feat(categories): Add activity for category management

app/src/main/AndroidManifest.xml

@@ -16,6 +16,9 @@
         android:supportsRtl="true"
         android:theme="@style/Theme.NeatCalendar"
         tools:targetApi="31">
+        <activity
+            android:name=".activities.CreateCategoryActivity"
+            android:exported="false" />
         <activity
             android:name=".activities.CategoriesActivity"
             android:exported="false" />

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

@@ -1,21 +1,133 @@
 package com.p_vacho.neat_calendar.activities
 
+import android.content.Intent
 import android.os.Bundle
+import android.view.View
+import android.widget.ImageButton
+import android.widget.TextView
+import android.widget.Toast
 import androidx.activity.enableEdgeToEdge
 import androidx.appcompat.app.AppCompatActivity
 import androidx.core.view.ViewCompat
 import androidx.core.view.WindowInsetsCompat
+import androidx.lifecycle.lifecycleScope
+import androidx.recyclerview.widget.LinearLayoutManager
+import androidx.recyclerview.widget.RecyclerView
+import com.p_vacho.neat_calendar.MyApplication
 import com.p_vacho.neat_calendar.R
+import com.p_vacho.neat_calendar.adapters.CategoryAdapter
+import com.p_vacho.neat_calendar.api.RetrofitClient
+import com.p_vacho.neat_calendar.api.models.CategoryResponse
+import com.p_vacho.neat_calendar.api.models.EventResponse
+import kotlinx.coroutines.Dispatchers
+import kotlinx.coroutines.launch
+import kotlinx.coroutines.withContext
 
 class CategoriesActivity : AppCompatActivity() {
+    private lateinit var rvCategories: RecyclerView
+    private lateinit var btnBack: ImageButton
+    private lateinit var btnAddCategory: ImageButton
+    private lateinit var tvEmptyState: TextView
+
+    private lateinit var categories: MutableList<CategoryResponse>
+
+    private val createActivityLauncher = registerForActivityResult(
+        androidx.activity.result.contract.ActivityResultContracts.StartActivityForResult()
+    ) { result ->
+        if (result.resultCode == RESULT_OK) {
+            @Suppress("DEPRECATION")
+            val newCategory: CategoryResponse? = result.data?.getParcelableExtra("newCategory")
+
+            newCategory?.let { categoryCreateReply(it) }
+        }
+    }
+
     override fun onCreate(savedInstanceState: Bundle?) {
         super.onCreate(savedInstanceState)
         enableEdgeToEdge()
         setContentView(R.layout.activity_categories)
+
         ViewCompat.setOnApplyWindowInsetsListener(findViewById(R.id.main)) { v, insets ->
             val systemBars = insets.getInsets(WindowInsetsCompat.Type.systemBars())
             v.setPadding(systemBars.left, systemBars.top, systemBars.right, systemBars.bottom)
             insets
         }
+
+        rvCategories = findViewById(R.id.rvCategories)
+        btnBack = findViewById(R.id.btnBack)
+        btnAddCategory = findViewById(R.id.btnAddCategory)
+        tvEmptyState = findViewById(R.id.tvEmptyState)
+
+        btnBack.setOnClickListener { finish() }
+        btnAddCategory.setOnClickListener { navigateToCreateCategory() }
+
+        rvCategories.layoutManager = LinearLayoutManager(this)
+
+        lifecycleScope.launch {
+            categories = fetchCategories().toMutableList()
+
+            val adapter = CategoryAdapter(categories, ::handleDeleteCategory)
+
+            rvCategories.adapter = adapter
+            updateEmptyState()
+        }
+    }
+
+    /**
+     * Fetches all categories for the current user from the backend.
+     */
+    private suspend fun fetchCategories(): List<CategoryResponse> {
+        val userId = (application as MyApplication).tokenManager.userId
+            ?: run {
+                finish()
+                return emptyList()
+            }
+
+        return withContext(Dispatchers.IO) {
+            RetrofitClient.categoryService.userCategories(userId)
+        }
+    }
+
+    /**
+     * A callback function triggered by the Category Adapter, when the user
+     * clicks on the delete button.
+     */
+    private fun handleDeleteCategory(category: CategoryResponse, position: Int) {
+        lifecycleScope.launch {
+            withContext(Dispatchers.IO) {
+                RetrofitClient.categoryService.deleteCategory(category.id)
+            }
+            // Remove category from the adapter and update the UI
+            (rvCategories.adapter as CategoryAdapter).removeCategoryAt(position)
+            Toast.makeText(this@CategoriesActivity, "Category deleted", Toast.LENGTH_SHORT).show()
+            updateEmptyState()
+        }
+    }
+
+    /**
+     * Navigates to the activity for adding a new category.
+     */
+    private fun navigateToCreateCategory() {
+        val intent = Intent(this, CreateCategoryActivity::class.java)
+        startActivity(intent)
+    }
+
+    /**
+     * Used as a callback, triggered when the CreateCategory Activity returns a result.
+     *
+     * The returned value (the new category data) is passed over as a parameter.
+     */
+    private fun categoryCreateReply(category: CategoryResponse) {
+        (rvCategories.adapter as CategoryAdapter).addCategory(category)
+    }
+
+    /**
+     * This is a helper function to toggle the visibility of the empty state message
+     * when no categories are available.
+     *
+     * This should be called whenever a category was removed or added.
+     */
+    private fun updateEmptyState() {
+        tvEmptyState.visibility = if (categories.isEmpty()) View.VISIBLE else View.GONE
     }
 }

