add "playername" parameter to spacecannon.can_shoot so it can be overridden elsewhere

fixes #10

cannon.lua

@@ -110,7 +110,9 @@ local register_spacecannon = function(def)
 
 		mesecons = {effector = {
 			action_on = function (pos)
-				spacecannon.fire(pos, def.color, def.speed, def.range)
+				local meta = minetest.get_meta(pos)
+				local owner = meta:get_string("owner")
+				spacecannon.fire(pos, owner, def.color, def.speed, def.range)
 			end
 		}},
 
@@ -175,7 +177,7 @@ local register_spacecannon = function(def)
 			local meta = minetest.get_meta(pos)
 
 			if fields.fire then
-				spacecannon.fire(pos, def.color, def.speed, def.range)
+				spacecannon.fire(pos, playername, def.color, def.speed, def.range)
 			end
 
 			if fields.set_digiline_channel and fields.digiline_channel then

readme.md

@@ -83,6 +83,15 @@ Example response from a "fire" request:
 }
 ```
 
+# Api
+
+Modify the ability to shoot depending on position or playername:
+```lua
+spacecannon.can_shoot = function(pos, playername)
+	return true
+end
+```
+
 # Contributors
 
 * @BuckarooBanzay

util.lua

@@ -28,7 +28,7 @@ spacecannon.update_formspec = function(meta)
 end
 
 spacecannon.can_shoot = function()
-	-- arguments: pos
+	-- arguments: pos, playername
 	return true
 end
 
@@ -37,9 +37,9 @@ spacecannon.can_destroy = function()
 	return true
 end
 
-spacecannon.fire = function(pos, color, speed, range)
+spacecannon.fire = function(pos, playername, color, speed, range)
 
-	if not spacecannon.can_shoot(pos) then
+	if not spacecannon.can_shoot(pos, playername) then
 		return
 	end