From 0255b5f7f31c4c6caefc736c59ba6959d671a92d Mon Sep 17 00:00:00 2001
From: Alex Vitkov <alexvitkov98@gmail.com>
Date: Sat, 20 Mar 2021 10:58:25 +0200
Subject: Broke up loggedin.js into modules

---
 front/util.ts | 105 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 105 insertions(+)
 create mode 100644 front/util.ts

(limited to 'front/util.ts')

diff --git a/front/util.ts b/front/util.ts
new file mode 100644
index 0000000..ded0f18
--- /dev/null
+++ b/front/util.ts
@@ -0,0 +1,105 @@
+
+// This is a widely abused helper function that creates a DOM element, attaches it as the 
+// last child of 'parent' and possibly gives it a class
+export function mk(parent: HTMLElement, type: keyof HTMLElementTagNameMap, _class?: string): HTMLElement {
+    var el = document.createElement(type);
+    parent.appendChild(el);
+    if (_class)
+        el.classList.add(_class);
+    return el;
+}
+
+export function path_combine(a, b) {
+    const last_char = a.slice(-1);
+    if (last_char == "/")
+        return a + b;
+    else
+        return a + "/" + b;
+}
+
+// Create a checkbocx with a label.
+// togglefn will be called when its value changes with an argument that's either true/false
+export function mkcheckbox(parent, label, togglefn): HTMLElement {
+    var hdiv = mkhdiv(parent);
+
+    var write_checkbox: HTMLInputElement = mk(hdiv, 'input') as any;
+    write_checkbox.type = 'checkbox';
+
+    var write_checkbox_label = mk(hdiv, 'label');
+    write_checkbox_label.innerText = label;
+    write_checkbox_label.onclick = (_e) => { write_checkbox.click(); }
+    write_checkbox_label.classList.add('noselect');
+
+    write_checkbox.onchange = (_e) => {
+        togglefn(write_checkbox.checked);
+    };
+
+    return hdiv;
+}
+
+// Crate a horizontal div
+export function mkhdiv(parent: HTMLElement): HTMLDivElement {
+    var hdiv = mk(parent, 'div') as HTMLDivElement;
+    hdiv.style.display    = "flex";
+    hdiv.style.alignItems = "center";
+    hdiv.style.padding    = "0.3rem";
+    hdiv.style.gap        = "0.3rem";
+    return hdiv;
+}
+
+// It's honestly really sad that we need this
+// We have an image viewer, but we load the uploaded via the XMLHttpRequest API, which gives us an array buffer
+// We need to base64 encode the image data so we can feed it into the <img src="...">
+// and the standart base64 encode API is shit
+// https://stackoverflow.com/questions/7370943/retrieving-binary-file-content-using-javascript-base64-encode-it-and-reverse-de
+export function base64ArrayBuffer(arrayBuffer) {
+  var base64    = ''
+  var encodings = 'ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/'
+
+  var bytes         = new Uint8Array(arrayBuffer)
+  var byteLength    = bytes.byteLength
+  var byteRemainder = byteLength % 3
+  var mainLength    = byteLength - byteRemainder
+
+  var a, b, c, d
+  var chunk
+
+  // Main loop deals with bytes in chunks of 3
+  for (var i = 0; i < mainLength; i = i + 3) {
+    // Combine the three bytes into a single integer
+    chunk = (bytes[i] << 16) | (bytes[i + 1] << 8) | bytes[i + 2]
+
+    // Use bitmasks to extract 6-bit segments from the triplet
+    a = (chunk & 16515072) >> 18 // 16515072 = (2^6 - 1) << 18
+    b = (chunk & 258048)   >> 12 // 258048   = (2^6 - 1) << 12
+    c = (chunk & 4032)     >>  6 // 4032     = (2^6 - 1) << 6
+    d = chunk & 63               // 63       = 2^6 - 1
+
+    // Convert the raw binary segments to the appropriate ASCII encoding
+    base64 += encodings[a] + encodings[b] + encodings[c] + encodings[d]
+  }
+
+  // Deal with the remaining bytes and padding
+  if (byteRemainder == 1) {
+    chunk = bytes[mainLength]
+
+    a = (chunk & 252) >> 2 // 252 = (2^6 - 1) << 2
+
+    // Set the 4 least significant bits to zero
+    b = (chunk & 3)   << 4 // 3   = 2^2 - 1
+
+    base64 += encodings[a] + encodings[b] + '=='
+  } else if (byteRemainder == 2) {
+    chunk = (bytes[mainLength] << 8) | bytes[mainLength + 1]
+
+    a = (chunk & 64512) >> 10 // 64512 = (2^6 - 1) << 10
+    b = (chunk & 1008)  >>  4 // 1008  = (2^6 - 1) << 4
+
+    // Set the 2 least significant bits to zero
+    c = (chunk & 15)    <<  2 // 15    = 2^4 - 1
+
+    base64 += encodings[a] + encodings[b] + encodings[c] + '='
+  }
+
+  return base64
+}
\ No newline at end of file
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