first implementation

backend/invite_utils.py

@@ -0,0 +1,60 @@
+"""Utilities for invite code generation and validation."""
+import random
+from pathlib import Path
+
+# Load BIP39 words from file
+_WORDS_FILE = Path(__file__).parent / "words.txt"
+with open(_WORDS_FILE) as f:
+    BIP39_WORDS = [line.strip() for line in f if line.strip()]
+
+assert len(BIP39_WORDS) == 2048, f"Expected 2048 BIP39 words, got {len(BIP39_WORDS)}"
+
+
+def generate_invite_identifier() -> str:
+    """
+    Generate a unique invite identifier.
+    
+    Format: word1-word2-NN where:
+    - word1, word2 are random BIP39 words
+    - NN is a two-digit number (00-99)
+    
+    Returns lowercase identifier.
+    """
+    word1 = random.choice(BIP39_WORDS)
+    word2 = random.choice(BIP39_WORDS)
+    number = random.randint(0, 99)
+    return f"{word1}-{word2}-{number:02d}"
+
+
+def normalize_identifier(identifier: str) -> str:
+    """
+    Normalize an invite identifier for comparison/lookup.
+    
+    - Converts to lowercase
+    - Strips whitespace
+    """
+    return identifier.strip().lower()
+
+
+def is_valid_identifier_format(identifier: str) -> bool:
+    """
+    Check if an identifier has valid format (word-word-NN).
+    
+    Does NOT check if words are valid BIP39 words.
+    """
+    parts = identifier.split("-")
+    if len(parts) != 3:
+        return False
+    
+    word1, word2, number = parts
+    
+    # Check words are non-empty
+    if not word1 or not word2:
+        return False
+    
+    # Check number is two digits
+    if len(number) != 2 or not number.isdigit():
+        return False
+    
+    return True
+