feat(perf): boucles par dépôt parallélisées et cache stale-while-revalidate (chantier A)

- _parallel_map : asyncio.gather borné (16) pour dashboard,
  /health, /forecast, /triage et le mur — le patron de /focus,
  généralisé. Avant : la page attendait la somme des allers-
  retours Gitea de tous les dépôts, en séquentiel.
- Client Gitea : les listes (dépôts, issues, jalons, étoiles)
  passent en stale-while-revalidate — une entrée périmée est
  servie immédiatement et rafraîchie en tâche de fond. Les
  mutations vident le cache et bumpent une génération qui
  désarme les rafraîchissements en vol.
- /forecast calcule des lignes de jalons tous projets (écart
  ETA/échéance) ; /health trie par sévérité et expose la
  pastille ; le détail santé reçoit la liste des projets.

app/gitea_client.py

@@ -17,8 +17,10 @@ Changes from the 0.1.0 client:
 - .env loading targets the project root only (no hardcoded home path).
 """
 
+import asyncio
 import logging
 import time
+from collections.abc import Awaitable, Callable
 from pathlib import Path
 from typing import Any
 
@@ -60,6 +62,8 @@ class GiteaClient:
         )
         self._user: dict | None = None
         self._cache: dict[str, tuple[float, Any]] = {}
+        self._refreshing: set[str] = set()
+        self._cache_gen = 0
 
     async def aclose(self) -> None:
         await self.client.aclose()
@@ -105,24 +109,62 @@ class GiteaClient:
             page += 1
         return items
 
-    def _cache_get(self, key: str) -> Any | None:
-        if self.cache_ttl <= 0:
-            return None
-        hit = self._cache.get(key)
-        if hit and (time.monotonic() - hit[0]) < self.cache_ttl:
-            return hit[1]
-        return None
-
     def _cache_put(self, key: str, value: Any) -> None:
         if self.cache_ttl > 0:
             self._cache[key] = (time.monotonic(), value)
 
     def _cache_clear(self) -> None:
         self._cache.clear()
+        # Invalidate in-flight background refreshes: a refresh that
+        # started before a mutation must not resurrect stale data.
+        self._cache_gen += 1
+
+    async def _cached_list(
+        self, key: str, fetcher: Callable[[], Awaitable[Any]]
+    ) -> Any:
+        """Stale-while-revalidate cache for list endpoints (0.19.0).
+
+        Fresh (< TTL): serve the cache. Stale: serve the cached
+        value IMMEDIATELY and refresh it in the background (once
+        per key) — the user never waits on Gitea for a page when
+        any earlier answer exists. Absent: fetch and wait.
+        Mutations clear the cache (see _cache_clear), so writes are
+        never hidden by a stale entry.
+        """
+        if self.cache_ttl <= 0:
+            return await fetcher()
+        hit = self._cache.get(key)
+        if hit is not None:
+            if (time.monotonic() - hit[0]) < self.cache_ttl:
+                return hit[1]
+            if key not in self._refreshing:
+                self._refreshing.add(key)
+                asyncio.create_task(
+                    self._refresh_entry(key, fetcher, self._cache_gen)
+                )
+            return hit[1]
+        value = await fetcher()
+        self._cache_put(key, value)
+        return value
+
+    async def _refresh_entry(
+        self,
+        key: str,
+        fetcher: Callable[[], Awaitable[Any]],
+        generation: int,
+    ) -> None:
+        try:
+            value = await fetcher()
+            if generation == self._cache_gen:
+                self._cache_put(key, value)
+        except Exception as exc:
+            logger.debug("background refresh failed for %s: %s", key, exc)
+        finally:
+            self._refreshing.discard(key)
 
     def invalidate_cache(self) -> None:
         """Drop every cached list response (called on webhook events)."""
-        self._cache.clear()
+        self._cache_clear()
 
