// Copyright (c) 2013-2014 Conformal Systems LLC.
// Use of this source code is governed by an ISC
// license that can be found in the LICENSE file.

package btcscript

import (
	"github.com/btcsuite/btcnet"
	"github.com/btcsuite/btcutil"
)

// ExtractPkScriptAddrs returns the type of script, addresses and required
// signatures associated with the passed PkScript.  Note that it only works for
// 'standard' transaction script types.  Any data such as public keys which are
// invalid are omitted from the results.
func ExtractPkScriptAddrs(pkScript []byte, net *btcnet.Params) (ScriptClass, []btcutil.Address, int, error) {
	var addrs []btcutil.Address
	var requiredSigs int

	// No valid addresses or required signatures if the script doesn't
	// parse.
	pops, err := parseScript(pkScript)
	if err != nil {
		return NonStandardTy, nil, 0, err
	}

	scriptClass := typeOfScript(pops)
	switch scriptClass {
	case PubKeyHashTy:
		// A pay-to-pubkey-hash script is of the form:
		//  OP_DUP OP_HASH160 <hash> OP_EQUALVERIFY OP_CHECKSIG
		// Therefore the pubkey hash is the 3rd item on the stack.
		// Skip the pubkey hash if it's invalid for some reason.
		requiredSigs = 1
		addr, err := btcutil.NewAddressPubKeyHash(pops[2].data, net)
		if err == nil {
			addrs = append(addrs, addr)
		}

	case PubKeyTy:
		// A pay-to-pubkey script is of the form:
		//  <pubkey> OP_CHECKSIG
		// Therefore the pubkey is the first item on the stack.
		// Skip the pubkey if it's invalid for some reason.
		requiredSigs = 1
		addr, err := btcutil.NewAddressPubKey(pops[0].data, net)
		if err == nil {
			addrs = append(addrs, addr)
		}

	case ScriptHashTy:
		// A pay-to-script-hash script is of the form:
		//  OP_HASH160 <scripthash> OP_EQUAL
		// Therefore the script hash is the 2nd item on the stack.
		// Skip the script hash if it's invalid for some reason.
		requiredSigs = 1
		addr, err := btcutil.NewAddressScriptHashFromHash(pops[1].data, net)
		if err == nil {
			addrs = append(addrs, addr)
		}

	case MultiSigTy:
		// A multi-signature script is of the form:
		//  <numsigs> <pubkey> <pubkey> <pubkey>... <numpubkeys> OP_CHECKMULTISIG
		// Therefore the number of required signatures is the 1st item
		// on the stack and the number of public keys is the 2nd to last
		// item on the stack.
		requiredSigs = asSmallInt(pops[0].opcode)
		numPubKeys := asSmallInt(pops[len(pops)-2].opcode)

		// Extract the public keys while skipping any that are invalid.
		addrs = make([]btcutil.Address, 0, numPubKeys)
		for i := 0; i < numPubKeys; i++ {
			addr, err := btcutil.NewAddressPubKey(pops[i+1].data, net)
			if err == nil {
				addrs = append(addrs, addr)
			}
		}

	case NullDataTy:
		// Null data transactions have no addresses or required
		// signatures.

	case NonStandardTy:
		// Don't attempt to extract addresses or required signatures for
		// nonstandard transactions.
	}

	return scriptClass, addrs, requiredSigs, nil
}