/*
 * Copyright (C) 2015 Dominik Schürmann <dominik@dominikschuermann.de>
 *
 * This program is free software: you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program.  If not, see <http://www.gnu.org/licenses/>.
 */

package org.sufficientlysecure.keychain.operations;


import java.io.ByteArrayOutputStream;
import java.io.FileNotFoundException;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.util.ArrayList;

import android.content.ClipDescription;
import android.content.Context;
import android.net.Uri;
import android.support.annotation.NonNull;
import android.text.TextUtils;
import android.webkit.MimeTypeMap;

import org.apache.james.mime4j.MimeException;
import org.apache.james.mime4j.codec.DecodeMonitor;
import org.apache.james.mime4j.dom.field.ContentDispositionField;
import org.apache.james.mime4j.field.DefaultFieldParser;
import org.apache.james.mime4j.parser.AbstractContentHandler;
import org.apache.james.mime4j.parser.MimeStreamParser;
import org.apache.james.mime4j.stream.BodyDescriptor;
import org.apache.james.mime4j.stream.Field;
import org.apache.james.mime4j.stream.MimeConfig;
import org.openintents.openpgp.OpenPgpMetadata;
import org.sufficientlysecure.keychain.operations.results.DecryptVerifyResult;
import org.sufficientlysecure.keychain.operations.results.InputDataResult;
import org.sufficientlysecure.keychain.operations.results.OperationResult.LogType;
import org.sufficientlysecure.keychain.operations.results.OperationResult.OperationLog;
import org.sufficientlysecure.keychain.pgp.PgpDecryptVerifyInputParcel;
import org.sufficientlysecure.keychain.pgp.PgpDecryptVerifyOperation;
import org.sufficientlysecure.keychain.pgp.Progressable;
import org.sufficientlysecure.keychain.provider.ProviderHelper;
import org.sufficientlysecure.keychain.provider.TemporaryFileProvider;
import org.sufficientlysecure.keychain.service.InputDataParcel;
import org.sufficientlysecure.keychain.service.input.CryptoInputParcel;
import org.sufficientlysecure.keychain.util.CharsetVerifier;


/** This operation deals with input data, trying to determine its type as it goes.
 *
 * We deal with four types of structures:
 *
 * - signed/encrypted non-mime data
 * - signed/encrypted mime data
 * - encrypted multipart/signed mime data
 * - multipart/signed mime data (WIP)
 *
 */
public class InputDataOperation extends BaseOperation<InputDataParcel> {

    private final byte[] buf = new byte[256];

    public InputDataOperation(Context context, ProviderHelper providerHelper, Progressable progressable) {
        super(context, providerHelper, progressable);
    }

    Uri mSignedDataUri;
    DecryptVerifyResult mSignedDataResult;

    @NonNull
    @Override
    public InputDataResult execute(InputDataParcel input, final CryptoInputParcel cryptoInput) {

        final OperationLog log = new OperationLog();

        log.add(LogType.MSG_DATA, 0);

        Uri currentInputUri;

        DecryptVerifyResult decryptResult = null;

        PgpDecryptVerifyInputParcel decryptInput = input.getDecryptInput();

        if (!input.getMimeDecode() && decryptInput == null) {
            throw new AssertionError("no decryption or mime decoding, this is probably a bug");
        }

        if (decryptInput != null) {

            log.add(LogType.MSG_DATA_OPENPGP, 1);

            PgpDecryptVerifyOperation op =
                    new PgpDecryptVerifyOperation(mContext, mProviderHelper, mProgressable);

            decryptInput.setInputUri(input.getInputUri());

            currentInputUri = TemporaryFileProvider.createFile(mContext);
            decryptInput.setOutputUri(currentInputUri);

            decryptResult = op.execute(decryptInput, cryptoInput);
            if (decryptResult.isPending()) {
                return new InputDataResult(log, decryptResult);
            }
            log.addByMerge(decryptResult, 1);

            if ( ! decryptResult.success()) {
                return new InputDataResult(InputDataResult.RESULT_ERROR, log);
            }

