Two proposals for a trade index synch message

src/SUMMARY.md

@@ -26,6 +26,7 @@
 - [Admin Cancel order](./admin_cancel_order.md)
 - [Admin Add Solver](./admin_add_solver.md)
 - [Restore session](./restore_session.md)
+- [Last Trade Index](./last_trade_index.md)
 - [Actions](./actions.md)
   - [Message suggestions for actions](./message_suggestions_for_actions.md)
 - [P2P Order event. NIP-69](./order_event.md)

src/last_trade_index.md

@@ -0,0 +1,54 @@
+# Last Trade Index
+
+Defines the `last-trade-index` action used to retrieve the user's last `trade_index`.
+
+## Request
+
+Client sends a Gift wrap Nostr event to Mostro with the following rumor's content. The request sends a `null` payload to indicate that the client is querying for the last trade index.
+
+```json
+{
+  "restore": {
+    "version": 1,
+    "action": "last-trade-index",
+    "payload": null
+  }
+}
+```
+
+## Response
+
+Mostro responds with the user's last trade index as a u32 directly in the `trade_index` field. If the user has never created a trade, the value SHOULD be `1`.
+
+```json
+{
+  "restore": {
+    "version": 1,
+    "action": "last-trade-index",
+    "trade_index": 42,
+    "payload": null
+  }
+}
+```
+
+### Fields
+
+* `restore.version`: Protocol version. Current is `1`.
+* `restore.action`: Must be `last-trade-index`.
+* `restore.trade_index` (response): u32 representing the last `trade_index` for the user. `1` if none.
+* `restore.payload` (response): Must be `null`.
+
+## Example
+
+Client requests the last trade index and receives `7`, meaning the next trade the client creates SHOULD use `trade_index = 8`.
+
+```json
+{
+  "restore": {
+    "version": 1,
+    "action": "last-trade-index",
+    "trade_index": 7,
+    "payload": null
+  }
+}
+```