driver/power/gude: Make gude.py generic for all Gude PDUs

- changed the assert upper limit to a dynamic value.
- changed api endpoint to status.json, as it should be supported for all Gude PDUs

Co-authored-by: Moritz Marquardt <moritz.marquardt@zeiss.com>

Author: BenM-github

labgrid/driver/power/gude.py

@@ -1,35 +1,53 @@
 import requests
 
-from ..exception import ExecutionError
+
+# Driver has been tested with:
+# * Gude Expert Power Control 8031-1
+# * Gude Expert Power Control 8316-1
+# * Gude Expert Power Control 87-1210-18
+# According to the manual it also should work with:
+# * Gude Expert Power Control 8316
+#
+# This device needs to be used in 'Basic Compatible' mode for HTTP GET
+# to be usable. Do not turn on session authentication.
+#
+# HTTP-GET API is defined in the Gude EPC-HTTP-Interface specification:
+# http://wiki.gude.info/EPC_HTTP_Interface
+#
+# The `components=<N>` parameter defines which status information are
+# included into the returned JSON.
+# * `components=0` happily returns an empty response but still switches the
+#   outputs as requested.
+# * `components=1` only includes the output's state into the JSON.
 
 PORT = 80
 
+
 def power_set(host, port, index, value):
     index = int(index)
-    assert 1 <= index <= 8
+    upper_limit = count_ports(host, port)
+    assert 1 <= index <= upper_limit, f'index ({index}) out of port range (1-{upper_limit})'
     # access the web interface...
     value = 1 if value else 0
-    r = requests.get(
-        f"http://{host}:{port}/switch.html?cmd=1&p={index}&s={value}"
-    )
+    r = requests.get(f"http://{host}:{port}/status.json?components=0&cmd=1&p={index}&s={value}")
     r.raise_for_status()
 
 
 def power_get(host, port, index):
     index = int(index)
-    assert 1 <= index <= 8
-    # get the contents of the main page
-    r = requests.get(f"http://{host}:{port}/")
+
+    # get the component status
+    r = requests.get(f"http://{host}:{port}/status.json?components=1")
+    r.raise_for_status()
+
+    body = r.json() 
+    assert 1 <= index <= len(body["outputs"]), f'index ({index}) out of port range (1-{len(body["outputs"])})'
+    state = body["outputs"][index - 1]["state"]
+
+    return state
+
+
+def count_ports(host, port):
+    r = requests.get(f"http://{host}:{port}/status.json?components=1")
     r.raise_for_status()
-    for line in r.text.splitlines():
-        power_pattern = f"Power Port {index}</td>"
-        switch_patern = f"SwitchPort {index}</td>"
-        if line.find(power_pattern) > 0 or line.find(switch_patern) > 0:
-            if line.find("OFF") > 0:
-                return False
-            if line.find("ON") > 0:
-                return True
-
-            raise ExecutionError("failed to parse the port status")
-    # if we got this far, something is wrong with the website
-    raise ExecutionError("failed to find the port")
+    return len(r.json()["outputs"])