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TopicViewModel.kt
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TopicViewModel.kt
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/*
* Copyright 2021 The Android Open Source Project
*
* 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
*
* https://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.google.samples.apps.nowinandroid.feature.topic
import androidx.lifecycle.SavedStateHandle
import androidx.lifecycle.ViewModel
import androidx.lifecycle.viewModelScope
import androidx.navigation.toRoute
import com.google.samples.apps.nowinandroid.core.data.repository.NewsResourceQuery
import com.google.samples.apps.nowinandroid.core.data.repository.TopicsRepository
import com.google.samples.apps.nowinandroid.core.data.repository.UserDataRepository
import com.google.samples.apps.nowinandroid.core.data.repository.UserNewsResourceRepository
import com.google.samples.apps.nowinandroid.core.model.data.FollowableTopic
import com.google.samples.apps.nowinandroid.core.model.data.Topic
import com.google.samples.apps.nowinandroid.core.model.data.UserNewsResource
import com.google.samples.apps.nowinandroid.core.result.Result
import com.google.samples.apps.nowinandroid.core.result.asResult
import com.google.samples.apps.nowinandroid.feature.topic.navigation.TopicDestination
import dagger.hilt.android.lifecycle.HiltViewModel
import kotlinx.coroutines.flow.Flow
import kotlinx.coroutines.flow.SharingStarted
import kotlinx.coroutines.flow.StateFlow
import kotlinx.coroutines.flow.combine
import kotlinx.coroutines.flow.map
import kotlinx.coroutines.flow.stateIn
import kotlinx.coroutines.launch
import javax.inject.Inject
@HiltViewModel
class TopicViewModel @Inject constructor(
savedStateHandle: SavedStateHandle,
private val userDataRepository: UserDataRepository,
topicsRepository: TopicsRepository,
userNewsResourceRepository: UserNewsResourceRepository,
) : ViewModel() {
private val topicDestination: TopicDestination = savedStateHandle.toRoute()
val topicId = topicDestination.id
val topicUiState: StateFlow<TopicUiState> = topicUiState(
topicId = topicDestination.id,
userDataRepository = userDataRepository,
topicsRepository = topicsRepository,
)
.stateIn(
scope = viewModelScope,
started = SharingStarted.WhileSubscribed(5_000),
initialValue = TopicUiState.Loading,
)
val newsUiState: StateFlow<NewsUiState> = newsUiState(
topicId = topicDestination.id,
userDataRepository = userDataRepository,
userNewsResourceRepository = userNewsResourceRepository,
)
.stateIn(
scope = viewModelScope,
started = SharingStarted.WhileSubscribed(5_000),
initialValue = NewsUiState.Loading,
)
fun followTopicToggle(followed: Boolean) {
viewModelScope.launch {
userDataRepository.setTopicIdFollowed(topicDestination.id, followed)
}
}
fun bookmarkNews(newsResourceId: String, bookmarked: Boolean) {
viewModelScope.launch {
userDataRepository.setNewsResourceBookmarked(newsResourceId, bookmarked)
}
}
fun setNewsResourceViewed(newsResourceId: String, viewed: Boolean) {
viewModelScope.launch {
userDataRepository.setNewsResourceViewed(newsResourceId, viewed)
}
}
}
private fun topicUiState(
topicId: String,
userDataRepository: UserDataRepository,
topicsRepository: TopicsRepository,
): Flow<TopicUiState> {
// Observe the followed topics, as they could change over time.
val followedTopicIds: Flow<Set<String>> =
userDataRepository.userData
.map { it.followedTopics }
// Observe topic information
val topicStream: Flow<Topic> = topicsRepository.getTopic(
id = topicId,
)
return combine(
followedTopicIds,
topicStream,
::Pair,
)
.asResult()
.map { followedTopicToTopicResult ->
when (followedTopicToTopicResult) {
is Result.Success -> {
val (followedTopics, topic) = followedTopicToTopicResult.data
TopicUiState.Success(
followableTopic = FollowableTopic(
topic = topic,
isFollowed = topicId in followedTopics,
),
)
}
is Result.Loading -> TopicUiState.Loading
is Result.Error -> TopicUiState.Error
}
}
}
private fun newsUiState(
topicId: String,
userNewsResourceRepository: UserNewsResourceRepository,
userDataRepository: UserDataRepository,
): Flow<NewsUiState> {
// Observe news
val newsStream: Flow<List<UserNewsResource>> = userNewsResourceRepository.observeAll(
NewsResourceQuery(filterTopicIds = setOf(element = topicId)),
)
// Observe bookmarks
val bookmark: Flow<Set<String>> = userDataRepository.userData
.map { it.bookmarkedNewsResources }
return combine(newsStream, bookmark, ::Pair)
.asResult()
.map { newsToBookmarksResult ->
when (newsToBookmarksResult) {
is Result.Success -> NewsUiState.Success(newsToBookmarksResult.data.first)
is Result.Loading -> NewsUiState.Loading
is Result.Error -> NewsUiState.Error
}
}
}
sealed interface TopicUiState {
data class Success(val followableTopic: FollowableTopic) : TopicUiState
data object Error : TopicUiState
data object Loading : TopicUiState
}
sealed interface NewsUiState {
data class Success(val news: List<UserNewsResource>) : NewsUiState
data object Error : NewsUiState
data object Loading : NewsUiState
}