1 files changed, 296 insertions, 0 deletions
diff --git a/advtrains_interlocking/aspect.lua b/advtrains_interlocking/aspect.lua
new file mode 100644
index 0000000..c7d5c81
--- /dev/null
+++ b/advtrains_interlocking/aspect.lua
@@ -0,0 +1,296 @@
+--- Signal aspect handling.
+-- @module advtrains.interlocking.aspect
+
+local registered_groups = {}
+
+local default_aspect = {
+	main = false,
+	dst = false,
+	shunt = true,
+	proceed_as_main = false,
+}
+
+local signal_aspect = {}
+
+local signal_aspect_metatable = {
+	__eq = function(asp1, asp2)
+		for _, k in pairs {"main", "dst", "shunt", "proceed_as_main"} do
+			local v1, v2 = (asp1[k] or false), (asp2[k] or false)
+			if v1 ~= v2 then
+				return false
+			end
+		end
+		if asp1.group and asp1.group == asp2.group then
+			return asp1.name == asp2.name
+		end
+		return true
+	end,
+	__index = function(asp, field)
+		local val = signal_aspect[field]
+		if val then
+			return val
+		end
+		val = default_aspect[field]
+		if val == nil then
+			return nil
+		end
+		local group = registered_groups[rawget(asp, "group")]
+		if group then
+			local aspdef = group.aspects[rawget(asp, "name")]
+			if aspdef[field] ~= nil then
+				val = aspdef[field]
+			end
+		end
+		return val
+	end,
+	__tostring = function(asp)
+		local st = {}
+		if asp.group and asp.name then
+			table.insert(st, ("%q in %q"):format(asp.name, asp.group))
+		end
+		if asp.main then
+			table.insert(st, ("current %d"):format(asp.main))
+		end
+		if asp.main ~= 0 then
+			if asp.dst then
+				table.insert(st, string.format("next %d", asp.dst))
+			end
+		end
+		if asp.main ~= 0 and asp.proceed_as_main then
+			table.insert(st, "proceed as main")
+		end
+		return ("[%s]"):format(table.concat(st, ", "))
+	end,
+}
+
+local function quicknew(t)
+	return setmetatable(t, signal_aspect_metatable)
+end
+
+--- Signal aspect class.
+-- @type signal_aspect
+
+--- Return a plain version of the signal aspect.
+-- @param[opt=false] raw Bypass metamethods when fetching signal aspects
+-- @return A plain copy of the signal aspect object.
+function signal_aspect:plain(raw)
+	local t = {}
+	for _, k in pairs {"main", "dst", "shunt", "proceed_as_main", "group", "name"} do
+		local v
+		if raw then
+			v = rawget(self, k)
+		else
+			v = self[k]
+		end
+		t[k] = v
+	end
+	return t
+end
+
+--- Create (or copy) a signal aspect object.
+-- Note that signal aspect objects can also be created by calling the `advtrains.interlocking.aspect` table.
+-- @return The newly created signal aspect object.
+function signal_aspect:new()
+	if type(self) ~= "table" then
+		return quicknew{}
+	end
+	local newasp = {}
+	for _, k in pairs {"main", "dst"} do
+		if type(self[k]) == "table" then
+			if self[k].free then
+				newasp[k] = self[k].speed
+			else
+				newasp[k] = 0
+			end
+		else
+			newasp[k] = self[k]
+		end
+	end
+	if type(self.shunt) == "table" then
+		newasp.shunt = self.shunt.free
+		newasp.proceed_as_main = self.shunt.proceed_as_main
+	else
+		newasp.shunt = self.shunt
+	end
+	for _, k in pairs {"group", "name"} do
+		newasp[k] = self[k]
+	end
+	return quicknew(newasp)
+end
+
+--- Modify the signal aspect in-place to fit in the specific signal group.
+-- @param group The signal group. The `nil` indicates a generic group.
+-- @return The (now modified) signal aspect itself.
