Add Follower Directory/Study hero links, fix country-map centroid gaps, and sync accumulated dashboard work

- Hero banner now shows Follower Directory / Follower Study links on the
  Followers tab only (not the sidebar), opening the standalone reports served
  from assets/.
- Followers by Country: _COUNTRY_CENTROIDS expanded from 14 hardcoded entries
  to a near-complete world table, so a country missing from the old dict no
  longer vanishes from the map silently; added a console warning for any
  country still missing a centroid, and a "N countries represented" caption
  computed from the same rollup the map uses so the two can never disagree.
- Added visitor_history.py: append-only observation log for the Visitors
  export's category breakdowns (Location/Seniority/Company size), since
  LinkedIn only shows a category if it clears a per-export minimum-visits
  threshold and otherwise silently drops it.
- Synced other accumulated app.py/build_static_export.py work not yet
  committed: calendar month drill-down tiles, follower-breakdown expand
  toggle, CTR explainer, manual post title overrides, and matching static-
  export precompute/JS for the calendar and content tabs.
- .gitignore: exclude the newer generated snapshot outputs (follower study/
  directory HTML copies, PDF report, visitor_category_history.json) using
  the same rationale as the existing growth_history.json/snapshot rules —
  regenerable from code + data, not itself code.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

.gitignore

@@ -2,9 +2,14 @@
 *.xls
 *.xlsx
 growth_history.json
+visitor_category_history.json
 
 # Generated output — regenerate locally with build_static_export.py, not shared code
 TXproducts_Dashboard_Snapshot.html
+TXproducts_Follower_Study_*.html
+LinkedIn_Dashboard_Daily_Report_*.pdf
+assets/follower_directory.html
+assets/follower_study.html
 
 # Python
 __pycache__/

build_static_export.py

@@ -6,7 +6,7 @@ component trees (dbc.Card/Row/Col are just Bootstrap-class wrappers) into plain
 so the same Bootstrap CSS renders them identically. Charts render via Plotly.js from
 embedded JSON. A handful of interactive elements (calendar month click, breakdown
 dropdowns, content month filter) have every possible state precomputed and swapped
-client-side with vanilla JS — everything else is a static snapshot of today's data.
+client-side with vanilla JS, everything else is a static snapshot of today's data.
 """
 import base64
 import html as html_escape_mod
@@ -60,11 +60,11 @@ def style_dict_to_css(style):
 
 def conditional_row_bg(conditional, row, idx):
     """Replays a DataTable's style_data_conditional row_index/filter_query rules for one
-    row — later rules override earlier ones on a match, same as Dash's own precedence — so
+    row, later rules override earlier ones on a match, same as Dash's own precedence, so
     the best-engagement/best-CTR highlight still shows up here, not just in the live app.
     Only supports the simple "{Col} = value" equality form filter_query uses in this
     codebase, not the full Dash query mini-language. Caller applies the result per-<td>,
-    not on the <tr> — Bootstrap 5 paints table backgrounds via a CSS variable applied
+    not on the <tr>, Bootstrap 5 paints table backgrounds via a CSS variable applied
     directly to each cell, which sits on top of and hides a tr-level background-color."""
     bg = None
     for rule in conditional:
@@ -134,13 +134,22 @@ def render(comp):
         if cid == "report-timeframe-select":
             return (f'<select id="{esc(cid)}" class="form-select compact-dropdown {esc(extra_class)}" '
                     f'style="{style};opacity:0.5;cursor:not-allowed" disabled '
-                    f'title="PDF generation needs the live tool — not available in this snapshot.">{opts}</select>')
+                    f'title="PDF generation needs the live tool, not available in this snapshot.">{opts}</select>')
         return f'<select id="{esc(cid)}" class="form-select compact-dropdown {esc(extra_class)}" style="{style}" onchange="window.__onSelect && window.__onSelect(this)">{opts}</select>'
 
