--[[
 *
 *  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.
 *
 *
--]]



-- The runtime an authored game is compiled against (PLAN section 58).
--
-- A game made with the authoring tools is not interpreted:  Singe/AuthorCompile.singe turns its
-- description into ordinary Lua, and this file is the library that Lua calls.  Rules become real
-- `if` statements, so nothing walks a table every frame and the result can be opened in ZeroBrane
-- and edited by hand like any other game.
--
-- Three nouns, and no notion of genre anywhere:
--
--   layers      which of the engine's own layers the game uses -- disc, overlay, scene, GUI.
--               A genre is only a choice of layers;  see AUTHOR.layers below.
--   entities    a thing on a layer:  a node, a look, and state.
--   behaviours  a bundle attached to an entity, over engine calls that already exist.
--
-- AUTHOR is also the manifest the compiler and (later) the editor read:  every condition, action
-- and behaviour declares its parameters and the Lua it emits, so a new genre is a pack of entries
-- here rather than a new release of anything.

AUTHOR = {
	layers     = {},
	looks      = {},
	behaviours = {},
	conditions = {},
	actions    = {}
}

AUTHOR_WORLD    = {}          -- Entities by id.
AUTHOR_ORDER    = {}          -- and in the order they were declared, which is draw order.
AUTHOR_LAYERS   = {}
AUTHOR_STARTED  = 0           -- singeGetTicks() when the game began.

local GRAVITY_DEFAULT = 1400  -- Overlay units a second squared;  a 480 tall screen wants about this.
local PLAYER_RADIUS   = 0.5   -- Fractions of an entity's box, for the capsule a platformer stands in.

AUTHOR_FONT_POINTS = 18       -- The default the text look draws at.


-- Seconds since the game started.  Every rule that talks about time uses this, so a game is
-- reproducible under --deterministic rather than depending on how fast the machine draws.
function authorTime()
	return (singeGetTicks() - AUTHOR_STARTED) / 1000.0
end


function authorEntity(id)
	return AUTHOR_WORLD[id]
end


-- ===== Layers =================================================================================
--
-- Each declares what it needs of the engine.  Nothing here knows what kind of game is being made.

AUTHOR.layers.world2d = {
	help  = "A flat world with gravity:  physics in the XY plane, drawn into the overlay.",
	params = { gravity = "number" },
	begin = function(layer)
		physicsSetEnabled(true)
		physicsSet2D(true)
		physicsSetGravity(0, layer.gravity or GRAVITY_DEFAULT, 0)
	end
}

AUTHOR.layers.overlay = {
	help   = "Flat drawing over everything:  scores, prompts, a HUD.",
	params = {},
	begin  = function() end
}

AUTHOR.layers.disc = {
	help   = "The video the game is played over.",
	params = { start = "number" },
	begin  = function(layer)
		discPlay()
		if layer.start then
			discSkipToFrame(layer.start)
		end
	end
}


-- ===== Looks ==================================================================================
--
-- How an entity is drawn.  A look draws itself;  it never knows which layer it is on.

AUTHOR.looks.box = {
	help   = "A filled rectangle, centred on the entity.",
	params = { w = "number", h = "number", r = "number", g = "number", b = "number" },
	draw   = function(entity)
		local look = entity.look
		local x, y = authorPosition(entity)
		local hw   = look.w / 2
		local hh   = look.h / 2
		local row

		colorForeground(look.r or 255, look.g or 255, look.b or 255, 255)
		-- overlayBox outlines;  a solid block is the outline drawn every row, which is cheap at
		-- these sizes and saves the game needing an image for a placeholder.
		for row = math.floor(y - hh), math.floor(y + hh) do
			overlayLine(x - hw, row, x + hw, row)
		end
	end
}

AUTHOR.looks.sprite = {
	help   = "An image, centred on the entity.",
	params = { file = "file" },
	load   = function(entity)
		entity.sprite = spriteLoad(entity.look.file)
	end,
	draw   = function(entity)
		local x, y = authorPosition(entity)

		spriteDraw(entity.sprite, x - spriteGetWidth(entity.sprite) / 2, y - spriteGetHeight(entity.sprite) / 2)
	end
}

AUTHOR.looks.text = {
	help   = "A line of text, its top left at the entity.",
	params = { text = "string", r = "number", g = "number", b = "number" },
	draw   = function(entity)
		local x, y = authorPosition(entity)

		colorForeground(entity.look.r or 255, entity.look.g or 255, entity.look.b or 255, 255)
		if entity.text ~= "" then
			fontPrint(x, y, entity.text)
		end
	end
}


-- ===== Behaviours =============================================================================
--
-- Each is a bundle over engine calls that already exist and are tested.  A platformer is a
-- checkbox over the character controller, not a reimplementation of one.

