//
//  Data+Compression.swift
//  ZIPFoundation
//
//  Copyright © 2017-2019 Thomas Zoechling, https://www.peakstep.com and the ZIP Foundation project authors.
//  Released under the MIT License.
//
//  See https://github.com/weichsel/ZIPFoundation/blob/master/LICENSE for license information.
//

import Foundation

/// An unsigned 32-Bit Integer representing a checksum.
public typealias CRC32 = UInt32
/// A custom handler that consumes a `Data` object containing partial entry data.
/// - Parameters:
///   - data: A chunk of `Data` to consume.
/// - Throws: Can throw to indicate errors during data consumption.
public typealias Consumer = (_ data: Data) throws -> Void
/// A custom handler that receives a position and a size that can be used to provide data from an arbitrary source.
/// - Parameters:
///   - position: The current read position.
///   - size: The size of the chunk to provide.
/// - Returns: A chunk of `Data`.
/// - Throws: Can throw to indicate errors in the data source.
public typealias Provider = (_ position: Int, _ size: Int) throws -> Data

/// The lookup table used to calculate `CRC32` checksums.
public let crcTable: [UInt32] = [
    0x00000000, 0x77073096, 0xee0e612c, 0x990951ba, 0x076dc419,
    0x706af48f, 0xe963a535, 0x9e6495a3, 0x0edb8832, 0x79dcb8a4,
    0xe0d5e91e, 0x97d2d988, 0x09b64c2b, 0x7eb17cbd, 0xe7b82d07,
    0x90bf1d91, 0x1db71064, 0x6ab020f2, 0xf3b97148, 0x84be41de,
    0x1adad47d, 0x6ddde4eb, 0xf4d4b551, 0x83d385c7, 0x136c9856,
    0x646ba8c0, 0xfd62f97a, 0x8a65c9ec, 0x14015c4f, 0x63066cd9,
    0xfa0f3d63, 0x8d080df5, 0x3b6e20c8, 0x4c69105e, 0xd56041e4,
    0xa2677172, 0x3c03e4d1, 0x4b04d447, 0xd20d85fd, 0xa50ab56b,
    0x35b5a8fa, 0x42b2986c, 0xdbbbc9d6, 0xacbcf940, 0x32d86ce3,
    0x45df5c75, 0xdcd60dcf, 0xabd13d59, 0x26d930ac, 0x51de003a,
    0xc8d75180, 0xbfd06116, 0x21b4f4b5, 0x56b3c423, 0xcfba9599,
    0xb8bda50f, 0x2802b89e, 0x5f058808, 0xc60cd9b2, 0xb10be924,
    0x2f6f7c87, 0x58684c11, 0xc1611dab, 0xb6662d3d, 0x76dc4190,
    0x01db7106, 0x98d220bc, 0xefd5102a, 0x71b18589, 0x06b6b51f,
    0x9fbfe4a5, 0xe8b8d433, 0x7807c9a2, 0x0f00f934, 0x9609a88e,
    0xe10e9818, 0x7f6a0dbb, 0x086d3d2d, 0x91646c97, 0xe6635c01,
    0x6b6b51f4, 0x1c6c6162, 0x856530d8, 0xf262004e, 0x6c0695ed,
    0x1b01a57b, 0x8208f4c1, 0xf50fc457, 0x65b0d9c6, 0x12b7e950,
    0x8bbeb8ea, 0xfcb9887c, 0x62dd1ddf, 0x15da2d49, 0x8cd37cf3,
    0xfbd44c65, 0x4db26158, 0x3ab551ce, 0xa3bc0074, 0xd4bb30e2,
    0x4adfa541, 0x3dd895d7, 0xa4d1c46d, 0xd3d6f4fb, 0x4369e96a,
    0x346ed9fc, 0xad678846, 0xda60b8d0, 0x44042d73, 0x33031de5,
    0xaa0a4c5f, 0xdd0d7cc9, 0x5005713c, 0x270241aa, 0xbe0b1010,
    0xc90c2086, 0x5768b525, 0x206f85b3, 0xb966d409, 0xce61e49f,
    0x5edef90e, 0x29d9c998, 0xb0d09822, 0xc7d7a8b4, 0x59b33d17,
    0x2eb40d81, 0xb7bd5c3b, 0xc0ba6cad, 0xedb88320, 0x9abfb3b6,
    0x03b6e20c, 0x74b1d29a, 0xead54739, 0x9dd277af, 0x04db2615,
    0x73dc1683, 0xe3630b12, 0x94643b84, 0x0d6d6a3e, 0x7a6a5aa8,
    0xe40ecf0b, 0x9309ff9d, 0x0a00ae27, 0x7d079eb1, 0xf00f9344,
    0x8708a3d2, 0x1e01f268, 0x6906c2fe, 0xf762575d, 0x806567cb,
    0x196c3671, 0x6e6b06e7, 0xfed41b76, 0x89d32be0, 0x10da7a5a,
    0x67dd4acc, 0xf9b9df6f, 0x8ebeeff9, 0x17b7be43, 0x60b08ed5,
    0xd6d6a3e8, 0xa1d1937e, 0x38d8c2c4, 0x4fdff252, 0xd1bb67f1,
    0xa6bc5767, 0x3fb506dd, 0x48b2364b, 0xd80d2bda, 0xaf0a1b4c,
    0x36034af6, 0x41047a60, 0xdf60efc3, 0xa867df55, 0x316e8eef,
    0x4669be79, 0xcb61b38c, 0xbc66831a, 0x256fd2a0, 0x5268e236,
    0xcc0c7795, 0xbb0b4703, 0x220216b9, 0x5505262f, 0xc5ba3bbe,
    0xb2bd0b28, 0x2bb45a92, 0x5cb36a04, 0xc2d7ffa7, 0xb5d0cf31,
    0x2cd99e8b, 0x5bdeae1d, 0x9b64c2b0, 0xec63f226, 0x756aa39c,
    0x026d930a, 0x9c0906a9, 0xeb0e363f, 0x72076785, 0x05005713,
    0x95bf4a82, 0xe2b87a14, 0x7bb12bae, 0x0cb61b38, 0x92d28e9b,
    0xe5d5be0d, 0x7cdcefb7, 0x0bdbdf21, 0x86d3d2d4, 0xf1d4e242,
    0x68ddb3f8, 0x1fda836e, 0x81be16cd, 0xf6b9265b, 0x6fb077e1,
    0x18b74777, 0x88085ae6, 0xff0f6a70, 0x66063bca, 0x11010b5c,
    0x8f659eff, 0xf862ae69, 0x616bffd3, 0x166ccf45, 0xa00ae278,
    0xd70dd2ee, 0x4e048354, 0x3903b3c2, 0xa7672661, 0xd06016f7,
    0x4969474d, 0x3e6e77db, 0xaed16a4a, 0xd9d65adc, 0x40df0b66,
    0x37d83bf0, 0xa9bcae53, 0xdebb9ec5, 0x47b2cf7f, 0x30b5ffe9,
    0xbdbdf21c, 0xcabac28a, 0x53b39330, 0x24b4a3a6, 0xbad03605,
    0xcdd70693, 0x54de5729, 0x23d967bf, 0xb3667a2e, 0xc4614ab8,
    0x5d681b02, 0x2a6f2b94, 0xb40bbe37, 0xc30c8ea1, 0x5a05df1b,
    0x2d02ef8d]

