--[[
 *
 *  Singe 3
 *  Copyright (C) 2006-2026 Scott Duensing <scott@kangaroopunch.com>
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License
 * as published by the Free Software Foundation; either version 3
 * of the License, or (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
 * 02110-1301, USA.
 *
 *
--]]



-- Turns a game description into an ordinary Singe game (PLAN section 58).
--
-- The output is Lua a person can read, keep, and edit by hand;  the description is kept beside it
-- so the editor can open it again.  Compiling rather than interpreting costs nothing at build time
-- and saves walking a rule table every frame on a Pi or a handheld -- and it means there is no wall
-- between what the tools make and what someone writes themselves.
--
-- This is written in Lua rather than in util/ as a Python script because the editor is itself a
-- Singe game:  it has to be able to compile what it is editing without leaving the engine.  It
-- lives with Forge rather than in Singe/ because only building needs it -- a finished game is
-- already Lua.  Author.singe, the runtime that game loads, travels with the game:  a copy is
-- written beside it when it is built, so a game handed to someone who has never installed Forge
-- still runs.  The compiler loads it too, for the vocabulary it emits against.

-- Where the runtime is taken from when a game is built.  Forge carries it;  a game gets a copy.
AUTHOR_RUNTIME = "Forge/Author.singe"

dofile(AUTHOR_RUNTIME)


local INDENT = "\t"


-- A Lua literal for a value that came out of a description.  Numbers and booleans go through as
-- they are;  everything else is quoted, because an author typing a name must not be able to end
-- the string and start writing code.  AUTHOR.actions.lua is the one deliberate way in.
local function literal(value)
	if type(value) == "number" or type(value) == "boolean" then
		return tostring(value)
	end

	return string.format("%q", tostring(value))
end


-- The table a description carries for an entity's look or behaviour, written back out as source.
local function tableSource(t)
	local parts = {}
	local keys  = {}

	for key in pairs(t) do
		keys[#keys + 1] = key
	end
	table.sort(keys, function(a, b) return tostring(a) < tostring(b) end)
	for _, key in ipairs(keys) do
		parts[#parts + 1] = string.format("%s = %s", key, literal(t[key]))
	end

	return "{ " .. table.concat(parts, ", ") .. " }"
end


-- One condition or action, through the manifest entry that owns it.  An unknown name is a fault in
-- the description rather than in the generated game, so it is reported here and not emitted.
local function emitOne(set, item, what)
	local entry = set[item[1]]

	if entry == nil then
		debugPrint(string.format("Author:  no %s called '%s'", what, tostring(item[1])))
		return nil
	end

	return entry.emit(item)
end


local function emitConditions(rule)
	local tests = {}

	for _, item in ipairs(rule.when or {}) do
		local test = emitOne(AUTHOR.conditions, item, "condition")

		if test ~= nil then
			tests[#tests + 1] = "(" .. test .. ")"
		end
	end
	if #tests == 0 then
		return "true"
	end

	-- Every condition on a rule has to hold.  A rule needing "either" is two rules, which reads
	-- better in a list than a nested group does.
	return table.concat(tests, " and ")
end


local function emitRule(out, rule, index)
	out[#out + 1] = string.format("%s-- %s", INDENT, rule.note or ("rule " .. index))
	out[#out + 1] = string.format("%sif %s then", INDENT, emitConditions(rule))
	for _, item in ipairs(rule.act or {}) do
		local statement = emitOne(AUTHOR.actions, item, "action")

		if statement ~= nil then
			out[#out + 1] = INDENT .. INDENT .. statement
		end
	end
	out[#out + 1] = INDENT .. "end"
	out[#out + 1] = ""
end


-- The whole game, as source.  Returns a string;  the caller decides where it goes.
--
-- Every built game loads the runtime sitting beside it.  There is no other copy to load:  nothing
-- of Forge ships inside Singe, so Author.singe travels with the game that needs it.  Framework is
-- the engine's, as it is for every game ever written for Singe.
function authorCompile(game)
	local out = {}

	out[#out + 1] = "-- Generated by Forge/AuthorCompile.singe from " .. (game.source or "a game description")
	out[#out + 1] = "-- " .. (game.title or "Untitled")
	out[#out + 1] = "--"
	out[#out + 1] = "-- This is an ordinary Singe game and can be edited by hand.  Doing so and then"
	out[#out + 1] = "-- recompiling the description will overwrite it, so keep one or the other."
	out[#out + 1] = ""
	out[#out + 1] = 'dofile("Singe/Framework.singe")'
	-- The game finds its own directory rather than trusting DIR.  Framework sets DIR from the
	-- script the *engine was launched with*, which is this file only when the game is played
	-- directly;  a game reached by dofile -- a test, a launcher, a menu that previews it -- would
	-- otherwise look for its runtime beside the caller and not find it.  debug.getinfo names the
	-- chunk actually running, either way.
	out[#out + 1] = 'local here = ((debug.getinfo(1, "S").source:gsub("^@", "")):match("^(.*[/\\\\])") or "")'
	out[#out + 1] = 'dofile(here .. "Author.singe")'
	out[#out + 1] = ""

	out[#out + 1] = "authorBegin({"
	for _, layer in ipairs(game.layers or {}) do
		out[#out + 1] = INDENT .. tableSource(layer) .. ","
	end
	out[#out + 1] = "})"
	out[#out + 1] = ""

	for _, entity in ipairs(game.entities or {}) do
		local parts = {}

		parts[#parts + 1] = string.format("id = %q", entity.id)
		parts[#parts + 1] = string.format("x = %s, y = %s", entity.x or 0, entity.y or 0)
		parts[#parts + 1] = "look = " .. tableSource(entity.look)
		if entity.behaviours ~= nil and #entity.behaviours > 0 then
			local made = {}

