hash_util: Extract hash_parser.ts.

This allows these functions to be used by modules that need this code
and cannot import people.ts without creating import cycles.

web/src/hash_parser.ts

@@ -0,0 +1,111 @@
+export function get_hash_category(hash?: string): string {
+    // given "#streams/subscribed", returns "streams"
+    return hash ? hash.replace(/^#/, "").split(/\//)[0] : "";
+}
+
+export function get_hash_section(hash?: string): string {
+    // given "#settings/profile", returns "profile"
+    // given '#streams/5/social", returns "5"
+    if (!hash) {
+        return "";
+    }
+
+    const parts = hash.replace(/\/$/, "").split(/\//);
+
+    return parts[1] || "";
+}
+
+export function get_current_hash_category(): string {
+    return get_hash_category(window.location.hash);
+}
+
+export function get_current_hash_section(): string {
+    return get_hash_section(window.location.hash);
+}
+
+export function is_overlay_hash(hash: string): boolean {
+    // Hash changes within this list are overlays and should not unnarrow (etc.)
+    const overlay_list = [
+        "streams",
+        "drafts",
+        "groups",
+        "settings",
+        "organization",
+        "invite",
+        "keyboard-shortcuts",
+        "message-formatting",
+        "search-operators",
+        "about-zulip",
+        "scheduled",
+    ];
+    const main_hash = get_hash_category(hash);
+
+    return overlay_list.includes(main_hash);
+}
+
+// this finds the stream that is actively open in the settings and focused in
+// the left side.
+export function is_editing_stream(desired_stream_id: number): boolean {
+    const hash_components = window.location.hash.slice(1).split(/\//);
+
+    if (hash_components[0] !== "streams") {
+        return false;
+    }
+
+    if (!hash_components[2]) {
+        return false;
+    }
+
+    // if the string casted to a number is valid, and another component
+    // after exists then it's a stream name/id pair.
+    const stream_id = Number.parseFloat(hash_components[1]);
+
+    return stream_id === desired_stream_id;
+}
+
+export function is_create_new_stream_narrow(): boolean {
+    return window.location.hash === "#streams/new";
+}
+
+export const allowed_web_public_narrows = [
+    "streams",
+    "stream",
+    "topic",
+    "sender",
+    "has",
+    "search",
+    "near",
+    "id",
+];
+
+export function is_spectator_compatible(hash: string): boolean {
+    // Defines which views are supported for spectators.
+    // This implementation should agree with the similar function in zerver/lib/narrow.py.
+    const web_public_allowed_hashes = [
+        "",
+        // full #narrow hash handled in filter.is_spectator_compatible
+        "narrow",
+        // TODO/compatibility: #recent_topics was renamed to #recent
+        // in 2022. We should support the old URL fragment at least
+        // until one cannot directly upgrade from Zulip 5.x.
+        "recent_topics",
+        "recent",
+        "keyboard-shortcuts",
+        "message-formatting",
+        "search-operators",
+        "all_messages",
+        "about-zulip",
+    ];
+
+    const main_hash = get_hash_category(hash);
+
+    if (main_hash === "narrow") {
+        const hash_section = get_hash_section(hash);
+        if (!allowed_web_public_narrows.includes(hash_section)) {
+            return false;
+        }
+        return true;
+    }
+
+    return web_public_allowed_hashes.includes(main_hash);
+}