extension Data {
    enum CompressionError: Error {
        case invalidStream
        case corruptedData
    }

    /// Calculates the `CRC32` checksum of the receiver.
    ///
    /// - Parameter checksum: The starting seed.
    /// - Returns: The checksum calcualted from the bytes of the receiver and the starting seed.
    public func crc32(checksum: CRC32) -> CRC32 {
        // The typecast is necessary on 32-bit platforms because of
        // https://bugs.swift.org/browse/SR-1774
        let mask = 0xffffffff as UInt32
        let bufferSize = self.count/MemoryLayout<UInt8>.size
        var result = checksum ^ mask
        #if swift(>=5.0)
        let bins = stride(from: 0, to: bufferSize, by: 256)
        for bin in bins {
            for binIndex in 0..<256 {
                let byteIndex = bin + binIndex
                guard byteIndex < bufferSize else { break }

                let byte = self[byteIndex]
                let index = Int((result ^ UInt32(byte)) & 0xff)
                result = (result >> 8) ^ crcTable[index]
            }
        }
        #else
        self.withUnsafeBytes { (bytes) in
            let bins = stride(from: 0, to: bufferSize, by: 256)
            for bin in bins {
                for binIndex in 0..<256 {
                    let byteIndex = bin + binIndex
                    guard byteIndex < bufferSize else { break }

                    let byte = bytes[byteIndex]
                    let index = Int((result ^ UInt32(byte)) & 0xff)
                    result = (result >> 8) ^ crcTable[index]
                }
            }
        }
        #endif
        return result ^ mask
    }

