Add session persistence and watchlist exit button

Persists watchlist and active ticker across browser refreshes via a
localStorage bridge (components/persistence.py), and adds a sidebar
"← Watchlist" button to clear the active ticker and return to the
QuoteTable landing page.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

1 files changed, 54 insertions, 0 deletions

diff --git a/components/persistence.py b/components/persistence.py
new file mode 100644
index 0000000..1dafdbe
--- /dev/null
+++ b/components/persistence.py
@@ -0,0 +1,54 @@
+import json
+import streamlit as st
+import streamlit.components.v1 as components
+from utils.security import escape_html
+
+
+def render_persistence_bridge() -> None:
+    """Sync watchlist + ticker to/from localStorage."""
+    restored_wl = st.session_state.get("_persist_wl", "")
+    restored_tk = st.session_state.get("_persist_tk", "")
+    if restored_wl and not st.session_state.get("_persist_loaded"):
+        try:
+            st.session_state["watchlist"] = json.loads(restored_wl)
+        except Exception:
+            pass
+        if restored_tk:
+            st.session_state["ticker"] = restored_tk
+        st.session_state["_persist_loaded"] = True
+        st.rerun()
+
+    st.text_input("persist_wl", key="_persist_wl", label_visibility="collapsed")
+    st.text_input("persist_tk", key="_persist_tk", label_visibility="collapsed")
+
+    wl_json = escape_html(json.dumps(st.session_state.get("watchlist", [])))
+    tk_val  = escape_html(st.session_state.get("ticker") or "")
+
+    html = (
+        "<div id='d' data-wl='" + wl_json + "' data-tk='" + tk_val + "'></div>"
+        "<script>"
+        "(function() {"
+        "  var d = document.getElementById('d');"
+        "  localStorage.setItem('prism_watchlist', d.dataset.wl);"
+        "  if (d.dataset.tk) localStorage.setItem('prism_ticker', d.dataset.tk);"
+        "  else localStorage.removeItem('prism_ticker');"
+        "  var stored_wl = localStorage.getItem('prism_watchlist');"
+        "  var stored_tk = localStorage.getItem('prism_ticker') || '';"
+        "  if (!stored_wl) return;"
+        "  function setInput(label, val) {"
+        "    var inputs = window.parent.document.querySelectorAll('input[type=text]');"
+        "    for (var i = 0; i < inputs.length; i++) {"
+        "      if (inputs[i].getAttribute('aria-label') === label) {"
+        "        var setter = Object.getOwnPropertyDescriptor(window.parent.HTMLInputElement.prototype, 'value').set;"
+        "        setter.call(inputs[i], val);"
+        "        inputs[i].dispatchEvent(new window.parent.Event('input', { bubbles: true }));"
+        "        return;"
+        "      }"
+        "    }"
+        "  }"
+        "  setInput('persist_wl', stored_wl);"
+        "  if (stored_tk) setInput('persist_tk', stored_tk);"
+        "})();"
+        "</script>"
+    )
+    components.html(html, height=0, scrolling=False)