From 07eacc7a5f1c1088307c608713203c526bec2d2e Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Bj=C3=B6rn=20Ritzl?= <bjorn.ritzl@gmail.com>
Date: Thu, 21 Jun 2018 11:33:20 +0200
Subject: [PATCH] Track when callbacks are invoked so that we can ensure that
 all screens are shown/hidden before invoking callbacks

---
 monarch/monarch.lua                | 23 ++++++++++++------
 monarch/utils/callback_tracker.lua | 39 ++++++++++++++++++++++++++++++
 2 files changed, 55 insertions(+), 7 deletions(-)
 create mode 100644 monarch/utils/callback_tracker.lua

diff --git a/monarch/monarch.lua b/monarch/monarch.lua
index 30fffe1..7f4b2ec 100644
--- a/monarch/monarch.lua
+++ b/monarch/monarch.lua
@@ -1,3 +1,5 @@
+local callback_tracker = require "monarch.utils.callback_tracker"
+
 local M = {}
 
 local CONTEXT = hash("monarch_context")
@@ -402,6 +404,8 @@ function M.show(id, options, data, cb)
 		log("show() monarch is busy, ignoring request")
 		return false
 	end
+
+	local callbacks = callback_tracker()
 	
 	id = tohash(id)
 	assert(screens[id], ("There is no screen registered with id %s"):format(tostring(id)))
@@ -423,13 +427,13 @@ function M.show(id, options, data, cb)
 			-- close all popups
 			while top.popup do
 				stack[#stack] = nil
-				show_out(top, screen)
+				show_out(top, screen, callbacks.track())
 				top = stack[#stack]
 			end
 			-- unload and transition out from top
 			-- unless we're showing the same screen as is already visible
 			if top and top.id ~= screen.id then
-				show_out(top, screen)
+				show_out(top, screen, callbacks.track())
 			end
 		end
 	end
@@ -446,7 +450,9 @@ function M.show(id, options, data, cb)
 	end
 
 	-- show screen
-	show_in(screen, top, options and options.reload, cb)
+	show_in(screen, top, options and options.reload, callbacks.track())
+
+	if cb then callbacks.when_done(cb) end
 
 	return true
 end
@@ -462,6 +468,8 @@ function M.back(data, cb)
 		return false
 	end
 
+	local callbacks = callback_tracker()
+	
 	local screen = table.remove(stack)
 	if screen then
 		log("back()", screen.id)
@@ -473,7 +481,7 @@ function M.back(data, cb)
 				if data then
 					top.data = data
 				end
-				back_in(top, screen, cb)
+				back_in(top, screen, callbacks.track())
 			end)
 		else
 			back_out(screen, top)
@@ -481,12 +489,13 @@ function M.back(data, cb)
 				if data then
 					top.data = data
 				end
-				back_in(top, screen, cb)
+				back_in(top, screen, callbacks.track())
 			end
 		end
-	elseif cb then
-		cb()
 	end
+
+	if cb then callbacks.when_done(cb) end
+	
 	return true
 end
 
diff --git a/monarch/utils/callback_tracker.lua b/monarch/utils/callback_tracker.lua
new file mode 100644
index 0000000..3153c80
--- /dev/null
+++ b/monarch/utils/callback_tracker.lua
@@ -0,0 +1,39 @@
+local M = {}
+
+
+function M.create()
+	local instance = {}
+
+	local callback = nil
+	local callback_count = 0
+
+	--- Create a callback function and track when it is done
+	-- @return Callback function
+	function instance.track()
+		callback_count = callback_count + 1
+		return function()
+			callback_count = callback_count - 1
+			if callback_count == 0 and callback then
+				callback()
+			end
+		end
+	end
+
+	--- Call a function when all callbacks have been triggered
+	-- @param cb Function to call when all 
+	function instance.when_done(cb)
+		callback = cb
+		if callback_count == 0 then
+			callback()
+		end
+	end
+
+	return instance
+end
+
+
+return setmetatable(M, {
+	__call = function(_, ...)
+		return M.create(...)
+	end
+})
\ No newline at end of file