    static func compress(size: Int, bufferSize: Int, provider: Provider, consumer: Consumer) throws -> CRC32 {
        #if os(macOS) || os(iOS) || os(watchOS) || os(tvOS)
        return try self.process(operation: COMPRESSION_STREAM_ENCODE, size: size, bufferSize: bufferSize,
                                provider: provider, consumer: consumer)
        #else
        return try self.encode(size: size, bufferSize: bufferSize, provider: provider, consumer: consumer)
        #endif
    }

    static func decompress(size: Int, bufferSize: Int, provider: Provider, consumer: Consumer) throws -> CRC32 {
        #if os(macOS) || os(iOS) || os(watchOS) || os(tvOS)
        return try self.process(operation: COMPRESSION_STREAM_DECODE, size: size, bufferSize: bufferSize,
                                provider: provider, consumer: consumer)
        #else
        return try self.decode(bufferSize: bufferSize, provider: provider, consumer: consumer)
        #endif
    }
}

// MARK: - Apple Platforms

#if os(macOS) || os(iOS) || os(watchOS) || os(tvOS)
import Compression

extension Data {
    static func process(operation: compression_stream_operation, size: Int, bufferSize: Int,
                        provider: Provider, consumer: Consumer) throws -> CRC32 {
        var checksum = CRC32(0)
        let destPointer = UnsafeMutablePointer<UInt8>.allocate(capacity: bufferSize)
        defer { destPointer.deallocate() }
        let streamPointer = UnsafeMutablePointer<compression_stream>.allocate(capacity: 1)
        defer { streamPointer.deallocate() }
        var stream = streamPointer.pointee
        var status = compression_stream_init(&stream, operation, COMPRESSION_ZLIB)
        guard status != COMPRESSION_STATUS_ERROR else { throw CompressionError.invalidStream }
        defer { compression_stream_destroy(&stream) }
        stream.src_size = 0
        stream.dst_ptr = destPointer
        stream.dst_size = bufferSize
        var position = 0
        var sourceData: Data?
        repeat {
            if stream.src_size == 0 {
                do {
                    sourceData = try provider(position, Swift.min((size - position), bufferSize))
                    if let sourceData = sourceData {
                        position += sourceData.count
                        stream.src_size = sourceData.count
                    }
                } catch { throw error }
            }
            if let sourceData = sourceData {
                sourceData.withUnsafeBytes { (rawBufferPointer) in
                    if let baseAddress = rawBufferPointer.baseAddress {
                        let pointer = baseAddress.assumingMemoryBound(to: UInt8.self)
                        stream.src_ptr = pointer.advanced(by: sourceData.count - stream.src_size)
                        let flags = sourceData.count < bufferSize ? Int32(COMPRESSION_STREAM_FINALIZE.rawValue) : 0
                        status = compression_stream_process(&stream, flags)
                    }
                }
                if operation == COMPRESSION_STREAM_ENCODE { checksum = sourceData.crc32(checksum: checksum) }
            }
            switch status {
            case COMPRESSION_STATUS_OK, COMPRESSION_STATUS_END:
                let outputData = Data(bytesNoCopy: destPointer, count: bufferSize - stream.dst_size, deallocator: .none)
                try consumer(outputData)
                if operation == COMPRESSION_STREAM_DECODE { checksum = outputData.crc32(checksum: checksum) }
                stream.dst_ptr = destPointer
                stream.dst_size = bufferSize
            default: throw CompressionError.corruptedData
            }
        } while status == COMPRESSION_STATUS_OK
        return checksum
    }
}

