From 050775af6aa1c623fd8eee6bc1ca0e5bb15528a0 Mon Sep 17 00:00:00 2001
From: Andreas Berthoud <andreasberthoud@gmail.com>
Date: Tue, 6 Jul 2021 21:00:38 +0200
Subject: [PATCH] backend: Echo commands send to STM32

---
 backend/command.py | 57 ++++++++++++++++++++++++++--------------------
 1 file changed, 32 insertions(+), 25 deletions(-)

diff --git a/backend/command.py b/backend/command.py
index 3064d74..7c68082 100644
--- a/backend/command.py
+++ b/backend/command.py
@@ -6,6 +6,8 @@ from dataclasses import dataclass
 from enum import Enum
 from multiprocessing import Process
 from multiprocessing import Queue
+from struct import pack
+from struct import unpack
 from typing import Optional
 
 from flask import Response
@@ -58,9 +60,9 @@ def worker_process(
     counter = 1
     with container.serial() as serial:
         while True:
-            logger.info(f"Ping {counter} {os.getpid()}")
+            logger.debug(f"Ping {counter} process_id={os.getpid()}")
             counter += 1
-            time.sleep(0.5)
+            time.sleep(0.1)
             receive_and_log(
                 serial=serial,
                 header_size=container.config.header_size(),
@@ -69,8 +71,19 @@ def worker_process(
             if queue is not None:
                 while not queue.empty():
                     command_id = queue.get()
-                    logger.debug(f"device_id {container.config.device_id()}")
-                    logger.info(f"would execute command: {command_id}")
+                    payload = "test value".encode()
+                    length = len(payload)
+
+                    data = pack(
+                        ">BHB" + "B" * length + "B",
+                        int(command_id),
+                        length,
+                        0,
+                        *list(payload),
+                        0xFF,
+                    )
+
+                    serial.write(data)
 
 
 class CommandId(Enum):
@@ -78,12 +91,6 @@ class CommandId(Enum):
     command_log = 0xFF
 
 
-@dataclass
-class CommandMeta:
-    command_id: CommandId
-    data_length: int
-
-
 @dataclass
 class LogCommand:
     """Command ID: command_log"""
@@ -128,31 +135,31 @@ def receive_and_log(
     while bytes_read:
 
         logger.debug(f"bytes: {bytes_read.hex()}")
+        command_id_int, data_length, _ = unpack(">BHB", bytes_read[:header_size])
+        payload = bytes(bytes_read[header_size : header_size + data_length])
+        stop_byte = bytes_read[header_size + data_length]
+
+        try:
+            command_id = CommandId(command_id_int)
+        except ValueError:
+            logger.error(
+                f"invalid command {command_id_int} with payload {str(payload)}",
+            )
+            bytes_read = bytes_read[header_size + data_length + 1 :]
+            continue
 
-        command_id = int(bytes_read[0])
-        logger.debug(f"command_id: {command_id}")
-
-        data_length = (int(bytes_read[1]) << 4) + int(bytes_read[2])
-        logger.debug(f"data_length: {data_length}")
-
-        meta = CommandMeta(
-            command_id=CommandId(command_id),
-            data_length=data_length,
-        )
-
-        if meta.command_id == CommandId.command_log:
+        if command_id == CommandId.command_log:
             command = LogCommand(
-                data=bytes_read[header_size : header_size + meta.data_length],
+                data=bytes_read[header_size : header_size + data_length],
             )
             command.execute()
         else:
             return
 
-        stop_byte = bytes_read[header_size + meta.data_length]
         logger.debug(f"stop_byte: {stop_byte}")
         assert stop_byte == 0xFF
 
-        bytes_read = bytes_read[header_size + meta.data_length + 1 :]
+        bytes_read = bytes_read[header_size + data_length + 1 :]
 
 
 def start_backgroup_process():