Refactor Tomorrow list detection for better code readability

[skempken]

Problem

The logic for detecting the "Tomorrow" list name in detect_list_names() is unnecessarily complex and hard to read:

# things_jxa.py:87-94
for locale, tomorrow_name in known_tomorrow.items():
    if locale in LOCALE_MAPPINGS:
        first_list = detected_mapping.get("inbox", "")
        # If we detected Inbox correctly, use the same locale for Tomorrow
        if first_list == LOCALE_MAPPINGS[locale]["inbox"]:
            detected_mapping["tomorrow"] = LOCALE_MAPPINGS[locale]["tomorrow"]
            break

Issues:

• Triple-nested logic (for → if → if)
• Indirect approach: checks if inbox matches to infer locale
• Variable name first_list is misleading (it's specifically the inbox)
• Could be simplified with a reverse lookup

Current Implementation

Location: things_jxa.py:79-98

The function:

1. Iterates through known translations of "Tomorrow"
2. Checks if locale exists in LOCALE_MAPPINGS
3. Compares detected inbox name to known inbox names
4. If match found, uses that locale's "Tomorrow" translation

Proposed Solution

Use a reverse mapping for cleaner logic:

# Build reverse mapping once at module level
REVERSE_LOCALE_MAP = {}
for locale, mappings in LOCALE_MAPPINGS.items():
    for key, value in mappings.items():
        if value not in REVERSE_LOCALE_MAP:
            REVERSE_LOCALE_MAP[value] = {}
        REVERSE_LOCALE_MAP[value][key] = locale

def detect_list_names():
    # ... existing detection ...
    
    # Detect locale from inbox name
    inbox_name = detected_mapping.get("inbox")
    if inbox_name and inbox_name in REVERSE_LOCALE_MAP:
        detected_locale = REVERSE_LOCALE_MAP[inbox_name].get("inbox")
        if detected_locale and detected_locale in LOCALE_MAPPINGS:
            detected_mapping["tomorrow"] = LOCALE_MAPPINGS[detected_locale]["tomorrow"]

Or even simpler:

def detect_locale_from_inbox(inbox_name: str) -> Optional[str]:
    """Return locale code if inbox name matches a known locale."""
    for locale, mappings in LOCALE_MAPPINGS.items():
        if mappings.get("inbox") == inbox_name:
            return locale
    return None

# In detect_list_names():
inbox_name = detected_mapping.get("inbox")
detected_locale = detect_locale_from_inbox(inbox_name)
if detected_locale:
    detected_mapping["tomorrow"] = LOCALE_MAPPINGS[detected_locale]["tomorrow"]

Impact

Priority: Medium - code quality improvement

Affected code: things_jxa.py:79-98

Breaking changes: None (internal refactoring)

Benefits:

• Improved readability
• Easier to test
• Reusable locale detection logic

Acceptance Criteria

• Logic simplified to 1-2 levels of nesting maximum
• Clear variable names that reflect what they contain
• Extract locale detection to separate function
• All existing tests still pass
• No change in behavior

Additional Context

This issue was identified during post-implementation review of #1 (multi-locale support).