refactor: split long functions and fix AGENTS.md violations

- Rename goos/goarch to os_name/arch_name (no domain jargon)
- Split _install_ffmpeg into _detect_os, _detect_arch, _build_ffmpeg_url, _download_url_bytes, _extract_ffmpeg
- Split _build_animated_gif_texture into _extract_gif_frames and _assemble_animated_texture
- Split _parse_gif_frame_delays into _skip_gif_header, _parse_gif_extension, _skip_gif_image_descriptor
- Replace _download_gif_bytes with _download_url_bytes (shared helper)
- All functions now under 50 lines

core/boxart_itch.gd

@@ -260,32 +260,52 @@ func _ensure_ffmpeg() -> String:
 ## the same way the itch plugin's butler installer does, then fetches
 ## the matching BtbN pre-built binary.
 func _install_ffmpeg() -> bool:
-	var goos := "linux"
+	var os_name := _detect_os()
-	var goarch := "64"
+	var arch_name := _detect_arch()
+	var archive_url := _build_ffmpeg_url(os_name, arch_name)
+	var body := await _download_url_bytes(archive_url)
+	if body.is_empty():
+		return false
+	return _extract_ffmpeg(body, os_name)
+
+
+## Detects the current OS as a short name for ffmpeg builds.
+func _detect_os() -> String:
 	if OS.get_name() == "Windows":
-		goos = "win"
+		return "win"
 	if OS.get_name() == "macOS":
-		goos = "macos"
+		return "macos"
+	return "linux"
+
+
+## Detects the CPU architecture as a short name for ffmpeg builds.
+func _detect_arch() -> String:
 	if Engine.has_method("get_architecture_name"):
 		var arch: String = Engine.get_architecture_name()
 		if "arm64" in arch or "aarch64" in arch:
-			goarch = "arm64"
+			return "arm64"
+	return "64"
 
-	var platform_slug := goos + goarch
+
+## Builds the download URL for the ffmpeg archive matching the given platform.
+func _build_ffmpeg_url(os_name: String, arch_name: String) -> String:
+	var platform_slug := os_name + arch_name
 	var archive_name := "ffmpeg-master-latest-%s-gpl" % platform_slug
-	var is_win: bool = goos == "win"
+	var ext := "zip" if os_name == "win" else "tar.xz"
-	var archive_url := "%s/%s.%s" % [FFMPEG_BUILDS_URL, archive_name,
+	return "%s/%s.%s" % [FFMPEG_BUILDS_URL, archive_name, ext]
-		"zip" if is_win else "tar.xz"]
 
+
+## Downloads bytes from a URL. Returns empty PackedByteArray on failure.
+func _download_url_bytes(url: String) -> PackedByteArray:
 	var http := HTTPRequest.new()
 	add_child.call_deferred(http)
 	await http.ready
 
-	if http.request(archive_url) != OK:
+	if http.request(url) != OK:
-		logger.error("Error requesting ffmpeg archive: " + archive_url)
+		logger.error("Error requesting: " + url)
 		remove_child(http)
 		http.queue_free()
-		return false
+		return PackedByteArray()
 
 	var args: Array = await http.request_completed
 	var result: int = args[0]
@@ -295,11 +315,16 @@ func _install_ffmpeg() -> bool:
 	http.queue_free()
 
 	if result != HTTPRequest.RESULT_SUCCESS or response_code != 200:
-		logger.error("ffmpeg download failed: HTTP %d for %s" % [response_code, archive_url])
+		logger.error("Download failed: HTTP %d for %s" % [response_code, url])
-		return false
+		return PackedByteArray()
+	return body
 
+
+## Extracts the ffmpeg binary from the downloaded archive.
+func _extract_ffmpeg(body: PackedByteArray, os_name: String) -> bool:
 	var globalized_dir := ProjectSettings.globalize_path(BOXART_DIR)
 	DirAccess.make_dir_recursive_absolute(globalized_dir)
+	var is_win: bool = os_name == "win"
 	var ext := "zip" if is_win else "tar.xz"
 	var archive_path := globalized_dir + "/ffmpeg." + ext
 	var file := FileAccess.open(archive_path, FileAccess.WRITE)
@@ -388,53 +413,7 @@ func _fetch_gif_as_texture(url: String, cache_flags: int) -> Texture2D:
 