            // inform the storage provider about the mime type for this uri
            if (decryptResult.getDecryptionMetadata() != null) {
                OpenPgpMetadata meta = decryptResult.getDecryptionMetadata();
                TemporaryFileProvider.setName(mContext, currentInputUri, meta.getFilename());
                TemporaryFileProvider.setMimeType(mContext, currentInputUri, meta.getMimeType());
            }

        } else {
            currentInputUri = input.getInputUri();
        }

        // don't even attempt if we know the data isn't suitable for mime content, or if we have a filename
        boolean skipMimeParsing = false;
        if (decryptResult != null && decryptResult.getDecryptionMetadata() != null) {
            OpenPgpMetadata metadata = decryptResult.getDecryptionMetadata();
            String fileName = metadata.getFilename();
            String contentType = metadata.getMimeType();
            if (!TextUtils.isEmpty(fileName)
                    || contentType != null
                        && !contentType.startsWith("multipart/")
                        && !contentType.startsWith("text/")
                        && !"application/octet-stream".equals(contentType)) {
                skipMimeParsing = true;
            }
        }

        // If we aren't supposed to attempt mime decode after decryption, we are done here
        if (skipMimeParsing || !input.getMimeDecode()) {

            log.add(LogType.MSG_DATA_SKIP_MIME, 1);

            ArrayList<Uri> uris = new ArrayList<>();
            uris.add(currentInputUri);
            ArrayList<OpenPgpMetadata> metadatas = new ArrayList<>();
            metadatas.add(decryptResult.getDecryptionMetadata());

            log.add(LogType.MSG_DATA_OK, 1);
            return new InputDataResult(InputDataResult.RESULT_OK, log, decryptResult, uris, metadatas);

        }

        final MimeStreamParser parser = new MimeStreamParser((MimeConfig) null);

        final ArrayList<Uri> outputUris = new ArrayList<>();
        final ArrayList<OpenPgpMetadata> metadatas = new ArrayList<>();

        parser.setContentDecoding(true);
        parser.setRecurse();
        parser.setContentHandler(new AbstractContentHandler() {
            private boolean mFoundHeaderWithFields = false;
            private Uri uncheckedSignedDataUri;
            String mFilename;

            @Override
            public void startMultipart(BodyDescriptor bd) throws MimeException {
                if ("signed".equals(bd.getSubType())) {
                    if (mSignedDataUri != null) {
                        // recursive signed data is not supported, and will just be parsed as-is
                        log.add(LogType.MSG_DATA_DETACHED_NESTED, 2);
                        return;
                    }
                    log.add(LogType.MSG_DATA_DETACHED, 2);
                    if (!outputUris.isEmpty()) {
                        // we can't have previous data if we parse a detached signature!
                        log.add(LogType.MSG_DATA_DETACHED_CLEAR, 3);
                        outputUris.clear();
                        metadatas.clear();
                    }
                    // this is signed data, we require the next part raw
                    parser.setRaw();
                }
            }

            @Override
            public void raw(InputStream is) throws MimeException, IOException {

                if (uncheckedSignedDataUri != null) {
                    throw new AssertionError("raw parts must only be received as first part of multipart/signed!");
                }

                log.add(LogType.MSG_DATA_DETACHED_RAW, 3);

                uncheckedSignedDataUri = TemporaryFileProvider.createFile(mContext, mFilename, "text/plain");
                OutputStream out = mContext.getContentResolver().openOutputStream(uncheckedSignedDataUri, "w");

                if (out == null) {
                    throw new IOException("Error getting file for writing!");
                }

                int len;
                while ((len = is.read(buf)) > 0) {
                    out.write(buf, 0, len);
                }

                out.close();
                // continue to next body part the usual way
                parser.setFlat();

            }

            @Override
            public void startHeader() throws MimeException {
                mFilename = null;
            }

            @Override
            public void endHeader() throws MimeException {
                if ( ! mFoundHeaderWithFields) {
                    parser.stop();
                }
            }

