7 files changed, 127 insertions, 66 deletions
diff --git a/app/src/lib/svelte/Navigation.svelte b/app/src/lib/svelte/Navigation.svelte
index 20c7d8b..fd3c914 100644
--- a/app/src/lib/svelte/Navigation.svelte
+++ b/app/src/lib/svelte/Navigation.svelte
@@ -7,5 +7,5 @@
   <svelte:fragment slot="lead">
     <AppRailAnchor href="/" selected={$page.url.pathname === '/'}>Home!</AppRailAnchor>
   </svelte:fragment>
-	<AppRailAnchor href="/crc32" selected={$page.url.pathname === '/crc32'}>CRC32</AppRailAnchor>
+	<AppRailAnchor href="/truncate" selected={$page.url.pathname === '/truncate'}>Truncate!</AppRailAnchor>
 </AppRail>
diff --git a/app/src/lib/ts/crc32.worker.ts b/app/src/lib/ts/crc32.worker.ts
deleted file mode 100644
index 57c1bc9..0000000
--- a/app/src/lib/ts/crc32.worker.ts
+++ /dev/null
@@ -1,10 +0,0 @@
-// TODO: Think about using a WebAssembly implementation of CRC32 instead of JavaScript.
-// WHY? The JavaScript implementation is not very extensible and is not very fast.
-import crc32 from 'crc/crc32';
-
-onmessage = async (message: MessageEvent<File>) => {
-  const file = message.data;
-  const buffer = await file.arrayBuffer();
-  const crc = crc32(buffer);
-  postMessage(crc);
-};
diff --git a/app/src/lib/ts/download.ts b/app/src/lib/ts/download.ts
new file mode 100644
index 0000000..a6167d7
--- /dev/null
+++ b/app/src/lib/ts/download.ts
@@ -0,0 +1,33 @@
+// Yoinked from https://web.dev/patterns/files/save-a-file/ for the polyfill
+
+export default async function saveFile(blob: ArrayBuffer, suggestedName: string | undefined) {
+	const supportsFSAccess = 'showSaveFilePicker' in window &&
+		(() => {
+			try {
+				return window.self === window.top;
+			} catch {
+				return false;
+			}
+		})();
+
+	if (supportsFSAccess) {
+		try {
+			const handle = await window.showSaveFilePicker({
+				suggestedName: suggestedName,
+			})
+			const writable = await handle.createWritable();
+			await writable.write(blob);
+			await writable.close();
+		} catch (err: unknown) {
+			// TypeScript
+			if ((err as Error)?.name !== 'AbortError') {
+				console.error(err);
+			}
+		}
+	} else {
+		const anchor = document.createElement('a');
+		anchor.download = suggestedName ?? 'truncated';
+		anchor.href = URL.createObjectURL(new Blob([blob]));
+		anchor.click();
+	}
+}
+\ No newline at end of file
diff --git a/app/src/lib/ts/truncate.worker.ts b/app/src/lib/ts/truncate.worker.ts
new file mode 100644
index 0000000..52eebb7
--- /dev/null
+++ b/app/src/lib/ts/truncate.worker.ts
@@ -0,0 +1,10 @@
+import type { TruncateRequest, TruncateResponse } from '../types/truncate-worker';
+
+
+onmessage = async (message: MessageEvent<TruncateRequest>) => {
+	const file = message.data.file;
+	const buffer = await file.arrayBuffer();
+	const truncated = buffer.slice(0, message.data.size);
+
+	postMessage({ file: truncated } as TruncateResponse);
+}
+\ No newline at end of file
diff --git a/app/src/lib/types/truncate-worker.ts b/app/src/lib/types/truncate-worker.ts
new file mode 100644
index 0000000..9b1872f
--- /dev/null
+++ b/app/src/lib/types/truncate-worker.ts
@@ -0,0 +1,8 @@
+export type TruncateRequest = {
+	file: File,
+	size: number,
+};
+
+export type TruncateResponse = {
+	file: ArrayBuffer,
+};
diff --git a/app/src/routes/crc32/+page.svelte b/app/src/routes/crc32/+page.svelte
deleted file mode 100644
index b88e52e..0000000
--- a/app/src/routes/crc32/+page.svelte
+++ /dev/null
@@ -1,55 +0,0 @@
-<script lang="ts">
-  import { FileDropzone, ProgressBar } from '@skeletonlabs/skeleton';
-  import { onMount } from 'svelte';
-
-  let disableInput = false;
-  let files: FileList;
-  let form: HTMLFormElement;
-  let worker: Worker;
-
-  function onUpload() {
-    disableInput = true;
-    worker.postMessage(files[0]);
-    form.reset();
-  }
