import struct

def parse_tx_inputs(tx_hex):
    # Convert hex to bytes
    tx_bytes = bytes.fromhex(tx_hex)

    # Skip Version (4 bytes)
    cursor = 4

    # Read Input Count (simplified VarInt logic for this example)
    # Most standard TXs have 1-252 inputs (1 byte)
    input_count = tx_bytes[cursor]
    cursor += 1

    print(f"--- Parsing {input_count} Transaction Inputs ---")

    for i in range(input_count):
        # 1. Read TXID (32 bytes, stored in little-endian)
        raw_txid = tx_bytes[cursor:cursor+32]
        # Reverse to display as Big-Endian (Block Explorer format)
        display_txid = raw_txid[::-1].hex()
        cursor += 32

        # 2. Read VOUT (4 bytes, little-endian uint32)
        raw_vout = tx_bytes[cursor:cursor+4]
        vout = struct.unpack('<I', raw_vout)[0]
        cursor += 4

        # Print results
        print(f"\n[Input {i}]")
        print(f"[*] Previous TXID: {display_txid}")
        print(f"[*] Output Index:  {vout}")

        # Skip ScriptSig Length and ScriptSig for this simulation
        script_len = tx_bytes[cursor]
        cursor += 1 + script_len

        # Skip Sequence (4 bytes)
        cursor += 4

# --- Simulation ---
# A real Bitcoin transaction hex (truncated for example)
sample_tx = (
    "01000000" + # Version
    "01" +       # Input Count (1)
    "81cd6495d3550e553c3066d40026a090ef666993a46610000000000000000000" + # TXID
    "00000000" + # VOUT (0)
    "016a" +     # ScriptLen (1) and ScriptSig (0x6a)
    "ffffffff"   # Sequence
)

parse_tx_inputs(sample_tx)