Subject

mail_intake.parsers.subject

Summary

Subject line normalization utilities for Mail Intake.

This module provides helper functions for normalizing email subject lines to enable reliable thread-level comparison and grouping.

Normalization is intentionally conservative to avoid altering semantic meaning while removing common reply and forward prefixes.

Functions

normalize_subject

normalize_subject(subject: str) -> str

Normalize an email subject for thread-level comparison.

Parameters:

Name	Type	Description	Default
subject	str	Raw subject line from a message header.	required

Returns:

Name	Type	Description
str	str	Normalized subject string suitable for thread grouping.

Notes

Responsibilities:

- Strips common prefixes such as `Re:`, `Fwd:`, and `FW:`.
- Repeats prefix stripping to handle stacked prefixes.
- Collapses excessive whitespace.
- Preserves original casing (no lowercasing).

Guarantees:

- This function is intentionally conservative and avoids aggressive
  transformations that could alter the semantic meaning of the subject.