import java.math.BigInteger

// TODO: add time conversion methods
/**
 * File attributes. The `type` and `dev` attributes are ignored since they are for kernel use only. Time is measured in
 * seconds, since the epoch (Jan 1 00:00 1970 GMT).
 */
class Stat {
    /**
     * The FID sent the T-stat message.
     */
    val fid: UInt

    /**
     * The QID of the file.
     */
    val qid: QID

    /**
     * Permissions and flags.
     */
    val mode: FilePermissions

    /**
     * Last acces time.
     */
    val atime: UInt

    /**
     * Last modification time.
     */
    val mtime: UInt

    /**
     * The length of the file in bytes.
     */
    val length: ULong

    /**
     * The file name, which is `/` if the file is the root directory.
     */
    val name: String

    /**
     * The owner's name.
     */
    val uid: String

    /**
     * The group's name.
     */
    val gid: String

    /**
     * The name of the user who last modified the file.
     */
    val muid: String

    /**
     * Make an instance of [Stat] from each of its fields.
     *
     * @param fid The FID sent the T-stat message.
     * @param qid The QID of the file.
     * @param mode Permissions and flags.
     * @param atime Last acces time.
     * @param mtime Last modification time.
     * @param length The length of the file in bytes.
     * @param name The file name, which is `/` if the file is the root directory.
     * @param uid The owner's name.
     * @param gid The group's name.
     * @param muid The name of the user who last modified the file.
     */
    constructor(fid: UInt, qid: QID, mode: FilePermissions, atime: UInt, mtime: UInt, length: ULong, name: String, uid: String, gid: String, muid: String) {
        this.fid = fid
        this.qid = qid
        this.mode = mode
        this.atime = atime
        this.mtime = mtime
        this.length = length
        this.name = name
        this.uid = uid
        this.gid = gid
        this.muid = muid
    }

    /**
     * Make an instance of [Stat] from raw data.
     *
     * @param fid The FID of the file associated with the stat instance.
     * @param raw The raw stat data.
     */
    constructor(fid: UInt, raw: List<UByte>) {
        var offset = 0
        val qid = QID(raw.slice(0..<13))
        offset += 13
        val mode = FilePermissions(raw.slice(offset+0..<offset+4))
        offset += 4

        val intFielSizes = listOf(4, 4, 8)
        val intFields: MutableList<BigInteger> = mutableListOf()
        for (size in intFielSizes) {
            intFields.add(InMessage.convInteger(raw, offset, size))
            offset += size
        }
        val atime = intFields[0].toInt().toUInt()
        val mtime = intFields[1].toInt().toUInt()
        val length = intFields[2].toLong().toULong()

        val strAmount = 4
        val strFields: MutableList<String> = mutableListOf()
        for (i in 0..strAmount) {
            val str = InMessage.convString(raw, offset)
            strFields.add(str)
            offset += str.length
        }
        val name = strFields[0]
        val uid = strFields[1]
        val gid = strFields[2]
        val muid = strFields[3]

        this.fid = fid
        this.qid = qid
        this.mode = mode
        this.atime = atime
        this.mtime = mtime
        this.length = length
        this.name = name
        this.uid = uid
        this.gid = gid
        this.muid = muid
    }

    /**
     * Turn a [Stat] instance into raw data. This leaves out the [fid] field.
     */
    fun toRaw(): List<UByte> {
        var bytes: List<UByte> = emptyList()
        bytes += this.qid.toRaw()
        bytes += OutMessage.convIntegerToBytes(BigInteger(this.mode.toPermissionInt().toString()), 4u)
        bytes += OutMessage.convIntegerToBytes(BigInteger(this.atime.toString()), 4u)
        bytes += OutMessage.convIntegerToBytes(BigInteger(this.mtime.toString()), 4u)
        bytes += OutMessage.convIntegerToBytes(BigInteger(this.length.toString()), 8u)
        bytes += OutMessage.convStringToBytes(this.name)
        bytes += OutMessage.convStringToBytes(this.uid)
        bytes += OutMessage.convStringToBytes(this.gid)
        bytes += OutMessage.convStringToBytes(this.muid)
        return bytes
    }
}