import net.InMessage
import net.OutMessage
import java.math.BigInteger

/**
 * This class holds information about a single QID.
 */
class QID {
    /**
     * Does the QID represent a directory?
     */
    val isDirectory get() = getIsDirectory()

    /**
     * Does the QID represent an append-only file?
     */
    val isAppendOnly get() = getIsAppendOnly()

    /**
     * Does the QID represent an exclusive-use file?
     */
    val isExclusive get() = getIsExclusive()

    /**
     * Does the QID represent a temporary file?
     */
    val isTemporary get() = getIsTemporary()

    /**
     * The QID type.
     */
    val type: UByte

    /**
     * The QID file version.
     */
    val version: UInt

    /**
     * The QID path.
     */
    val path: ULong

    /**
     * Constructor for a QID with separate fields. See the `stat(5)` manual page for more information about [type],
     * [version], and [path].
     *
     * @param type The QID type.
     * @param version The QID file version.
     * @param path The QID path.
     */
    constructor(type: UByte, version: UInt, path: ULong) {
        this.type = type
        this.version = version
        this.path = path
    }

    /**
     * Constructor for raw QID data. Only the first 13 elements are read.
     *
     * @param raw The raw QID data.
     * @throws IllegalArgumentException if [raw] does not have at least 13 elements.
     */
    constructor(raw: List<UByte>) {
        require(raw.size >= 13)
        this.type = raw.first()
        val rawVersion = raw.slice(1..4)
        val rawPath = raw.slice(5..12)
        this.version = InMessage.convInteger(rawVersion, 0, rawVersion.size).toInt().toUInt()
        this.path = InMessage.convInteger(rawPath, 0, rawPath.size).toLong().toULong()
    }

    /**
     * Check bit values in [type]. In case of multiple bits, the method returns true if at least one of them is 1.
     *
     * @param bits A byte whose bits set to 1 are checked.
     */
    private fun checkTypeBits(bits: UByte): Boolean {
        return this.type.and(bits) != 0u.toUByte()
    }

    private fun getIsDirectory(): Boolean {
        return checkTypeBits(0x80u)
    }

    private fun getIsAppendOnly(): Boolean {
        return checkTypeBits(0x40u)
    }

    private fun getIsExclusive(): Boolean {
        return checkTypeBits(0x20u)
    }

    private fun getIsTemporary(): Boolean {
        return checkTypeBits(0x04u)
    }

    fun toRaw(): List<UByte> {
        var bytes: List<UByte> = emptyList()
        bytes += this.type
        bytes += OutMessage.convIntegerToBytes(BigInteger(this.version.toString()), 4u)
        bytes += OutMessage.convIntegerToBytes(BigInteger(this.path.toString()), 8u)
        return bytes
    }
}