     # ── API ────────────────────────────────────────────────
 
@@ -141,20 +183,21 @@ class GiteaClient:
         return self._user
 
     async def search_repos(self) -> list[dict]:
-        """All repos visible to the token owner (paginated, cached)."""
-        cached = self._cache_get("search_repos")
-        if cached is not None:
-            return cached
-        params: dict[str, Any] = {}
-        try:
-            user = await self.get_user()
-            if user and user.get("id"):
-                params["uid"] = user["id"]
-        except Exception as exc:  # no/invalid token → public search
-            logger.debug("get_user failed, falling back to public search: %s", exc)
-        repos = await self._get_all_pages("/repos/search", **params)
-        self._cache_put("search_repos", repos)
-        return repos
+        """All repos visible to the token owner (paginated, SWR-cached)."""
+
+        async def _fetch() -> list[dict]:
+            params: dict[str, Any] = {}
+            try:
+                user = await self.get_user()
+                if user and user.get("id"):
+                    params["uid"] = user["id"]
+            except Exception as exc:  # no/invalid token → public search
+                logger.debug(
+                    "get_user failed, falling back to public search: %s", exc
+                )
+            return await self._get_all_pages("/repos/search", **params)
+
+        return await self._cached_list("search_repos", _fetch)
 
     async def get_repo(self, owner: str, repo: str) -> dict:
         return await self._get(f"/repos/{owner}/{repo}")
@@ -178,14 +221,12 @@ class GiteaClient:
         (see app.main._is_issue).
         """
         key = f"issues:{owner}/{repo}:{state}"
-        cached = self._cache_get(key)
-        if cached is not None:
-            return cached
-        issues = await self._get_all_pages(
-            f"/repos/{owner}/{repo}/issues", state=state
+        return await self._cached_list(
+            key,
+            lambda: self._get_all_pages(
+                f"/repos/{owner}/{repo}/issues", state=state
+            ),
         )
-        self._cache_put(key, issues)
-        return issues
 
     async def get_all_issues(
         self, repos: list[dict], state: str = "open"
@@ -308,25 +349,19 @@ class GiteaClient:
         self, owner: str, repo: str, state: str = "open"
     ) -> list[dict]:
         key = f"milestones:{owner}/{repo}:{state}"
-        cached = self._cache_get(key)
-        if cached is not None:
-            return cached
-        milestones = await self._get_all_pages(
-            f"/repos/{owner}/{repo}/milestones", state=state
+        return await self._cached_list(
+            key,
+            lambda: self._get_all_pages(
+                f"/repos/{owner}/{repo}/milestones", state=state
+            ),
         )
-        self._cache_put(key, milestones)
-        return milestones
 
     async def list_starred(self) -> list[dict]:
         """Repos starred by the token user (issue #20: pinning rides
         on Gitea stars — the forge stays the source of truth)."""
-        key = "user:starred"
-        cached = self._cache_get(key)
-        if cached is not None:
-            return cached
-        repos = await self._get_all_pages("/user/starred")
-        self._cache_put(key, repos)
-        return repos
+        return await self._cached_list(
+            "user:starred", lambda: self._get_all_pages("/user/starred")
+        )
 
     async def set_starred(self, owner: str, repo: str, starred: bool) -> None:
         """Star / unstar a repo for the token user."""

app/main.py

@@ -378,6 +378,27 @@ def _parse_datetime(value: str | None) -> datetime | None:
         return None
 
