chore(mvvm): CalendarActivity ViewModel

app/src/main/java/com/p_vacho/neat_calendar/activities/CalendarActivity.kt

@@ -5,35 +5,27 @@ import android.os.Bundle
 import android.widget.ImageButton
 import android.widget.TextView
 import androidx.activity.enableEdgeToEdge
+import androidx.activity.viewModels
 import androidx.appcompat.app.AppCompatActivity
 import androidx.core.view.ViewCompat
 import androidx.core.view.WindowInsetsCompat
 import androidx.recyclerview.widget.GridLayoutManager
 import androidx.recyclerview.widget.RecyclerView
-import androidx.lifecycle.lifecycleScope
-import com.p_vacho.neat_calendar.MyApplication
 import com.p_vacho.neat_calendar.R
 import com.p_vacho.neat_calendar.adapters.CalendarDayItemAdapter
-import com.p_vacho.neat_calendar.api.RetrofitClient
-import com.p_vacho.neat_calendar.api.models.EventResponse
 import com.p_vacho.neat_calendar.models.CalendarDay
-import kotlinx.coroutines.launch
+import com.p_vacho.neat_calendar.viewmodels.CalendarViewModel
 import java.time.YearMonth
-import java.time.ZoneId
-import java.time.format.TextStyle
-import java.util.Locale
-
 
 class CalendarActivity : AppCompatActivity() {
+    private val viewModel: CalendarViewModel by viewModels()
+    private lateinit var adapter: CalendarDayItemAdapter
+
     private lateinit var tvMonthYear: TextView
     private lateinit var rvCalendar: RecyclerView
     private lateinit var btnPreviousMonth: ImageButton
     private lateinit var btnNextMonth: ImageButton
 
-    private val tokenManager by lazy { (application as MyApplication).tokenManager }
-
-    private var currentYearMonth: YearMonth = YearMonth.now()
-
     override fun onCreate(savedInstanceState: Bundle?) {
         super.onCreate(savedInstanceState)
         enableEdgeToEdge()
@@ -44,125 +36,31 @@ class CalendarActivity : AppCompatActivity() {
             insets
         }
 
+        initializeViews()
+
+        // Observers
+        viewModel.monthYearText.observe(this) { text -> tvMonthYear.text = text }
+        viewModel.calendarDays.observe(this) {days -> adapter.updateDays(days) }
+
+        // Listeners
+        btnPreviousMonth.setOnClickListener { viewModel.prevMonth() }
+        btnNextMonth.setOnClickListener { viewModel.nextMonth() }
+
+        // Setup for current month
+        viewModel.setCalendarMonth(YearMonth.now())
+    }
+
+    private fun initializeViews() {
         tvMonthYear = findViewById(R.id.tvMonthYear)
         rvCalendar = findViewById(R.id.rvCalendar)
         btnPreviousMonth = findViewById(R.id.btnPreviousMonth)
         btnNextMonth = findViewById(R.id.btnNextMonth)
 
-        setCalendarForMonth(currentYearMonth)
+        adapter = CalendarDayItemAdapter(listOf(), ::navigateToDayActivity)
-
+        rvCalendar.layoutManager = GridLayoutManager(this@CalendarActivity, 7) // 7 columns for days of the week
-        btnPreviousMonth.setOnClickListener {
+        rvCalendar.adapter = adapter
-            currentYearMonth = currentYearMonth.minusMonths(1)
-            setCalendarForMonth(currentYearMonth)
-        }
-
-        btnNextMonth.setOnClickListener {
-            currentYearMonth = currentYearMonth.plusMonths(1)
-            setCalendarForMonth(currentYearMonth)
-        }
     }
 
