provide draft docs for overall flows from gemini interactive session

README.md

@@ -34,3 +34,97 @@ run with `--metrics` argument,
 e.g. `--metrics 127.0.0.1:9001`.
 Metrics can then be retrieved with
 `curl http://127.0.0.1:9001/metrics`.
+
+
+## DRAFT [NEEDS REVIEW]: How notifications flow from core to relay to push proxy
+
+In the **chatmail** architecture, push notifications follow a highly specialized path 
+designed to minimize battery drain and maximize privacy.
+By leveraging Dovecot's **dictproxy** protocol 
+and a dedicated **notifiers** service with debouncing logic, 
+chatmail avoids the need for a persistent IMAP connection.
+
+---
+
+### 1. `chatmail/core`: The IMAP Client Logic
+
+The **chatmail core** is the Rust-based engine used by the mobile and desktop clients.
+It initiates the registration process via the IMAP protocol.
+
+* **Capability Discovery:**
+The core identifies compatible servers by looking for the `XCHATMAIL` or `XDELTAPUSH` strings in the IMAP `CAPABILITY` response.
+* **Location:** `src/capabilities.rs`
+
+
+* **Token Registration:**
+When the mobile OS provides a device token (FCM or APNs), 
+the core uploads it using the **IMAP SETMETADATA** command.
+* **Key:** `/private/vendor/deltachat/push-token`
+* **Location:** `src/imap/metadata.rs`
+
+
+* **Push Orchestration:**
+The core tracks the token's lifecycle.
+If the token is updated or the account is newly configured, 
+this module flags the IMAP worker to sync the metadata.
+* **Location:** `src/push.rs`
+
+
+
+---
+
+### 2. `chatmail/relay`: The Metadata Service & DictProxy
+
+The **relay** repository handles the server-side delegation of metadata storage and the triggering of notifications.
+
+* **`chatmaild/src/chatmaild/metadata.py` (The DictProxy Interface):**
+This script is the backend for Dovecot’s **dictproxy**.
+Dovecot is configured to proxy all metadata requests to this service over a Unix socket.
+* **Command Handling:** It implements the line-based `dictproxy` protocol.
+* **The `S` (Set) Command:** When the core sends an IMAP `SETMETADATA` command, Dovecot translates it into an `S` command.
+The script then parses the `push-token` key and stores the opaque token in a local SQLite database.
+
+
+* **`chatmaild/src/chatmaild/notifier.py` (The Trigger):**
+This service reacts to new mail arrival events.
+* **Logic:** It queries the metadata database for the recipient’s token.
+* **Transmission:** It queues the token in a `PriorityQueue` and uses `NotifyThreads` to POST the token to the central notification proxy.
+* **Location:** `chatmaild/src/chatmaild/notifier.py`
+
+
+
+---
+
+### 3. `chatmail/notifiers`: The Debouncing Proxy
+
+The **notifiers** repository is a standalone Rust service deployed at `notifications.delta.chat`.
+It acts as the final gateway to Apple (APNs) and Google (FCM).
+
+* **Debouncing Logic:**
+To protect battery life, this service implements a "coalescing" or debouncing window.
+* **Location:** `src/server.rs` (Search for `feat: debounce notifications`)
+* **The Window:** When a request arrives, the server checks if a timer (typically **10 seconds**) is already running for that specific `device_token`.
+* **The Action:** If a timer is active, subsequent notification requests for the same token are ignored during that window.
+Only **one** push "tickle" is sent to the phone at the end of the period.
+
+
+* **Performance Benefit:**
+Since the mobile app's **Core** fetches *all* pending messages upon waking up, a single push is sufficient even if 50 emails arrived.
+* **Rate Limiting:**
+This module also prevents the server from exceeding the strict rate limits imposed by Apple and Google.
+* **Location:** `src/rate_limiter.rs`
+
+
+
+---
+
+### Summary of the Push Flow
+
+| Stage | Component | Protocol / Action |
+| --- | --- | --- |
+| **Registration** | `chatmail/core` | `IMAP SETMETADATA` |
+| **Delegation** | **Dovecot** | **`dictproxy` protocol (`S` command)** |
+| **Bridge** | `chatmail/relay` | `metadata.py` stores token in SQLite |
+| **Trigger** | `chatmail/relay` | `notifier.py` POSTs to proxy |
+| **Debounce** | `chatmail/notifiers` | 10s Coalescing window |
+| **Delivery** | `chatmail/notifiers` | APNs / FCM "Tickle" |