package ziputils

import java.nio.ByteBuffer
import java.nio.ByteOrder

/**
 * Represents a partial ZIP central directory file header.
 */
internal class CentralDirectoryFileHeader(
    val compressedSize: UInt,
    val uncompressedSize: UInt,
    val nameLength: UShort,
    val extraFieldLength: UShort,
    val commentLength: UShort,
    val disk: UShort,
    val localHeaderOffset: UInt,
    val fileName: String,
    val extraFieldRecords: List<ExtraFieldRecord>
) {
    val size: Int
        get() = SIZE + nameLength.toInt() + extraFieldLength.toInt() + commentLength.toInt()

    companion object {
        const val SIGNATURE = 0x02014b50U
        const val SIZE = 46

        /**
         * Create `CentralDirectoryFileHeader` from raw byte data.
         * @throws InvalidDataException provided `ByteArray` is not a supported CEN.
         * @param data Raw byte data.
         * @param offset Skip first <offset> bytes in data array.
         * @return A `CentralDirectoryFileHeader`.
         */
        @Throws(InvalidDataException::class)
        fun fromByteArray(data: ByteArray, offset: Int): CentralDirectoryFileHeader {
            if (data.size - offset < SIZE) {
                throw InvalidDataException("CEN must be at least 46 bytes")
            }
            val buf = ByteBuffer.wrap(data, offset, 46).order(ByteOrder.LITTLE_ENDIAN)
            if (buf.getInt().toUInt() != SIGNATURE) {
                throw InvalidSignatureException("Invalid signature")
            }

            val extraFieldRecords = mutableListOf<ExtraFieldRecord>()
            val nameLength = buf.getShort(offset + 28).toUShort()
            buf.position(offset + 20)
            val cen = CentralDirectoryFileHeader(
                compressedSize = buf.getInt().toUInt(),
                uncompressedSize = buf.getInt().toUInt(),
                nameLength = nameLength
                    .also { buf.position(offset + 30) },
                extraFieldLength = buf.getShort().toUShort(),
                commentLength = buf.getShort().toUShort(),
                disk = buf.getShort().toUShort()
                    .also { buf.position(offset + 42) },
                localHeaderOffset = buf.getInt().toUInt(),
                fileName = String(data.sliceArray(offset + SIZE..<offset + SIZE + nameLength.toInt())),
                extraFieldRecords = extraFieldRecords
            )
            if (data.size - offset < cen.size) {
                throw InvalidDataException("CEN is too short")
            }

            // Parse extra field records
            val extraFieldsBuf = ByteBuffer.wrap(
                data, offset + SIZE + cen.nameLength.toInt(), cen.extraFieldLength.toInt()
            ).order(ByteOrder.LITTLE_ENDIAN)
            while (extraFieldsBuf.remaining() > 0) {
                val id = extraFieldsBuf.getShort().toUShort()
                val size = extraFieldsBuf.getShort().toUShort()
                extraFieldRecords.add(when (id) {
                    Zip64ExtraFieldRecord.ID -> {
                        Zip64ExtraFieldRecord(
                            size,
                            if (cen.uncompressedSize == 0xffffffffU) {
                                extraFieldsBuf.getLong().toULong()
                            } else null,
                            if (cen.compressedSize == 0xffffffffU) {
                                extraFieldsBuf.getLong().toULong()
                            } else null,
                            if (cen.localHeaderOffset == 0xffffffffU) {
                                extraFieldsBuf.getLong().toULong()
                            } else null,
                            if (cen.disk == 0xffffU.toUShort()) {
                                extraFieldsBuf.getInt().toUInt()
                            } else null
                        )
                    }
                    else -> {
                        extraFieldsBuf.position(extraFieldsBuf.position() + size.toInt())
                        ExtraFieldRecord(id, size)
                    }
                })
            }

            return cen
        }
    }
}