     # --- Stores/Download: no static equivalent needed (Download requires a live backend) ---
     if isinstance(comp, (dcc.Store, dcc.Download)):
         return ""
 
+    # --- Upload: disabled in the snapshot, saving files needs a live Python backend ---
+    if isinstance(comp, dcc.Upload):
+        style = style_dict_to_css({**{k: v for k, v in (getattr(comp, "style", None) or {}).items()},
+                                    "opacity": "0.5", "cursor": "not-allowed"})
+        cid = getattr(comp, "id", "") or next_chart_id()
+        return (f'<div id="{esc(cid)}" style="{style}" '
+                f'title="Uploading new data needs the live tool (requires a Python backend), not available in this snapshot.">'
+                f'{render(getattr(comp, "children", None))}</div>')
+
     # --- DataTable: render a plain HTML table from data/columns ---
     if isinstance(comp, dash_table.DataTable):
         cols = comp.columns
@@ -231,16 +240,19 @@ def render(comp):
                 disabled_style = style_dict_to_css({**{k: v for k, v in (getattr(comp, "style", None) or {}).items()},
                                                      "opacity": "0.5", "cursor": "not-allowed"})
                 return (f'<button type="button"{id_attr}{class_attr} style="{disabled_style}" disabled '
-                        f'title="PDF generation needs the live tool (requires a Python backend) — not available in this snapshot.">'
+                        f'title="PDF generation needs the live tool (requires a Python backend), not available in this snapshot.">'
                         f'{children_html}</button>')
             onclick = f' onclick="window.__onClick && window.__onClick(this)"'
             return f'<button type="button"{id_attr}{class_attr} style="{style}"{onclick}{title_attr}>{children_html}</button>'
         if cid.startswith("info-"):
             onclick = f' onclick="window.__onClick && window.__onClick(this)"'
             return f'<{tag}{id_attr}{class_attr} style="{style}"{title_attr}{onclick}>{children_html}</{tag}>'
+        if cid == "growth-indicator-btn":
+            onclick = f' onclick="switchTab(\'growth\')"'
+            return f'<{tag}{id_attr}{class_attr} style="{style}"{title_attr}{onclick}>{children_html}</{tag}>'
         return f'<{tag}{id_attr}{class_attr} style="{style}"{title_attr}>{children_html}</{tag}>'
 
-    # Unknown component type — best-effort render children
+    # Unknown component type, best-effort render children
     return render(getattr(comp, "children", None))
 
 
@@ -250,7 +262,7 @@ def fig_json(fig):
 
 def precompute_calendar_states():
     """Every month's tile-row + daily graph (+ Overview's 4 metric charts), for both
-    calendar instances — this is what the month-box click swaps between."""
+    calendar instances, this is what the month-box click swaps between."""
     states = {}
     year = int(A.D["fts"]["Date"].dt.year.max())
     for prefix in ("overview", "followers"):
@@ -275,33 +287,109 @@ def precompute_calendar_states():
 