 ## Downloads GIF bytes from the given URL. Returns empty PackedByteArray on failure.
 func _download_gif_bytes(url: String) -> PackedByteArray:
-	var http := HTTPClient.new()
+	return await _download_url_bytes(url)
-	var parts := url.split("/")
-	var use_tls := parts[0] == "https:"
-	var err := http.connect_to_host(parts[2], 443 if use_tls else 80, TLSOptions.client() if use_tls else null)
-	if err != OK:
-		logger.warn("GIF fetch: HTTP connect failed for %s: %d" % [url.left(LOG_URL_MAX_LEN), err])
-		return PackedByteArray()
-	var deadline := Time.get_ticks_msec() + HTTP_TIMEOUT_MS
-	while http.get_status() == HTTPClient.STATUS_CONNECTING or http.get_status() == HTTPClient.STATUS_RESOLVING:
-		http.poll()
-		if Time.get_ticks_msec() > deadline:
-			http.close()
-			logger.warn("GIF fetch: connect timed out")
-			return PackedByteArray()
-		OS.delay_msec(CONNECT_POLL_DELAY_MS)
-	if http.get_status() != HTTPClient.STATUS_CONNECTED:
-		logger.warn("GIF fetch: not connected (status=%d)" % http.get_status())
-		http.close()
-		return PackedByteArray()
-
-	http.request(HTTPClient.METHOD_GET, "/" + "/".join(parts.slice(3)), PackedStringArray())
-	deadline = Time.get_ticks_msec() + HTTP_TIMEOUT_MS
-	while http.get_status() == HTTPClient.STATUS_REQUESTING:
-		http.poll()
-		if Time.get_ticks_msec() > deadline:
-			http.close()
-			logger.warn("GIF fetch: request timed out")
-			return PackedByteArray()
-		OS.delay_msec(READ_POLL_DELAY_MS)
-
-	var body := PackedByteArray()
-	while http.get_status() == HTTPClient.STATUS_BODY:
-		http.poll()
-		var chunk: PackedByteArray = http.read_response_body_chunk()
-		if chunk.is_empty():
-			if Time.get_ticks_msec() > deadline:
-				http.close()
-				logger.warn("GIF fetch: body read timed out")
-				return PackedByteArray()
-			OS.delay_msec(READ_POLL_DELAY_MS)
-			continue
-		body.append_array(chunk)
-	http.close()
-
-	if body.is_empty():
-		logger.warn("GIF fetch: empty response for %s" % url.left(LOG_URL_MAX_LEN))
-	return body
 
 
 ## Extracts the first frame of a GIF using ffmpeg. Returns a static ImageTexture.
@@ -465,10 +444,15 @@ func _build_static_gif_texture(ffmpeg_bin: String, gif_path: String, png_path: S
 ## Extracts all frames from a GIF using ffmpeg and builds an AnimatedTexture.
 ## The animation is paused by default — the focus handler unpauses it.
 func _build_animated_gif_texture(ffmpeg_bin: String, gif_path: String, frames_dir: String, gif_bytes: PackedByteArray, url: String) -> AnimatedTexture:
-	# Parse frame delays from the GIF binary.
 	var delays: Array = _parse_gif_frame_delays(gif_bytes)
+	var frame_files: PackedStringArray = _extract_gif_frames(ffmpeg_bin, gif_path, frames_dir)
+	if frame_files.is_empty():
+		return null
+	return _assemble_animated_texture(frame_files, frames_dir, delays, url)
 
-	# Extract all frames with ffmpeg.
+
+## Extracts all frames from a GIF file using ffmpeg. Returns sorted frame filenames.
+func _extract_gif_frames(ffmpeg_bin: String, gif_path: String, frames_dir: String) -> PackedStringArray:
 	DirAccess.make_dir_recursive_absolute(frames_dir)
 	var ffmpeg_args: PackedStringArray = [
 		"-y", "-i", gif_path,
@@ -478,11 +462,10 @@ func _build_animated_gif_texture(ffmpeg_bin: String, gif_path: String, frames_di
 	var ret: Array = []
 	OS.execute(ffmpeg_bin, ffmpeg_args, ret)
 
-	# Collect extracted frame files.
 	var dir := DirAccess.open(frames_dir)
 	if dir == null:
 		logger.warn("GIF fetch: cannot open frames dir")
-		return null
+		return PackedStringArray()
 	dir.list_dir_begin()
 	var frame_files: PackedStringArray = []
 	var fname := dir.get_next()
@@ -492,13 +475,11 @@ func _build_animated_gif_texture(ffmpeg_bin: String, gif_path: String, frames_di
 		fname = dir.get_next()
 	dir.list_dir_end()
 	frame_files.sort()
+	return frame_files
 
-	if frame_files.is_empty():
-		logger.warn("GIF fetch: no frames extracted for %s" % url.left(LOG_URL_MAX_LEN))
-		DirAccess.remove_absolute(frames_dir)
-		return null
 
-	# Build AnimatedTexture.
+## Loads extracted frame images and assembles them into an AnimatedTexture.
+func _assemble_animated_texture(frame_files: PackedStringArray, frames_dir: String, delays: Array, url: String) -> AnimatedTexture:
 	var anim_tex := AnimatedTexture.new()
 	anim_tex.frames_count = frame_files.size()
 	anim_tex.pause = true  # Start paused — focus handler unpauses.
@@ -511,7 +492,6 @@ func _build_animated_gif_texture(ffmpeg_bin: String, gif_path: String, frames_di
 			logger.warn("GIF fetch: failed to load frame %d" % i)
 			continue
 		anim_tex.set_frame_texture(i, ImageTexture.create_from_image(image))
-		# Use parsed delay if available, otherwise default.
 		var delay_ms: int = delays[i] if i < delays.size() else GIF_DEFAULT_FRAME_DELAY_MS
 		anim_tex.set_frame_delay(i, delay_ms / 1000.0)  # AnimatedTexture uses seconds.
 
