throws(function(){Expression.parseOperand({$substr:["$s", "$start"]}).evaluate({s:s, start:start, end:end});});
			}

		}

	}

};

if (!module.parent)(new(require("mocha"))()).ui("exports").reporter("spec").addFile(__filename).run(process.exit);