 
 def precompute_fb_states():
-    """Followers-By dropdown x Show-all-toggle states."""
+    """Followers-By dropdown x Show-all-toggle x calendar-month states — mirrors the live
+    app's _render_followers_breakdown callback, which re-renders on fb-select, fb-expanded,
+    AND the selected calendar month (so June shows June's actual demographic snapshot, not
+    always the latest one)."""
     states = {}
+    months = sorted(A.D["breakdown_history"]) + [None]  # None = no month context (fallback/current)
     for key, _label in A.FOLLOWER_BREAKDOWNS:
         for expanded in (False, True):
-            _lbl, fig, total_n = A._breakdown_figure(key, expanded)
+            for ym in months:
+                year, month = ym if ym is not None else (None, None)
+                _lbl, fig, total_n = A._breakdown_figure(key, expanded, year, month)
+                fig = A._std(fig)
+                needs_toggle = total_n > 10
+                btn_label = "Show top 10" if expanded else f"Show all {total_n}"
+                month_label = f"as of {A._MONTH_NAMES[month - 1]} {year}" if year and month else ""
+                month_key = f"{year}-{month}" if year and month else "none"
+                states[f"{key}|{str(expanded).lower()}|{month_key}"] = {
+                    "fig": fig_json(fig),
+                    "btnLabel": btn_label,
+                    "btnDisplay": "inline-block" if needs_toggle else "none",
+                    "monthLabel": month_label,
+                }
+    return states
+
+
+def precompute_fb_delta_states():
+    """Followers-By month-over-month delta states — one per breakdown key x delta-eligible
+    month, mirroring the live app's _breakdown_delta_figure branch of _render_followers_breakdown."""
+    states = {}
+    for key, _label in A.FOLLOWER_BREAKDOWNS:
+        for year, month in A._followers_delta_months():
+            _lbl, fig, changed_n, overflow = A._breakdown_delta_figure(key, year, month)
             fig = A._std(fig)
-            needs_toggle = total_n > 10
-            btn_label = "Show top 10" if expanded else f"Show all {total_n}"
-            states[f"{key}|{str(expanded).lower()}"] = {
+            month_label = f"{A._MONTH_NAMES[month - 1]} {year}: {changed_n} categories gained or lost followers vs the prior month"
+            if overflow > 0:
+                month_label += f" · showing top {A._DELTA_MONTH_CAP}, +{overflow} more with smaller changes"
+            states[f"{key}|{year}-{month}"] = {
                 "fig": fig_json(fig),
-                "btnLabel": btn_label,
-                "btnDisplay": "inline-block" if needs_toggle else "none",
+                "monthLabel": month_label,
             }
     return states
 
 
-def precompute_vb_states():
-    """Visitors-By dropdown states."""
+def precompute_fb_count_only_states():
+    """Months with real follower-count activity but no category snapshot to attribute it to
+    (currently just June 2026) — mirrors the live app's count-only branch of
+    _render_followers_breakdown, which shows a plain explanation instead of a bar chart."""
     states = {}
+    for year, month in A._followers_count_only_months():
+        net, sign, detail = A._monthly_count_summary(year, month)
+        month_label = f"{A._MONTH_NAMES[month - 1]} {year} — no category breakdown available"
+        note_html = (
+            f'<div style="padding:20px 4px;">'
+            f'<div style="margin-bottom:8px;font-weight:700;color:#1a2533;">'
+            f'Net {esc(sign)}{net} follower{"s" if abs(net) != 1 else ""} in '
+            f'{A._MONTH_NAMES[month - 1]} {year}: {esc(detail)}.</div>'
+            f'<div style="color:#6b7a8d;font-size:0.8rem;">'
+            f'Category breakdown (location, industry, etc.) isn\'t available for these &mdash; '
+            f'LinkedIn\'s demographic export wasn\'t captured yet at this point, so there\'s no '
+            f'earlier snapshot to know which category they belong to.</div>'
+            f'</div>'
+        )
+        states[f"{year}-{month}"] = {"noteHtml": note_html, "monthLabel": month_label}
+    return states
+
+
+def precompute_vb_states():
+    """Visitors-By dropdown x Show-all-toggle x period states — mirrors precompute_fb_states.
+    'total' means the running total (no month scope); other keys are 'YYYY-M' month cutoffs
+    against the persistent running total (see visitor_history.py)."""
+    states = {}
+    periods = [("total", None, None)] + [
+        (f"{y}-{m}", y, m) for y, m in A._visitor_category_months()
+    ]
     for key, _label in A.VISITOR_BREAKDOWNS:
-        _lbl, fig = A._visitor_breakdown_figure(key)
-        states[key] = {"fig": fig_json(A._std(fig))}
+        for expanded in (False, True):
+            for period_key, year, month in periods:
+                _lbl, fig, total_n = A._visitor_breakdown_figure(key, expanded, year, month)
+                fig = A._std(fig)
+                needs_toggle = total_n > 10
+                btn_label = "Show top 10" if expanded else f"Show all {total_n}"
+                month_label = f"as of {A._MONTH_NAMES[month - 1]} {year}" if year and month else ""
+                states[f"{key}|{str(expanded).lower()}|{period_key}"] = {
+                    "fig": fig_json(fig),
+                    "btnLabel": btn_label,
+                    "btnDisplay": "inline-block" if needs_toggle else "none",
+                    "monthLabel": month_label,
+                }
+    return states
+
+
+def precompute_frr_states():
+    """Follow Rate Relative to Reach month-dropdown states."""
+    states = {}
+    for opt in A._frr_month_options(A.D["frr"]):
+        year, month = (int(p) for p in opt["value"].split("-"))
+        fig = A._std(A.follow_rate_figure(A.D["frr"], year, month))
+        states[opt["value"]] = {"fig": fig_json(fig)}
     return states
 
