feat: markov bigram nick generator for natural-looking identities

Replace uniform random chars with English bigram frequency table.
Enforces max 2 consecutive consonants for pronounceability. Nicks,
idents, and realnames now look like plausible human-chosen words.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

src/bouncer/network.py

@@ -5,7 +5,6 @@ from __future__ import annotations
 import asyncio
 import logging
 import random
-import string
 from enum import Enum, auto
 from typing import Callable
 
@@ -28,30 +27,86 @@ class State(Enum):
     READY = auto()
 
 
+# English bigram transitions tuned for pronounceability.
+# Consonants -> vowel-heavy followers, vowels -> consonant-heavy followers.
+_BIGRAMS: dict[str, str] = {
+    "a": "ntrslcdmgbpkivwfyh",
+    "b": "eeoaruiy",
+    "c": "ooehaakri",
+    "d": "eeioaury",
+    "e": "rnsdltacmxpvwiy",
+    "f": "iioeerau",
+    "g": "eeohairu",
+    "h": "eeaoitru",
+    "i": "nstcldemorgav",
+    "j": "ooueeai",
+    "k": "eeinsay",
+    "l": "eeioalduys",
+    "m": "eeaoipuy",
+    "n": "gdeetioauc",
+    "o": "nfrumtlswpcdvbgk",
+    "p": "eeroalih",
+    "q": "u",
+    "r": "eeioastundy",
+    "s": "teehioaupl",
+    "t": "hheiaorusy",
+    "u": "rnstlcpmgdba",
+    "v": "eeiiao",
+    "w": "aaihone",
+    "x": "iieea",
+    "y": "seomtaiwn",
+    "z": "eaaio",
+}
+
+_VOWELS = set("aeiou")
+
+# Starting letter weights (English word-initial frequency)
+_STARTERS = "ttssaaccmmppddhhiibbrrffggll"
+
+
+def _markov_word(min_len: int, max_len: int) -> str:
+    """Generate a pronounceable word using English bigram frequencies."""
+    length = random.randint(min_len, max_len)
+    ch = random.choice(_STARTERS)
+    word = [ch]
+    consonant_run = 0 if ch in _VOWELS else 1
+
+    for _ in range(length - 1):
+        followers = _BIGRAMS.get(ch, "aeiou")
+        # If we've had 2 consonants in a row, force a vowel
+        if consonant_run >= 2:
+            vowels = [c for c in followers if c in _VOWELS]
+            ch = random.choice(vowels) if vowels else random.choice("aeiou")
+        else:
+            ch = random.choice(followers)
+
+        if ch in _VOWELS:
+            consonant_run = 0
+        else:
+            consonant_run += 1
+
+        word.append(ch)
+    return "".join(word)
+
+
 def _random_nick() -> str:
-    """Generate a nick that looks like a typical human-chosen IRC nick."""
-    # Mix of patterns seen on real IRC networks
-    length = random.randint(6, 10)
-    # Start with a letter, rest is alphanumeric
-    first = random.choice(string.ascii_lowercase)
-    rest = "".join(random.choices(string.ascii_lowercase + string.digits, k=length - 1))
-    return first + rest
+    """Generate a pronounceable nick that looks human-chosen."""
+    base = _markov_word(5, 8)
+    # Occasionally append a digit suffix (common IRC pattern)
+    if random.random() < 0.3:
+        base += str(random.randint(0, 99))
+    return base
 
 
 def _random_user() -> str:
-    """Generate a generic-looking ident."""
-    length = random.randint(4, 8)
-    first = random.choice(string.ascii_lowercase)
-    rest = "".join(random.choices(string.ascii_lowercase, k=length - 1))
-    return first + rest
+    """Generate a pronounceable ident."""
+    return _markov_word(4, 7)
 
 
 def _random_realname() -> str:
-    """Generate a plausible realname."""
-    length = random.randint(4, 8)
-    first = random.choice(string.ascii_uppercase)
-    rest = "".join(random.choices(string.ascii_lowercase, k=length - 1))
-    return first + rest
+    """Generate a plausible first-name-like realname."""
+    name = _markov_word(4, 7)
+    return name[0].upper() + name[1:]
 
 
 class Network: