feat: Create/edit logic for new categories

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

@@ -18,7 +18,6 @@ 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
@@ -38,7 +37,12 @@ class CategoriesActivity : AppCompatActivity() {
             @Suppress("DEPRECATION")
             val newCategory: CategoryResponse? = result.data?.getParcelableExtra("newCategory")
 
-            newCategory?.let { categoryCreateReply(it) }
+            @Suppress("DEPRECATION")
+            val editedCategory: CategoryResponse? = result.data?.getParcelableExtra("editedCategory")
+
+            if (newCategory != null && editedCategory != null) throw IllegalStateException("Got both edit & new response")
+            if (newCategory != null) categoryCreateReply(newCategory, CategoryMode.CREATE)
+            if (editedCategory != null) categoryCreateReply(editedCategory, CategoryMode.EDIT)
         }
     }
 
@@ -59,14 +63,14 @@ class CategoriesActivity : AppCompatActivity() {
         tvEmptyState = findViewById(R.id.tvEmptyState)
 
         btnBack.setOnClickListener { finish() }
-        btnAddCategory.setOnClickListener { navigateToCreateCategory() }
+        btnAddCategory.setOnClickListener { handleCreateCategory() }
 
         rvCategories.layoutManager = LinearLayoutManager(this)
 
         lifecycleScope.launch {
             categories = fetchCategories().toMutableList()
 
-            val adapter = CategoryAdapter(categories, ::handleDeleteCategory)
+            val adapter = CategoryAdapter(categories, ::handleDeleteCategory, ::handleEditCategory)
 
             rvCategories.adapter = adapter
             updateEmptyState()
@@ -105,20 +109,44 @@ class CategoriesActivity : AppCompatActivity() {
     }
 
     /**
-     * Navigates to the activity for adding a new category.
+     * Handle create category button getting pressed.
+     *
+     * Navigates to the create category activity in create mode.
      */
-    private fun navigateToCreateCategory() {
+    private fun handleCreateCategory() {
-        val intent = Intent(this, CreateCategoryActivity::class.java)
+        val intent = Intent(this, CreateCategoryActivity::class.java).apply {
-        startActivity(intent)
+            putExtra("mode", CategoryMode.CREATE.name)
+        }
+        createActivityLauncher.launch(intent)
+    }
+
+    /**
+     * Handle edit category button being pressed.
+     *
+     * Navigates to the create category activity in edit mode.
+     */
+    private fun handleEditCategory(category: CategoryResponse, position: Int) {
+        val intent = Intent(this, CreateCategoryActivity::class.java).apply {
+            putExtra("mode", CategoryMode.EDIT.name)
+            putExtra("category", category)
+        }
+        createActivityLauncher.launch(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.
+     * The returned value (the new / edited category data) is passed over as a parameter.
      */
-    private fun categoryCreateReply(category: CategoryResponse) {
+    private fun categoryCreateReply(category: CategoryResponse, mode: CategoryMode) {
-        (rvCategories.adapter as CategoryAdapter).addCategory(category)
+        val adapter = (rvCategories.adapter as CategoryAdapter)
+        when (mode) {
+            CategoryMode.CREATE -> {
+                adapter.addCategory(category)
+                updateEmptyState()
+            }
+            CategoryMode.EDIT -> { adapter.editCategory(category) }
+        }
     }
 
     /**

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

@@ -1,13 +1,48 @@
 package com.p_vacho.neat_calendar.activities
 
+import android.content.Intent
+import android.content.res.ColorStateList
+import android.graphics.Color
 import android.os.Bundle
+import android.util.Log
+import android.widget.Toast
 import androidx.activity.enableEdgeToEdge
 import androidx.appcompat.app.AppCompatActivity
+import androidx.core.content.ContextCompat
 import androidx.core.view.ViewCompat
 import androidx.core.view.WindowInsetsCompat
+import androidx.lifecycle.lifecycleScope
+import com.github.dhaval2404.colorpicker.ColorPickerDialog
+import com.google.android.material.button.MaterialButton
+import com.google.android.material.textfield.TextInputEditText
+import com.google.gson.Gson
 import com.p_vacho.neat_calendar.R
+import com.p_vacho.neat_calendar.api.RetrofitClient
+import com.p_vacho.neat_calendar.api.models.CategoryRequest
+import com.p_vacho.neat_calendar.api.models.CategoryResponse
+import com.p_vacho.neat_calendar.api.models.PartialCategoryRequest
+import com.p_vacho.neat_calendar.api.models.ValidationError
+import kotlinx.coroutines.Dispatchers
+import kotlinx.coroutines.launch
+import kotlinx.coroutines.withContext
+import retrofit2.HttpException
+import kotlin.properties.Delegates
+
+enum class CategoryMode {
+    CREATE, EDIT
+}
 
