<?php

declare(strict_types=1);

namespace BitWasp\Bitcoin\Script;

use BitWasp\Bitcoin\Exceptions\MissingScriptException;
use BitWasp\Bitcoin\Exceptions\ScriptHashMismatch;
use BitWasp\Bitcoin\Exceptions\ScriptQualificationError;
use BitWasp\Bitcoin\Exceptions\SuperfluousScriptData;
use BitWasp\Bitcoin\Script\Classifier\OutputClassifier;
use BitWasp\Bitcoin\Script\Classifier\OutputData;
use BitWasp\Bitcoin\Script\Interpreter\Stack;
use BitWasp\Bitcoin\Transaction\Factory\SignData;
use BitWasp\Bitcoin\Transaction\Factory\SigValues;
use BitWasp\Bitcoin\Transaction\SignatureHash\SigHash;
use BitWasp\Buffertools\BufferInterface;

class FullyQualifiedScript
{

    /**
     * @var OutputData
     */
    private $spkData;

    /**
     * @var OutputData|null
     */
    private $rsData;

    /**
     * @var OutputData|null
     */
    private $wsData;

    /**
     * @var OutputData
     */
    private $signData;

    /**
     * @var int
     */
    private $sigVersion;

    /**
     * This is responsible for checking that the script-hash
     * commitments between scripts were satisfied, and determines
     * the sigVersion.
     *
     * It rejects superfluous redeem & witness scripts, and refuses
     * to construct unless all necessary scripts are provided.
     *
     * @param OutputData $spkData
     * @param OutputData|null $rsData
     * @param OutputData|null $wsData
     */
    public function __construct(
        OutputData $spkData,
        OutputData $rsData = null,
        OutputData $wsData = null
    ) {
        $signScript = $spkData;
        $sigVersion = SigHash::V0;

        if ($spkData->getType() === ScriptType::P2SH) {
            if (!($rsData instanceof OutputData)) {
                throw new MissingScriptException("Missing redeemScript");
            }
            if (!$rsData->getScript()->getScriptHash()->equals($spkData->getSolution())) {
                throw new ScriptHashMismatch("Redeem script fails to solve pay-to-script-hash");
            }
            $signScript = $rsData;
        } else if ($rsData) {
            throw new SuperfluousScriptData("Data provided for redeemScript was not necessary");
        }

        if ($signScript->getType() === ScriptType::P2WKH) {
            $classifier = new OutputClassifier();
            $signScript = $classifier->decode(ScriptFactory::scriptPubKey()->p2pkh($signScript->getSolution()));
            $sigVersion = SigHash::V1;
        } else if ($signScript->getType() === ScriptType::P2WSH) {
            if (!($wsData instanceof OutputData)) {
                throw new MissingScriptException("Missing witnessScript");
            }
            if (!$wsData->getScript()->getWitnessScriptHash()->equals($signScript->getSolution())) {
                $origin = $rsData ? "redeemScript" : "scriptPubKey";
                throw new ScriptHashMismatch("Witness script does not match witness program in $origin");
            }
            $signScript = $wsData;
            $sigVersion = SigHash::V1;
        } else if ($wsData) {
            throw new SuperfluousScriptData("Data provided for witnessScript was not necessary");
        }

        $this->spkData = $spkData;
        $this->rsData = $rsData;
        $this->wsData = $wsData;
        $this->signData = $signScript;
        $this->sigVersion = $sigVersion;
    }

    /**
     * Checks $chunks (a decompiled scriptSig) for it's last element,
     * or defers to SignData. If both are provided, it checks the
     * value obtained from $chunks against SignData.
     *
     * @param BufferInterface[] $chunks
     * @param SignData $signData
     * @return P2shScript
     */
    public static function findRedeemScript(array $chunks, SignData $signData)
    {
        if (count($chunks) > 0) {
            $redeemScript = new Script($chunks[count($chunks) - 1]);
            if ($signData->hasRedeemScript()) {
                if (!$redeemScript->equals($signData->getRedeemScript())) {
                    throw new ScriptQualificationError('Extracted redeemScript did not match sign data');
                }
            }
        } else {
            if (!$signData->hasRedeemScript()) {
                throw new ScriptQualificationError('Redeem script not provided in sign data or scriptSig');
            }
            $redeemScript = $signData->getRedeemScript();
        }

        if (!($redeemScript instanceof P2shScript)) {
            $redeemScript = new P2shScript($redeemScript);
        }

        return $redeemScript;
    }

    /**
     * Checks the witness for it's last element, or whatever
     * the SignData happens to have. If SignData has a WS,
     * it will ensure that if chunks has a script, it matches WS.
     * @param ScriptWitnessInterface $witness
     * @param SignData $signData
     * @return Script|ScriptInterface|WitnessScript
     */
    public static function findWitnessScript(ScriptWitnessInterface $witness, SignData $signData)
    {
        if (count($witness) > 0) {
            $witnessScript = new Script($witness->bottom());
            if ($signData->hasWitnessScript()) {
                if (!$witnessScript->equals($signData->getWitnessScript())) {
                    throw new ScriptQualificationError('Extracted witnessScript did not match sign data');
                }
            }
        } else {
            if (!$signData->hasWitnessScript()) {
                throw new ScriptQualificationError('Witness script not provided in sign data or witness');
            }
            $witnessScript = $signData->getWitnessScript();
        }

        if (!($witnessScript instanceof WitnessScript)) {
            $witnessScript = new WitnessScript($witnessScript);
        }

        return $witnessScript;
    }

    /**
     * This function attempts to produce a FQS from
     * raw scripts and witnesses. High level checking
     * of script types is done to determine what we need
     * from all this, before initializing the constructor
     * for final validation.
     *
     * @param ScriptInterface $scriptPubKey
     * @param ScriptInterface $scriptSig
     * @param ScriptWitnessInterface $witness
     * @param SignData|null $signData
     * @param OutputClassifier|null $classifier
     * @return FullyQualifiedScript
     */
    public static function fromTxData(
        ScriptInterface $scriptPubKey,
        ScriptInterface $scriptSig,
        ScriptWitnessInterface $witness,
        SignData $signData = null,
        OutputClassifier $classifier = null
    ) {
        $classifier = $classifier ?: new OutputClassifier();
        $signData = $signData ?: new SignData();

