PicoWireless: ppwhttp fix to support JSON content type

This is a bit of a fudge, and was only tested against the Cheerlights API.

Detects JSON content type, parses out the content length and truncates the response body to length.

Should probably do this *before* decoding from utf-8.

Updates cheerlights.py API example to support XML, JSON and TEXT endpoints.

micropython/examples/pico_wireless/cheerlights.py

@@ -1,4 +1,10 @@
 import time
+import json
+try:
+    import xmltok  # https://pypi.org/project/micropython-xmltok/
+    import io
+except ImportError:
+    xmltok = None
 from micropython import const
 
 try:
@@ -23,7 +29,23 @@ print("Local IP: {}.{}.{}.{}".format(*my_ip))
 
 def handler(head, body):
     if head["Status"] == "200 OK":
-        color = body[1:]
+        if HTTP_REQUEST_PATH.endswith(".json"):
+            # Parse as JSON
+            data = json.loads(body)
+            color = data['field2'][1:]
+
+        elif HTTP_REQUEST_PATH.endswith(".xml") and xmltok is not None:
+            # Parse as XML
+            data = xmltok.tokenize(io.StringIO(body))
+            color = xmltok.text_of(data, "field2")[1:]
+
+        elif HTTP_REQUEST_PATH.endswith(".txt"):
+            # Parse as plain text
+            color = body[1:]
+
+        else:
+            print("Unable to parse API response!")
+            return
         r = int(color[0:2], 16)
         g = int(color[2:4], 16)
         b = int(color[4:6], 16)

micropython/examples/pico_wireless/ppwhttp.py

@@ -158,6 +158,14 @@ Connection: close
         key, value = line.split(": ", 1)
         dhead[key] = value
 
+    # Fudge to handle JSON data type, which is prefixed with a content length.
+    # This ignores the charset, if specified, since we've already assumed utf-8 above!
+    # TODO maybe pay attention to Content-Type charset
+    if "Content-Type" in dhead and dhead["Content-Type"].startswith("application/json"):
+        length, body = body.split("\n", 1)
+        length = int(length, 16)
+        body = body[:length]
+
     handler(dhead, body)
 
     picowireless.client_stop(client_sock)