DRY-up ALiS parsing and serialization

asciinema · Jan 28, 2025 · 2a33f6d · 2a33f6d
1 parent 7e29541
commit 2a33f6d
Show file tree

Hide file tree

Showing 2 changed files with 42 additions and 57 deletions.
diff --git a/lib/asciinema/streaming/parser/alis_v1.ex b/lib/asciinema/streaming/parser/alis_v1.ex
@@ -69,37 +69,22 @@ defmodule Asciinema.Streaming.Parser.AlisV1 do
     {time, bytes} = decode_varint(bytes)
     {cols, bytes} = decode_varint(bytes)
     {rows, bytes} = decode_varint(bytes)
-
-    {theme, bytes} =
-      case bytes do
-        <<0::8, rest::binary>> ->
-          {nil, rest}
-
-        <<8::8, theme::binary-size((2 + 8) * 3), rest::binary>> ->
-          {parse_theme(theme), rest}
-
-        <<16::8, theme::binary-size((2 + 16) * 3), rest::binary>> ->
-          {parse_theme(theme), rest}
-      end
-
-    {term_init_len, bytes} = decode_varint(bytes)
-    <<term_init::binary-size(term_init_len)>> = bytes
+    {theme, bytes} = parse_theme(bytes)
+    {term_init, ""} = parse_string(bytes)
 
     %{time: time, term_size: {cols, rows}, term_init: term_init, term_theme: theme}
   end
 
   defp parse_output(bytes) do
     {time, bytes} = decode_varint(bytes)
-    {text_len, bytes} = decode_varint(bytes)
-    <<text::binary-size(text_len)>> = bytes
+    {text, ""} = parse_string(bytes)
 
     {time, text}
   end
 
   defp parse_input(bytes) do
     {time, bytes} = decode_varint(bytes)
-    {text_len, bytes} = decode_varint(bytes)
-    <<text::binary-size(text_len)>> = bytes
+    {text, ""} = parse_string(bytes)
 
     {time, text}
   end
@@ -114,8 +99,7 @@ defmodule Asciinema.Streaming.Parser.AlisV1 do
 
   defp parse_marker(bytes) do
     {time, bytes} = decode_varint(bytes)
-    {label_len, bytes} = decode_varint(bytes)
-    <<label::binary-size(label_len)>> = bytes
+    {label, ""} = parse_string(bytes)
 
     {time, label}
   end
@@ -126,13 +110,29 @@ defmodule Asciinema.Streaming.Parser.AlisV1 do
     time
   end
 
-  defp decode_varint(bytes) do
-    {value, rest} = Leb128.decode(bytes)
+  defp decode_varint(bytes), do: Leb128.decode(bytes)
+
+  defp parse_string(bytes) do
+    {len, bytes} = decode_varint(bytes)
+    <<text::binary-size(len), rest::binary>> = bytes
+
+    {text, rest}
+  end
+
+  defp parse_theme(bytes) do
+    case bytes do
+      <<0::8, rest::binary>> ->
+        {nil, rest}
+
+      <<8::8, theme::binary-size((2 + 8) * 3), rest::binary>> ->
+        {do_parse_theme(theme), rest}
 
-    {value, rest}
+      <<16::8, theme::binary-size((2 + 16) * 3), rest::binary>> ->
+        {do_parse_theme(theme), rest}
+    end
   end
 
-  defp parse_theme(theme) do
+  defp do_parse_theme(theme) do
     colors = for <<r::8, g::8, b::8 <- theme>>, do: {r, g, b}
 
     %{

diff --git a/lib/asciinema_web/live_stream_consumer_socket.ex b/lib/asciinema_web/live_stream_consumer_socket.ex
@@ -204,54 +204,29 @@ defmodule AsciinemaWeb.LiveStreamConsumerSocket do
 
   defp magic_string, do: {:binary, "ALiS\x01"}
 
-  defp serialize_init(time, term_size, term_init, nil) do
-    {cols, rows} = term_size
-    term_init = term_init || ""
-    term_init_len = byte_size(term_init)
-
-    msg =
-      <<1::8>> <>
-        encode_varint(time) <>
-        encode_varint(cols) <>
-        encode_varint(rows) <>
-        <<0::8>> <>
-        encode_varint(term_init_len) <>
-        term_init
-
-    {:binary, msg}
-  end
-
   defp serialize_init(time, term_size, term_init, theme) do
     {cols, rows} = term_size
-    theme_format = length(theme.palette)
-    true = theme_format in [8, 16]
-    theme = serialize_theme(theme)
     term_init = term_init || ""
-    term_init_len = byte_size(term_init)
 
     msg =
       <<1::8>> <>
         encode_varint(time) <>
         encode_varint(cols) <>
         encode_varint(rows) <>
-        <<theme_format::8>> <>
-        theme <>
-        encode_varint(term_init_len) <>
-        term_init
+        serialize_theme(theme) <>
+        serialize_string(term_init)
 
     {:binary, msg}
   end
 
   defp serialize_output(time, text) do
-    text_len = byte_size(text)
-    msg = <<?o>> <> encode_varint(time) <> encode_varint(text_len) <> text
+    msg = <<?o>> <> encode_varint(time) <> serialize_string(text)
 
     {:binary, msg}
   end
 
   defp serialize_input(time, text) do
-    text_len = byte_size(text)
-    msg = <<?i>> <> encode_varint(time) <> encode_varint(text_len) <> text
+    msg = <<?i>> <> encode_varint(time) <> serialize_string(text)
 
     {:binary, msg}
   end
@@ -264,8 +239,7 @@ defmodule AsciinemaWeb.LiveStreamConsumerSocket do
   end
 
   defp serialize_marker(time, label) do
-    label_len = byte_size(label)
-    msg = <<?m>> <> encode_varint(time) <> encode_varint(label_len) <> label
+    msg = <<?m>> <> encode_varint(time) <> serialize_string(label)
 
     {:binary, msg}
   end
@@ -278,7 +252,18 @@ defmodule AsciinemaWeb.LiveStreamConsumerSocket do
 
   defp encode_varint(value), do: Leb128.encode(value)
 
-  defp serialize_theme(%{fg: fg, bg: bg, palette: palette}) do
+  defp serialize_string(text), do: encode_varint(byte_size(text)) <> text
+
+  defp serialize_theme(nil), do: <<0::8>>
+
+  defp serialize_theme(theme) do
+    format = length(theme.palette)
+    true = format in [8, 16]
+
+    <<format::8>> <> do_serialize_theme(theme)
+  end
+
+  defp do_serialize_theme(%{fg: fg, bg: bg, palette: palette}) do
     for {r, g, b} <- [fg, bg | palette], into: <<>> do
       <<r::8, g::8, b::8>>
     end