AUTHOR.behaviours.solid = {
	help   = "Immovable ground or a wall.",
	params = {},
	attach = function(entity)
		bodyNew(entity.node, BODY_STATIC, SHAPE_BOX, entity.look.w / 2, entity.look.h / 2, entity.look.w / 2)
	end
}

AUTHOR.behaviours.platformer = {
	help   = "Runs, falls and jumps:  the engine's character controller in 2D.",
	params = { speed = "number", jump = "number" },
	attach = function(entity, params)
		entity.speed = params.speed or 200
		entity.jump  = params.jump or 500
		playerNew(entity.node, SHAPE_CAPSULE, entity.look.w * PLAYER_RADIUS, entity.look.h)
	end,
	step   = function(entity)
		-- The rules say which way;  this clears it each frame so releasing a key stops the run.
		playerMove(entity.node, entity.drive * entity.speed)
		entity.drive = 0
	end
}

AUTHOR.behaviours.drift = {
	help   = "Moves steadily, for a cloud, a platform or a target.",
	params = { vx = "number", vy = "number" },
	attach = function(entity, params)
		entity.vx = params.vx or 0
		entity.vy = params.vy or 0
	end,
	step   = function(entity, dt)
		local x, y, z = nodeGetPosition(entity.node)

		nodeSetPosition(entity.node, x + entity.vx * dt, y + entity.vy * dt, z)
	end
}


-- ===== Conditions =============================================================================
--
-- Every entry emits a Lua expression.  The helpers they call are further down;  keeping the test
-- in a named function rather than inlining it is what makes the generated game readable.

AUTHOR.conditions.keyHeld = {
	help   = "A key is down.",
	params = { key = "scancode" },
	emit   = function(p) return string.format("authorKeyHeld(SCANCODE.%s)", p.key) end
}

AUTHOR.conditions.switchHeld = {
	help   = "A pad or gun switch is down.",
	params = { switch = "switch" },
	emit   = function(p) return string.format("authorSwitchHeld(%s)", p.switch) end
}

AUTHOR.conditions.timeBetween = {
	help   = "The game is between two moments, in seconds.",
	params = { from = "number", to = "number" },
	emit   = function(p) return string.format("authorTime() >= %s and authorTime() < %s", p.from, p.to) end
}

AUTHOR.conditions.discBetween = {
	help   = "The disc is between two frames -- the window a QTE is answered in.",
	params = { from = "number", to = "number" },
	emit   = function(p) return string.format("authorDiscBetween(%s, %s)", p.from, p.to) end
}

AUTHOR.conditions.onGround = {
	help   = "An entity has ground under it.",
	params = { entity = "entity" },
	emit   = function(p) return string.format("authorOnGround(%q)", p.entity) end
}

AUTHOR.conditions.touching = {
	help   = "Two entities overlap.",
	params = { entity = "entity", other = "entity" },
	emit   = function(p) return string.format("authorTouching(%q, %q)", p.entity, p.other) end
}

AUTHOR.conditions.below = {
	help   = "An entity has fallen past a line -- a pit, or the bottom of the screen.",
	params = { entity = "entity", y = "number" },
	emit   = function(p) return string.format("authorBelow(%q, %s)", p.entity, p.y) end
}

AUTHOR.conditions.flagSet = {
	help   = "A named flag the rules set themselves.",
	params = { flag = "string" },
	emit   = function(p) return string.format("AUTHOR_FLAG[%q] == true", p.flag) end
}

AUTHOR.conditions.once = {
	help   = "Only the first time this rule would run.",
	params = { tag = "string" },
	emit   = function(p) return string.format("authorOnce(%q)", p.tag) end
}


-- ===== Actions ================================================================================
--
-- Every entry emits a Lua statement.