 
+async def _parallel_map(items, fn, limit: int = 16) -> list:
+    """Run an async fn over items with bounded concurrency (0.19.0).
+
+    Cross-project pages used to await each repo in sequence, so the
+    page took the SUM of every Gitea round trip. Gathering with a
+    per-call semaphore (created here, bound to the current loop)
+    cuts that to roughly the slowest single repo, without letting
+    a big instance stampede Gitea. Exceptions come back in place —
+    callers decide what a failed repo means for them.
+    """
+    semaphore = asyncio.Semaphore(limit)
+
+    async def _run(item):
+        async with semaphore:
+            return await fn(item)
+
+    return await asyncio.gather(
+        *(_run(item) for item in items), return_exceptions=True
+    )
+
+
 def classify_repos(
     repos: list[dict], now: datetime | None = None
 ) -> tuple[list[dict], list[dict], list[dict]]:
@@ -585,7 +606,7 @@ async def dashboard(request: Request):
     except Exception as exc:  # stars are decoration, never fatal (#20)
         logger.debug("starred list failed: %s", exc)
         starred_names = set()
-    for repo_info in active:
+    async def _enrich_active(repo_info: dict) -> None:
         full_name = repo_info["full_name"]
         owner, _, repo = full_name.partition("/")
         repo_info["forecast_label"] = _repo_forecast_label(
@@ -599,6 +620,8 @@ async def dashboard(request: Request):
             logger.debug("health dot failed for %s: %s", full_name, exc)
             repo_info["health_dot"] = None
         repo_info["starred"] = full_name in starred_names
+
+    await _parallel_map(active, _enrich_active)
     for repo_info in inactive:
         repo_info["starred"] = repo_info["full_name"] in starred_names
     activity_by_repo = get_project_activity()
@@ -1013,19 +1036,18 @@ async def triage_picker(request: Request):
     """Triage mode (issue #11): pick a project by its backlog size."""
     repos = await gitea.search_repos()
     active, _inactive, _archived = classify_repos(repos)
-    projects = []
-    for repo_info in active:
+
+    async def _one_triage(repo_info: dict) -> dict | None:
         owner, _, name = repo_info["full_name"].partition("/")
-        try:
-            all_items = await gitea.get_repo_issues(owner, name, state="all")
-        except Exception:
-            continue
+        all_items = await gitea.get_repo_issues(owner, name, state="all")
         columns, _display, _state = _board_columns_for(owner, name, all_items)
         backlog = len(columns["backlog"])
         if backlog:
-            projects.append(
-                {"full_name": repo_info["full_name"], "backlog": backlog}
-            )
+            return {"full_name": repo_info["full_name"], "backlog": backlog}
+        return None
+
+    results = await _parallel_map(active, _one_triage)
+    projects = [r for r in results if isinstance(r, dict)]
     projects.sort(key=lambda p: -p["backlog"])
     return render(request, "triage.html", projects=projects)
 
@@ -1554,30 +1576,52 @@ async def health_index(request: Request):
     """Flow health, global summary (issue #9)."""
     repos = await gitea.search_repos()
     active, _inactive, _archived = classify_repos(repos)
-    projects = []
-    for repo_info in active:
+
+    async def _one_health(repo_info: dict) -> dict:
         owner, _, name = repo_info["full_name"].partition("/")
-        try:
-            projects.append(await _project_health(owner, name))
-        except Exception as exc:
-            logger.warning("Health failed for %s: %s", repo_info["full_name"], exc)
+        return await _project_health(owner, name)
+
+    results = await _parallel_map(active, _one_health)
+    projects = []
+    for repo_info, result in zip(active, results):
+        if isinstance(result, Exception):
+            logger.warning(
+                "Health failed for %s: %s", repo_info["full_name"], result
+            )
+            continue
+        result["dot"] = _health_dot(result)
+        projects.append(result)
+    severity_rank = {"red": 0, "orange": 1, "green": 2}
+    projects.sort(
+        key=lambda p: (
+            severity_rank.get(p["dot"]["level"], 3),
+            -len(p["zombies"]),
+        )
+    )
     return render(request, "health.html", projects=projects)
 
 
 @app.get("/health/{owner}/{repo}", response_class=HTMLResponse)
 async def health_project(request: Request, owner: str, repo: str):
-    """Flow health of one project: dwell per column + zombies."""
+    """Flow health of one project: dwell per column + zombies.
+
+    Passes the active project list so the page can offer a project
+    switcher — no more back-to-the-index round trip (0.19.0, C).
+    """
     repos = await gitea.search_repos()
-    known = {r["full_name"] for r in repos}
-    if f"{owner}/{repo}" not in known:
+    active, _inactive, _archived = classify_repos(repos)
+    project_names = [r["full_name"] for r in active]
+    if f"{owner}/{repo}" not in {r["full_name"] for r in repos}:
         return render(
             request, "health_project.html",
             health=None, full_name=f"{owner}/{repo}",
+            project_names=project_names,
         )
     health = await _project_health(owner, repo)
     return render(
         request, "health_project.html",
         health=health, full_name=f"{owner}/{repo}",
+        project_names=project_names,
     )
 