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

@@ -0,0 +1,21 @@
+package com.p_vacho.neat_calendar.activities
+
+import android.os.Bundle
+import androidx.activity.enableEdgeToEdge
+import androidx.appcompat.app.AppCompatActivity
+import androidx.core.view.ViewCompat
+import androidx.core.view.WindowInsetsCompat
+import com.p_vacho.neat_calendar.R
+
+class CreateCategoryActivity : AppCompatActivity() {
+    override fun onCreate(savedInstanceState: Bundle?) {
+        super.onCreate(savedInstanceState)
+        enableEdgeToEdge()
+        setContentView(R.layout.activity_create_category)
+        ViewCompat.setOnApplyWindowInsetsListener(findViewById(R.id.main)) { v, insets ->
+            val systemBars = insets.getInsets(WindowInsetsCompat.Type.systemBars())
+            v.setPadding(systemBars.left, systemBars.top, systemBars.right, systemBars.bottom)
+            insets
+        }
+    }
+}

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

@@ -0,0 +1,68 @@
+package com.p_vacho.neat_calendar.adapters
+
+import android.graphics.Color
+import android.view.LayoutInflater
+import android.view.View
+import android.view.ViewGroup
+import android.widget.ImageButton
+import android.widget.TextView
+import androidx.recyclerview.widget.RecyclerView
+import com.p_vacho.neat_calendar.R
+import com.p_vacho.neat_calendar.api.models.CategoryResponse
+
+class CategoryAdapter(
+    private val categories: MutableList<CategoryResponse>,
+    private val onDeleteClick: (CategoryResponse, Int) -> Unit
+) : RecyclerView.Adapter<CategoryAdapter.CategoryViewHolder>() {
+
+    inner class CategoryViewHolder(view: View) : RecyclerView.ViewHolder(view) {
+        val colorIndicator: View = view.findViewById(R.id.colorIndicator)
+        val categoryName: TextView = view.findViewById(R.id.tvCategoryName)
+        val deleteButton: ImageButton = view.findViewById(R.id.btnDeleteCategory)
+    }
+
+    override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): CategoryViewHolder {
+        val view = LayoutInflater.from(parent.context)
+            .inflate(R.layout.item_category, parent, false)
+        return CategoryViewHolder(view)
+    }
+
+    override fun onBindViewHolder(holder: CategoryViewHolder, position: Int) {
+        val category = categories[position]
+
+        // Bind category data to the views
+        holder.colorIndicator.setBackgroundColor(category.color.toArgb())
+        holder.categoryName.text = category.name
+
+        // Set click listener for the delete button
+        holder.deleteButton.setOnClickListener {
+            onDeleteClick(category, position)
+        }
+    }
+
+    override fun getItemCount(): Int = categories.size
+
+    /**
+     * Remove a category from the list and notify the adapter.
+     *
+     * Call this after the onDeleteClick callback deletes the category from the backend API.
+     */
+    fun removeCategoryAt(position: Int) {
+        categories.removeAt(position)
+        notifyItemRemoved(position)
+
+        // Annoyingly, we can't just use notifyItemRemoved for the single removed item,
+        // as all the items below it would now be using the wrong position that was
+        // already bound to the callbacks from the click listeners, so we need to refresh
+        // all of the categories below this one as well.
+        notifyItemRangeChanged(position, categories.size - position)
+    }
+
+    /**
+     * Add a new category to the end of the list and notify the adapter.
+     */
+    fun addCategory(category: CategoryResponse) {
+        categories.add(category)
+        notifyItemInserted(categories.size)
+    }
+}

