implemented

backend/validation.py

@@ -0,0 +1,135 @@
+"""Validation utilities for user profile fields."""
+import re
+from email_validator import validate_email, EmailNotValidError
+from bech32 import bech32_decode
+
+
+def validate_contact_email(value: str | None) -> str | None:
+    """
+    Validate contact email format.
+    
+    Returns None if valid, error message if invalid.
+    Empty/None values are valid (field is optional).
+    """
+    if not value:
+        return None
+    
+    try:
+        validate_email(value, check_deliverability=False)
+        return None
+    except EmailNotValidError as e:
+        return str(e)
+
+
+def validate_telegram(value: str | None) -> str | None:
+    """
+    Validate Telegram handle.
+    
+    Must start with @ if provided.
+    Returns None if valid, error message if invalid.
+    Empty/None values are valid (field is optional).
+    """
+    if not value:
+        return None
+    
+    if not value.startswith("@"):
+        return "Telegram handle must start with @"
+    
+    if len(value) < 2:
+        return "Telegram handle must have at least one character after @"
+    
+    # Telegram usernames: 5-32 characters, alphanumeric and underscores
+    # But we store with @, so check 6-33 total
+    handle = value[1:]  # Remove @
+    if len(handle) < 5:
+        return "Telegram handle must be at least 5 characters (after @)"
+    
+    if len(handle) > 32:
+        return "Telegram handle must be at most 32 characters (after @)"
+    
+    if not re.match(r'^[a-zA-Z][a-zA-Z0-9_]*$', handle):
+        return "Telegram handle must start with a letter and contain only letters, numbers, and underscores"
+    
+    return None
+
+
+def validate_signal(value: str | None) -> str | None:
+    """
+    Validate Signal username.
+    
+    Any non-empty string is valid.
+    Returns None if valid, error message if invalid.
+    Empty/None values are valid (field is optional).
+    """
+    if not value:
+        return None
+    
+    # Signal usernames are fairly permissive, just check it's not empty
+    if len(value.strip()) == 0:
+        return "Signal username cannot be empty"
+    
+    if len(value) > 64:
+        return "Signal username must be at most 64 characters"
+    
+    return None
+
+
+def validate_nostr_npub(value: str | None) -> str | None:
+    """
+    Validate Nostr npub (public key in bech32 format).
+    
+    Must be valid bech32 with 'npub' prefix.
+    Returns None if valid, error message if invalid.
+    Empty/None values are valid (field is optional).
+    """
+    if not value:
+        return None
+    
+    if not value.startswith("npub1"):
+        return "Nostr npub must start with 'npub1'"
+    
+    # Decode bech32 to validate checksum
+    hrp, data = bech32_decode(value)
+    
+    if hrp is None or data is None:
+        return "Invalid Nostr npub: bech32 checksum failed"
+    
+    if hrp != "npub":
+        return "Nostr npub must have 'npub' prefix"
+    
+    # npub should decode to 32 bytes (256 bits) for a public key
+    # In bech32, each character encodes 5 bits, so 32 bytes = 52 characters of data
+    if len(data) != 52:
+        return "Invalid Nostr npub: incorrect length"
+    
+    return None
+
+
+def validate_profile_fields(
+    contact_email: str | None = None,
+    telegram: str | None = None,
+    signal: str | None = None,
+    nostr_npub: str | None = None,
+) -> dict[str, str]:
+    """
+    Validate all profile fields at once.
+    
+    Returns a dict of field_name -> error_message for any invalid fields.
+    Empty dict means all fields are valid.
+    """
+    errors: dict[str, str] = {}
+    
+    if err := validate_contact_email(contact_email):
+        errors["contact_email"] = err
+    
+    if err := validate_telegram(telegram):
+        errors["telegram"] = err
+    
+    if err := validate_signal(signal):
+        errors["signal"] = err
+    
+    if err := validate_nostr_npub(nostr_npub):
+        errors["nostr_npub"] = err
+    
+    return errors
+