generator share links; secure send copy message

plugins/tools/frontend/sharelink.js

@@ -0,0 +1,116 @@
+/**
+ * A link that opens the generator with somebody's work already in it.
+ *
+ * WHY THE FRAGMENT
+ *
+ * Everything rides after the `#`. A fragment is never transmitted: it does not
+ * reach Flask, it is not in the IIS log, and the proxy between the two never
+ * sees it. A query string would put the encoded content in all three, and the
+ * whole point of this feature is to send somebody a code they can print - which
+ * means the content is often an asset number, a serial, or a URL somebody would
+ * rather not scatter through logs.
+ *
+ * It is NOT secrecy. The link still sits in a chat message, in browser history
+ * and in whatever archives that chat. Anyone holding the link has the content.
+ * Secure Send exists for the case where that matters.
+ *
+ * WHAT TRAVELS
+ *
+ * What was typed (content, label, copies, the CSV) plus the settings that
+ * change how the label looks. Not the picture: a data URL runs to megabytes and
+ * would produce a link no chat client will carry.
+ */
+
+// Short keys because the whole thing has to survive being pasted into a chat
+// box. `c` is the content, `t` the code type, `p` the label preset.
+const SHORT = {
+  c: 'content',
+  l: 'label',
+  n: 'copies',
+  b: 'back',
+  v: 'csv',
+  s: 'source',
+  t: 'codetype',
+  e: 'errorcorrection',
+  p: 'preset',
+}
+
+// Layout values travel under their own names - there are enough of them that
+// abbreviating would cost more in confusion than it saves in characters.
+const PASSTHROUGH = [
+  'labelwidth', 'labelheight', 'padding', 'quiet', 'gap', 'codesize',
+  'barheight', 'labelfont', 'layout', 'align', 'valign',
+  'contentx', 'contenty', 'nudgex', 'nudgey', 'dpi',
+  'backenabled', 'backsource', 'backcodetype', 'backtext', 'backlayout',
+  'backorder',
+]
+
+const LONG = Object.fromEntries(Object.entries(SHORT).map(([k, v]) => [v, k]))
+
+/**
+ * Build the fragment for a state object. Returns '' when there is nothing to
+ * share, so a caller can disable its button rather than emit a bare '#'.
+ */
+export function buildFragment (state, defaults = {}) {
+  const params = new URLSearchParams()
+
+  for (const [key, name] of Object.entries(SHORT)) {
+    const value = state[name]
+    if (value === undefined || value === null || value === '') continue
+    // Copies of 1 is what everybody has; it does not need saying.
+    if (name === 'copies' && Number(value) === 1) continue
+    params.set(key, String(value))
+  }
+
+  // Only the layout values that DIFFER from this browser's current settings.
+  // Sending all twenty would make a link four times longer for no gain, and the
+  // recipient's own saved settings are a reasonable starting point.
+  for (const name of PASSTHROUGH) {
+    const value = state[name]
+    if (value === undefined || value === null || value === '') continue
+    if (defaults[name] !== undefined && String(defaults[name]) === String(value)) continue
+    params.set(name, String(value))
+  }
+
+  const encoded = params.toString()
+  return encoded ? '#' + encoded : ''
+}
+
+/**
+ * Read a fragment back into a partial state object.
+ *
+ * Unknown keys are ignored rather than refused: a link made by a newer version
+ * must still open here, minus whatever this version does not understand.
+ */
+export function readFragment (hash) {
+  const raw = String(hash || '').replace(/^#/, '')
+  if (!raw) return {}
+
+  const params = new URLSearchParams(raw)
+  const state = {}
+
+  for (const [key, value] of params.entries()) {
+    const name = SHORT[key] || (PASSTHROUGH.includes(key) ? key : null)
+    if (!name) continue
+    state[name] = value
+  }
+  return state
+}
+
+/**
+ * Coerce a fragment value to the type the ref already holds.
+ *
+ * Everything arrives as a string. Assigning '203' to a numeric input renders,
+ * but the moment it is used in arithmetic it concatenates - so a nudge of 0
+ * plus '2' becomes '02'. Match the current value's type instead.
+ */
+export function coerce (value, current) {
+  if (typeof current === 'number') {
+    const number = Number(value)
+    return Number.isFinite(number) ? number : current
+  }
+  if (typeof current === 'boolean') {
+    return value === 'true' || value === '1'
+  }
+  return value
+}