			for _, b in ipairs(entity.behaviours) do
				made[#made + 1] = tableSource(b)
			end
			parts[#parts + 1] = "behaviours = { " .. table.concat(made, ", ") .. " }"
		end
		out[#out + 1] = "authorMake({ " .. table.concat(parts, ", ") .. " })"
	end
	out[#out + 1] = ""

	out[#out + 1] = "-- The rules, in the order they were written.  Every one is tested every frame."
	out[#out + 1] = "local function rules()"
	for index, rule in ipairs(game.rules or {}) do
		emitRule(out, rule, index)
	end
	out[#out + 1] = "end"
	out[#out + 1] = ""

	out[#out + 1] = "onKeyPressed    = authorKeyDown"
	out[#out + 1] = "onKeyReleased   = authorKeyUp"
	out[#out + 1] = "onInputPressed  = authorSwitchDown"
	out[#out + 1] = "onInputReleased = authorSwitchUp"
	out[#out + 1] = ""
	out[#out + 1] = "function onOverlayUpdate()"
	out[#out + 1] = INDENT .. "authorFrame(rules)"
	out[#out + 1] = ""
	out[#out + 1] = INDENT .. "return OVERLAY_UPDATED"
	out[#out + 1] = "end"
	out[#out + 1] = ""

	return table.concat(out, "\n")
end


-- Compiles a description file to a game beside it.  Returns the path written.
-- Copies a file through the VFS, so the source may be inside a database and the destination is an
-- ordinary file on disc.  Used to put the runtime beside a released game.
function authorCopy(fromPath, toPath)
	local input = io.open(fromPath, "rb")
	local output

	if input == nil then
		debugPrint("Author:  cannot read " .. tostring(fromPath))
		return false
	end
	output = io.open(toPath, "wb")
	if output == nil then
		input:close()
		debugPrint("Author:  cannot write " .. tostring(toPath))
		return false
	end
	output:write(input:read("a"))
	input:close()
	output:close()

	return true
end


-- The directory part of a path, with its separator, or "" for a bare name.
local function directoryOf(path)
	return (string.match(path, "^(.*[/\\])") or "")
end


-- Compiles a description and puts the runtime beside the result, because that is what the result
-- loads.  Building without copying it would produce a game that cannot start.
function authorBuild(descriptionFile, outputFile)
	local chunk = assert(loadfile(descriptionFile))
	local game  = chunk()
	local file

	game.source = descriptionFile
	file = assert(io.open(outputFile, "w"))
	file:write(authorCompile(game))
	file:close()
	authorCopy(AUTHOR_RUNTIME, directoryOf(outputFile) .. "Author.singe")

	return outputFile
end


-- ===== Reading and writing a description ======================================================
--
-- The editor produces descriptions, so the format has to survive a round trip:  load, change
-- nothing, save, and the result must compile to the same game.  scene54 asserts exactly that.


local function indentOf(depth)
	return string.rep(INDENT, depth)
end


-- Whether a table holds only leaves, in which case it is written on one line.  A rule reads far
-- better as { "keyHeld", key = "LEFT" } than as six lines, and it is what an author typed.
local function isLeaf(t)
	for key, value in pairs(t) do
		if type(value) == "table" then
			return false
		end
	end

	return true
end


-- A value written back as Lua source.  A condition or an action is a mixed table -- an array part
-- naming it, plus named parameters -- so both parts have to be written or the name survives and
-- the parameters do not.  The array part keeps its order;  the named keys are sorted, because a
-- description that reorders itself on every save makes every diff unreadable.
local function valueSource(value, depth)
	local parts = {}
	local keys  = {}
	local count = 0
	local sep
	local open
	local close

	if type(value) ~= "table" then
		return literal(value)
	end
	count = #value
	for _, item in ipairs(value) do
		parts[#parts + 1] = valueSource(item, depth + 1)
	end
	for key in pairs(value) do
		-- Skip the array part, which has already been written in order.
		if not (type(key) == "number" and key >= 1 and key <= count and key == math.floor(key)) then
			keys[#keys + 1] = key
		end
	end
	table.sort(keys, function(a, b) return tostring(a) < tostring(b) end)
	for _, key in ipairs(keys) do
		parts[#parts + 1] = string.format("%s = %s", key, valueSource(value[key], depth + 1))
	end
	if #parts == 0 then
		return "{}"
	end
	if isLeaf(value) then
		return "{ " .. table.concat(parts, ", ") .. " }"
	end
	sep   = ",\n" .. indentOf(depth + 1)
	open  = "{\n" .. indentOf(depth + 1)
	close = "\n" .. indentOf(depth) .. "}"

	return open .. table.concat(parts, sep) .. close
end


function authorLoad(path)
	local chunk, problem = loadfile(path)

	if chunk == nil then
		debugPrint("Author:  cannot read " .. tostring(path) .. ":  " .. tostring(problem))
		return nil
	end

	return chunk()
end


function authorSave(game, path)
	local file = assert(io.open(path, "w"))
	local copy = {}

	-- source says where a description came from and is set by the loader, so writing it back out
	-- would make a description that had been through the editor differ from one that had not.
	for key in pairs(game) do
		if key ~= "source" then
			copy[key] = game[key]
		end
	end
	file:write("-- Written by Forge/AuthorCompile.singe.  Edit by hand or in the editor;  either is fine.\n")
	file:write("return " .. valueSource(copy, 0) .. "\n")
	file:close()

	return path
end