From 063de7ee3e884b8a8a452d87c0666a395a43d5bc Mon Sep 17 00:00:00 2001
From: Toutsu <hegin4@yandex.ru>
Date: Thu, 7 May 2026 13:12:39 +0300
Subject: [PATCH] feat(#14): add get_group_attendance_stats SQL function

---
 .../Migrations/V012__add_attendance_stats.sql | 66 +++++++++++++++++++
 1 file changed, 66 insertions(+)
 create mode 100644 src/GmRelay.Bot/Migrations/V012__add_attendance_stats.sql

diff --git a/src/GmRelay.Bot/Migrations/V012__add_attendance_stats.sql b/src/GmRelay.Bot/Migrations/V012__add_attendance_stats.sql
new file mode 100644
index 0000000..693115b
--- /dev/null
+++ b/src/GmRelay.Bot/Migrations/V012__add_attendance_stats.sql
@@ -0,0 +1,66 @@
+-- =============================================================
+-- Attendance statistics view for GM analytics
+-- Returns per-player aggregated metrics for a given game group.
+-- NOTE: waitlist count reflects CURRENT registration_status only.
+--       Full historical waitlist tracking will come with #15.
+-- =============================================================
+
+CREATE OR REPLACE FUNCTION get_group_attendance_stats(p_group_id UUID)
+RETURNS TABLE (
+    player_id           UUID,
+    display_name        VARCHAR,
+    telegram_username   VARCHAR,
+    total_sessions      BIGINT,
+    confirmed_count     BIGINT,
+    declined_count      BIGINT,
+    no_response_count   BIGINT,
+    waitlisted_count    BIGINT,
+    cancellation_affected_count BIGINT,
+    attendance_rate     NUMERIC
+) AS $$
+BEGIN
+    RETURN QUERY
+    WITH player_sessions AS (
+        SELECT
+            sp.player_id,
+            s.id                AS session_id,
+            sp.rsvp_status,
+            sp.registration_status,
+            s.status            AS session_status,
+            s.scheduled_at
+        FROM session_participants sp
+        JOIN sessions s ON s.id = sp.session_id
+        WHERE s.group_id = p_group_id
+    ),
+    player_totals AS (
+        SELECT
+            ps.player_id,
+            COUNT(*) FILTER (WHERE ps.session_status <> 'Cancelled')                      AS total_sessions,
+            COUNT(*) FILTER (WHERE ps.rsvp_status = 'Confirmed' AND ps.session_status <> 'Cancelled') AS confirmed_count,
+            COUNT(*) FILTER (WHERE ps.rsvp_status = 'Declined' AND ps.session_status <> 'Cancelled')  AS declined_count,
+            COUNT(*) FILTER (WHERE ps.rsvp_status = 'Pending' AND ps.scheduled_at < NOW() AND ps.session_status <> 'Cancelled') AS no_response_count,
+            COUNT(*) FILTER (WHERE ps.registration_status = 'Waitlisted' AND ps.session_status <> 'Cancelled') AS waitlisted_count,
+            COUNT(*) FILTER (WHERE ps.session_status = 'Cancelled')                        AS cancellation_affected_count
+        FROM player_sessions ps
+        GROUP BY ps.player_id
+    )
+    SELECT
+        pt.player_id,
+        p.display_name,
+        p.telegram_username,
+        pt.total_sessions,
+        pt.confirmed_count,
+        pt.declined_count,
+        pt.no_response_count,
+        pt.waitlisted_count,
+        pt.cancellation_affected_count,
+        ROUND(
+            100.0 * pt.confirmed_count
+            / NULLIF(pt.total_sessions, 0),
+            1
+        ) AS attendance_rate
+    FROM player_totals pt
+    JOIN players p ON p.id = pt.player_id
+    ORDER BY pt.confirmed_count DESC, pt.total_sessions DESC;
+END;
+$$ LANGUAGE plpgsql STABLE;