/**
 * The permissions of a newly created file.
 */
class FilePermissions {

    /**
     * The permissions for the file's owning user.
     */
    val userPerms: Permissions

    /**
     * The permissions for the file's owning group.
     */
    val groupPerms: Permissions

    /**
     * The permissions for everyone else.
     */
    val elsePerms: Permissions

    /**
     * Is the file a directory? If not, it's a regular file.
     */
    val isDirectory: Boolean

    enum class Permissions(val bits: UByte) {
        READ(0x4u),
        WRITE(0x2u),
        EXECUTE(0x1u),
        READ_WRITE(READ.bits.or(WRITE.bits)),
        READ_EXECUTE(READ.bits.or(EXECUTE.bits)),
        WRITE_EXECUTE(WRITE.bits.or(EXECUTE.bits)),
        READ_WRITE_EXECUTE(READ.bits.or(WRITE.bits.or(EXECUTE.bits)))
    }

    /**
     * Constructor for file permissions with separate fields.
     *
     * @param userPerms The permissions for the file's owning user.
     * @param groupPerms The permissions for the file's owning group.
     * @param elsePerms The permissions for everyone else.
     * @param isDirectory Is the file a directory? If not, it's a regular file.
     */
    constructor(userPerms: Permissions, groupPerms: Permissions, elsePerms: Permissions, isDirectory: Boolean) {
        this.userPerms = userPerms
        this.groupPerms = groupPerms
        this.elsePerms = elsePerms
        this.isDirectory = isDirectory
    }

    /**
     * Turn the permissions described by the [FilePermissions] fields into a permission integer (4 bytes).
     */
    fun toPermissionInt(): UInt {
        val permFileds = listOf(userPerms, groupPerms, elsePerms)
        val perms: UInt = 0u
        for (i in 0..permFileds.size) {
            perms.or(permFileds[i].bits.toUInt().shl(8 * (permFileds.size - 1 - i)))
        }
        if (isDirectory) {
            perms.or(0x80000000u)
        }
        return perms
    }
}