bin/djbdns-logparse.py: refactor handle_* types again.

Instead of using True/False to signal success after possibly using
print() to actually write the result, we not just return either the
processed string, or None.

diff --git a/bin/djbdns-logparse.py b/bin/djbdns-logparse.py
index 97182b677c6fe2ff40f854159d7e25b73495a06a..709de6072e6dfcb699bd6c0ed6ef1bafe989f4e8 100755 (executable)
--- a/bin/djbdns-logparse.py
+++ b/bin/djbdns-logparse.py
@@ -5,8 +5,8 @@ Convert tinydns and dnscache logs to human-readable form
 
 import re, typing
 from struct import pack
-from time import strftime, gmtime
 from subprocess import Popen, PIPE
+from time import strftime, gmtime
 
 
 ## Regular expressions for matching tinydns/dnscache log lines. We
@@ -128,7 +128,7 @@ def decode_type(words, i):
     qt = words[i]
     words[i] = query_type.get(int(qt), qt)
 
-def handle_dnscache_log(line) -> bool:
+def handle_dnscache_log(line) -> typing.Optional[str]:
     """
     Handle a single log line if it matches the ``dnscache_log_re`` regex.
 
@@ -141,45 +141,40 @@ def handle_dnscache_log(line) -> bool:
     Returns
     -------
 
-    ``True`` if the log line was handled (that is, if it was really a
-    dnscache log line), and ``False`` otherwise.
+    Either the human-readable string if the log line was handled (that
+    is, if it was really a dnscache log line), or ``None`` if it was
+    not.
 
     Examples
     --------
 
         >>> line = "2022-09-15 18:37:33.863805500 query 1 7f000001:a3db:4fb9 1 www.example.com."
         >>> handle_dnscache_log(line)
-        2022-09-15 18:37:33.863805500 query #1 127.0.0.1:41947 (id 20409) a www.example.com.
-        True
+        '2022-09-15 18:37:33.863805500 query #1 127.0.0.1:41947 (id 20409) a www.example.com.'
 
         >>> line = "2022-09-15 18:37:33.863874500 tx 0 1 www.example.com. . c0a80101"
         >>> handle_dnscache_log(line)
-        2022-09-15 18:37:33.863874500 tx g=0 a www.example.com. . 192.168.1.1
-        True
+        '2022-09-15 18:37:33.863874500 tx g=0 a www.example.com. . 192.168.1.1'
 
         >>> line = "2022-09-15 18:37:33.878529500 rr c0a80101 20865 1 www.example.com. 5db8d822"
         >>> handle_dnscache_log(line)
-        2022-09-15 18:37:33.878529500 rr 192.168.1.1 TTL=20865 a www.example.com. 93.184.216.34
-        True
+        '2022-09-15 18:37:33.878529500 rr 192.168.1.1 TTL=20865 a www.example.com. 93.184.216.34'
 
         >>> line = "2022-09-15 18:37:33.878532500 stats 1 43 1 0"
         >>> handle_dnscache_log(line)
-        2022-09-15 18:37:33.878532500 stats count=1 motion=43 udp-active=1 tcp-active=0
-        True
+        '2022-09-15 18:37:33.878532500 stats count=1 motion=43 udp-active=1 tcp-active=0'
 
         >>> line = "2022-09-15 18:37:33.878602500 sent 1 49"
         >>> handle_dnscache_log(line)
-        2022-09-15 18:37:33.878602500 sent #1 49
-        True
+        '2022-09-15 18:37:33.878602500 sent #1 49'
 
         >>> line = "this line is nonsense"
         >>> handle_dnscache_log(line)
-        False
 
     """
     match = dnscache_log_re.match(line)
     if not match:
-        return False
+        return None
 
     (timestamp, event, data) = match.groups()
 
@@ -249,11 +244,11 @@ def handle_dnscache_log(line) -> bool:
     elif event in ("tcpopen", "tcpclose"):
         decode_client(words, 0)
 
-    print(timestamp, event, " ".join(words))
-    return True
+    return f"{timestamp} {event} " + " ".join(words)
+
 
 
-def handle_tinydns_log(line : str) -> bool:
+def handle_tinydns_log(line : str) -> typing.Optional[str]:
     """
     Handle a single log line if it matches the ``tinydns_log_re`` regex.
 
@@ -266,25 +261,24 @@ def handle_tinydns_log(line : str) -> bool:
     Returns
     -------
 
-    ``True`` if the log line was handled (that is, if it was really a
-    tinydns log line), and ``False`` otherwise.
+    Either the human-readable string if the log line was handled (that
+    is, if it was really a tinydns log line), or ``None`` if it was
+    not.
 
     Examples
     --------
 
         >>> line = "2022-09-14 21:04:40.206516500 7f000001:9d61:be69 - 0001 www.example.com"
         >>> handle_tinydns_log(line)
-        2022-09-14 21:04:40.206516500 dropped query (no authority) from 127.0.0.1:40289 (id 48745): a www.example.com
-        True
+        '2022-09-14 21:04:40.206516500 dropped query (no authority) from 127.0.0.1:40289 (id 48745): a www.example.com'
 
         >>> line = "this line is nonsense"
         >>> handle_tinydns_log(line)
-        False
 
     """
     match = tinydns_log_re.match(line)
     if not match:
-        return False
+        return None
 
     (timestamp, ip, port, id, code, type, name) = match.groups()
     ip = convert_ip(ip)
@@ -297,25 +291,25 @@ def handle_tinydns_log(line : str) -> bool:
     type = int(type, 16)                # "001c" -> 28
     type = query_type.get(type, type)   # 28 -> "aaaa"
 
-    print(timestamp, end=' ')
+    line_tpl = "{timestamp} "
 
     reason = query_drop_reason[code]
     if code == "+":
-        line_tpl = "sent response to {ip}:{port} (id {id}): {type} {name}"
+        line_tpl += "sent response to {ip}:{port} (id {id}): {type} {name}"
     else:
-        line_tpl = "dropped query ({reason}) from {ip}:{port}"
+        line_tpl += "dropped query ({reason}) from {ip}:{port}"
         if code != "/":
             # If the query can actually be parsed, the log line is a
             # bit more informative than it would have been otherwise.
             line_tpl += " (id {id}): {type} {name}"
 
-    print(line_tpl.format(reason=reason,
-                          ip=ip,
-                          port=port,
-                          id=id,
-                          type=type,
-                          name=name))
-    return True
+    return line_tpl.format(timestamp=timestamp,
+                           reason=reason,
+                           ip=ip,
+                           port=port,
+                           id=id,
+                           type=type,
+                           name=name)
 
 
 def parse_logfile(file : typing.TextIO):
@@ -352,9 +346,13 @@ def parse_logfile(file : typing.TextIO):
         tai.stdin.write(line)
         line = tai.stdout.readline()
 
-        if not handle_tinydns_log(line):
-            if not handle_dnscache_log(line):
-                print(line, end='')
+        friendly_line = handle_tinydns_log(line)
+        if not friendly_line:
+            friendly_line = handle_dnscache_log(line)
+            if not friendly_line:
+                friendly_line = line
+
+        print(friendly_line)
 
 def main():
     r"""