import base64

def audit_psbt(psbt_base64):
    try:
        # 1. Decode Base64 to Raw Bytes
        raw_bytes = base64.b64decode(psbt_base64)
    except Exception as e:
        print("[ERROR] Invalid Base64 string!")
        return

    print(f"--- PSBT Binary Audit ---")
    print(f"[*] Total Length: {len(raw_bytes)} bytes")

    # 2. Check Magic Bytes (psbt\\xff)
    magic = raw_bytes[:5]
    if magic == b'psbt\\xff' or magic == b'psbt\\xdf': # Handling different encodings
        print(f"[*] Magic Bytes:   VALID ({magic.hex()})")
    elif magic.startswith(b'psbt'):
        print(f"[*] Magic Bytes:   VALID (psbt header found)")
    else:
        print(f"[!] WARNING: Magic bytes mismatch! Found: {magic.hex()}")

    # 3. Locate the Global Map
    # The Global Map starts immediately after the 5 magic bytes
    # Each map entry: [KeyLen][KeyType][KeyData][ValLen][ValData]

    print(f"[*] Internal Map Structure Detected...")

    # 4. Heuristic: Look for partial signatures (Key Type 0x02)
    sig_count = raw_bytes.count(b'\\x02', 5) # Rough estimate
    print(f"[*] Estimated Partial Signatures: {sig_count}")

    # 5. Extraction Logic (Simplified)
    # A real decoder would iterate through keys 0x00 to 0x05
    if b'\\x00' in raw_bytes[5:20]:
        print("[*] Global Unsigned Transaction: FOUND")

# --- Simulation ---

# A real PSBT usually looks like this:
# cHNidP8BAHUCAAAAARm...
example_psbt = "cHNidP8BAHUCAAAAAf//////////////////////////////////////////AAAAAAD/////Af6p6A8AAAAAABYAFH6nE39Y6S77CIs+Vn0fCgE8E8E8AAAAAA=="

audit_psbt(example_psbt)