 
 def precompute_content_states():
-    """Content tab's month-filter dropdown states — 6 charts + the posts table."""
+    """Content tab's month-filter dropdown states, 6 charts + the posts table."""
     states = {}
     for opt in A._content_month_options():
         value = opt["value"]
@@ -337,16 +425,26 @@ def precompute_content_states():
 JS_TEMPLATE = r"""
 const CHARTS = %(charts)s;
 const TAB_HERO = %(tab_hero)s;
+const TAB_HERO_INFO = %(tab_hero_info)s;
 const CAL_STATES = %(cal_states)s;
 const CAL_YEAR = %(cal_year)s;
 const CAL_DEFAULT_MONTH = %(cal_default_month)s;
 const FB_STATES = %(fb_states)s;
+const FB_DELTA_STATES = %(fb_delta_states)s;
+const FB_COUNT_ONLY_STATES = %(fb_count_only_states)s;
 const VB_STATES = %(vb_states)s;
 const CONTENT_STATES = %(content_states)s;
+const FRR_STATES = %(frr_states)s;
+
+const DELTA_LEGEND_HTML = '<div style="margin-top:10px;display:flex;flex-wrap:wrap;align-items:center;">'
+  + '<span style="margin-right:16px;white-space:nowrap;"><span style="width:12px;height:12px;background-color:#52C41A;display:inline-block;margin-right:5px;vertical-align:middle;border-radius:2px;"></span><span style="font-size:0.72rem;color:#6b7a8d;">Gained</span></span>'
+  + '<span style="margin-right:16px;white-space:nowrap;"><span style="width:12px;height:12px;background-color:#d43f3a;display:inline-block;margin-right:5px;vertical-align:middle;border-radius:2px;"></span><span style="font-size:0.72rem;color:#6b7a8d;">Lost</span></span>'
+  + '</div>';
 
 const calMonth = {overview: CAL_DEFAULT_MONTH, followers: CAL_DEFAULT_MONTH};
-let fbActive = 'company_size', fbExpanded = false;
-let vbActive = 'seniority';
+let fbActive = 'company_size', fbExpanded = false, fbPeriod = 'total';
+let vbActive = 'seniority', vbExpanded = false, vbPeriod = 'total';
+let frrPeriod = %(frr_default_period)s;
 
 function renderChart(divId, figSpec) {
   if (!figSpec || !document.getElementById(divId)) return;
@@ -378,7 +476,10 @@ function switchTab(key) {
   var hero = TAB_HERO[key];
   if (hero) {
     document.getElementById('hero-title').textContent = hero[0];
-    document.getElementById('hero-subtitle').textContent = hero[1];
+    var subEl = document.getElementById('hero-subtitle');
+    subEl.textContent = hero[1];
+    var infoHtml = TAB_HERO_INFO[key];
+    if (infoHtml) subEl.insertAdjacentHTML('beforeend', infoHtml);
   }
   window.dispatchEvent(new Event('resize'));
 }
@@ -397,12 +498,41 @@ function selectCalendarMonth(prefix, month) {
   if (state.metrics) {
     Object.keys(state.metrics).forEach(function (divId) { renderChart(divId, state.metrics[divId]); });
   }
+  if (prefix === 'followers') renderFollowersBreakdown();
 }
 
