refactor: split subtitle processing into discrete functions with error handling

src/main.ts

@@ -19,21 +19,62 @@ const lang_codes = {
   "tur": "tr",
 };
 
-function main() {
+function subtitlesLookup(file: string): videoFile {
+  console.log("Looking up subtitles from " + file);
   const command = new Deno.Command("mkvmerge", {
-    args: ["-J", input],
+    args: ["-J", file],
   });
-
-  const { code, stdout, stderr } = command.outputSync();
-
-  const mkvmerge_output = JSON.parse(
-    new TextDecoder().decode(stdout),
-  ) as videoFile;
+  const { code, stderr, stdout } = command.outputSync();
   const error = new TextDecoder().decode(stderr);
   if (code !== 0) {
     console.error(error);
-    return;
+    throw new Error(error);
   }
+  return JSON.parse(new TextDecoder().decode(stdout)) as videoFile;
+}
+
+function ripSubtitles(file: string, languages: Record<string, string>) {
+  console.log("Ripping subtitles from " + file);
+  const command = new Deno.Command("mkvextract", {
+    args: [
+      "tracks",
+      file,
+      ...Object.entries(languages).map(([id, lang]) => `${id}:${lang}`),
+    ],
+  });
+  const { code, stderr } = command.outputSync();
+  const error = new TextDecoder().decode(stderr);
+  if (code !== 0) {
+    console.error(error);
+    throw new Error(error);
+  }
+}
+
+async function convertSubtitles(languages: Record<string, string>) {
+  console.log("Converting subtitles");
+  const pool: Deno.ChildProcess[] = [];
+  for (const [_, lang] of Object.entries(languages)) {
+    const child = new Deno.Command("vobsub2srt", {
+      args: ["-l", lang, "--blacklist", "|", lang],
+    }).spawn();
+    pool.push(child);
+  }
+  for (const child of pool) {
+    await child.status;
+  }
+}
+
+function cleanUp(languages: Record<string, string>) {
+  console.log("Cleaning up");
+  for (const [_, lang] of Object.entries(languages)) {
+    Deno.remove(lang + ".srt");
+    Deno.remove(lang + ".idx");
+    Deno.remove(lang + ".sub");
+  }
+}
+
+async function main() {
+  const mkvmerge_output = subtitlesLookup(input);
   const languages_in_file: Record<string, string> = {};
   for (const track of mkvmerge_output.tracks) {
     if (!(track.type === "subtitles")) {
@@ -47,21 +88,9 @@ function main() {
     }
     languages_in_file[track.id] = lang;
   }
-  const formatted_language_string = Object.entries(languages_in_file)
-    .map(([id, lang]) => `${id}:${lang}`);
-  const rip_cmd = new Deno.Command("mkvextract", {
-    args: ["tracks", input, ...formatted_language_string],
-  });
-  rip_cmd.outputSync();
+  ripSubtitles(input, languages_in_file);
 
-  for (const [_, lang] of Object.entries(languages_in_file)) {
-    const convert_cmd = new Deno.Command("vobsub2srt", {
-      args: ["-l", lang, "--blacklist", "|", lang],
-    });
-    convert_cmd.outputSync();
-    Deno.remove(lang + ".idx");
-    Deno.remove(lang + ".sub");
-  }
+  await convertSubtitles(languages_in_file);
 
   const ffmpeg_cmd_raw = [];
   const subTracksById = new Map(
@@ -104,13 +133,14 @@ function main() {
   const ffmpeg_error = new TextDecoder().decode(ffmpeg_stderr);
   if (ffmpeg_code !== 0) {
     console.error(ffmpeg_error);
-    return;
-  }
-  for (const [_, lang] of Object.entries(languages_in_file)) {
-    Deno.remove(lang + ".srt");
+    throw new Error(ffmpeg_error);
   }
+  cleanUp(languages_in_file);
 }
 
 if (import.meta.main) {
-  main();
+  main().catch((e) => {
+    console.error(e);
+    Deno.exit(1);
+  });
 }