app/src/main/java/com/p_vacho/neat_calendar/api/services/CategoryService.kt

@@ -1,6 +1,7 @@
 package com.p_vacho.neat_calendar.api.services
 
 import com.p_vacho.neat_calendar.api.models.CategoryResponse
+import retrofit2.http.DELETE
 import retrofit2.http.GET
 import retrofit2.http.Path
 
@@ -11,6 +12,9 @@ interface CategoryService {
     @GET("/events/{event_id}/categories")
     suspend fun eventCategories(@Path("event_id") eventId: String): List<CategoryResponse>
 
-    @GET("/category/{category_id}")
+    @GET("/categories/{category_id}")
     suspend fun getCategory(@Path("category_id") categoryId: String): CategoryResponse
+
+    @DELETE("/categories/{category_id}")
+    suspend fun deleteCategory(@Path("category_id") categoryId: String): Unit
 }

app/src/main/res/layout/activity_categories.xml

@@ -1,5 +1,6 @@
 <?xml version="1.0" encoding="utf-8"?>
-<androidx.constraintlayout.widget.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
+<androidx.constraintlayout.widget.ConstraintLayout
+    xmlns:android="http://schemas.android.com/apk/res/android"
     xmlns:app="http://schemas.android.com/apk/res-auto"
     xmlns:tools="http://schemas.android.com/tools"
     android:id="@+id/main"
@@ -7,4 +8,84 @@
     android:layout_height="match_parent"
     tools:context=".activities.CategoriesActivity">
 
+    <!-- Title Bar -->
+    <LinearLayout
+        android:id="@+id/titleBar"
+        android:layout_width="0dp"
+        android:layout_height="wrap_content"
+        android:orientation="horizontal"
+        android:gravity="center_vertical"
+        android:background="?android:attr/dividerHorizontal"
+        android:paddingStart="8dp"
+        android:paddingEnd="8dp"
+        app:layout_constraintTop_toTopOf="parent"
+        app:layout_constraintStart_toStartOf="parent"
+        app:layout_constraintEnd_toEndOf="parent">
+
+        <!-- Back Button -->
+        <ImageButton
+            android:id="@+id/btnBack"
+            android:layout_width="40dp"
+            android:layout_height="40dp"
+            android:background="?attr/selectableItemBackgroundBorderless"
+            android:src="@drawable/ic_arrow_back"
+            android:contentDescription="@string/back"
+            app:tint="?android:attr/textColorPrimary" />
+
+        <!-- Title -->
+        <TextView
+            android:id="@+id/tvTitle"
+            android:layout_width="0dp"
+            android:layout_height="wrap_content"
+            android:layout_weight="1"
+            android:textSize="18sp"
+            android:textStyle="bold"
+            android:gravity="center"
+            android:text="@string/categories"
+            tools:text="Categories" />
+
+        <!-- Add Button -->
+        <ImageButton
+            android:id="@+id/btnAddCategory"
+            android:layout_width="40dp"
+            android:layout_height="40dp"
+            android:background="?attr/selectableItemBackgroundBorderless"
+            android:src="@drawable/ic_add"
+            android:contentDescription="@string/add_category"
+            app:tint="?android:attr/textColorPrimary" />
+    </LinearLayout>
+
+    <!-- RecyclerView for displaying categories -->
+    <androidx.recyclerview.widget.RecyclerView
+        android:id="@+id/rvCategories"
+        android:layout_width="0dp"
+        android:layout_height="0dp"
+        app:layout_constraintTop_toBottomOf="@id/titleBar"
+        app:layout_constraintBottom_toBottomOf="parent"
+        app:layout_constraintStart_toStartOf="parent"
+        app:layout_constraintEnd_toEndOf="parent"
+        tools:listitem="@layout/item_category"
+        tools:itemCount="5"
+        android:clipToPadding="false"
+        android:padding="16dp"
+        android:paddingBottom="24dp"
+        android:scrollbars="vertical"
+        android:layout_marginBottom="16dp"
+        android:layout_marginTop="8dp" />
+
+    <!-- Empty State -->
+    <TextView
+        android:id="@+id/tvEmptyState"
+        android:layout_width="0dp"
+        android:layout_height="wrap_content"
+        android:text="@string/no_categories"
+        android:textSize="16sp"
+        android:textColor="?android:attr/textColorSecondary"
+        android:gravity="center"
+        android:visibility="gone"
+        app:layout_constraintTop_toBottomOf="@id/titleBar"
+        app:layout_constraintBottom_toBottomOf="parent"
+        app:layout_constraintStart_toStartOf="parent"
+        app:layout_constraintEnd_toEndOf="parent" />
+
 </androidx.constraintlayout.widget.ConstraintLayout>