-
-  onMount(async () => {
-    worker = new Worker(new URL('$lib/ts/crc32.worker.ts', import.meta.url), { type: 'module' });
-    worker.onmessage = (e: MessageEvent<number>) => {
-      disableInput = false;
-      console.log(e.data);
-    };
-  });
-</script>
-
-<svelte:head>
-  <title>CRC32</title>
-</svelte:head>
-
-<div class="container h-full mx-auto flex justify-center items-center">
-  <div class="space-y-10 text-center flex flex-col items-center">
-    <form bind:this={form} on:submit|preventDefault={onUpload} method="POST" action="?/TODO">
-      <FileDropzone
-        name="checksumMe"
-        bind:files
-        on:change={() => form.requestSubmit()}
-        required
-        disabled={disableInput}
-      >
-        <svelte:fragment slot="lead">
-          <h2 class="h2">Drop a file here to get its CRC32 checksum.</h2>
-        </svelte:fragment>
-      </FileDropzone>
-      <br />
-      <noscript>
-        <button type="submit" class="btn variant-filled">
-          After adding a file, click to submit! (Not yet implemented)
-        </button>
-      </noscript>
-      {#if disableInput}
-        <h3 class="h3">Calculating the checksum, this may take time!</h3> <br />
-        <ProgressBar />
-      {/if}
-    </form>
-  </div>
-</div>
diff --git a/app/src/routes/truncate/+page.svelte b/app/src/routes/truncate/+page.svelte
new file mode 100644
index 0000000..9e2545f
--- /dev/null
+++ b/app/src/routes/truncate/+page.svelte
@@ -0,0 +1,75 @@
+<script lang="ts">
+    import saveFile from '$lib/ts/download';
+  import type { TruncateRequest, TruncateResponse } from '$lib/types/truncate-worker';
+  import { FileDropzone, ProgressBar } from '@skeletonlabs/skeleton';
+  import { onMount } from 'svelte';
+
+  let disableInput = false;
+  let files: FileList;
+  let form: HTMLFormElement;
+  let worker: Worker;
+  $: truncateTo = 1;
+  let originalName: string;
+
+  function onUpload() {
+    disableInput = true;
+    originalName = files[0].name;
+    worker.postMessage({
+      file: files[0],
+      size: truncateTo,
+    } as TruncateRequest);
+    form.reset();
+    truncateTo = 1;
+  }
+
+  onMount(async () => {
+    worker = new Worker(new URL('$lib/ts/truncate.worker.ts', import.meta.url), { type: 'module' });
+    worker.onmessage = (e: MessageEvent<TruncateResponse>) => {
+      disableInput = false;
+      saveFile(e.data.file, `trunc-${originalName}`);
+
+    };
+  });
+</script>
+
+<svelte:head>
+  <title>Truncate</title>
+</svelte:head>
+
+<div class="container h-full mx-auto flex justify-center items-center">
+  <div class="space-y-10 text-center flex flex-col items-center">
+    <form bind:this={form} on:submit|preventDefault={onUpload} method="POST" action="?/TODO">
+      <label class="label" for="truncateMe">
+        <FileDropzone
+          id="truncateMe"
+          name="truncateMe"
+          bind:files
+          on:change={() => form.requestSubmit()}
+          required
+          disabled={disableInput}
+        >
+          <svelte:fragment slot="lead">
+            <h2 class="h2">Drop a file here to truncate it.</h2>
+          </svelte:fragment>
+        </FileDropzone>
+      </label>
+      <br />
+      <label class="label">
+        <span>Truncate up to... (in bytes)</span>
+        <input class="input" type="number" name="truncateTo" bind:value={truncateTo} min="1" required />
+
+      </label>
+      <br />
+      <noscript>
+        <button type="submit" class="btn variant-filled"
+          >After adding a file, click to submit! (Not yet implemented)</button
+        >
+      </noscript>
+      {#if disableInput}
+        <h3 class="h3">Truncating the file, this may take time!</h3>
+        <br />
+        <ProgressBar />
+      {/if}
+    </form>
+  </div>
+</div>