+function signal_aspect:to_group(group)
+	local cg = self.group
+	local gdef = registered_groups[group]
+	if type(self.name) ~= "string" then
+		self.name = nil
+	end
+	if not gdef then
+		for k in pairs(default_aspect) do
+			rawset(self, k, self[k])
+		end
+		self.group = nil
+		self.name = nil
+		return self
+	elseif cg == group and gdef.aspects[self.name] then
+		return self
+	end
+	local newidx = 1
+	if self.main == 0 then
+		newidx = #gdef.aspects
+	end
+	local cgdef = registered_groups[cg]
+	if cgdef then
+		local idx = (cgdef.aspects[self.name] or {}).index
+		if idx then
+			if idx >= #cgdef.aspects then
+				idx = #gdef.aspects
+			elseif idx >= #gdef.aspects then
+				idx = #gdef.aspects-1
+			end
+			newidx = idx
+		end
+	end
+	self.group = group
+	self.name = gdef.aspects[newidx][1]
+	return self
+end
+
+--- Modify the signal aspect in-place to indicate a specific distant aspect.
+-- @param dst The distant aspect
+-- @param[opt=1] shift The phase shift of the current signal.
+-- @return The (now modified) signal aspect itself.
+function signal_aspect:adjust_distant(dst, shift)
+	if (shift or -1) < 0 then
+		shift = 1
+	end
+	if not dst then
+		self.dst = nil
+		return self
+	end
+	if self.main ~= 0 then
+		self.dst = dst.main
+	else
+		self.dst = nil
+		return self
+	end
+	local dgdef = registered_groups[dst.group]
+	if dgdef then
+		if self.group == dst.group and shift == 0 then
+			self.name = dst.name
+		else
+			local idx = (dgdef.aspects[dst.name] or {}).index
+			if idx then
+				idx = math.max(idx-shift, 1)
+				self.group = dst.group
+				self.name = dgdef.aspects[idx][1]
+			end
+		end
+	end
+	return self
+end
+
+--- Signal groups.
+-- @section signal_group
+
+--- Register a signal group.
+-- @function register_group
+-- @param def The definition table.
+local function register_group(def)
+	local t = {}
+	local name = def.name
+	if type(name) ~= "string" then
+		return error("Expected signal group name to be a string, got " .. type(name))
+	elseif registered_groups[name] then
+		return error(string.format("Attempt to redefine signal group %q, previously defined in %s", name, registered_groups[name].defined))
+	end
+	t.name = name
+
+	t.defined = debug.getinfo(2, "S").short_src or "[?]"
+
+	local label = def.label or name
+	if type(label) ~= "string" then
+		return error("Label is not a string")
+	end
+	t.label = label
+
+	local mainasps = {}
+	for idx, asp in pairs(def.aspects) do
+		local idxtp = type(idx)
+		if idxtp == "string" then
+			local t = {}
+			t.name = idx
+
+			local label = asp.label or idx
+			if type(label) ~= "string" then
+				return error("Aspect label is not a string")
+			end
+			t.label = label
+
+			for _, k in pairs{"main", "dst", "shunt"} do
+				t[k] = asp[k]
+			end
+
+			mainasps[idx] = t
+		end
+	end
+	if #def.aspects < 2 then
+		return error("Insufficient entries in signal aspect list")
+	end
+	for idx, asplist in ipairs(def.aspects) do
+		if type(asplist) ~= "table" then
+			asplist = {asplist}
+		else
+			asplist = table.copy(asplist)
+		end
+		if #asplist < 1 then
+			error("Invalid entry in signal aspect list")
+		end
+		for _, k in ipairs(asplist) do
+			if type(k) ~= "string" then
+				return error("Invalid signal aspect ID")
+			end
+			local asp = mainasps[k]
+			if not asp then
+				return error("Invalid signal aspect ID")
+			end
+			if asp.index ~= nil then
+				return error("Attempt to assign a signal aspect to multiple numeric indices")
+			end
+			asp.index = idx
+		end
+		mainasps[idx] = asplist
+	end
+	t.aspects = mainasps
+
+	registered_groups[name] = t
+end
+
+--- Get the definition of a signal group.
+-- @function get_group_definition
+-- @param name The name of the signal group.
+-- @return[1] The definition for the signal group (if present).
+-- @return[2] The nil constant (otherwise).
+local function get_group_definition(name)
+	local t = registered_groups[name]
+	if t then
+		return table.copy(t)
+	else
+		return nil
+	end
+end
+
+local lib = {
+	register_group = register_group,
+	get_group_definition = get_group_definition,
+}
+
+local libmt = {
+	__call = function(_, ...)
+		return signal_aspect.new(...)
+	end,
+}
+
+return setmetatable(lib, libmt)