app/src/main/res/layout/activity_create_category.xml

@@ -0,0 +1,10 @@
+<?xml version="1.0" encoding="utf-8"?>
+<androidx.constraintlayout.widget.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
+    xmlns:app="http://schemas.android.com/apk/res-auto"
+    xmlns:tools="http://schemas.android.com/tools"
+    android:id="@+id/main"
+    android:layout_width="match_parent"
+    android:layout_height="match_parent"
+    tools:context=".activities.CreateCategoryActivity">
+
+</androidx.constraintlayout.widget.ConstraintLayout>

app/src/main/res/layout/item_category.xml

@@ -0,0 +1,50 @@
+<?xml version="1.0" encoding="utf-8"?>
+<androidx.constraintlayout.widget.ConstraintLayout
+    xmlns:android="http://schemas.android.com/apk/res/android"
+    xmlns:app="http://schemas.android.com/apk/res-auto"
+    xmlns:tools="http://schemas.android.com/tools"
+    android:layout_width="match_parent"
+    android:layout_height="wrap_content"
+    android:padding="8dp">
+
+    <!-- Color Indicator -->
+    <View
+        android:id="@+id/colorIndicator"
+        android:layout_width="8dp"
+        android:layout_height="match_parent"
+        android:background="@android:color/holo_blue_dark"
+        app:layout_constraintTop_toTopOf="parent"
+        app:layout_constraintBottom_toBottomOf="parent"
+        app:layout_constraintStart_toStartOf="parent" />
+
+    <!-- Category Name -->
+    <TextView
+        android:id="@+id/tvCategoryName"
+        android:layout_width="0dp"
+        android:layout_height="wrap_content"
+        android:textSize="16sp"
+        android:textColor="?android:attr/textColorPrimary"
+        android:paddingStart="16dp"
+        android:paddingEnd="8dp"
+        android:ellipsize="end"
+        android:maxLines="1"
+        tools:text="Work"
+        app:layout_constraintTop_toTopOf="parent"
+        app:layout_constraintBottom_toBottomOf="parent"
+        app:layout_constraintStart_toEndOf="@id/colorIndicator"
+        app:layout_constraintEnd_toStartOf="@id/btnDeleteCategory" />
+
+    <!-- Delete Button -->
+    <ImageButton
+        android:id="@+id/btnDeleteCategory"
+        android:layout_width="40dp"
+        android:layout_height="40dp"
+        android:background="?attr/selectableItemBackgroundBorderless"
+        android:src="@drawable/ic_trashbin"
+        android:contentDescription="@string/delete_category"
+        app:tint="?android:attr/textColorSecondary"
+        app:layout_constraintTop_toTopOf="parent"
+        app:layout_constraintBottom_toBottomOf="parent"
+        app:layout_constraintEnd_toEndOf="parent" />
+
+</androidx.constraintlayout.widget.ConstraintLayout>

app/src/main/res/values/strings.xml

@@ -81,4 +81,7 @@
     <string name="view_event">View Event</string>
     <string name="swipe_to_delete_hint">Swipe right on a notification to delete it.</string>
     <string name="no_notifications">You\'re all caught up! No notifications right now.</string>
+    <string name="no_categories">No categories found</string>
+    <string name="categories">Categories</string>
+    <string name="delete_category">Delete category</string>
 </resources>