-    /**
-     * Obtain all of the events that occur for each day in the given month from the API.
-     *
-     * The returned structure is a hashmap with int keys, being the day numbers in the month.
-     * If an event spans multiple days, it will be added for each of those days.
-     *
-     * Note that this also includes the events this user was invited into.
-     */
-    private suspend fun fetchEventsForMonth(yearMonth: YearMonth): Map<Int, List<EventResponse>> {
-        // Use the system's default time zone
-        val zoneId = ZoneId.systemDefault()
-
-        // Get the start and end of the month in the local time zone
-        val startFrom = yearMonth.atDay(1).atStartOfDay(zoneId).toOffsetDateTime()
-        val endTo = yearMonth.atEndOfMonth().atTime(23, 59, 59).atZone(zoneId).toOffsetDateTime()
-
-        val userId = tokenManager.userId
-
-        if (userId.isNullOrEmpty()) {
-            navigateToMainActivity()
-            return emptyMap()
-        }
-
-        // BUG: Events that last longer than a month will not show
-        // up in the following month due to the startFrom filter here.
-        val userEvents = RetrofitClient.eventsService.userEvents(
-            userId = userId,
-            startFrom = startFrom,
-            startTo = endTo
-        )
-        val invitedEvents = RetrofitClient.eventsService.userEventsInvited(
-            userId = userId,
-            startFrom = startFrom,
-            startTo = endTo,
-            inviteStatus = "accepted"
-        )
-
-        val allEvents = userEvents + invitedEvents
-
-        // Create a mapping of days to events
-        val eventsByDay = mutableMapOf<Int, MutableList<EventResponse>>()
-
-        for (event in allEvents) {
-            val startDay = maxOf(event.start_time.dayOfMonth, 1)
-            val endDay = minOf(event.end_time.dayOfMonth, yearMonth.lengthOfMonth())
-
-            for (day in startDay..endDay) {
-                eventsByDay.computeIfAbsent(day) { mutableListOf() }.add(event)
-            }
-        }
-
-        return eventsByDay
-    }
-
-    private fun setCalendarForMonth(yearMonth: YearMonth) {
-        lifecycleScope.launch {
-            val firstDayOfMonth = yearMonth.atDay(1)
-            val daysInMonth = yearMonth.lengthOfMonth()
-
-            val eventsByDay = fetchEventsForMonth(yearMonth)
-
-            // Get localized month name and year
-            val monthYearText = "${
-                yearMonth.month.getDisplayName(
-                    TextStyle.FULL,
-                    Locale.getDefault()
-                )
-            } ${yearMonth.year}"
-            tvMonthYear.text = monthYearText
-
-            // Calculate the amount of placeholder slots until the first day in the month
-            // (Our calendar starts from Monday, but not all months start on monday, so we need fillers)
-            val startOffset = firstDayOfMonth.dayOfWeek.ordinal // Gives 0 (Monday) to 6 (Sunday)
-
-            // Generate calendar days
-            val days = mutableListOf<CalendarDay?>()
-
-            // Add padding (placeholder items) for days of the previous month
-            for (i in 1..startOffset) {
-                days.add(null)
-            }
-
-            // Add the actual days of the current month
-            for (i in 1..daysInMonth) {
-                val fullDate = yearMonth.atDay(i)
-                val eventsForDay = eventsByDay[i] ?: emptyList()
-                days.add(CalendarDay(date = fullDate, events = eventsForDay))
-            }
-
-            // Set up RecyclerView
-            rvCalendar.layoutManager = GridLayoutManager(this@CalendarActivity, 7) // 7 columns for days of the week
-            rvCalendar.adapter = CalendarDayItemAdapter(days) { day -> navigateToDayActivity(day) }
-        }
-    }
-
-    private fun navigateToMainActivity() {
-        val intent = Intent(this, MainActivity::class.java)
-        intent.flags = Intent.FLAG_ACTIVITY_CLEAR_TOP or Intent.FLAG_ACTIVITY_NEW_TASK
-        startActivity(intent)
-        finish() // Close the login screen
-    }
 
     private fun navigateToDayActivity(day: CalendarDay) {
         var intent = Intent(this, DayViewActivity::class.java)
@@ -177,6 +75,6 @@ class CalendarActivity : AppCompatActivity() {
         // Events could've been modified or even deleted, so make sure we have a fresh copy
         // it would probably be better to pass these around through extras, this extra lookup
         // isn't a huge deal, it's a potential future optimization though
-        setCalendarForMonth(currentYearMonth)
+        viewModel.refetch()
     }
 }

app/src/main/java/com/p_vacho/neat_calendar/adapters/CalendarDayItemAdapter.kt

@@ -9,7 +9,7 @@ import androidx.recyclerview.widget.RecyclerView
 import com.p_vacho.neat_calendar.R
 import com.p_vacho.neat_calendar.models.CalendarDay
 
-class CalendarDayItemAdapter(private val days: List<CalendarDay?>, private val onDayClicked: (CalendarDay) -> Unit) :
+class CalendarDayItemAdapter(private var days: List<CalendarDay?>, private val onDayClicked: (CalendarDay) -> Unit) :
     RecyclerView.Adapter<CalendarDayItemAdapter.DayViewHolder>() {
 
     class DayViewHolder(itemView: View) : RecyclerView.ViewHolder(itemView) {
@@ -49,4 +49,17 @@ class CalendarDayItemAdapter(private val days: List<CalendarDay?>, private val o
     }
 
     override fun getItemCount(): Int = days.size
+
+    /**
+     * This function allows updating the day list.
+     *
+     * This will entirely overwrite the original data.
+     */
+    fun updateDays(newDays: List<CalendarDay?>) {
+        days = newDays
+
+        // We're resetting to an entirely new list, this is needed
+        @Suppress("NotifyDataSetChanged")
+        notifyDataSetChanged()
+    }
 }