 function renderFollowersBreakdown() {
-  var s = FB_STATES[fbActive + '|' + fbExpanded];
+  if (fbPeriod !== 'total') {
+    var cs = FB_COUNT_ONLY_STATES[fbPeriod];
+    if (cs) {
+      var area = document.getElementById('followers-breakdown-area');
+      if (area) area.innerHTML = cs.noteHtml;
+      var clabel = document.getElementById('fb-month-label');
+      if (clabel) clabel.textContent = cs.monthLabel;
+      var cbtn = document.getElementById('fb-expand-btn');
+      if (cbtn) cbtn.style.display = 'none';
+      return;
+    }
+    var ds = FB_DELTA_STATES[fbActive + '|' + fbPeriod];
+    if (!ds) return;
+    var area2 = document.getElementById('followers-breakdown-area');
+    if (area2) area2.innerHTML = '<div class="js-plotly-chart" id="fb-breakdown-chart"></div>' + DELTA_LEGEND_HTML;
+    renderChartWithin('followers-breakdown-area', ds.fig);
+    var dlabel = document.getElementById('fb-month-label');
+    if (dlabel) dlabel.textContent = ds.monthLabel;
+    var dbtn = document.getElementById('fb-expand-btn');
+    if (dbtn) dbtn.style.display = 'none';
+    return;
+  }
+  var month = calMonth.followers;
+  var monthKey = month ? (CAL_YEAR + '-' + month) : 'none';
+  var s = FB_STATES[fbActive + '|' + fbExpanded + '|' + monthKey] || FB_STATES[fbActive + '|' + fbExpanded + '|none'];
   if (!s) return;
+  var totalArea = document.getElementById('followers-breakdown-area');
+  if (totalArea) totalArea.innerHTML = '<div class="js-plotly-chart" id="fb-breakdown-chart"></div>';
   renderChartWithin('followers-breakdown-area', s.fig);
+  var label = document.getElementById('fb-month-label');
+  if (label) label.textContent = s.monthLabel;
   var btn = document.getElementById('fb-expand-btn');
   if (btn) {
     btn.textContent = s.btnLabel;
@@ -411,9 +541,28 @@ function renderFollowersBreakdown() {
 }
 
 function renderVisitorBreakdown() {
-  var s = VB_STATES[vbActive];
+  var s = VB_STATES[vbActive + '|' + vbExpanded + '|' + vbPeriod];
   if (!s) return;
+  var area = document.getElementById('visitor-breakdown-area');
+  if (area) area.innerHTML = '<div class="js-plotly-chart" id="vb-breakdown-chart"></div>';
   renderChartWithin('visitor-breakdown-area', s.fig);
+  var label = document.getElementById('vb-month-label');
+  if (label) label.textContent = s.monthLabel;
+  var btn = document.getElementById('vb-expand-btn');
+  if (btn) {
+    btn.textContent = s.btnLabel;
+    btn.style.display = s.btnDisplay;
+  }
+}
+
+function renderFollowRate() {
+  var s = FRR_STATES[frrPeriod];
+  if (!s) return;
+  var area = document.getElementById('frr-area');
+  if (area && !area.querySelector('.js-plotly-chart')) {
+    area.innerHTML = '<div class="js-plotly-chart" id="frr-chart"></div>';
+  }
+  renderChartWithin('frr-area', s.fig);
 }
 
 function renderContentState(value) {
@@ -459,11 +608,19 @@ window.__onClick = function (el) {
     renderFollowersBreakdown();
     return;
   }
+  if (id === 'vb-expand-btn') {
+    vbExpanded = !vbExpanded;
+    renderVisitorBreakdown();
+    return;
+  }
 };
 