AUTHOR.actions.run = {
	help   = "Drive a platformer left (-1) or right (1) this frame.",
	params = { entity = "entity", direction = "number" },
	emit   = function(p) return string.format("authorRun(%q, %s)", p.entity, p.direction) end
}

AUTHOR.actions.jump = {
	help   = "Ask a platformer to jump.",
	params = { entity = "entity" },
	emit   = function(p) return string.format("authorJump(%q)", p.entity) end
}

AUTHOR.actions.moveTo = {
	help   = "Put an entity somewhere.",
	params = { entity = "entity", x = "number", y = "number" },
	emit   = function(p) return string.format("authorMoveTo(%q, %s, %s)", p.entity, p.x, p.y) end
}

AUTHOR.actions.setText = {
	help   = "Change what a text entity says.",
	params = { entity = "entity", text = "expression" },
	emit   = function(p) return string.format("authorSetText(%q, %s)", p.entity, p.text) end
}

AUTHOR.actions.show = {
	help   = "Show or hide an entity.",
	params = { entity = "entity", visible = "boolean" },
	emit   = function(p) return string.format("authorShow(%q, %s)", p.entity, tostring(p.visible)) end
}

AUTHOR.actions.addScore = {
	help   = "Add to the score.",
	params = { amount = "number" },
	emit   = function(p) return string.format("AUTHOR_SCORE = AUTHOR_SCORE + %s", p.amount) end
}

AUTHOR.actions.setFlag = {
	help   = "Set or clear a named flag.",
	params = { flag = "string", value = "boolean" },
	emit   = function(p) return string.format("AUTHOR_FLAG[%q] = %s", p.flag, tostring(p.value)) end
}

AUTHOR.actions.discTo = {
	help   = "Send the disc to a frame -- the branch a QTE takes.",
	params = { frame = "number" },
	emit   = function(p) return string.format("discSkipToFrame(%s)", p.frame) end
}

AUTHOR.actions.lua = {
	help   = "Anything the vocabulary cannot say.  The way out, and it is meant to be used.",
	params = { code = "lua" },
	emit   = function(p) return p.code end
}


-- ===== The runtime the generated Lua calls ====================================================

AUTHOR_SCORE = 0
AUTHOR_FLAG  = {}

local onceSeen = {}
local lastTime = 0


-- Where an entity is, in overlay coordinates.  Everything is a node, whether or not the scene is
-- drawing:  nodes exist without a GPU, which is what lets a 2D game run on a machine with none.
function authorPosition(entity)
	local x, y = nodeGetPosition(entity.node)

	return x, y
end


function authorKeyHeld(scancode)
	return AUTHOR_KEYS[scancode] == true
end


function authorSwitchHeld(switch)
	return AUTHOR_SWITCHES[switch] == true
end


function authorDiscBetween(from, to)
	local frame = discGetFrame()

	return (frame >= from) and (frame < to)
end


function authorOnGround(id)
	return playerIsOnGround(AUTHOR_WORLD[id].node)
end


function authorBelow(id, y)
	local _, ey = authorPosition(AUTHOR_WORLD[id])

	return ey > y
end


function authorTouching(idA, idB)
	local a = AUTHOR_WORLD[idA]
	local b = AUTHOR_WORLD[idB]
	local ax, ay = authorPosition(a)
	local bx, by = authorPosition(b)

	return collideRects(ax - a.look.w / 2, ay - a.look.h / 2, a.look.w, a.look.h,
	                    bx - b.look.w / 2, by - b.look.h / 2, b.look.w, b.look.h)
end