 class CreateCategoryActivity : AppCompatActivity() {
+    private var selectedColor by Delegates.notNull<Int>()
+    private var existingCategory: CategoryResponse? = null
+    private lateinit var mode: CategoryMode
+
+    // UI components
+    private lateinit var etCategoryName: TextInputEditText
+    private lateinit var btnColorPicker: MaterialButton
+    private lateinit var btnSaveCategory: MaterialButton
+    private lateinit var btnCancel: MaterialButton
+
     override fun onCreate(savedInstanceState: Bundle?) {
         super.onCreate(savedInstanceState)
         enableEdgeToEdge()
@@ -17,5 +52,107 @@ class CreateCategoryActivity : AppCompatActivity() {
             v.setPadding(systemBars.left, systemBars.top, systemBars.right, systemBars.bottom)
             insets
         }
+
+        initializeViews()
+        mode = intent.getStringExtra("mode")!!.let { CategoryMode.valueOf(it) }
+
+        if (mode == CategoryMode.EDIT) {
+            @Suppress("DEPRECATION")
+            existingCategory = intent.getParcelableExtra("category")!!
+
+            etCategoryName.setText(existingCategory?.name)
+            selectedColor = existingCategory?.color?.toArgb() ?: ContextCompat.getColor(this, R.color.category_indicator_color)
+            btnSaveCategory.setText(R.string.update_category)
+        } else {
+            selectedColor = ContextCompat.getColor(this, R.color.category_indicator_color)
+        }
+
+        btnColorPicker.iconTint = ColorStateList.valueOf(selectedColor)
+        setupListeners()
     }
-}
+
+    private fun initializeViews() {
+        etCategoryName = findViewById(R.id.etCategoryName)
+        btnColorPicker = findViewById(R.id.btnColorPicker)
+        btnSaveCategory = findViewById(R.id.btnSaveCategory)
+        btnCancel = findViewById(R.id.btnCancel)
+    }
+
+    private fun setupListeners() {
+        btnColorPicker.setOnClickListener { openColorPickerDialog() }
+        btnSaveCategory.setOnClickListener { saveCategory() }
+        btnCancel.setOnClickListener { finish() }
+    }
+
+    private fun saveCategory() {
+        val categoryName = etCategoryName.text.toString().trim()
+        if (categoryName.isEmpty()) {
+            Toast.makeText(this, getString(R.string.please_enter_a_category_name), Toast.LENGTH_SHORT).show()
+            return
+        }
+
+        lifecycleScope.launch(Dispatchers.IO) {
+            try {
+                val resultCategory = if (mode == CategoryMode.CREATE) {
+                    val request =
+                        CategoryRequest(name = categoryName, color = Color.valueOf(selectedColor))
+                    RetrofitClient.categoryService.createCategory(request)
+                } else {
+                    val request = PartialCategoryRequest(
+                        name = categoryName.takeIf { it != existingCategory?.name },
+                        color = Color.valueOf(selectedColor)
+                            .takeIf { it != existingCategory?.color }
+                    )
+                    RetrofitClient.categoryService.updateCategory(existingCategory!!.id, request)
+                }
+
+                withContext(Dispatchers.Main) { handleCategorySaved(resultCategory) }
+            } catch (e: HttpException) {
+                if (e.code() != 422) {
+                    throw e
+                }
+
+                val errorBody = e.response()?.errorBody()?.string()
+                val validationError = Gson().fromJson(errorBody, ValidationError::class.java)
+                val errMsg = validationError.detail.joinToString("\n")
+
+                Log.e("CategoryCreate", "Got HTTP 422: $validationError")
+
+                withContext(Dispatchers.Main) {
+                    Toast.makeText(
+                        this@CreateCategoryActivity,
+                        getString(R.string.failed_to_save_category, errMsg),
+                        Toast.LENGTH_SHORT
+                    ).show()
+                }
+            }
+        }
+    }
+
+    private fun handleCategorySaved(category: CategoryResponse) {
+        Log.w("CreateCategory", "Ending")
+        val intent = Intent().apply {
+            if (mode == CategoryMode.CREATE) {
+                putExtra("newCategory", category)
+                Log.w("CreateCategory", "New")
+            } else {
+                putExtra("editedCategory", category)
+                Log.w("CreateCategory", "Edit")
+            }
+        }
+        setResult(RESULT_OK, intent)
+        finish()
+    }
+
+    private fun openColorPickerDialog() {
+        ColorPickerDialog
+            .Builder(this)
+            .setTitle(getString(R.string.select_color))
+            .setDefaultColor(selectedColor)
+            .setColorListener { color, _ ->
+                selectedColor = color
+                btnColorPicker.iconTint = ColorStateList.valueOf(color)
+            }
+            .show()
+    }
+}

