fix: resolve asyncpg str vs datetime TypeError in invite key creation

[ismaeldouglasdev]

Summary

Fixes asyncpg.exceptions.DataError when calling engram_init / engram_status / rotate_invite_key — the expiry datetime was serialized to an ISO string via .isoformat(), but asyncpg's TIMESTAMPTZ columns expect a datetime.datetime object.

Root Cause

Three call sites called .isoformat() on the expiry datetime before passing it to storage:

1. server.py:engram_init (L532)
2. server.py:engram_status (L361)
3. engine.py:rotate_invite_key (L3072)

Additionally, the type hints in storage.py (base + SQLiteStorage) and postgres_storage.py declared expires_at: str | None, misleading callers into thinking strings were acceptable for the Postgres backend.

Changes

Commit 1 — Type hints

• storage.py: Storage.insert_invite_key (base class) + SQLiteStorage.insert_invite_key: expires_at: str | None → datetime | None
• postgres_storage.py: PostgresStorage.insert_invite_key: expires_at: str | None → datetime | None

Commit 2 — Call sites

• server.py lines 361, 532: removed .isoformat()
• engine.py line 3072: removed .isoformat()

Why SQLiteStorage still has .isoformat()

SQLite uses TEXT columns, so the SQLiteStorage implementation correctly continues to call .isoformat() internally — that's its concern, not the caller's. The interface now accurately reflects both backends' requirements.

Verification

• All type hints confirmed as datetime | None (not str | None)
• No .isoformat() calls remain in the Postgres-bound insert_invite_key paths
• SQLiteStorage correctly retains its internal .isoformat() for TEXT column storage
• All imports and module-level AST verification pass

Summary by CodeRabbit

• Bug Fixes
  • Corrected invite key expiration timestamp calculations to ensure accurate date computations across the system.

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No actionable comments were generated in the recent review. 🎉

ℹ️ Recent review info

⚙️ Run configuration

Configuration used: defaults

Review profile: CHILL

Plan: Pro Plus

Run ID: 4135cfab-b5d7-4ad0-bf6d-30f7004b1197

📥 Commits

Reviewing files that changed from the base of the PR and between cab14fe and 750d25e.

📒 Files selected for processing (4)

• src/engram/engine.py
• src/engram/postgres_storage.py
• src/engram/server.py
• src/engram/storage.py

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📝 Walkthrough

Walkthrough

Storage interfaces and implementations updated to accept datetime | None instead of str | None for invite key expiration timestamps. SQLiteStorage converts datetime to ISO strings for database storage. Server and engine timestamp calculations corrected to produce timezone-aware datetime objects.

Changes

Invite key expiration timestamp handling

Layer / File(s)	Summary
Storage interface type update src/engram/storage.py, src/engram/postgres_storage.py	BaseStorage and PostgresStorage insert_invite_key signatures updated to accept expires_at: datetime | None instead of str | None.
SQLiteStorage datetime-to-string conversion src/engram/storage.py	SQLiteStorage.insert_invite_key converts incoming datetime objects to ISO format strings before inserting into the database.
Server and engine timestamp creation src/engram/server.py, src/engram/engine.py	Server timestamp calculations in engram_status and engram_init produce timezone-aware datetime objects; rotate_invite_key datetime construction corrected.

Estimated code review effort

🎯 2 (Simple) | ⏱️ ~10 minutes

Poem

🐰 Timestamps once lived as strings so plain,
Now datetime objects dance through the chain,
From server to storage, with care they flow,
SQLite converts them to strings we know,
A coordinated hop, both type-safe and true! 🌟

🚥 Pre-merge checks | ✅ 4 | ❌ 1

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Docstring Coverage	⚠️ Warning	Docstring coverage is 66.67% which is insufficient. The required threshold is 80.00%.	Write docstrings for the functions missing them to satisfy the coverage threshold.

✅ Passed checks (4 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title accurately describes the main issue being fixed: resolving a TypeError with asyncpg related to datetime vs string type mismatches in invite key creation.
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.

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✨ Finishing Touches

🧪 Generate unit tests (beta)

• Create PR with unit tests

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