Added ability to define output directory

2026-02-02 22:00:08 +00:00
parent a0e7a494e4
commit 1a7be7fddf
3 changed files with 111 additions and 1 deletions
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+# CLAUDE.md
+
+This file provides guidance to Claude Code (claude.ai/code) when working with code in this repository.
+
+## Project Overview
+
+This is a single-file Python script (`imapdown.py`) that downloads all emails from an IMAP server into individual EML files, preserving the folder hierarchy. It uses only Python's standard library and has no external dependencies.
+
+## Development Environment
+
+- Python 3.6+ required
+- Virtual environment is set up in `.venv` - activate it before running:
+  ```bash
+  source .venv/bin/activate
+  ```
+
+## Running the Script
+
+Basic usage (incremental mode - only downloads new emails):
+```bash
+./imapdown.py --server imap.example.com --email user@example.com --user user@example.com --password "password" --ssl
+```
+
+Full download (ignores previous state, requires empty target directory):
+```bash
+./imapdown.py --server imap.example.com --email user@example.com --user user@example.com --password "password" --ssl --full
+```
+
+Testing/debugging with limited emails:
+```bash
+./imapdown.py --server imap.example.com --email user@example.com --user user@example.com --password "password" --ssl --limit 10
+```
+
+Custom storage directory:
+```bash
+./imapdown.py --server imap.example.com --email user@example.com --user user@example.com --password "password" --ssl --store /path/to/backup
+```
+
+## Architecture
+
+### Single-File Design
+The entire application is contained in `imapdown.py` (13KB). This is intentional - no modules or packages.
+
+### State Tracking
+- The script maintains a `.imapdown_state.json` file in each email account's download folder
+- Tracks the highest UID (unique identifier) downloaded per IMAP folder
+- Format: `{"INBOX": 19334, "INBOX.Archive": 1770, "Sent": 892}`
+- Enables efficient incremental downloads (default mode)
+
+### Download Flow
+1. Parse arguments
+2. Connect to IMAP server (SSL, STARTTLS, or plain)
+3. List all folders and decode modified UTF-7 folder names
+4. For each folder:
+   - Load last downloaded UID from state file (if incremental mode)
+   - Search for new messages (UID > last_uid)
+   - Download each message as RFC822
+   - Save as `.eml` file with naming: `{UID}_{date}_{subject}.eml`
+   - Extract attachments into `.zip` file (same base name)
+   - Update state with highest UID
+5. Save state file
+
+### Key Implementation Details
+
+**Modified UTF-7 Decoding**: IMAP folder names use modified UTF-7 encoding (see `decode_modified_utf7()` at line 39). This is not standard base64 - it uses `,` instead of `/` and has special `&` handling.
+
+**Filename Sanitization**: Two-stage process:
+- `sanitize_filename()`: Removes invalid filesystem characters, max 50 chars for subjects
+- `sanitize_folder_path()`: Converts IMAP folder separators (`.` or `/`) to OS path separators
+
+**UID-Based Incremental Updates**: Uses IMAP UIDs (not sequence numbers) because UIDs are persistent. The search `UID {last_uid + 1}:*` fetches only new messages. Some servers return the highest UID even when searching for higher UIDs, so there's additional filtering at line 251.
+
+**Full Mode Safety**: `--full` mode checks if the download folder already contains `.eml` files and refuses to run (line 325). This prevents accidental duplicates. Users must delete the folder first.
+
+**Attachment Handling**:
+- Walks message parts looking for `Content-Disposition: attachment` or `inline`
+- Handles duplicate attachment filenames by appending `_{counter}`
+- All attachments for one email go into a single `.zip` file
+
+## Output Structure
+
+```
+{store_dir}/           # default: ./download
+└── {email_address}/   # sanitized email address
+    ├── .imapdown_state.json
+    ├── INBOX/
+    │   ├── 123_20240115_Meeting_notes.eml
+    │   └── 124_20240116_Report.zip
+    └── Sent/
+        └── 456_20240114_RE_Question.eml
+```
+
+## Testing
+
+No formal test suite exists. Manual testing approach:
+- Use `--limit 10` to download a small batch for verification
+- Test SSL vs STARTTLS connections
+- Test incremental mode by running twice
+- Verify `.eml` files open correctly in email clients
+- Check that folders with special characters (non-ASCII) are handled correctly