first commit

backend/app/kyc_validators.py

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+import re
+
+PAN_PATTERN = re.compile(r"^[A-Z]{5}[0-9]{4}[A-Z]$")
+GST_PATTERN = re.compile(r"^[0-9]{2}[A-Z]{5}[0-9]{4}[A-Z][1-9A-Z]Z[0-9A-Z]$")
+
+
+def normalize_pan(value: str) -> str:
+    return value.strip().upper()
+
+
+def normalize_gst(value: str) -> str:
+    return value.strip().upper()
+
+
+def validate_pan(value: str) -> str:
+    pan = normalize_pan(value)
+    if not PAN_PATTERN.match(pan):
+        raise ValueError("PAN must match format ABCDE1234F")
+    return pan
+
+
+def validate_gst(value: str) -> str:
+    gst = normalize_gst(value)
+    if not GST_PATTERN.match(gst):
+        raise ValueError("GST must be a valid 15-character Indian GSTIN")
+    return gst