// MARK: - Linux

#else
import CZlib

extension Data {
    static func encode(size: Int, bufferSize: Int, provider: Provider, consumer: Consumer) throws -> CRC32 {
        var stream = z_stream()
        let streamSize = Int32(MemoryLayout<z_stream>.size)
        var result = deflateInit2_(&stream, Z_DEFAULT_COMPRESSION,
                                   Z_DEFLATED, -MAX_WBITS, 9, Z_DEFAULT_STRATEGY, ZLIB_VERSION, streamSize)
        defer { deflateEnd(&stream) }
        guard result == Z_OK else { throw CompressionError.invalidStream }
        var flush = Z_NO_FLUSH
        var position = 0
        var zipCRC32 = CRC32(0)
        repeat {
            let readSize = Swift.min((size - position), bufferSize)
            var inputChunk = try provider(position, readSize)
            stream.avail_in = UInt32(inputChunk.count)
            inputChunk.withUnsafeMutableBytes { (rawBufferPointer) in
                if let baseAddress = rawBufferPointer.baseAddress, rawBufferPointer.count > 0 {
                    let pointer = baseAddress.assumingMemoryBound(to: UInt8.self)
                    stream.next_in = pointer
                }
            }
            zipCRC32 = inputChunk.crc32(checksum: zipCRC32)
            flush = position + bufferSize >= size ? Z_FINISH : Z_NO_FLUSH
            var outputChunk = Data(count: bufferSize)
            repeat {
                stream.avail_out = UInt32(bufferSize)
                outputChunk.withUnsafeMutableBytes { (rawBufferPointer) in
                    if let baseAddress = rawBufferPointer.baseAddress, rawBufferPointer.count > 0 {
                        let pointer = baseAddress.assumingMemoryBound(to: UInt8.self)
                        stream.next_out = pointer
                    }
                }
                result = deflate(&stream, flush)
                guard result >= Z_OK  else {
                    throw CompressionError.corruptedData
                }
                outputChunk.count = bufferSize - Int(stream.avail_out)
                try consumer(outputChunk)
            } while stream.avail_out == 0
            position += readSize
        } while flush != Z_FINISH
        return zipCRC32
    }

    static func decode(bufferSize: Int, provider: Provider, consumer: Consumer) throws -> CRC32 {
        var stream = z_stream()
        let streamSize = Int32(MemoryLayout<z_stream>.size)
        var result = inflateInit2_(&stream, -MAX_WBITS, ZLIB_VERSION, streamSize)
        defer { inflateEnd(&stream) }
        guard result == Z_OK else { throw CompressionError.invalidStream }
        var unzipCRC32 = CRC32(0)
        var position = 0
        repeat {
            let inputBytes = malloc(bufferSize)
            defer { free(inputBytes) }
            stream.avail_in = UInt32(bufferSize)
            var chunk = try provider(position, bufferSize)
            position += chunk.count
            chunk.withUnsafeMutableBytes { (rawBufferPointer) in
                if let baseAddress = rawBufferPointer.baseAddress, rawBufferPointer.count > 0 {
                    let pointer = baseAddress.assumingMemoryBound(to: UInt8.self)
                    stream.next_in = pointer
                }
            }
            repeat {
                var outputData = Data(count: bufferSize)
                stream.avail_out = UInt32(bufferSize)
                outputData.withUnsafeMutableBytes { (rawBufferPointer) in
                    if let baseAddress = rawBufferPointer.baseAddress, rawBufferPointer.count > 0 {
                        let pointer = baseAddress.assumingMemoryBound(to: UInt8.self)
                        stream.next_out = pointer
                    }
                }
                result = inflate(&stream, Z_NO_FLUSH)
                guard result != Z_NEED_DICT &&
                    result != Z_DATA_ERROR &&
                    result != Z_MEM_ERROR else {
                        throw CompressionError.corruptedData
                }
                let remainingLength = UInt32(bufferSize) - stream.avail_out
                outputData.count = Int(remainingLength)
                try consumer(outputData)
                unzipCRC32 = outputData.crc32(checksum: unzipCRC32)
            } while stream.avail_out == 0
        } while result != Z_STREAM_END
        return unzipCRC32
    }
}

#endif

#if !swift(>=5.0)

// Since Swift 5.0, `Data.withUnsafeBytes()` passes an `UnsafeRawBufferPointer` instead of an `UnsafePointer<UInt8>`
// into `body`.
// We provide a compatible method for targets that use Swift 4.x so that we can use the new version
// across all language versions.

internal extension Data {
    func withUnsafeBytes<T>(_ body: (UnsafeRawBufferPointer) throws -> T) rethrows -> T {
        let count = self.count
        return try withUnsafeBytes { (pointer: UnsafePointer<UInt8>) throws -> T in
            try body(UnsafeRawBufferPointer(start: pointer, count: count))
        }
    }

    #if os(macOS) || os(iOS) || os(watchOS) || os(tvOS)
    #else
    mutating func withUnsafeMutableBytes<T>(_ body: (UnsafeMutableRawBufferPointer) throws -> T) rethrows -> T {
        let count = self.count
        guard count > 0 else {
            return try body(UnsafeMutableRawBufferPointer(start: nil, count: count))
        }
        return try withUnsafeMutableBytes { (pointer: UnsafeMutablePointer<UInt8>) throws -> T in
            try body(UnsafeMutableRawBufferPointer(start: pointer, count: count))
        }
    }
    #endif
}
#endif
