From fce146cb613ee6d6e334d9bee8430ff430cd7619 Mon Sep 17 00:00:00 2001
From: Maria Matejka <mq@ucw.cz>
Date: Thu, 18 Jul 2024 23:34:07 +0200
Subject: [PATCH] CLI module: basic show route parsing

---
 python/BIRD/CLI.py       |   8 ++-
 python/BIRD/ShowRoute.py | 138 +++++++++++++++++++++++++++++++++++++++
 python/BIRD/Test.py      |   3 +-
 3 files changed, 146 insertions(+), 3 deletions(-)
 create mode 100644 python/BIRD/ShowRoute.py

diff --git a/python/BIRD/CLI.py b/python/BIRD/CLI.py
index d4695391..72d1500a 100644
--- a/python/BIRD/CLI.py
+++ b/python/BIRD/CLI.py
@@ -1,3 +1,5 @@
+from . import ShowRoute
+
 class Transport:
     pass
 
@@ -20,4 +22,8 @@ class CLI:
             cmd.append("table")
             cmd.append(t)
 
-        return await self.transport.send_cmd(*cmd)
+        result = await self.transport.send_cmd(*cmd)
+        if len(result["err"]):
+            raise Exception(f"Command {cmd} returned {result['err'].decode()}, stdout={result['out'].decode()}")
+
+        return ShowRoute.parse(result["out"].decode())
diff --git a/python/BIRD/ShowRoute.py b/python/BIRD/ShowRoute.py
new file mode 100644
index 00000000..7ff2420b
--- /dev/null
+++ b/python/BIRD/ShowRoute.py
@@ -0,0 +1,138 @@
+import re
+
+class ParserException(Exception):
+    pass
+
+def subparser(base):
+    def decorator(cls):
+        base.subparsers = { **base.subparsers, cls.entryRegex: cls }
+        return cls
+    return decorator
+
+class CLIParser:
+    subparsers = {}
+    def __init__(self, groups=None, parent=None):
+        self.result = {}
+        self.parent = parent
+        self.cur = None
+
+        if parent is None:
+            assert(groups is None)
+            return
+
+        self.enter(groups)
+        print("subparser inited", self, self.result)
+
+    def parse(self, line: str):
+        print(f"in {self} parsing line {line}")
+        assert(self.cur == None)
+        if line is not None:
+            for k,v in self.subparsers.items():
+                print(f"trying to match {k} for {v}")
+                if m := k.match(line):
+                    self.cur = (c := v(groups=m.groups(), parent=self))
+                    while c.cur is not None:
+                        c = c.cur
+                    return c
+        elif self.parent is None:
+            print("overall exit", self, self.result)
+            return self
+
+        try:
+            print(f"exiting {self} with result {self.result}")
+            self.exit()
+            self.parent.cur = None
+            return self.parent.parse(line)
+
+        except Exception as e:
+            print(f"Failed to parse line: {line}")
+            raise e
+
+    def exit(self):
+        raise ParserException(f"Failed to match line to all regexes")
+
+@subparser(CLIParser)
+class VersionParser(CLIParser):
+    entryRegex = re.compile("BIRD ([0-9a-z._-]+) ready.")
+    def enter(self, groups):
+        self.version ,= groups
+
+    def exit(self):
+        if "version" in self.parent.result:
+            raise ParserException(f"Duplicate version line")
+
+        self.parent.result["version"] = self.version
+
+class ShowRouteParser(CLIParser):
+    def __init__(self):
+        super().__init__()
+        self.result["tables"] = {}
+        print("parser init", self, self.result)
+
+@subparser(ShowRouteParser)
+class NothingParser(CLIParser):
+    entryRegex = re.compile("^$")
+    def enter(self, _):
+        pass
+
+    def exit(self):
+        pass
+
+@subparser(ShowRouteParser)
+class TableParser(CLIParser):
+    entryRegex = re.compile("^Table (.*):$")
+    def enter(self, groups):
+        self.name ,= groups
+        self.result["networks"] = {}
+
+    def exit(self):
+        if self.name in self.parent.result["tables"]:
+            raise ParserException(f"Duplicate table name")
+
+        self.parent.result["tables"][self.name] = self.result
+
+@subparser(TableParser)
+class NetworkParser(CLIParser):
+    entryRegex = re.compile("([0-9a-f:.]+/[0-9]+)(\\s+.*)")
+    def enter(self, groups):
+        self.network, rest = groups
+        self.result["routes"] = []
+        self.parse(rest)
+
+    def exit(self):
+        self.parent.result["networks"][self.network] = self.result
+
+@subparser(NetworkParser)
+class RouteParser(CLIParser):
+    entryRegex = re.compile("\\s+(unicast|unreachable) \\[(.*) ((?:[0-9]{2}:){2}[0-9]{2}\\.[0-9]{3})\\] (.*)")
+    def enter(self, groups):
+        self.result = {
+                k: v for k,v in zip(("dest", "proto", "when", "args"), groups)
+                }
+        if self.result["dest"] == "unicast":
+            self.result["nexthop"] = []
+
+    def exit(self):
+        self.parent.result["routes"].append(self.result)
+
+@subparser(RouteParser)
+class NextHopParser(CLIParser):
+    entryRegex = re.compile("\\s+via ([0-9a-f:.]+) on (.*)")
+    def enter(self, groups):
+        self.result = { 
+                k: v for k,v in zip(("nexthop", "iface"), groups)
+                }
+
+    def exit(self):
+        self.parent.result["nexthop"].append(self.result)
+
+def parse(data: str):
+    parser = ShowRouteParser()
+    print("created parser", parser)
+    for line in data.split("\n"):
+        parser = parser.parse(line)
+
+    parser = parser.parse(None)
+
+    print("returning result", parser.result)
+    return parser.result
diff --git a/python/BIRD/Test.py b/python/BIRD/Test.py
index 8d269d9b..d35636ff 100644
--- a/python/BIRD/Test.py
+++ b/python/BIRD/Test.py
@@ -203,8 +203,7 @@ class Test:
                     ]
 
         print(*[
-            f["out"].decode()
-            for f in await asyncio.gather(*[
+            await asyncio.gather(*[
                 where.show_route()
                 for where in machines
                 ])