feat(api): add SRS Cloudflare Worker with email digest, charts, and D1 integration

apps/api/src/stats.ts

@@ -0,0 +1,107 @@
+/**
+ * GET /api/stats — the one JSON document behind the docs progress page.
+ * Read-only aggregation over D1; shape is the page's contract, change both
+ * together. A problem counts as "done" once it entered the ladder
+ * (stage != 'new').
+ */
+import {
+  CAMPAIGN_DAYS,
+  CAMPAIGN_START,
+  addDays,
+  campaignDay,
+  campaignWeek,
+  streak,
+} from "./srs.ts";
+
+const PHASE_NAMES: Record<number, string> = {
+  1: "I — Linear",
+  2: "II — Nodal & Grid",
+  3: "III — Hierarchical",
+  4: "IV — Relational",
+  5: "V — Decision Space",
+};
+
+export async function buildStats(db: D1Database, today: string): Promise<object> {
+  const { results: phaseRows } = await db
+    .prepare(
+      `SELECT t.milestone AS milestone, p.set_label AS set_label,
+              COUNT(*) AS total,
+              SUM(CASE WHEN p.stage != 'new' THEN 1 ELSE 0 END) AS done
+       FROM problems p JOIN topics t ON t.issue = p.topic_issue
+       WHERE t.milestone IS NOT NULL
+       GROUP BY t.milestone, p.set_label
+       ORDER BY t.milestone`,
+    )
+    .all<{ milestone: number; set_label: string; total: number; done: number }>();
+  const phases = new Map<
+    number,
+    { milestone: number; name: string } & Record<string, number | string>
+  >();
+  for (const row of phaseRows) {
+    const phase =
+      phases.get(row.milestone) ??
+      ({
+        milestone: row.milestone,
+        name: PHASE_NAMES[row.milestone] ?? `Phase ${row.milestone}`,
+        core_done: 0,
+        core_total: 0,
+        optional_done: 0,
+        optional_total: 0,
+        deferred_done: 0,
+        deferred_total: 0,
+      } as { milestone: number; name: string } & Record<string, number | string>);
+    phase[`${row.set_label}_done`] = row.done;
+    phase[`${row.set_label}_total`] = row.total;
+    phases.set(row.milestone, phase);
+  }
+
+  const { results: ladderRows } = await db
+    .prepare("SELECT stage, COUNT(*) AS n FROM problems GROUP BY stage")
+    .all<{ stage: string; n: number }>();
+  const ladder: Record<string, number> = { new: 0, "+2": 0, "+5": 0, "+10": 0, retired: 0 };
+  for (const row of ladderRows) ladder[row.stage] = row.n;
+
+  const { results: gates } = await db
+    .prepare("SELECT week, issue, pass_rate, closed_on FROM gates ORDER BY week")
+    .all<{ week: number; issue: number | null; pass_rate: number | null; closed_on: string | null }>();
+
+  // Review-queue depth for the next 14 days: everything due by that day.
+  const queue: { date: string; due: number }[] = [];
+  for (let i = 0; i < 14; i++) {
+    const date = addDays(today, i);
+    const row = await db
+      .prepare(
+        `SELECT COUNT(*) AS n FROM problems
+         WHERE stage != 'retired' AND next_review IS NOT NULL AND next_review <= ?1
+           AND (defer_until IS NULL OR defer_until <= ?1)`,
+      )
+      .bind(date)
+      .first<{ n: number }>();
+    queue.push({ date, due: row?.n ?? 0 });
+  }
+
+  const recent: { date: string; attempts: number; passes: number }[] = [];
+  for (let i = 6; i >= 0; i--) {
+    const date = addDays(today, -i);
+    const row = await db
+      .prepare(
+        `SELECT COUNT(*) AS attempts,
+                SUM(CASE WHEN result = 'pass' THEN 1 ELSE 0 END) AS passes
+         FROM attempts WHERE date = ?`,
+      )
+      .bind(date)
+      .first<{ attempts: number; passes: number | null }>();
+    recent.push({ date, attempts: row?.attempts ?? 0, passes: row?.passes ?? 0 });
+  }
+
+  return {
+    generated: new Date().toISOString(),
+    campaign: { day: campaignDay(today), week: campaignWeek(today), start: CAMPAIGN_START, days: CAMPAIGN_DAYS },
+    phases: [...phases.values()],
+    ladder,
+    gates,
+    streak: await streak(db, today),
+    queue,
+    recent,
+  };
+}