amethyst/app/src/main/java/com/vitorpamplona/amethyst/ui/screen/FeedViewModel.kt

package com.vitorpamplona.amethyst.ui.screen

import android.os.Handler
import android.os.Looper
import androidx.lifecycle.ViewModel
import androidx.lifecycle.viewModelScope
import com.vitorpamplona.amethyst.model.LocalCache
import com.vitorpamplona.amethyst.model.LocalCacheState
import com.vitorpamplona.amethyst.model.Note
import com.vitorpamplona.amethyst.service.NostrChannelDataSource
import com.vitorpamplona.amethyst.service.NostrChatRoomDataSource
import com.vitorpamplona.amethyst.service.NostrChatroomListDataSource
import com.vitorpamplona.amethyst.service.NostrDataSource
import com.vitorpamplona.amethyst.service.NostrGlobalDataSource
import com.vitorpamplona.amethyst.service.NostrHomeDataSource
import com.vitorpamplona.amethyst.service.NostrThreadDataSource
import com.vitorpamplona.amethyst.service.NostrUserProfileDataSource
import com.vitorpamplona.amethyst.service.NostrUserProfileFollowersDataSource
import com.vitorpamplona.amethyst.service.NostrUserProfileFollowsDataSource
import kotlin.time.ExperimentalTime
import kotlin.time.measureTimedValue
import kotlinx.coroutines.CoroutineScope
import kotlinx.coroutines.Dispatchers
import kotlinx.coroutines.Job
import kotlinx.coroutines.cancel
import kotlinx.coroutines.flow.MutableStateFlow
import kotlinx.coroutines.flow.asStateFlow
import kotlinx.coroutines.flow.update
import kotlinx.coroutines.launch

class NostrChannelFeedViewModel: FeedViewModel(NostrChannelDataSource)
class NostrChatroomListFeedViewModel: FeedViewModel(NostrChatroomListDataSource)
class NostrChatRoomFeedViewModel: FeedViewModel(NostrChatRoomDataSource)
class NostrHomeFeedViewModel: FeedViewModel(NostrHomeDataSource)
class NostrGlobalFeedViewModel: FeedViewModel(NostrGlobalDataSource)
class NostrThreadFeedViewModel: FeedViewModel(NostrThreadDataSource)
class NostrUserProfileFeedViewModel: FeedViewModel(NostrUserProfileDataSource)


abstract class FeedViewModel(val dataSource: NostrDataSource<Note>): ViewModel() {
    private val _feedContent = MutableStateFlow<FeedState>(FeedState.Loading)
    val feedContent = _feedContent.asStateFlow()

    fun refresh() {
        val scope = CoroutineScope(Job() + Dispatchers.Main)
        scope.launch {
            val notes = dataSource.loadTop()

            val oldNotesState = feedContent.value
            if (oldNotesState is FeedState.Loaded) {
                if (notes != oldNotesState.feed) {
                    updateFeed(notes)
                }
            } else {
                updateFeed(notes)
            }
        }
    }

    fun updateFeed(notes: List<Note>) {
        if (notes.isEmpty()) {
            _feedContent.update { FeedState.Empty }
        } else {
            _feedContent.update { FeedState.Loaded(notes) }
        }
    }

    fun refreshCurrentList() {
        val state = feedContent.value
        if (state is FeedState.Loaded) {
            _feedContent.update { FeedState.Loaded(state.feed) }
        }
    }

    val filterHandler = Handler(Looper.getMainLooper())
    var handlerWaiting = false
    @Synchronized
    fun invalidateData() {
        if (handlerWaiting) return

        handlerWaiting = true
        filterHandler.postDelayed({
            refresh()
            handlerWaiting = false
        }, 100)
    }

    private val cacheListener: (LocalCacheState) -> Unit = {
        invalidateData()
    }

    init {
        LocalCache.live.observeForever(cacheListener)
    }

    override fun onCleared() {
        LocalCache.live.removeObserver(cacheListener)

        dataSource.stop()
        viewModelScope.cancel()
        super.onCleared()
    }
}