From 3412296a768d2e587088244d8212fc8ef33fb821 Mon Sep 17 00:00:00 2001
From: Ferdinand Linnenberg <ferdinand@linnenberg.dev>
Date: Tue, 17 Sep 2024 10:37:11 +0200
Subject: [PATCH] feat: working decompression

---
 package-lock.json                           |  6 ++
 package.json                                |  1 +
 src/core/operations/ZStandardDecompress.mjs | 90 +++++++++++++++++++++
 3 files changed, 97 insertions(+)
 create mode 100644 src/core/operations/ZStandardDecompress.mjs

diff --git a/package-lock.json b/package-lock.json
index 3904f840..70cf3227 100644
--- a/package-lock.json
+++ b/package-lock.json
@@ -44,6 +44,7 @@
         "fernet": "^0.4.0",
         "file-saver": "^2.0.5",
         "flat": "^6.0.1",
+        "fzstd": "^0.1.1",
         "geodesy": "1.1.3",
         "highlight.js": "^11.9.0",
         "ieee754": "^1.2.1",
@@ -7916,6 +7917,11 @@
         "url": "https://github.com/sponsors/ljharb"
       }
     },
+    "node_modules/fzstd": {
+      "version": "0.1.1",
+      "resolved": "https://registry.npmjs.org/fzstd/-/fzstd-0.1.1.tgz",
+      "integrity": "sha512-dkuVSOKKwh3eas5VkJy1AW1vFpet8TA/fGmVA5krThl8YcOVE/8ZIoEA1+U1vEn5ckxxhLirSdY837azmbaNHA=="
+    },
     "node_modules/gamma": {
       "version": "1.0.0",
       "license": "MIT"
diff --git a/package.json b/package.json
index cc3517d3..e092ad49 100644
--- a/package.json
+++ b/package.json
@@ -128,6 +128,7 @@
     "fernet": "^0.4.0",
     "file-saver": "^2.0.5",
     "flat": "^6.0.1",
+    "fzstd": "^0.1.1",
     "geodesy": "1.1.3",
     "highlight.js": "^11.9.0",
     "ieee754": "^1.2.1",
diff --git a/src/core/operations/ZStandardDecompress.mjs b/src/core/operations/ZStandardDecompress.mjs
new file mode 100644
index 00000000..9d68a401
--- /dev/null
+++ b/src/core/operations/ZStandardDecompress.mjs
@@ -0,0 +1,90 @@
+/**
+ * @author Scarjit [ferdinand@linnenberg.dev]
+ * @copyright Crown Copyright 2024
+ * @license Apache-2.0
+ */
+
+global.document = {};
+import Operation from "../Operation.mjs";
+import OperationError from "../errors/OperationError.mjs";
+import {isWorkerEnvironment} from "../Utils.mjs";
+import * as fzstd from "fzstd";
+
+/**
+ * ZStandard Decompress operation
+ */
+class ZStandardDecompress extends Operation {
+
+    /**
+     * ZStandardDecompress constructor
+     */
+    constructor() {
+        super();
+
+        this.name = "ZStandard Decompress";
+        this.module = "Compress";
+        this.description = "ZStandard is a compression algorithm focused on fast decompression.";
+        this.infoURL = "https://wikipedia.org/wiki/Zstd"; // Usually a Wikipedia link. Remember to remove localisation (i.e. https://wikipedia.org/etc rather than https://en.wikipedia.org/etc)
+        this.inputType = "ArrayBuffer";
+        this.outputType = "ArrayBuffer";
+        this.args = [
+            {
+                "name": "Chunk Size (bytes)",
+                "type": "number",
+                "value": 65536
+            }
+        ];
+    }
+
+    /**
+     * @param {ArrayBuffer} input
+     * @param {Object[]} args
+     * @returns {ArrayBuffer}
+     */
+    run(input, args) {
+        const chunkSize = args[0];
+        if (input.byteLength <= 0) {
+            throw new OperationError("Please provide an input.");
+        }
+        // Validate input starts with ZStandard magic number
+        const magicNumber = new Uint8Array(input, 0, 4);
+        if (magicNumber[0] !== 0x28 || magicNumber[1] !== 0xb5 || magicNumber[2] !== 0x2f || magicNumber[3] !== 0xfd) {
+            throw new OperationError("Invalid ZStandard input: does not start with magic number.");
+        }
+
+        if (isWorkerEnvironment()) self.sendStatusMessage("Loading ZStandard...");
+        return new Promise(async (resolve, reject) => {
+            const compressed = new Uint8Array(input);
+            try {
+                const outChunks = []; // Array of Uint8Array chunks
+                const stream = new fzstd.Decompress((chunk, isLast) => {
+                    // Add to list of output chunks
+                    outChunks.push(chunk);
+                    // Log after all chunks decompressed
+                    if (isLast) {
+                        // Combine all chunks into a single Uint8Array
+                        const totalLength = outChunks.reduce((sum, chunk) => sum + chunk.length, 0);
+                        const result = new Uint8Array(totalLength);
+                        let offset = 0;
+                        for (const chunk of outChunks) {
+                            result.set(chunk, offset);
+                            offset += chunk.length;
+                        }
+                        resolve(result.buffer);
+                    }
+                });
+                for (let i = 0; i < compressed.length; i += chunkSize) {
+                    if (isWorkerEnvironment()) self.sendStatusMessage(`Decompressing chunk ${i / chunkSize + 1} of ${Math.ceil(compressed.length / chunkSize)}`);
+                    const chunk = compressed.subarray(i, i + chunkSize);
+                    stream.push(chunk);
+                }
+                stream.push(new Uint8Array(0), true); // Signal end of stream
+            } catch (error) {
+                reject(new OperationError("Decompression failed: " + error.message));
+            }
+        });
+    }
+
+}
+
+export default ZStandardDecompress;