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