V.1

app/lib/view-state.ts

@@ -0,0 +1,77 @@
+import type { SortKey } from './dump-store'
+
+/**
+ * Everything about "what am I looking at" that is worth putting in a link.
+ *
+ * Types are carried as names rather than as the numeric ids the store uses.
+ * Ids are assigned in first-seen order, so they are stable for a given dump —
+ * but only for that dump, and a link that silently means something else
+ * against a different dump is worse than one that drops a filter it cannot
+ * resolve.
+ */
+export interface ViewState {
+  prefix: string
+  name: string
+  path: string
+  sort: SortKey
+  desc: boolean
+  types: string[]
+}
+
+export const emptyView = (): ViewState => ({
+  prefix: '',
+  name: '',
+  path: '',
+  sort: 'natural',
+  desc: false,
+  types: [],
+})
+
+const SORTS: SortKey[] = ['natural', 'path', 'address', 'offset', 'name', 'type']
+
+export function sameView(a: ViewState, b: ViewState): boolean {
+  return (
+    a.prefix === b.prefix &&
+    a.name === b.name &&
+    a.path === b.path &&
+    a.sort === b.sort &&
+    a.desc === b.desc &&
+    a.types.length === b.types.length &&
+    a.types.every((t, i) => t === b.types[i])
+  )
+}
+
+/**
+ * Only non-default fields are written, so the common case — a dump open with
+ * no filters — is a URL you can read aloud.
+ */
+export function encodeView(dump: string, v: ViewState): string {
+  const q = new URLSearchParams()
+  if (dump) q.set('d', dump)
+  if (v.prefix) q.set('p', v.prefix)
+  if (v.name) q.set('n', v.name)
+  if (v.path) q.set('q', v.path)
+  if (v.sort !== 'natural') q.set('s', v.sort)
+  if (v.desc) q.set('o', 'desc')
+  if (v.types.length) q.set('t', v.types.join(','))
+  const s = q.toString()
+  return s ? '?' + s : location.pathname
+}
+
+export function decodeView(search: string): { dump: string; view: ViewState } {
+  const q = new URLSearchParams(search)
+  const sort = q.get('s') as SortKey | null
+  return {
+    dump: q.get('d') ?? '',
+    view: {
+      prefix: q.get('p') ?? '',
+      name: q.get('n') ?? '',
+      path: q.get('q') ?? '',
+      sort: sort && SORTS.includes(sort) ? sort : 'natural',
+      desc: q.get('o') === 'desc',
+      // Sorted on the way in as well as out: `sameView` compares positionally,
+      // and a hand-edited URL should not read as a different view.
+      types: (q.get('t') ?? '').split(',').filter(Boolean).sort(),
+    },
+  }
+}