Unique GUID shim - Closes #153

lib/instances/HttpService.lua

@@ -4,6 +4,30 @@ local json = import("../json")
 
 local HttpService = BaseInstance:extend("HttpService")
 
+-- Credit to https://stackoverflow.com/a/32389020
+local AND, OR = 1, 4
+
+local function bit(a, b, oper)
+	local r, m, s = 0, 2^52
+	repeat
+		s, a, b = a + b + m, a % m, b % m
+		r, m = r + m * oper % (s - a - b), m / 2
+	until m < 1
+	return r
+end
+
+local function band(a, b)
+	return bit(a, b, AND)
+end
+
+local function bor(a, b)
+	return bit(a, b, OR)
+end
+
+local function tohex(number)
+	return ("%02x"):format(number)
+end
+
 function HttpService.prototype:JSONEncode(input)
 	return json.encode(input)
 end
@@ -18,15 +42,41 @@ function HttpService.prototype:GenerateGUID(wrapInCurlyBraces)
 		error(("Unable to cast %s to bool"):format(argType), 2)
 	end
 
+	local random = math.random
+
+	local guid =
+		("%s%s%s%s-%s%s-%s%s-%s%s-%s%s%s%s%s%s"):format(
+			tohex(random(0, 255), 2),
+			tohex(random(0, 255)),
+			tohex(random(0, 255)),
+			tohex(random(0, 255)),
+
+			tohex(random(0, 255)),
+			tohex(random(0, 255)),
+
+			tohex(bor(band(random(0, 255), 0x0F), 0x40)),
+			tohex(random(0, 255)),
+
+			tohex(bor(band(random(0, 255), 0x3F), 0x80)),
+			tohex(random(0, 255)),
+
+			tohex(random(0, 255)),
+			tohex(random(0, 255)),
+			tohex(random(0, 255)),
+			tohex(random(0, 255)),
+			tohex(random(0, 255)),
+			tohex(random(0, 255))
+		)
+
 	--[[
 		`GenerateGUID` allows any value type for `wrapInCurlyBraces`, but it
 		only omits the curly braces when `wrapInCurlyBraces` is set to `false`
 	]]
-	if wrapInCurlyBraces == false then
-		return "04AEBFEA-87FC-480F-A98B-E5E221007A90"
-	else
-		return "{04AEBFEA-87FC-480F-A98B-E5E221007A90}"
+	if wrapInCurlyBraces ~= false then
+		guid = "{" .. guid .. "}"
 	end
+
+	return guid
 end
 
 return HttpService

lib/instances/HttpService_spec.lua

@@ -20,6 +20,29 @@ describe("instances.HttpService", function()
 	end)
 
 	describe("GenerateGUID", function()
+		it("should have proper length guids", function()
+			local instance = HttpService:new()
+			local guid = instance:GenerateGUID(false)
+
+			assert.equal(36, #guid)
+		end)
+
+		it("should give unique guids", function()
+			local instance = HttpService:new()
+			local guids = {}
+
+			for _ = 1, 100 do
+				guids[instance:GenerateGUID()] = true
+			end
+
+			local guidsGenerated = 0
+			for _ in pairs(guids) do
+				guidsGenerated = guidsGenerated + 1
+			end
+
+			assert.equal(100, guidsGenerated)
+		end)
+
 		it("should omit curly braces when wrapInCurlyBraces is false", function()
 			local instance = HttpService:new()
 			local guid = instance:GenerateGUID(false)