From 9a09ecb86557c3949c884675478137a80a6b87fb Mon Sep 17 00:00:00 2001
From: Lara Aydin <daydin@zendesk.com>
Date: Thu, 9 Jan 2020 17:25:47 -0800
Subject: [PATCH] Add a rand() that can handle 0-2 arguments to generate random
 numbers using math/rand

Co-authored-by: Lara Aydin <ayd.dilara@gmail.com>
Co-authored-by: Michael Grosser <michael@grosser.it>
---
 vm/class.go      | 21 +++++++++++++++++++--
 vm/class_test.go | 44 +++++++++++++++++++++++++++++++++++++++-----
 2 files changed, 58 insertions(+), 7 deletions(-)

diff --git a/vm/class.go b/vm/class.go
index 2528004a1..940d9a4ec 100644
--- a/vm/class.go
+++ b/vm/class.go
@@ -8,6 +8,7 @@ import (
 	"time"
 
 	"sort"
+	"math/rand"
 
 	"github.com/goby-lang/goby/vm/classes"
 	"github.com/goby-lang/goby/vm/errors"
@@ -36,14 +37,14 @@ type RClass struct {
 var externalClasses = map[string][]ClassLoader{}
 var externalClassLock sync.Mutex
 
-// RegisterExternalClass will add the given class to the global registry of available classes
+// RegisterExternalClass will add the given class to the global registery of available classes
 func RegisterExternalClass(path string, c ...ClassLoader) {
 	externalClassLock.Lock()
 	externalClasses[path] = c
 	externalClassLock.Unlock()
 }
 
-// ClassLoader can be registered with a vm so that it can load this library at vm creation
+// ClassLoader can be registerd with a vm so that it can load this library at vm creation
 type ClassLoader = func(*VM) error
 
 func buildMethods(m map[string]Method) []*BuiltinMethodObject {
@@ -1308,6 +1309,22 @@ var builtinClassCommonInstanceMethods = []*BuiltinMethodObject{
 
 		},
 	},
+	{
+		Name: "rand",
+		Fn: func(receiver Object, sourceLine int, t *Thread, args []Object, blockFrame *normalCallFrame) Object {
+			aLen := len(args)
+			switch aLen {
+			case 0:
+				return t.vm.initFloatObject(rand.Float64())
+			case 1:
+				return t.vm.InitIntegerObject(rand.Intn(args[0].Value().(int)))
+			case 2:
+				return t.vm.InitIntegerObject(rand.Intn(args[1].Value().(int) - args[0].Value().(int) + 1) + args[0].Value().(int))
+			default:
+				return t.vm.InitErrorObject(errors.ArgumentError, sourceLine, errors.WrongNumberOfArgument, 2, aLen)
+			}
+		},
+	},
 	{
 		// A predicate class method that returns `true` if the object has an ability to respond to the method, otherwise `false`.
 		// Note that signs like `+` or `?` should be String literal.
diff --git a/vm/class_test.go b/vm/class_test.go
index 87fda0081..fcd4d0bae 100644
--- a/vm/class_test.go
+++ b/vm/class_test.go
@@ -985,7 +985,7 @@ func TestInheritsMethodMissingMethod(t *testing.T) {
 		{`
 		class Bar
 		end
-		
+
 		Bar.new.inherits_method_missing?
 
 `, false},
@@ -993,7 +993,7 @@ func TestInheritsMethodMissingMethod(t *testing.T) {
 		class Bar
 		  inherits_method_missing
 		end
-		
+
 		Bar.new.inherits_method_missing?
 
 `, true},
@@ -1132,6 +1132,40 @@ func TestRaiseMethodFail(t *testing.T) {
 	}
 }
 
+func TestRandMethod(t *testing.T) {
+	tests := []struct {
+		input    string
+		expected string
+	}{
+		{`rand.class.name`, "Float"},
+		{`rand(1).class.name`, "Integer"},
+		{`rand(1, 2).class.name`, "Integer"},
+		{`(60 < rand(64, 66)).to_s`, "true"},
+		{`(70 > rand(64, 66)).to_s`, "true"},
+	}
+	for i, tt := range tests {
+		v := initTestVM()
+		evaluated := v.testEval(t, tt.input, getFilename())
+		VerifyExpected(t, i, evaluated, tt.expected)
+		v.checkCFP(t, i, 0)
+		v.checkSP(t, i, 1)
+	}
+}
+
+func TestRandMethodFail(t *testing.T) {
+	testsFail := []errorTestCase{
+		{`rand(1, 10, 100)`, "ArgumentError: Expect 2 argument(s). got: 3", 1},
+	}
+
+	for i, tt := range testsFail {
+		v := initTestVM()
+		evaluated := v.testEval(t, tt.input, getFilename())
+		checkErrorMsg(t, i, evaluated, tt.expected)
+		v.checkCFP(t, i, tt.expectedCFP)
+		v.checkSP(t, i, 1)
+	}
+}
+
 func TestRespondToMethod(t *testing.T) {
 	tests := []struct {
 		input    string
@@ -1642,7 +1676,7 @@ func TestClassSingletonClassMethod(t *testing.T) {
 		`, "#<Class:Bar>"},
 		{`
 		module Bar; end
-		
+
 		Bar.singleton_class.name
 		`, "#<Class:Bar>"},
 		// Check if this works on non-class objects
@@ -1654,12 +1688,12 @@ func TestClassSingletonClassMethod(t *testing.T) {
 		// Below is for testing module inheritance chain
 		{`
 		module Bar; end
-		
+
 		Bar.singleton_class.class.name
 		`, "Class"},
 		{`
 		module Bar; end
-		
+
 		Bar.singleton_class.superclass.name
 		`, "Module"},
 	}