fix(discord): suppress pairing reply in groups without @mention (#1091)

[mrgoonie]

Summary

Hotfix for #1091. Discord channels with pairing group policy + Require @mention in groups enabled were spamming pairing codes on every group message.

Root cause: handleMessage called checkGroupPolicy (which fires sendPairingReply on PolicyNeedsPairing) before the mention gate ran, so the pairing reply bypassed the mention requirement.

Fix: Pre-compute the mentioned flag once at the top of handleMessage, pass it into checkGroupPolicy, and skip sendPairingReply when RequireMention() is enabled and the bot was not addressed. The existing mention gate later in the function reuses the same flag (deduped).

DMs are intentionally unchanged — every DM is implicitly directed at the bot, so checkDMPolicy keeps its current pairing-reply behavior.

Behavior after fix

Scenario	Before	After
Group, paired user, mentioned	reply	reply (unchanged)
Group, paired user, not mentioned	record history	record history (unchanged)
Group, unpaired user, mentioned	pairing code	pairing code (unchanged)
Group, unpaired user, not mentioned, require_mention=true	pairing code (bug)	silent (fixed)
Group, unpaired user, not mentioned, require_mention=false	pairing code	pairing code (unchanged)
DM, unpaired user	pairing code	pairing code (unchanged)

Test plan

• go build ./... (PG)
• go build -tags sqliteonly ./... (Desktop)
• go vet ./internal/channels/discord/...
• go test ./internal/channels/discord/...
• Manual: Discord group with pairing + require_mention=true, send message without mention → bot stays silent
• Manual: same group, @-mention bot from unpaired account → bot replies with pairing code
• Manual: DM unpaired bot → bot replies with pairing code (no regression)

Fixes #1091

[clark-cant]

🔍 Code Review — fix(discord): suppress pairing reply in groups without @mention (#1091)

🎯 Tổng quan

Hotfix: Discord channels với pairing policy + Require @mention enabled bị spam pairing code trên mọi group message. Root cause: checkGroupPolicy fires sendPairingReply trước khi mention gate chạy.

Scope: 1 file, +25/-15, 1 commit

---

🤖 CI Status + Merge Conflicts

CI: ✅ All checks passed — go: pass (7m18s), web: pass (46s)
Merge conflicts: ✅ No conflicts (MERGEABLE, mergeStateStatus: CLEAN)

---

✅ Điểm Tốt

1. Root cause analysis chính xác. handleMessage gọi checkGroupPolicy → sendPairingReply trước khi mention gate chạy → pairing code bypass mention requirement. Correct diagnosis.

2. Fix đúng pattern. Pre-compute mentioned flag một lần ở đầu handleMessage, pass vào checkGroupPolicy, dedup mention check (không duplicate code). Clean refactor.

3. Mention detection đầy đủ. Check cả m.Mentions (direct @mention) và m.ReferencedMessage (reply to bot) — covers cả 2 trường hợp user tương tác với bot trong group.

4. DM không bị ảnh hưởng. Explicitly noted: DMs implicitly directed at bot, checkDMPolicy giữ nguyên behavior. Good scope discipline.

5. Behavior table rõ ràng. PR body có table Before/After cho 6 scenarios — easy to verify correctness.

6. Test plan thực tế. Manual test scenarios cụ thể cho paired/unpaired + mentioned/not mentioned + DM.

---

🟢 LOW (Nit)

1. mentioned flag computed cho cả DM path. Line 47-61 compute mentioned với if !isDM guard — good, không waste computation cho DM. Nhưng nếu sau này có thêm channel type khác (không DM không group), flag sẽ mặc định false. Không blocking, chỉ nên note.

2. checkGroupPolicy signature change. Thêm param mentioned bool — breaking change cho interface nếu có chỗ nào khác gọi trực tiếp (nhưng search codebase thì chỉ có handleMessage gọi, nên safe).

---

📊 Summary

Severity	Count	Issues
🔴 CRITICAL	0	—
🟡 MEDIUM	0	—
🟢 LOW	2	mentioned flag scope note, signature change note

---

💡 Recommendation

🟢 APPROVED

Hotfix nhỏ, clean, đúng root cause, không side effects. Code refactor dedup mention check — improvement chứ không chỉ là band-aid fix.

Ready to merge! 🚀