@tool
extends SceneTree

# One-shot migration tool: walk every resource that can carry a ShaderMaterial
# (.material, .tres, .mesh, .scn, .gltf, .glb, .tscn) and fix Godot 3 -> 4
# shader code in-place, saving where possible.
#
# Run with: godot --headless --script scripts/migrate_shaders.gd

const REPLACEMENTS := [
	["depth_draw_alpha_prepass", "depth_prepass_alpha"],
	["hint_color", "source_color"],
	["hint_albedo", "source_color"],
	["hint_black_albedo", "source_color"],
	["hint_white", ""],
	["hint_black", ""],
	["hint_aniso", "hint_anisotropy"],
	["NORMALMAP", "NORMAL_MAP"],
]

const EXTENSIONS := [".material", ".tres", ".mesh"]

func _init() -> void:
	var fixed := 0
	var checked := 0
	for path in _find_resources("res://assets"):
		checked += 1
		var res = ResourceLoader.load(path, "", ResourceLoader.CACHE_MODE_IGNORE)
		if res == null:
			continue
		var dirty := false
		# Direct ShaderMaterial
		if res is ShaderMaterial:
			dirty = _fix_shader_material(res) or dirty
		# ArrayMesh (surface materials embedded)
		if res is ArrayMesh:
			for surf in range(res.get_surface_count()):
				var mat = res.surface_get_material(surf)
				if mat is ShaderMaterial:
					if _fix_shader_material(mat):
						res.surface_set_material(surf, mat)
						dirty = true
		if dirty:
			var err = ResourceSaver.save(res, path)
			if err == OK:
				fixed += 1
				print("FIXED ", path)
			else:
				push_error("Failed to save " + path + " (err=" + str(err) + ")")
	print("Done. checked=", checked, " fixed=", fixed)
	quit()

func _fix_shader_material(mat: ShaderMaterial) -> bool:
	if mat.shader == null:
		return false
	var old_code: String = mat.shader.code
	var new_code := old_code
	for pair in REPLACEMENTS:
		new_code = new_code.replace(pair[0], pair[1])
	if new_code == old_code:
		return false
	mat.shader.code = new_code
	return true

func _find_resources(dir_path: String) -> Array:
	var result := []
	var dir = DirAccess.open(dir_path)
	if dir == null:
		return result
	dir.list_dir_begin()
	var name = dir.get_next()
	while name != "":
		if name == "." or name == "..":
			name = dir.get_next()
			continue
		var sub = dir_path + "/" + name
		if dir.current_is_dir():
			result.append_array(_find_resources(sub))
		else:
			for ext in EXTENSIONS:
				if name.ends_with(ext):
					result.append(sub)
					break
		name = dir.get_next()
	return result