render: extract static M2 build resource observer

src/render/m2/m2_static_build_resource_observer.gd

@@ -0,0 +1,126 @@
+class_name M2StaticBuildResourceObserver
+extends RefCounted
+
+## Resolves or requests one static M2 build Mesh and fills a resource snapshot.
+
+const OUTCOME_REJECTED := &"rejected"
+const OUTCOME_CACHED := &"cached"
+const OUTCOME_PENDING := &"pending"
+const OUTCOME_REQUESTED := &"requested"
+const OUTCOME_MISSING := &"missing"
+
+
+## Observes cache/request state and adopts the exact static result into snapshot.
+func observe(
+	resource_snapshot: RefCounted,
+	normalized_relative_path: String,
+	cache_directory: String,
+	mesh_cache_state: RefCounted,
+	prototype_cache_state: RefCounted,
+	load_pipeline_state: RefCounted
+) -> StringName:
+	if (
+		resource_snapshot == null
+		or normalized_relative_path.is_empty()
+		or mesh_cache_state == null
+		or prototype_cache_state == null
+		or load_pipeline_state == null
+	):
+		return OUTCOME_REJECTED
+	if bool(mesh_cache_state.call("has_mesh", normalized_relative_path)):
+		resource_snapshot.call(
+			"adopt_static_observation",
+			mesh_cache_state.call("find_mesh", normalized_relative_path) as Mesh,
+			false
+		)
+		return OUTCOME_CACHED
+	if bool(prototype_cache_state.call("is_model_missing", normalized_relative_path)):
+		resource_snapshot.call("adopt_static_observation", null, true)
+		return OUTCOME_MISSING
+	if bool(load_pipeline_state.call("has_request", normalized_relative_path)):
+		resource_snapshot.call("adopt_static_observation", null, false)
+		return OUTCOME_PENDING
+
+	for cache_resource_path in cache_resource_paths(
+		cache_directory,
+		normalized_relative_path,
+		[".tscn", ".glb"]
+	):
+		if not ResourceLoader.exists(cache_resource_path):
+			continue
+		if (
+			cache_resource_path.get_extension().to_lower() == "glb"
+			and glb_animation_schema(cache_resource_path) == "pivot_prefix_v1"
+		):
+			continue
+		var request_error := ResourceLoader.load_threaded_request(
+			cache_resource_path,
+			"",
+			false,
+			ResourceLoader.CACHE_MODE_REUSE
+		)
+		if request_error == OK or request_error == ERR_BUSY:
+			load_pipeline_state.call(
+				"remember_request",
+				normalized_relative_path,
+				cache_resource_path
+			)
+			resource_snapshot.call("adopt_static_observation", null, false)
+			return OUTCOME_REQUESTED
+		break
+
+	prototype_cache_state.call("mark_model_missing", normalized_relative_path)
+	resource_snapshot.call("adopt_static_observation", null, true)
+	return OUTCOME_MISSING
+
+
+## Returns historical nested/lowercase/basename cache candidates without I/O.
+func cache_resource_paths(
+	cache_directory: String,
+	relative_path: String,
+	extensions: Array[String]
+) -> PackedStringArray:
+	var normalized := relative_path.replace("\\", "/")
+	var lower := normalized.to_lower()
+	var stems := [
+		normalized.get_basename(),
+		lower.get_basename(),
+		normalized.get_file().get_basename(),
+		lower.get_file().get_basename(),
+	]
+	var result := PackedStringArray()
+	for extension in extensions:
+		for stem in stems:
+			if stem.is_empty():
+				continue
+			var path := cache_directory.path_join(stem + extension)
+			if not result.has(path):
+				result.append(path)
+	return result
+
+
+## Reads only the OpenWC animation schema marker from a GLB JSON chunk.
+func glb_animation_schema(cache_resource_path: String) -> String:
+	var absolute_path := ProjectSettings.globalize_path(cache_resource_path)
+	if not FileAccess.file_exists(absolute_path):
+		return ""
+	var file := FileAccess.open(absolute_path, FileAccess.READ)
+	if file == null or file.get_length() < 20:
+		return ""
+	var magic := file.get_32()
+	var version := file.get_32()
+	file.get_32()
+	if magic != 0x46546c67 or version != 2:
+		return ""
+	var json_length := int(file.get_32())
+	var chunk_type := file.get_32()
+	if json_length <= 0 or chunk_type != 0x4e4f534a:
+		return ""
+	var parsed: Variant = JSON.parse_string(
+		file.get_buffer(json_length).get_string_from_utf8()
+	)
+	if not (parsed is Dictionary):
+		return ""
+	var asset: Dictionary = (parsed as Dictionary).get("asset", {})
+	var extras: Dictionary = asset.get("extras", {})
+	return String(extras.get("openwc_m2_anim_schema", ""))

src/render/m2/m2_static_build_resource_observer.gd.uid

@@ -0,0 +1 @@
+uid://c0e3p80ld1dfb