// Copyright 2024 Google LLC

//

// Licensed under the Apache License, Version 2.0 (the "License");

// you may not use this file except in compliance with the License.

// You may obtain a copy of the License at

//

// http://www.apache.org/licenses/LICENSE-2.0

//

// Unless required by applicable law or agreed to in writing, software

// distributed under the License is distributed on an "AS IS" BASIS,

// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.

// See the License for the specific language governing permissions and

// limitations under the License.

package com.example.mountainmarkers.presentation

import androidx.lifecycle.ViewModel

import androidx.lifecycle.viewModelScope

import com.example.mountainmarkers.data.local.MountainsRepository

import com.example.mountainmarkers.data.local.is14er

import com.example.mountainmarkers.domain.mappers.toLatLngBounds

import com.example.mountainmarkers.presentation.MountainsViewModelEvent.OnToggleAllPeaks

import com.example.mountainmarkers.presentation.MountainsViewModelEvent.OnZoomAll

import dagger.hilt.android.lifecycle.HiltViewModel

import kotlinx.coroutines.channels.Channel

import kotlinx.coroutines.flow.receiveAsFlow

import kotlinx.coroutines.launch

import javax.inject.Inject

import kotlinx.coroutines.flow.MutableStateFlow

import kotlinx.coroutines.flow.SharingStarted

import kotlinx.coroutines.flow.combine

import kotlinx.coroutines.flow.stateIn

/**

* ViewModel for loading and managing the list of mountains

*/

@HiltViewModel

class MountainsViewModel

@Inject

constructor(

mountainsRepository: MountainsRepository

) : ViewModel() {

private val _eventChannel = Channel<MountainsScreenEvent>()

// Event channel to send events to the UI

internal fun getEventChannel() = _eventChannel.receiveAsFlow()

// Whether or not to show all of the high peaks

private var showAllMountains = MutableStateFlow(false)

val mountainsScreenViewState =

mountainsRepository.mountains.combine(showAllMountains) { allMountains, showAllMountains ->

if (allMountains.isEmpty()) {

MountainsScreenViewState.Loading

} else {

val filteredMountains =

if (showAllMountains) allMountains else allMountains.filter { it.is14er() }

val boundingBox = filteredMountains.map { it.location }.toLatLngBounds()

MountainsScreenViewState.MountainList(

mountains = filteredMountains,

boundingBox = boundingBox,

showingAllPeaks = showAllMountains,

)

}

}.stateIn(

scope = viewModelScope,

started = SharingStarted.WhileSubscribed(5000),

initialValue = MountainsScreenViewState.Loading

)

init {

// Load the full set of mountains

viewModelScope.launch {

mountainsRepository.loadMountains()

}

}

// Handle user events

fun onEvent(event: MountainsViewModelEvent) {

when (event) {

OnZoomAll -> onZoomAll()

OnToggleAllPeaks -> toggleAllPeaks()

}

}

private fun onZoomAll() {

sendScreenEvent(MountainsScreenEvent.OnZoomAll)

}

private fun toggleAllPeaks() {

showAllMountains.value = !showAllMountains.value

}

// Send events back to the UI via the event channel

private fun sendScreenEvent(event: MountainsScreenEvent) {

viewModelScope.launch { _eventChannel.send(event) }

}

}