Random thought on this

crud-with-cache.kt

data class RepositoryItem<T>(
    val value: T,
    val status: Adding | AddingFailed | Added | Removing | RemovingFailed
    
    override fun equals(other: RepositoryItem<T>) {
        return value == other.value
    }
)

interface ListRepository<T> {
    val fetched: Flow<List<T>>
    val isFetching: Flow<Boolean>
    
    fun list(offset: Int, size: Int) {
        fetch(offset, size)
        return fetched
    }
    
    suspend fun fetch(offset: Int, size: Int): Unit
    
    suspend fun add(item: T): T
    
    suspend fun remove(item: T): T
    
    suspend fun removeAll(predicate: (item: T) -> Boolean): Collection<T>
    
    suspend fun find(predicate: (item: T) -> Boolean): Collection<T>
    
    suspend fun first(predicate: (item: T) -> Boolean): T
}

class RemoteListRepository<T>(
    private val serverApis : ListApi,
    private val localDb: ListDb
) : ListRepository<T> {}

interface ListDb<T> {
    val all: Flow<List<T>>
    
    suspend fun add(item: T): T
    
    suspend fun remove(item: T): T
    
    suspend fun removeAll(predicate: (item: T) -> Boolean): Collection<T>
    
    suspend fun find(predicate: (item: T) -> Boolean): Collection<T>
    
    suspend fun first(predicate: (item: T) -> Boolean): T
}

interface ListApi<T> {
    suspend fun fetch(offset: Int, size: Int): List<T>
    
    suspend fun add(item: T): T
    
    suspend fun remove(item: T): T
    
    suspend fun removeAll(predicate: (item: T) -> Boolean): Collection<T>
    
    suspend fun find(predicate: (item: T) -> Boolean): Collection<T>
    
    suspend fun first(predicate: (item: T) -> Boolean): T
}

interface SimpleListApi<T>(val baseUrl: String, val name: String) : ListApi<T> {
    @Get("$baseUrl/$name/")
    suspend fun fetch(offset: Int, size: Int): List<T>
    
    @Post("$baseUrl/$name/")
    suspend fun add(item: T): T
    
    @Delete("$baseUrl/$name/")
    suspend fun remove(item: T): T
    
    @Delete("$baseUrl/$name/all/")
    suspend fun removeAll(predicate: (item: T) -> Boolean): Collection<T>
    
    @Post("$baseUrl/$name/")
    suspend fun find(predicate: (item: T) -> Boolean): Collection<T>
    
    @Post("$baseUrl/$name/")
    suspend fun first(predicate: (item: T) -> Boolean): T
}