            @Override
            public void field(Field field) throws MimeException {
                field = DefaultFieldParser.getParser().parse(field, DecodeMonitor.SILENT);
                if (field instanceof ContentDispositionField) {
                    mFilename = ((ContentDispositionField) field).getFilename();
                }
                mFoundHeaderWithFields = true;
            }

            private void bodySignature(BodyDescriptor bd, InputStream is) throws MimeException, IOException {

                if (!"application/pgp-signature".equals(bd.getMimeType())) {
                    log.add(LogType.MSG_DATA_DETACHED_UNSUPPORTED, 3);
                    uncheckedSignedDataUri = null;
                    parser.setRecurse();
                    return;
                }

                log.add(LogType.MSG_DATA_DETACHED_SIG, 3);

                ByteArrayOutputStream detachedSig = new ByteArrayOutputStream();

                int len, totalLength = 0;
                while ((len = is.read(buf)) > 0) {
                    totalLength += len;
                    detachedSig.write(buf, 0, len);
                    if (totalLength > 4096) {
                        throw new IOException("detached signature is unreasonably large!");
                    }
                }
                detachedSig.close();

                PgpDecryptVerifyInputParcel decryptInput = new PgpDecryptVerifyInputParcel();
                decryptInput.setInputUri(uncheckedSignedDataUri);
                decryptInput.setDetachedSignature(detachedSig.toByteArray());

                PgpDecryptVerifyOperation op =
                        new PgpDecryptVerifyOperation(mContext, mProviderHelper, mProgressable);
                DecryptVerifyResult verifyResult = op.execute(decryptInput, cryptoInput);

                log.addByMerge(verifyResult, 4);

                mSignedDataUri = uncheckedSignedDataUri;
                mSignedDataResult = verifyResult;

                // reset parser state
                uncheckedSignedDataUri = null;
                parser.setRecurse();

            }

            @Override
            public void body(BodyDescriptor bd, InputStream is) throws MimeException, IOException {

                // if we have signed data waiting, we expect a signature for checking
                if (uncheckedSignedDataUri != null) {
                    bodySignature(bd, is);
                    return;
                }

                // we read first, no need to create an output file if nothing was read!
                int len = is.read(buf);
                if (len < 0) {
                    return;
                }

                // If mSignedDataUri is non-null, we already parsed a signature. If mSignedDataResult is non-null
                // too, we are still in the same parsing stage, so this is trailing data - skip it!
                if (mSignedDataUri != null && mSignedDataResult != null) {
                    log.add(LogType.MSG_DATA_DETACHED_TRAILING, 2);
                    return;
                }

                log.add(LogType.MSG_DATA_MIME_PART, 2);

                String mimeType = bd.getMimeType();

                if (mFilename != null) {
                    log.add(LogType.MSG_DATA_MIME_FILENAME, 3, mFilename);
                    boolean isGenericMimeType = ClipDescription.compareMimeTypes(mimeType, "application/octet-stream")
                            || ClipDescription.compareMimeTypes(mimeType, "application/x-download");
                    if (isGenericMimeType) {
                        String extension = MimeTypeMap.getFileExtensionFromUrl(mFilename);
                        String extMimeType = MimeTypeMap.getSingleton().getMimeTypeFromExtension(extension);
                        if (extMimeType != null) {
                            mimeType = extMimeType;
                            log.add(LogType.MSG_DATA_MIME_FROM_EXTENSION, 3);
                        }
                    }
                }
                log.add(LogType.MSG_DATA_MIME_TYPE, 3, mimeType);

                Uri uri = TemporaryFileProvider.createFile(mContext, mFilename, mimeType);
                OutputStream out = mContext.getContentResolver().openOutputStream(uri, "w");

                if (out == null) {
                    throw new IOException("Error getting file for writing!");
                }

