/*
 * Copyright (C) 2009 The Android Open Source Project
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

// See imgdiff.c in this directory for a description of the patch file
// format.

#include <stdio.h>
#include <sys/cdefs.h>
#include <sys/stat.h>
#include <errno.h>
#include <unistd.h>
#include <string.h>

#include <string>
#include <vector>

#include "zlib.h"
#include "openssl/sha.h"
#include "applypatch/applypatch.h"
#include "imgdiff.h"
#include "utils.h"

int ApplyImagePatch(const unsigned char* old_data, ssize_t old_size,
                    const unsigned char* patch_data, ssize_t patch_size,
                    SinkFn sink, void* token) {
    Value patch(VAL_BLOB, std::string(
            reinterpret_cast<const char*>(patch_data), patch_size));

    return ApplyImagePatch(old_data, old_size, &patch, sink, token, nullptr, nullptr);
}

/*
 * Apply the patch given in 'patch_filename' to the source data given
 * by (old_data, old_size).  Write the patched output to the 'output'
 * file, and update the SHA context with the output data as well.
 * Return 0 on success.
 */
int ApplyImagePatch(const unsigned char* old_data, ssize_t old_size,
                    const Value* patch,
                    SinkFn sink, void* token, SHA_CTX* ctx,
                    const Value* bonus_data) {
    if (patch->data.size() < 12) {
        printf("patch too short to contain header\n");
        return -1;
    }

    // IMGDIFF2 uses CHUNK_NORMAL, CHUNK_DEFLATE, and CHUNK_RAW.
    // (IMGDIFF1, which is no longer supported, used CHUNK_NORMAL and
    // CHUNK_GZIP.)
    size_t pos = 12;
    const char* header = &patch->data[0];
    if (memcmp(header, "IMGDIFF2", 8) != 0) {
        printf("corrupt patch file header (magic number)\n");
        return -1;
    }

    int num_chunks = Read4(header+8);

    for (int i = 0; i < num_chunks; ++i) {
        // each chunk's header record starts with 4 bytes.
        if (pos + 4 > patch->data.size()) {
            printf("failed to read chunk %d record\n", i);
            return -1;
        }
        int type = Read4(&patch->data[pos]);
        pos += 4;

        if (type == CHUNK_NORMAL) {
            const char* normal_header = &patch->data[pos];
            pos += 24;
            if (pos > patch->data.size()) {
                printf("failed to read chunk %d normal header data\n", i);
                return -1;
            }

            size_t src_start = Read8(normal_header);
            size_t src_len = Read8(normal_header+8);
            size_t patch_offset = Read8(normal_header+16);

            if (src_start + src_len > static_cast<size_t>(old_size)) {
                printf("source data too short\n");
                return -1;
            }
            ApplyBSDiffPatch(old_data + src_start, src_len,
                             patch, patch_offset, sink, token, ctx);
        } else if (type == CHUNK_RAW) {
            const char* raw_header = &patch->data[pos];
            pos += 4;
            if (pos > patch->data.size()) {
                printf("failed to read chunk %d raw header data\n", i);
                return -1;
            }

            ssize_t data_len = Read4(raw_header);

            if (pos + data_len > patch->data.size()) {
                printf("failed to read chunk %d raw data\n", i);
                return -1;
            }
            if (ctx) SHA1_Update(ctx, &patch->data[pos], data_len);
            if (sink(reinterpret_cast<const unsigned char*>(&patch->data[pos]),
                     data_len, token) != data_len) {
                printf("failed to write chunk %d raw data\n", i);
                return -1;
            }
            pos += data_len;
        } else if (type == CHUNK_DEFLATE) {
            // deflate chunks have an additional 60 bytes in their chunk header.
            const char* deflate_header = &patch->data[pos];
            pos += 60;
            if (pos > patch->data.size()) {
                printf("failed to read chunk %d deflate header data\n", i);
                return -1;
            }

            size_t src_start = Read8(deflate_header);
            size_t src_len = Read8(deflate_header+8);
            size_t patch_offset = Read8(deflate_header+16);
            size_t expanded_len = Read8(deflate_header+24);
            size_t target_len = Read8(deflate_header+32);
            int level = Read4(deflate_header+40);
            int method = Read4(deflate_header+44);
            int windowBits = Read4(deflate_header+48);
            int memLevel = Read4(deflate_header+52);
            int strategy = Read4(deflate_header+56);

            if (src_start + src_len > static_cast<size_t>(old_size)) {
                printf("source data too short\n");
                return -1;
            }

            // Decompress the source data; the chunk header tells us exactly
            // how big we expect it to be when decompressed.