@@ -528,56 +508,68 @@ func _parse_gif_frame_delays(data: PackedByteArray) -> Array:
 	if data.size() < 13:
 		return delays
 
-	# Skip header (6) + Logical Screen Descriptor (7).
+	var pos := _skip_gif_header(data)
-	var pos := 13
+	while pos < data.size() - 1:
-	# Skip Global Color Table if present.
+		var byte: int = data[pos]
+		if byte == 0x21:
+			var result: Array = _parse_gif_extension(data, pos)
+			if result[0] >= 0:
+				delays.append(result[0])
+			pos = result[1]
+		elif byte == 0x2C:
+			pos = _skip_gif_image_descriptor(data, pos)
+		elif byte == 0x3B:
+			break
+		else:
+			pos += 1
+
+	return delays
+
+
+## Skips the GIF header, Logical Screen Descriptor, and Global Color Table.
+## Returns the byte offset past all header data.
+func _skip_gif_header(data: PackedByteArray) -> int:
+	var pos := 13  # Header (6) + Logical Screen Descriptor (7).
 	var packed_byte: int = data[10]
 	if packed_byte & 0x80 != 0:
 		var gct_size := 3 * (1 << ((packed_byte & 0x07) + 1))
 		pos += gct_size
+	return pos
 
-	while pos < data.size() - 1:
+
-		var byte: int = data[pos]
+## Parses an extension block starting at `pos`. Returns [delay_ms, new_pos].
-		if byte == 0x21:
+## If the extension is not a Graphics Control Extension, returns [-1, new_pos].
-			# Extension block.
+func _parse_gif_extension(data: PackedByteArray, pos: int) -> Array:
-			var label: int = data[pos + 1]
+	var label: int = data[pos + 1]
-			if label == 0xF9:
+	var delay_ms := -1
-				# Graphics Control Extension — contains frame delay.
+	if label == 0xF9:
-				var delay_cs: int = data[pos + 4] | (data[pos + 5] << 8)  # Centiseconds.
+		var delay_cs: int = data[pos + 4] | (data[pos + 5] << 8)
-				var delay_ms: int = delay_cs * 10 if delay_cs > 0 else GIF_DEFAULT_FRAME_DELAY_MS
+		delay_ms = delay_cs * 10 if delay_cs > 0 else GIF_DEFAULT_FRAME_DELAY_MS
-				delays.append(delay_ms)
+	pos += 2
-			# Skip extension block.
+	while pos < data.size():
-			pos += 2
+		var block_size: int = data[pos]
-			while pos < data.size():
+		pos += 1
-				var block_size: int = data[pos]
+		if block_size == 0:
-				pos += 1
-				if block_size == 0:
-					break
-				pos += block_size
-		elif byte == 0x2C:
-			# Image descriptor — skip it.
-			pos += 10
-			# Skip Local Color Table if present.
-			var img_packed: int = data[pos - 1]
-			if img_packed & 0x80 != 0:
-				var lct_size := 3 * (1 << ((img_packed & 0x07) + 1))
-				pos += lct_size
-			# Skip LZW Minimum Code Size + sub-blocks.
-			pos += 1  # LZW min code size.
-			while pos < data.size():
-				var block_size: int = data[pos]
-				pos += 1
-				if block_size == 0:
-					break
-				pos += block_size
-		elif byte == 0x3B:
-			# Trailer.
 			break
-		else:
+		pos += block_size
-			# Unknown block — skip.
+	return [delay_ms, pos]
-			pos += 1
 
-	return delays
+
+## Skips an image descriptor and its associated data at `pos`.
+func _skip_gif_image_descriptor(data: PackedByteArray, pos: int) -> int:
+	pos += 10
+	var img_packed: int = data[pos - 1]
+	if img_packed & 0x80 != 0:
+		var lct_size := 3 * (1 << ((img_packed & 0x07) + 1))
+		pos += lct_size
+	pos += 1  # LZW Minimum Code Size.
+	while pos < data.size():
+		var block_size: int = data[pos]
+		pos += 1
+		if block_size == 0:
+			break
+		pos += block_size
+	return pos
 
 
 ## Combines two textures side-by-side into a single banner image.