                // If this data looks like text, we pipe the incoming data into a charset
                // decoder, to see if the data is legal for the assumed charset.
                String charset = bd.getCharset();
                CharsetVerifier charsetVerifier = new CharsetVerifier(buf, mimeType, charset);

                int totalLength = 0;
                do {
                    totalLength += len;
                    out.write(buf, 0, len);
                    charsetVerifier.readBytesFromBuffer(0, len);
                } while ((len = is.read(buf)) > 0);

                log.add(LogType.MSG_DATA_MIME_LENGTH, 3, Long.toString(totalLength));

                OpenPgpMetadata metadata;
                if (charsetVerifier.isDefinitelyBinary()) {
                    metadata = new OpenPgpMetadata(mFilename, mimeType, 0L, totalLength);
                } else {
                    if (charsetVerifier.isCharsetFaulty() && charsetVerifier.isCharsetGuessed()) {
                        log.add(LogType.MSG_DATA_MIME_CHARSET_UNKNOWN, 3, charsetVerifier.getMaybeFaultyCharset());
                    } else if (charsetVerifier.isCharsetFaulty()) {
                        log.add(LogType.MSG_DATA_MIME_CHARSET_FAULTY, 3, charsetVerifier.getCharset());
                    } else if (charsetVerifier.isCharsetGuessed()) {
                        log.add(LogType.MSG_DATA_MIME_CHARSET_GUESS, 3, charsetVerifier.getCharset());
                    } else {
                        log.add(LogType.MSG_DATA_MIME_CHARSET, 3, charsetVerifier.getCharset());
                    }

                    metadata = new OpenPgpMetadata(mFilename, charsetVerifier.getGuessedMimeType(), 0L, totalLength,
                            charsetVerifier.getCharset());
                }

                out.close();
                outputUris.add(uri);
                metadatas.add(metadata);

            }

        });

        try {

            log.add(LogType.MSG_DATA_MIME, 1);

            try {

                // open current uri for input
                InputStream in = mContext.getContentResolver().openInputStream(currentInputUri);
                parser.parse(in);

                if (mSignedDataUri != null) {

                    if (decryptResult != null) {
                        decryptResult.setSignatureResult(mSignedDataResult.getSignatureResult());
                    } else {
                        decryptResult = mSignedDataResult;
                    }

                    // the actual content is the signed data now (and will be passed verbatim, if parsing fails)
                    currentInputUri = mSignedDataUri;
                    in = mContext.getContentResolver().openInputStream(currentInputUri);
                    // reset signed data result, to indicate to the parser that it is in the inner part
                    mSignedDataResult = null;
                    parser.parse(in);

                }
            } catch (MimeException e) {
                // a mime error likely means that this wasn't mime data, after all
                e.printStackTrace();
                log.add(LogType.MSG_DATA_MIME_BAD, 2);
            }

            // if we found data, return success
            if (!outputUris.isEmpty()) {
                log.add(LogType.MSG_DATA_MIME_OK, 2);

                log.add(LogType.MSG_DATA_OK, 1);
                return new InputDataResult(InputDataResult.RESULT_OK, log, decryptResult, outputUris, metadatas);
            }

            // if no mime data parsed, just return the raw data as fallback
            log.add(LogType.MSG_DATA_MIME_NONE, 2);

            OpenPgpMetadata metadata;
            if (decryptResult != null) {
                metadata = decryptResult.getDecryptionMetadata();
            } else {
                // if we neither decrypted nor mime-decoded, should this be treated as an error?
                // either way, we know nothing about the data
                metadata = new OpenPgpMetadata();
            }

            outputUris.add(currentInputUri);
            metadatas.add(metadata);

            log.add(LogType.MSG_DATA_OK, 1);
            return new InputDataResult(InputDataResult.RESULT_OK, log, decryptResult, outputUris, metadatas);

        } catch (FileNotFoundException e) {
            log.add(LogType.MSG_DATA_ERROR_IO, 2);
            return new InputDataResult(InputDataResult.RESULT_ERROR, log);
        } catch (IOException e) {
            e.printStackTrace();
            log.add(LogType.MSG_DATA_ERROR_IO, 2);
            return new InputDataResult(InputDataResult.RESULT_ERROR, log);
        }

    }

}