            // Note: expanded_len will include the bonus data size if
            // the patch was constructed with bonus data.  The
            // deflation will come up 'bonus_size' bytes short; these
            // must be appended from the bonus_data value.
            size_t bonus_size = (i == 1 && bonus_data != NULL) ? bonus_data->data.size() : 0;

            std::vector<unsigned char> expanded_source(expanded_len);

            // inflate() doesn't like strm.next_out being a nullptr even with
            // avail_out being zero (Z_STREAM_ERROR).
            if (expanded_len != 0) {
                z_stream strm;
                strm.zalloc = Z_NULL;
                strm.zfree = Z_NULL;
                strm.opaque = Z_NULL;
                strm.avail_in = src_len;
                strm.next_in = (unsigned char*)(old_data + src_start);
                strm.avail_out = expanded_len;
                strm.next_out = expanded_source.data();

                int ret;
                ret = inflateInit2(&strm, -15);
                if (ret != Z_OK) {
                    printf("failed to init source inflation: %d\n", ret);
                    return -1;
                }

                // Because we've provided enough room to accommodate the output
                // data, we expect one call to inflate() to suffice.
                ret = inflate(&strm, Z_SYNC_FLUSH);
                if (ret != Z_STREAM_END) {
                    printf("source inflation returned %d\n", ret);
                    return -1;
                }
                // We should have filled the output buffer exactly, except
                // for the bonus_size.
                if (strm.avail_out != bonus_size) {
                    printf("source inflation short by %zu bytes\n", strm.avail_out-bonus_size);
                    return -1;
                }
                inflateEnd(&strm);

                if (bonus_size) {
                    memcpy(expanded_source.data() + (expanded_len - bonus_size),
                           &bonus_data->data[0], bonus_size);
                }
            }

            // Next, apply the bsdiff patch (in memory) to the uncompressed
            // data.
            std::vector<unsigned char> uncompressed_target_data;
            if (ApplyBSDiffPatchMem(expanded_source.data(), expanded_len,
                                    patch, patch_offset,
                                    &uncompressed_target_data) != 0) {
                return -1;
            }
            if (uncompressed_target_data.size() != target_len) {
                printf("expected target len to be %zu, but it's %zu\n",
                       target_len, uncompressed_target_data.size());
                return -1;
            }

            // Now compress the target data and append it to the output.

            // we're done with the expanded_source data buffer, so we'll
            // reuse that memory to receive the output of deflate.
            if (expanded_source.size() < 32768U) {
                expanded_source.resize(32768U);
            }

            {
                std::vector<unsigned char>& temp_data = expanded_source;

                // now the deflate stream
                z_stream strm;
                strm.zalloc = Z_NULL;
                strm.zfree = Z_NULL;
                strm.opaque = Z_NULL;
                strm.avail_in = uncompressed_target_data.size();
                strm.next_in = uncompressed_target_data.data();
                int ret = deflateInit2(&strm, level, method, windowBits, memLevel, strategy);
                if (ret != Z_OK) {
                    printf("failed to init uncompressed data deflation: %d\n", ret);
                    return -1;
                }
                do {
                    strm.avail_out = temp_data.size();
                    strm.next_out = temp_data.data();
                    ret = deflate(&strm, Z_FINISH);
                    ssize_t have = temp_data.size() - strm.avail_out;

                    if (sink(temp_data.data(), have, token) != have) {
                        printf("failed to write %zd compressed bytes to output\n",
                               have);
                        return -1;
                    }
                    if (ctx) SHA1_Update(ctx, temp_data.data(), have);
                } while (ret != Z_STREAM_END);
                deflateEnd(&strm);
            }
        } else {
            printf("patch chunk %d is unknown type %d\n", i, type);
            return -1;
        }
    }

    return 0;
}