 
@@ -1604,11 +1648,29 @@ async def standup_page(request: Request):
 
 @app.get("/forecast", response_class=HTMLResponse)
 async def forecast_page(request: Request):
-    """Forecasts (issue #7): real-pace ETAs per project + milestone."""
+    """Forecasts (issue #7; portfolio table in 0.19.0, chantier C).
+
+    One row per open milestone across every active project,
+    sorted by risk (largest ETA-vs-deadline gap first) — the
+    cross-project question the old per-project card wall could
+    not answer without reading everything. Per-project pace
+    (weekly bars + backlog ETA) stays as a compact second table.
+    """
     repos = await gitea.search_repos()
     active, _inactive, _archived = classify_repos(repos)
-    projects = []
-    for repo_info in active:
+
+    async def _fetch_milestones(repo_info: dict) -> list[dict]:
+        owner, _, name = repo_info["full_name"].partition("/")
+        try:
+            return await gitea.get_milestones(owner, name)
+        except Exception:
+            return []
+
+    ms_results = await _parallel_map(active, _fetch_milestones)
+
+    rows: list[dict] = []
+    projects: list[dict] = []
+    for repo_info, ms_list in zip(active, ms_results):
         full = repo_info["full_name"]
         owner, _, name = full.partition("/")
         weekly = forecast_service.weekly_closures(
@@ -1623,50 +1685,100 @@ async def forecast_page(request: Request):
             }
             for b in weekly
         ]
+        stats = forecast_service.throughput_stats(weekly)
         remaining = repo_info.get("open_issues_count") or 0
         est = forecast_service.estimate(remaining, weekly)
-        milestones = []
-        try:
-            ms_list = await gitea.get_milestones(owner, name)
-        except Exception:
-            ms_list = []
-        for ms in ms_list:
-            if ms.get("state") not in (None, "open"):
-                continue
-            rem = ms.get("open_issues") or 0
-            if rem == 0 and not (ms.get("closed_issues") or 0):
-                continue
-            m_est = forecast_service.estimate(rem, weekly)
-            verdict = None
-            due_raw = ms.get("due_on")
-            if m_est and not m_est.get("done") and due_raw:
-                due = _parse_datetime(str(due_raw))
-                if due is not None:
-                    verdict = (
-                        "⚠️ en retard à ce rythme"
-                        if m_est["central"] > due.date()
-                        else "✅ dans les temps à ce rythme"
-                    )
-            milestones.append(
-                {
-                    "title": ms.get("title", ""),
-                    "due_on": (due_raw or "")[:10],
-                    "remaining": rem,
-                    "eta": forecast_service.eta_label(m_est),
-                    "verdict": verdict,
-                }
-            )
         projects.append(
             {
                 "full_name": full,
                 "bars": bars,
-                "stats": forecast_service.throughput_stats(weekly),
+                "stats": stats,
                 "remaining": remaining,
                 "eta_label": forecast_service.eta_label(est),
-                "milestones": milestones,
             }
         )
-    return render(request, "forecast.html", projects=projects)
+        if isinstance(ms_list, Exception):
+            ms_list = []
+        next_title = None
+        next_due = None
+        for ms in ms_list:
+            if ms.get("state") not in (None, "open"):
+                continue
+            rem = ms.get("open_issues") or 0
+            closed_n = ms.get("closed_issues") or 0
+            if rem == 0 and not closed_n:
+                continue
+            total = rem + closed_n
+            m_est = forecast_service.estimate(rem, weekly)
+            due_raw = ms.get("due_on")
+            due_dt = _parse_datetime(str(due_raw)) if due_raw else None
+            due_date = due_dt.date() if due_dt else None
+            gap_days = None
+            verdict = "noeta"
+            if due_date is None:
+                verdict = "nodue"
+            elif m_est and not m_est.get("done"):
+                gap_days = (m_est["central"] - due_date).days
+                verdict = "late" if gap_days > 0 else "ontime"
+            elif m_est and m_est.get("done"):
+                verdict = "ontime"
+            rows.append(
+                {
+                    "project": full,
+                    "owner": owner,
+                    "repo": name,
+                    "title": ms.get("title", ""),
+                    "due_label": (
+                        forecast_service.french_date(due_date, short=True)
+                        if due_date else "—"
+                    ),
+                    "due_sort": due_date.isoformat() if due_date else "9999",
+                    "remaining": rem,
+                    "closed": closed_n,
+                    "total": total,
+                    "pct": round(100 * closed_n / total) if total else 0,
+                    "eta": forecast_service.eta_label(m_est),
+                    "gap_days": gap_days,
+                    "verdict": verdict,
+                    "throughput": stats["avg"] if stats else None,
+                    "anchor": False,
+                }
+            )
+            if (
+                due_date is not None
+                and (next_due is None or due_date < next_due)
+            ):
+                next_due, next_title = due_date, ms.get("title", "")
+        for row in rows:
+            if (
+                row["project"] == full
+                and row["title"] == next_title
+                and next_title is not None
+            ):
+                row["anchor"] = True
+
+    def _risk_key(row: dict):
+        # Late first (worst gap first), then dated on-time by due
+        # date, then no-ETA, then no due date.
+        order = {"late": 0, "ontime": 1, "noeta": 2, "nodue": 3}
+        return (
+            order.get(row["verdict"], 4),
+            -(row["gap_days"] or 0) if row["verdict"] == "late" else 0,
+            row["due_sort"],
+            row["project"],
+            row["title"],
+        )
+
+    rows.sort(key=_risk_key)
+    summary = {
+        "late": sum(1 for r in rows if r["verdict"] == "late"),
+        "ontime": sum(1 for r in rows if r["verdict"] == "ontime"),
+        "total": len(rows),
+    }
+    return render(
+        request, "forecast.html",
+        rows=rows, projects=projects, summary=summary,
+    )
 
