Sylpheed/port/scripts/export_tree.gd

# Locating and reading the open export tree.
#
# The Godot project NEVER reads a disc format (docs/MISSION.md §2). Everything
# it draws comes from `export/`, which is derived, gitignored and regenerated
# wholesale by `crates/sylpheed-export`. This class is the only place that knows
# where that tree is on disk.
class_name ExportTree
extends RefCounted

const FORMAT_SCREEN := "sylpheed.screen/3"
const FORMAT_MANIFEST := "sylpheed.manifest/1"

var root: String = ""
## The override tree, or "" when there is none. MODDING rule 4: a mod replaces a
## file by SHADOWING ITS PATH, so `mods/screens/title/main_menu.json` stands in
## for `<root>/screens/title/main_menu.json` and nothing under the derived tree
## is touched. That is what makes re-exporting always safe.
var mods: String = ""
## Relative paths a mod actually replaced this run, in the order they were first
## read. Recorded because MODDING says "did I break it?" is answered by disabling
## a mod -- which only works if a modded run does not look like an unmodded one.
var shadowed: Array[String] = []
var error: String = ""


# `SYLPHEED_EXPORT` wins, so a modder can point the game at their own tree
# without touching the project. Otherwise `<project>/../export`, which is the
# layout this repository has.
static func locate() -> ExportTree:
	var t := ExportTree.new()
	var env := OS.get_environment("SYLPHEED_EXPORT")
	var candidate := env
	if candidate == "":
		candidate = ProjectSettings.globalize_path("res://").path_join("../export").simplify_path()
	if not FileAccess.file_exists(candidate.path_join("manifest.json")):
		t.error = "no manifest.json under %s -- run `sylpheed-export` first" % candidate
		return t
	t.root = candidate

	# The override tree. `SYLPHEED_MODS` wins for the same reason
	# `SYLPHEED_EXPORT` does; otherwise `data/mods/`, which is the directory
	# MODDING.md's own layout diagram names and the one this repository ships.
	#
	# Absent is normal and silent: an unmodded run is the common case, and a
	# warning about a directory nobody created would be noise.
	var m := OS.get_environment("SYLPHEED_MODS")
	if m == "":
		m = ProjectSettings.globalize_path("res://").path_join("../data/mods").simplify_path()
	if DirAccess.dir_exists_absolute(m):
		t.mods = m
	return t


## Where a relative path actually comes from: the mod tree if it has one, else
## the derived tree.
##
## Every read in this class goes through here, so a mod can replace a screen's
## JSON, a sprite, a cue, a music bed or a movie by dropping a file at the same
## relative path. There is deliberately no manifest of what a mod contains and no
## registration step -- the path IS the registration, which is the whole of
## MODDING rule 4.
##
## ⚠️ One tree, not a stack. Several mods layering over each other needs an
## order, and an order needs a rule nobody has asked for yet. Say so rather than
## invent one.
func resolve(rel: String) -> String:
	if mods != "":
		var over := mods.path_join(rel)
		if FileAccess.file_exists(over):
			if not shadowed.has(rel):
				shadowed.append(rel)
				# Announced the moment it happens, not summarised at startup.
				# The first version printed a summary in `_ready`, before a
				# single asset had been read, so it always said "nothing
				# shadowed yet" -- a report that is structurally incapable of
				# reporting anything is worse than none, because it looks like
				# an answer.
				print("mod: %s  <-  %s" % [rel, over])
			return over
	return root.path_join(rel)


# `authored/` sits beside `export/`, never inside it: it is hand-written and
# committed, and a re-export must not be able to touch it.
func authored(name: String) -> Variant:
	var path := root.path_join("../authored").simplify_path().path_join(name)
	var text := FileAccess.get_file_as_string(path)
	if text == "":
		error = "cannot read %s" % path
		return null
	return JSON.parse_string(text)


func read_json(rel: String) -> Variant:
	var path := resolve(rel)
	var text := FileAccess.get_file_as_string(path)
	if text == "":
		error = "cannot read %s" % path
		return null
	var parsed: Variant = JSON.parse_string(text)
	if parsed == null:
		error = "%s is not JSON" % path
		return null
	return parsed


func manifest() -> Dictionary:
	var m: Variant = read_json("manifest.json")
	if m == null:
		return {}
	if m.get("format") != FORMAT_MANIFEST:
		error = "manifest.json is %s, this build reads %s" % [m.get("format"), FORMAT_MANIFEST]
		return {}
	return m


# Screens are addressed by their manifest name, not by a path, so the caller
# never has to know the archive's subdirectory.
func screen(name: String) -> Dictionary:
	var m := manifest()
	if m.is_empty():
		return {}
	for entry: Dictionary in m.get("screens", []):
		if entry.get("name") == name:
			var s: Variant = read_json(entry["file"])
			if s == null:
				return {}
			if s.get("format") != FORMAT_SCREEN:
				error = "%s is %s, this build reads %s" % [name, s.get("format"), FORMAT_SCREEN]
				return {}
			return s
	error = "no screen named %s in manifest.json" % name
	return {}


# A transcoded movie, addressed by manifest name. The port never reads WMV --
# the exporter emits Ogg Theora, which Godot plays natively (MISSION §2, §6).
func video(name: String) -> Dictionary:
	for entry: Dictionary in manifest().get("videos", []):
		if entry.get("name") == name:
			var path := resolve(String(entry["file"]))
			if not FileAccess.file_exists(path):
				error = "manifest lists %s but %s is not there" % [name, path]
				return {}
			return {"path": path, "command": entry.get("command", "")}
	error = "no video named %s in manifest.json" % name
	return {}


func screen_names() -> PackedStringArray:
	var names := PackedStringArray()
	for entry: Dictionary in manifest().get("screens", []):
		names.append(entry["name"])
	return names


# Textures live outside res://, so they are read as bytes and decoded at
# runtime rather than imported. Nearest-neighbour: the export is a 1:1 copy of
# the disc's own texels and several elements are drawn at 200 %, where a
# bilinear filter would invent detail the disc does not have.
func texture(rel: String) -> Texture2D:
	var bytes := FileAccess.get_file_as_bytes(resolve(rel))
	if bytes.is_empty():
		error = "cannot read sprite %s" % rel
		return null
	var img := Image.new()
	if img.load_png_from_buffer(bytes) != OK:
		error = "%s is not a PNG" % rel
		return null
	return ImageTexture.create_from_image(img)


## One line naming what a mod replaced, or "" when nothing did.
##
## Printed by every run that loads a tree. A modded run that looked identical to
## an unmodded one in the log would make "disable the mod and see" the only
## debugging tool a modder has; this makes it the second one.
func mod_report() -> String:
	if mods == "":
		return ""
	if shadowed.is_empty():
		return "mods: %s is present; each file it replaces is logged as it is read" % mods
	return "mods: %s -- %d file(s) shadowed: %s" % [mods, shadowed.size(), ", ".join(shadowed)]