 window.__onSelect = function (el) {
   if (el.id === 'fb-select') { fbActive = el.value; fbExpanded = false; renderFollowersBreakdown(); return; }
-  if (el.id === 'vb-select') { vbActive = el.value; renderVisitorBreakdown(); return; }
+  if (el.id === 'fb-period-select') { fbPeriod = el.value; renderFollowersBreakdown(); return; }
+  if (el.id === 'vb-select') { vbActive = el.value; vbExpanded = false; renderVisitorBreakdown(); return; }
+  if (el.id === 'vb-period-select') { vbPeriod = el.value; renderVisitorBreakdown(); return; }
+  if (el.id === 'frr-month-select') { frrPeriod = el.value; renderFollowRate(); return; }
   if (el.id === 'content-month-select') { renderContentState(el.value); return; }
 };
 
@@ -482,10 +639,20 @@ def build():
 
     sidebar_html = render(A.sidebar)
     hero_html = render(A.hero)
+    # Per-tab extra markup appended after the hero subtitle text (e.g. the Growth tab's
+    # "what does growth measure" info popover) — switchTab() re-appends this on tab change
+    # since setting textContent wipes any previously-injected popover markup.
+    tab_hero_info_html = {key: render(A.info_popover(f"hero-{key}", info))
+                           for key, info in A.TAB_HERO_INFO.items()}
 
     cal_states, cal_year, cal_default_month = precompute_calendar_states()
     fb_states = precompute_fb_states()
+    fb_delta_states = precompute_fb_delta_states()
+    fb_count_only_states = precompute_fb_count_only_states()
     vb_states = precompute_vb_states()
+    frr_states = precompute_frr_states()
+    _frr_opts = A._frr_month_options(A.D["frr"])
+    frr_default_period = _frr_opts[0]["value"] if _frr_opts else None
     content_states = precompute_content_states()
 
     with open(os.path.join(ASSETS_DIR, "custom.css")) as f:
@@ -500,11 +667,16 @@ def build():
     js = JS_TEMPLATE % {
         "charts": json.dumps(CHARTS),
         "tab_hero": json.dumps(A.TAB_HERO),
+        "tab_hero_info": json.dumps(tab_hero_info_html),
         "cal_states": json.dumps(cal_states),
         "cal_year": json.dumps(cal_year),
         "cal_default_month": json.dumps(cal_default_month),
         "fb_states": json.dumps(fb_states),
+        "fb_delta_states": json.dumps(fb_delta_states),
+        "fb_count_only_states": json.dumps(fb_count_only_states),
         "vb_states": json.dumps(vb_states),
+        "frr_states": json.dumps(frr_states),
+        "frr_default_period": json.dumps(frr_default_period),
         "content_states": json.dumps(content_states),
     }
 
@@ -512,7 +684,7 @@ def build():
 <html lang="en">
 <head>
 <meta charset="utf-8"/>
-<title>TXproducts LinkedIn Analytics — Snapshot ({A.D['last_updated'].strftime('%b %d, %Y')})</title>
+<title>TXproducts LinkedIn Analytics, Snapshot ({A.D['last_updated'].strftime('%b %d, %Y')})</title>
 <meta name="viewport" content="width=device-width, initial-scale=1"/>
 <link href="https://cdn.jsdelivr.net/npm/bootstrap@5.3.0/dist/css/bootstrap.min.css" rel="stylesheet">
 <script src="https://cdn.plot.ly/plotly-2.35.2.min.js"></script>
@@ -538,7 +710,7 @@ details[open] > .static-accordion-title:before {{ content:'\\25BE  '; }}
 </style>
 </head>
 <body>
-<div class="snapshot-banner">Static snapshot as of {A.D['last_updated'].strftime('%B %d, %Y')} — dropdowns, month clicks,
+<div class="snapshot-banner">Static snapshot as of {A.D['last_updated'].strftime('%B %d, %Y')}, dropdowns, month clicks,
  and breakdown selectors work, but this file does not update with new data. Open the live tool for current numbers.</div>
 <div class="app-shell">
 {sidebar_html}