app/src/main/java/com/p_vacho/neat_calendar/viewmodels/CalendarViewModel.kt

@@ -0,0 +1,141 @@
+package com.p_vacho.neat_calendar.viewmodels
+
+import android.app.Application
+import androidx.lifecycle.AndroidViewModel
+import androidx.lifecycle.LiveData
+import androidx.lifecycle.MutableLiveData
+import androidx.lifecycle.viewModelScope
+import com.p_vacho.neat_calendar.MyApplication
+import com.p_vacho.neat_calendar.api.RetrofitClient
+import com.p_vacho.neat_calendar.api.models.EventResponse
+import com.p_vacho.neat_calendar.models.CalendarDay
+import kotlinx.coroutines.Dispatchers
+import kotlinx.coroutines.launch
+import kotlinx.coroutines.withContext
+import java.time.YearMonth
+import java.time.ZoneId
+import java.time.format.TextStyle
+import java.util.Locale
+
+class CalendarViewModel(application: Application) : AndroidViewModel(application) {
+    private var currentYearMonth: YearMonth? = null
+
+    private val _calendarDays = MutableLiveData<List<CalendarDay?>>()
+    val calendarDays: LiveData<List<CalendarDay?>> = _calendarDays
+
+    private val _monthYearText = MutableLiveData<String>()
+    val monthYearText: LiveData<String> = _monthYearText
+
+    /**
+     * Move to the next month.
+     *
+     * Can only be used after the initial setCalendarMonth.
+     */
+    fun prevMonth() {
+        setCalendarMonth(currentYearMonth!!.minusMonths(1))
+    }
+
+    /**
+     * Move to the next month.
+     *
+     * Can only be used after the initial setCalendarMonth.
+     */
+    fun nextMonth() {
+        setCalendarMonth(currentYearMonth!!.plusMonths(1))
+    }
+
+    /**
+     * Refetch the data for the currently selected month.
+     *
+     * Can only be used after the initial setCalendarMonth.
+     */
+    fun refetch() {
+        setCalendarMonth(currentYearMonth!!)
+    }
+
+    /**
+     * Set up the view model for a specific month.
+     */
+    fun setCalendarMonth(yearMonth: YearMonth) {
+        currentYearMonth = yearMonth
+
+        val firstDayOfMonth = yearMonth.atDay(1)
+        val daysInMonth = yearMonth.lengthOfMonth()
+
+        // Get localized month name and year name
+        val monthYearText = "${
+            yearMonth.month.getDisplayName(
+                TextStyle.FULL,
+                Locale.getDefault()
+            )
+        } ${yearMonth.year}"
+        _monthYearText.value = monthYearText
+
+        viewModelScope.launch {
+            val eventsByDay = withContext(Dispatchers.IO) { fetchEventsForMonthInternal(yearMonth) }
+
+            val startOffset = firstDayOfMonth.dayOfWeek.ordinal
+            val days = mutableListOf<CalendarDay?>()
+
+            for (i in 1..startOffset) {
+                days.add(null)
+            }
+
+            for (i in 1..daysInMonth) {
+                val fullDate = yearMonth.atDay(i)
+                val eventsForDay = eventsByDay[i] ?: emptyList()
+                days.add(CalendarDay(date = fullDate, events = eventsForDay))
+            }
+
+            _calendarDays.value = days
+        }
+    }
+
+    /**
+     * Obtain all of the events that occur for each day in the given month from the API.
+     *
+     * The returned structure is a hashmap with int keys, being the day numbers in the month.
+     * If an event spans multiple days, it will be added for each of those days.
+     *
+     * Note that this also includes the events this user was invited into.
+     */
+    private suspend fun fetchEventsForMonthInternal(yearMonth: YearMonth): Map<Int, List<EventResponse>> {
+        // Use the system's default time zone
+        val zoneId = ZoneId.systemDefault()
+
+        // Get the start and end of the month in the local time zone
+        val startFrom = yearMonth.atDay(1).atStartOfDay(zoneId).toOffsetDateTime()
+        val endTo = yearMonth.atEndOfMonth().atTime(23, 59, 59).atZone(zoneId).toOffsetDateTime()
+
+        // Obtain current (logged in) user ID
+        val userId = (getApplication<MyApplication>()).tokenManager.userId ?: throw IllegalStateException("User ID is not set")
+
+        // BUG: Events that last longer than a month will not show
+        // up in the following month due to the startFrom filter here.
+        val userEvents = RetrofitClient.eventsService.userEvents(
+            userId = userId,
+            startFrom = startFrom,
+            startTo = endTo
+        )
+        val invitedEvents = RetrofitClient.eventsService.userEventsInvited(
+            userId = userId,
+            startFrom = startFrom,
+            startTo = endTo,
+            inviteStatus = "accepted"
+        )
+
+        val allEvents = userEvents + invitedEvents
+
+        // Create a mapping of days to events
+        val eventsByDay = mutableMapOf<Int, MutableList<EventResponse>>()
+        for (event in allEvents) {
+            val startDay = maxOf(event.start_time.dayOfMonth, 1)
+            val endDay = minOf(event.end_time.dayOfMonth, yearMonth.lengthOfMonth())
+            for (day in startDay..endDay) {
+                eventsByDay.computeIfAbsent(day) { mutableListOf() }.add(event)
+            }
+        }
+
+        return eventsByDay
+    }
+}