-- True the first time only.  Rules run every frame, so anything that should happen once -- a door
-- opening, a score awarded -- needs this rather than a flag the author has to remember to clear.
function authorOnce(tag)
	if onceSeen[tag] then
		return false
	end
	onceSeen[tag] = true

	return true
end


function authorRun(id, direction)
	AUTHOR_WORLD[id].drive = direction
end


function authorJump(id)
	local entity = AUTHOR_WORLD[id]

	playerJump(entity.node, entity.jump)
end


function authorMoveTo(id, x, y)
	local entity = AUTHOR_WORLD[id]

	if entity.player then
		playerSetPosition(entity.node, x, y, 0)
	else
		nodeSetPosition(entity.node, x, y, 0)
	end
end


function authorSetText(id, text)
	AUTHOR_WORLD[id].text = tostring(text)
end


function authorShow(id, visible)
	AUTHOR_WORLD[id].visible = visible
end


-- Builds one entity from its description.  Called by the generated game, once each, at startup.
function authorMake(description)
	local entity = {
		id         = description.id,
		look       = description.look,
		behaviours = description.behaviours or {},
		text       = (description.look and description.look.text) or "",
		visible    = true,
		drive      = 0,
		node       = nodeNew()
	}
	local look = AUTHOR.looks[entity.look.kind]
	local b

	nodeSetPosition(entity.node, description.x or 0, description.y or 0, 0)
	if look.load then
		look.load(entity)
	end
	AUTHOR_WORLD[entity.id]         = entity
	AUTHOR_ORDER[#AUTHOR_ORDER + 1] = entity

	for _, b in ipairs(entity.behaviours) do
		local kind = AUTHOR.behaviours[b.kind]

		if kind == nil then
			debugPrint("Author:  no behaviour called '" .. tostring(b.kind) .. "'")
		else
			entity.player = entity.player or (b.kind == "platformer")
			kind.attach(entity, b)
		end
	end

	return entity
end


-- Starts the layers the game declared.  Anything a layer needs of the engine is asked for here and
-- nowhere else, which is what keeps the rest of this file free of genre.
function authorBegin(layers)
	local layer

	-- A font, because the text look draws with fontPrint and fontPrint ends the game when none is
	-- selected.  Every test had a scene select one first;  a released game has nobody to do that,
	-- and died on its first text entity.  A game that wants its own calls fontSelect afterwards.
	if AUTHOR_FONT == nil then
		AUTHOR_FONT = fontLoad("Singe/FreeSansBold.ttf", AUTHOR_FONT_POINTS)
		fontSelect(AUTHOR_FONT)
		fontQuality(FONT_QUALITY_BLENDED)
	end

	AUTHOR_STARTED = singeGetTicks()
	lastTime       = 0
	for _, layer in ipairs(layers) do
		local kind = AUTHOR.layers[layer.kind]

		if kind == nil then
			debugPrint("Author:  no layer called '" .. tostring(layer.kind) .. "'")
		else
			AUTHOR_LAYERS[#AUTHOR_LAYERS + 1] = layer
			kind.begin(layer)
		end
	end
end


-- One frame:  the behaviours step, then the rules the compiler wrote, then everything is drawn in
-- the order it was declared.  The generated game calls this from onOverlayUpdate and does no more.
function authorFrame(rules)
	local now = authorTime()
	local dt  = now - lastTime
	local entity

	lastTime = now
	for _, entity in ipairs(AUTHOR_ORDER) do
		local b

		for _, b in ipairs(entity.behaviours) do
			local kind = AUTHOR.behaviours[b.kind]

			if kind ~= nil and kind.step ~= nil then
				kind.step(entity, dt)
			end
		end
	end

	if rules ~= nil then
		rules()
	end

	overlayClear()
	for _, entity in ipairs(AUTHOR_ORDER) do
		if entity.visible then
			AUTHOR.looks[entity.look.kind].draw(entity)
		end
	end
end


-- ===== Input ==================================================================================
--
-- Held state, because rules ask "is this key down" rather than "was it just pressed".  The
-- generated game points the engine's callbacks straight at these.

AUTHOR_KEYS     = {}
AUTHOR_SWITCHES = {}


function authorKeyDown(keysym, scancode)
	AUTHOR_KEYS[scancode] = true
end


function authorKeyUp(keysym, scancode)
	AUTHOR_KEYS[scancode] = nil
end


function authorSwitchDown(what)
	AUTHOR_SWITCHES[what] = true
end


function authorSwitchUp(what)
	AUTHOR_SWITCHES[what] = nil
end