visitor_history.py

@@ -0,0 +1,98 @@
+"""Persists every weekly Visitors export's category breakdown (Location/Seniority/Company
+size) as an append-only observation log, so a location that drops out of one week's export
+(LinkedIn only shows a category if it clears a minimum-visits threshold that week) isn't lost
+just because a later export didn't happen to include it.
+
+Each observation is one (file date, category type, category value, count) reading. Nothing
+is ever overwritten — a category's running total "as of" any given month is the sum of every
+observation for it up to that date. This is a running additive tally, not a deduplicated
+unique-visitor count: LinkedIn's per-export numbers are a rolling window (not a fresh daily
+count), so consecutive weekly exports likely overlap in which underlying visits they're
+counting. Treat the totals here as a cumulative activity signal, not a precise headcount.
+
+Zero import-time dependency on app.py, same reason growth.py has none: app.py runs as
+"__main__", so `import app` here would re-execute it as a second module copy still mid-import
+when these functions get called.
+"""
+import json
+import os
+
+import pandas as pd
+
+_SHEET_TYPES = {
+    "location": "Location",
+    "seniority": "Seniority",
+    "company_size": "Company size",
+}
+
+
+def _history_path(upload_dir):
+    return os.path.join(upload_dir, "visitor_category_history.json")
+
+
+def load_history(upload_dir):
+    path = _history_path(upload_dir)
+    if not os.path.exists(path):
+        return []
+    with open(path) as f:
+        return json.load(f)
+
+
+def _save_history(upload_dir, history):
+    with open(_history_path(upload_dir), "w") as f:
+        json.dump(history, f, indent=2)
+
+
+def backfill_history(upload_dir, visitor_files):
+    """Scans every visitor export file and appends any observation not already recorded
+    (keyed by exact file date + category type + category value, so re-running this on
+    every app refresh never double-counts the same file twice)."""
+    history = load_history(upload_dir)
+    seen_keys = {(h["file_date"], h["type"], h["category"]) for h in history}
+    added = 0
+
+    for fp in visitor_files:
+        file_date = pd.Timestamp(os.path.getmtime(fp), unit="s").strftime("%Y-%m-%d")
+        for type_key, sheet_name in _SHEET_TYPES.items():
+            try:
+                df = pd.read_excel(fp, sheet_name=sheet_name)
+            except ValueError:
+                continue  # sheet missing from this particular export, skip it
+            col = df.columns[0]
+            for _, row in df.iterrows():
+                category = str(row[col])
+                key = (file_date, type_key, category)
+                if key in seen_keys:
+                    continue
+                history.append({
+                    "file_date": file_date,
+                    "type": type_key,
+                    "category": category,
+                    "count": int(row["Total views"]),
+                })
+                seen_keys.add(key)
+                added += 1
+
+    if added:
+        _save_history(upload_dir, history)
+    return history
+
+
+def rollup_as_of(history, type_key, on_or_before=None):
+    """Running additive total per category for one breakdown type, summed across every
+    observation on or before `on_or_before` (a 'YYYY-MM-DD' string or None for everything)."""
+    rows = [h for h in history if h["type"] == type_key]
+    if on_or_before is not None:
+        rows = [h for h in rows if h["file_date"] <= on_or_before]
+    if not rows:
+        return pd.DataFrame(columns=["Category", "Total views"])
+    df = pd.DataFrame(rows)
+    out = df.groupby("category", as_index=False)["count"].sum()
+    out.columns = ["Category", "Total views"]
+    return out.sort_values("Total views", ascending=False).reset_index(drop=True)
+
+
+def available_months(history):
+    """Every (year, month) with at least one observation, sorted oldest first."""
+    months = {tuple(int(p) for p in h["file_date"].split("-")[:2]) for h in history}
+    return sorted(months)