[refactor] #92 LiveData -> StateFlow 이전

app/src/main/java/com/android/go/sopt/winey/presentation/main/feed/upload/content/ContentViewModel.kt

@@ -1,21 +1,30 @@
 package com.android.go.sopt.winey.presentation.main.feed.upload.content
 
-import androidx.lifecycle.LiveData
-import androidx.lifecycle.MutableLiveData
 import androidx.lifecycle.ViewModel
-import androidx.lifecycle.map
+import androidx.lifecycle.viewModelScope
+import kotlinx.coroutines.flow.MutableStateFlow
+import kotlinx.coroutines.flow.SharingStarted.Companion.WhileSubscribed
+import kotlinx.coroutines.flow.StateFlow
+import kotlinx.coroutines.flow.map
+import kotlinx.coroutines.flow.stateIn
 
 class ContentViewModel : ViewModel() {
-    val _content = MutableLiveData<String>()
-    val content: String get() = _content.value ?: ""
+    val _content = MutableStateFlow("")
+    val content: String get() = _content.value
 
-    val isValidContent: LiveData<Boolean> = _content.map { validateLength(it) }
+    val isValidContent: StateFlow<Boolean> = _content.map { validateContent(it) }
+        .stateIn(
+            initialValue = false,
+            scope = viewModelScope,
+            started = WhileSubscribed(PRODUCE_STOP_TIMEOUT)
+        )
 
-    private fun validateLength(content: String): Boolean =
+    private fun validateContent(content: String): Boolean =
         content.length in MIN_CONTENT_LENGTH..MAX_CONTENT_LENGTH
 
     companion object {
-        const val MIN_CONTENT_LENGTH = 6
+        private const val MIN_CONTENT_LENGTH = 6
         const val MAX_CONTENT_LENGTH = 36
+        private const val PRODUCE_STOP_TIMEOUT = 5000L
     }
 }