# Users.kt

    /*
     * The MIT License
     *
     * Original work sponsored and donated by The Danish Health Data Authority (http://www.sundhedsdatastyrelsen.dk)
     *
     * Copyright (C) 2025 The Danish Health Data Authority (http://www.sundhedsdatastyrelsen.dk)
     *
     *
     * Permission is hereby granted, free of charge, to any person obtaining a copy of
     * this software and associated documentation files (the "Software"), to deal in
     * the Software without restriction, including without limitation the rights to
     * use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies
     * of the Software, and to permit persons to whom the Software is furnished to do
     * so, subject to the following conditions:
     *
     *
     * The above copyright notice and this permission notice shall be included in all
     * copies or substantial portions of the Software.
     *
     *
     * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
     * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
     * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
     * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
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    package dk.nsp.mingraviditet.core.datastore

    import android.content.Context
    import androidx.datastore.core.DataStore
    import androidx.datastore.core.Serializer
    import androidx.datastore.dataStore
    import dk.nsp.mingraviditet.core.datastore.crypto.DecryptionManagerImpl
    import dk.nsp.mingraviditet.core.datastore.crypto.EncryptionManagerImpl
    import kotlinx.coroutines.Dispatchers
    import kotlinx.coroutines.withContext
    import kotlinx.serialization.Serializable
    import kotlinx.serialization.json.Json
    import java.io.InputStream
    import java.io.OutputStream
    import java.util.Base64

    @Serializable
    data class Users(
        val users: List<String>? = null,
    )

    object UserIdSerializer : Serializer<Users> {

        val Context.usersDataStore: DataStore<Users> by dataStore(
            fileName = "user-id",
            serializer = UserIdSerializer,
        )

        private const val KEY_ALIAS = "user_id_key"

        val encryptionManager by lazy {
            EncryptionManagerImpl()
        }

        val decryptionManager by lazy {
            DecryptionManagerImpl()
        }

        override val defaultValue: Users
            get() = Users()

        override suspend fun readFrom(input: InputStream): Users {
            val encryptedBytes = withContext(Dispatchers.IO) {
                input.use {
                    it.readBytes()
                }
            }
            val encryptedBytesDecoded = Base64.getDecoder().decode(encryptedBytes)
            val decryptedBytes = decryptionManager.decrypt(encryptedBytesDecoded, KEY_ALIAS)
            val json: String? = decryptedBytes?.decodeToString()
            return json?.let {
                Json.decodeFromString(Users.serializer(), json)
            } ?: Users()
        }

        override suspend fun writeTo(
            t: Users,
            output: OutputStream,
        ) {
            val json: String = Json.encodeToString(Users.serializer(), t)
            val bytes: ByteArray = json.toByteArray()
            val encryptedBytes: ByteArray = encryptionManager.encrypt(
                data = bytes,
                keyAlias = KEY_ALIAS,
            )
            val encryptedBytesBase64 = Base64.getEncoder().encode(encryptedBytes)
            withContext(Dispatchers.IO) {
                output.use {
                    it.write(encryptedBytesBase64)
                }
            }
        }
    }