From f93d84c457ad6936d417fc93790c1aa29894df2c Mon Sep 17 00:00:00 2001
From: dumbmoron <log@riseup.net>
Date: Tue, 13 Aug 2024 15:33:30 +0000
Subject: [PATCH] web/libav: add ffprobe wrapper

---
 pnpm-lock.yaml       | 10 ++++++++++
 web/package.json     |  1 +
 web/src/lib/libav.ts | 40 ++++++++++++++++++++++++++++++++++++++++
 3 files changed, 51 insertions(+)

diff --git a/pnpm-lock.yaml b/pnpm-lock.yaml
index a61bd324..84a135e4 100644
--- a/pnpm-lock.yaml
+++ b/pnpm-lock.yaml
@@ -131,6 +131,9 @@ importers:
       '@types/eslint__js':
         specifier: ^8.42.3
         version: 8.42.3
+      '@types/fluent-ffmpeg':
+        specifier: ^2.1.25
+        version: 2.1.25
       '@types/node':
         specifier: ^20.14.10
         version: 20.14.14
@@ -695,6 +698,9 @@ packages:
   '@types/estree@1.0.5':
     resolution: {integrity: sha512-/kYRxGDLWzHOB7q+wtSUQlFrtcdUccpfy+X+9iMBpHK8QLLhx2wIPYuS5DYtR9Wa/YlZAbIovy7qVdB1Aq6Lyw==}
 
+  '@types/fluent-ffmpeg@2.1.25':
+    resolution: {integrity: sha512-a9/Jtv/RVaCG4lUwWIcuClWE5eXJFoFS/oHOecOv/RS8n+lQdJzcJVmDlxA8Xbk4B82YpO88Dijcoljb6sYTcA==}
+
   '@types/json-schema@7.0.15':
     resolution: {integrity: sha512-5+fP8P8MFNC+AyZCDxrB2pkZFPGzqQWUzpSeuuVLvm8VMcorNYavBqoFcxK8bQz4Qsbn4oUEEem4wDLfcysGHA==}
 
@@ -2634,6 +2640,10 @@ snapshots:
 
   '@types/estree@1.0.5': {}
 
+  '@types/fluent-ffmpeg@2.1.25':
+    dependencies:
+      '@types/node': 20.14.14
+
   '@types/json-schema@7.0.15': {}
 
   '@types/node@10.17.60': {}
diff --git a/web/package.json b/web/package.json
index 19fa7c17..c9454818 100644
--- a/web/package.json
+++ b/web/package.json
@@ -30,6 +30,7 @@
         "@sveltejs/kit": "^2.0.0",
         "@sveltejs/vite-plugin-svelte": "^3.0.0",
         "@types/eslint__js": "^8.42.3",
+        "@types/fluent-ffmpeg": "^2.1.25",
         "@types/node": "^20.14.10",
         "compare-versions": "^6.1.0",
         "eslint": "^8.57.0",
diff --git a/web/src/lib/libav.ts b/web/src/lib/libav.ts
index d24e1847..ff68c267 100644
--- a/web/src/lib/libav.ts
+++ b/web/src/lib/libav.ts
@@ -1,6 +1,7 @@
 import mime from "mime";
 import LibAV, { type LibAV as LibAVInstance } from "@imput/libav.js-remux-cli";
 import type { FFmpegProgressCallback, FFmpegProgressEvent, FFmpegProgressStatus, FileInfo, RenderParams } from "./types/libav";
+import type { FfprobeData } from "fluent-ffmpeg";
 
 export default class LibAVWrapper {
     libav: Promise<LibAVInstance> | null;
@@ -22,6 +23,45 @@ export default class LibAVWrapper {
         }
     }
 
+    async probe(blob: Blob) {
+        if (!this.libav) throw new Error("LibAV wasn't initialized");
+        const libav = await this.libav;
+
+        const OUT_FILE = 'output.json';
+        await libav.mkreadaheadfile('input', blob);
+        await libav.mkwriterdev(OUT_FILE);
+
+        let writtenData = new Uint8Array(0);
+
+        libav.onwrite = (name, pos, data) => {
+            if (name !== OUT_FILE) return;
+
+            const newLen = Math.max(pos + data.length, writtenData.length);
+            if (newLen > writtenData.length) {
+                const newData = new Uint8Array(newLen);
+                newData.set(writtenData);
+                writtenData = newData;
+            }
+            writtenData.set(data, pos);
+        };
+
+        await libav.ffprobe([
+            '-v', 'quiet',
+            '-print_format', 'json',
+            '-show_format',
+            '-show_streams',
+            'input',
+            '-o', OUT_FILE
+        ]);
+
+        await libav.unlink(OUT_FILE);
+        await libav.unlinkreadaheadfile('input');
+
+        const copy = new Uint8Array(writtenData);
+        const text = new TextDecoder().decode(copy);
+        return JSON.parse(text) as FfprobeData;
+    }
+
     async render({ blob, output, args }: RenderParams) {
         if (!this.libav) throw new Error("LibAV wasn't initialized");
         const libav = await this.libav;