        $wsData = null;
        $rsData = null;
        $solution = $spkData = $classifier->decode($scriptPubKey);

        $sigChunks = [];
        if (!$scriptSig->isPushOnly($sigChunks)) {
            throw new ScriptQualificationError("Invalid script signature - must be PUSHONLY.");
        }

        if ($solution->getType() === ScriptType::P2SH) {
            $redeemScript = self::findRedeemScript($sigChunks, $signData);
            $solution = $rsData = $classifier->decode($redeemScript);
        }

        if ($solution->getType() === ScriptType::P2WSH) {
            $witnessScript = self::findWitnessScript($witness, $signData);
            $wsData = $classifier->decode($witnessScript);
        }

        return new FullyQualifiedScript($spkData, $rsData, $wsData);
    }

    /**
     * Was the FQS's scriptPubKey P2SH?
     * @return bool
     */
    public function isP2SH(): bool
    {
        return $this->rsData instanceof OutputData;
    }

    /**
     * Was the FQS's scriptPubKey, or redeemScript, P2WSH?
     * @return bool
     */
    public function isP2WSH(): bool
    {
        return $this->wsData instanceof OutputData;
    }

    /**
     * Returns the scriptPubKey.
     * @return OutputData
     */
    public function scriptPubKey(): OutputData
    {
        return $this->spkData;
    }

    /**
     * Returns the sign script we qualified from
     * the spk/rs/ws. Essentially this is the script
     * that actually locks the coins (the CScript
     * passed into EvalScript in interpreter.cpp)
     *
     * @return OutputData
     */
    public function signScript(): OutputData
    {
        return $this->signData;
    }

    /**
     * Returns the signature hashing algorithm version.
     * Defaults to V0, unless script was segwit.
     * @return int
     */
    public function sigVersion(): int
    {
        return $this->sigVersion;
    }

    /**
     * Returns the redeemScript, if we had one.
     * Throws an exception otherwise.
     * @return OutputData
     * @throws \RuntimeException
     */
    public function redeemScript(): OutputData
    {
        if (null === $this->rsData) {
            throw new \RuntimeException("No redeemScript for this script!");
        }

        return $this->rsData;
    }

    /**
     * Returns the witnessScript, if we had one.
     * Throws an exception otherwise.
     * @return OutputData
     * @throws \RuntimeException
     */
    public function witnessScript(): OutputData
    {
        if (null === $this->wsData) {
            throw new \RuntimeException("No witnessScript for this script!");
        }

        return $this->wsData;
    }

    /**
     * Encodes the stack (the stack passed as an
     * argument to EvalScript in interpreter.cpp)
     * into a scriptSig and witness structure. These
     * are suitable for directly encoding in a transaction.
     * @param Stack $stack
     * @return SigValues
     */
    public function encodeStack(Stack $stack): SigValues
    {
        $scriptSigChunks = $stack->all();
        $witness = [];

        $solution = $this->spkData;
        $p2sh = false;
        if ($solution->getType() === ScriptType::P2SH) {
            $p2sh = true;
            $solution = $this->rsData;
        }

        if ($solution->getType() === ScriptType::P2WKH) {
            $witness = $stack->all();
            $scriptSigChunks = [];
        } else if ($solution->getType() === ScriptType::P2WSH) {
            $witness = $stack->all();
            $witness[] = $this->wsData->getScript()->getBuffer();
            $scriptSigChunks = [];
        }

        if ($p2sh) {
            $scriptSigChunks[] = $this->rsData->getScript()->getBuffer();
        }

        return new SigValues(
            ScriptFactory::pushAll($scriptSigChunks),
            new ScriptWitness(...$witness)
        );
    }

    /**
     * @param ScriptInterface $scriptSig
     * @param ScriptWitnessInterface $witness
     * @return Stack
     */
    public function extractStack(ScriptInterface $scriptSig, ScriptWitnessInterface $witness): Stack
    {
        $sigChunks = [];
        if (!$scriptSig->isPushOnly($sigChunks)) {
            throw new \RuntimeException("Invalid signature script - must be push only");
        }

        $solution = $this->spkData;
        if ($solution->getType() === ScriptType::P2SH) {
            $solution = $this->rsData;
            $nChunks = count($sigChunks);
            if ($nChunks > 0 && $sigChunks[$nChunks - 1]->equals($this->rsData->getScript()->getBuffer())) {
                $sigChunks = array_slice($sigChunks, 0, -1);
            }
        }

        if ($solution->getType() === ScriptType::P2WKH) {
            $sigChunks = $witness->all();
        } else if ($solution->getType() === ScriptType::P2WSH) {
            $sigChunks = $witness->all();
            $nChunks = count($sigChunks);
            if ($nChunks > 0 && $sigChunks[$nChunks - 1]->equals($this->wsData->getScript()->getBuffer())) {
                $sigChunks = array_slice($sigChunks, 0, -1);
            }
        }

        return new Stack($sigChunks);
    }
}