 
 @app.get("/focus", response_class=HTMLResponse)
@@ -1739,15 +1851,14 @@ async def _collect_wall_data(only_repo: str | None) -> list[dict]:
                 closed_today.get(event["repo_full_name"], 0) + 1
             )
 
-    slides = []
-    for repo in repos:
+    async def _one_slide(repo: dict) -> dict | None:
         full_name = repo["full_name"]
         owner, _, name = full_name.partition("/")
         try:
             items = await gitea.get_repo_issues(owner, name, state="open")
         except Exception as exc:
             logger.debug("wall: issues failed for %s: %s", full_name, exc)
-            continue
+            return None
         open_issues = [i for i in items if _is_issue(i)]
         _adopt_label_columns(full_name, open_issues, get_board_state(full_name))
         board_state = get_board_state(full_name)
@@ -1769,17 +1880,17 @@ async def _collect_wall_data(only_repo: str | None) -> list[dict]:
                         "aging": days is not None and days >= aging_days,
                     }
                 )
-        slides.append(
-            {
-                "full_name": full_name,
-                "counts": {col: len(columns[col]) for col in KANBAN_COLUMNS},
-                "open_total": len(open_issues),
-                "cards": cards[:9],
-                "cards_total": len(cards),
-                "closed_today": closed_today.get(full_name, 0),
-            }
-        )
-    return slides
+        return {
+            "full_name": full_name,
+            "counts": {col: len(columns[col]) for col in KANBAN_COLUMNS},
+            "open_total": len(open_issues),
+            "cards": cards[:9],
+            "cards_total": len(cards),
+            "closed_today": closed_today.get(full_name, 0),
+        }
+
+    results = await _parallel_map(repos, _one_slide)
+    return [r for r in results if isinstance(r, dict)]
 
 
 @app.get("/wall", response_class=HTMLResponse)