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

@@ -1,15 +1,51 @@
 package com.p_vacho.neat_calendar.activities
 
 import android.os.Bundle
+import android.util.Log
+import android.view.View
+import android.widget.ImageButton
+import android.widget.TextView
 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.google.android.material.chip.Chip
+import com.p_vacho.neat_calendar.MyApplication
 import com.p_vacho.neat_calendar.R
+import com.p_vacho.neat_calendar.adapters.CategoryChipAdapter
+import com.p_vacho.neat_calendar.adapters.UserChipAdapter
+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 com.p_vacho.neat_calendar.api.models.UserResponse
+import kotlinx.coroutines.Deferred
+import kotlinx.coroutines.Dispatchers
+import kotlinx.coroutines.async
+import kotlinx.coroutines.launch
+import kotlinx.coroutines.withContext
+import java.time.format.DateTimeFormatter
 
 class EventDetailsActivity : AppCompatActivity() {
     private lateinit var event: EventResponse
+    private lateinit var categories: Map<String, CategoryResponse>
+    private lateinit var users: Map<String, UserResponse>
+
+    // UI components
+    private lateinit var btnBack: ImageButton
+    private lateinit var tvEventTitle: TextView
+    private lateinit var tvEventStartTime: TextView
+    private lateinit var tvEventEndTime: TextView
+    private lateinit var tvEventDescription: TextView
+    private lateinit var rvEventCategories: RecyclerView
+    private lateinit var rvEventAttendees: RecyclerView
+    private lateinit var tvEventCreatedAt: TextView
+    private lateinit var tvNoCategories: TextView
+    private lateinit var tvNoAttendees: TextView
+    private lateinit var tvEventOwner: TextView
+    private lateinit var chipEventOwner: Chip
 
     override fun onCreate(savedInstanceState: Bundle?) {
         super.onCreate(savedInstanceState)
@@ -21,7 +57,205 @@ class EventDetailsActivity : AppCompatActivity() {
             insets
         }
 
+        initializeViews()
+
         @Suppress("DEPRECATION")
-        event = intent.getParcelableExtra<EventResponse>("event")!!
+        event = intent.getParcelableExtra("event")!!
+
+        @Suppress("DEPRECATION")
+        categories = intent.getParcelableArrayListExtra<CategoryResponse>("categories")?.associateBy { it.id } ?: emptyMap()
+
+        @Suppress("DEPRECATION")
+        users = intent.getParcelableArrayListExtra<UserResponse>("users")?.associateBy { it.user_id } ?: emptyMap()
+
+        lifecycleScope.launch {
+            // Collect tasks for missing data
+            // This will also start the fetching coroutines
+            val fetchCategoriesTask = determineCategoryFetchTask()
+            val fetchUsersTask = determineUserFetchTask()
+
+            // Await results
+            val fetchedCategories = fetchCategoriesTask?.await()
+            val fetchedUsers = fetchUsersTask?.await()
+
+            // Update data maps
+            if (fetchedCategories != null) categories = categories + fetchedCategories
+            if (fetchedUsers != null) users = users + fetchedUsers
+
+            setEventDetails()
+        }
     }
-}
+
+    private fun initializeViews() {
+        btnBack = findViewById(R.id.btnBack)
+        tvEventTitle = findViewById(R.id.tvEventTitle)
+        tvEventStartTime = findViewById(R.id.tvEventStartTime)
+        tvEventEndTime = findViewById(R.id.tvEventEndTime)
+        tvEventDescription = findViewById(R.id.tvEventDescription)
+        rvEventCategories = findViewById(R.id.rvEventCategories)
+        rvEventAttendees = findViewById(R.id.rvEventAttendees)
+        tvEventCreatedAt = findViewById(R.id.tvEventCreatedAt)
+        tvNoCategories = findViewById(R.id.tvNoCategories)
+        tvNoAttendees = findViewById(R.id.tvNoAttendees)
+        tvEventOwner = findViewById(R.id.tvEventOwner)
+        chipEventOwner = findViewById(R.id.chipEventOwner)
+
+        rvEventCategories.layoutManager = LinearLayoutManager(this, LinearLayoutManager.HORIZONTAL, false)
+        rvEventCategories.adapter = CategoryChipAdapter(emptyList(), isRemovable = false)
+
+        rvEventAttendees.layoutManager = LinearLayoutManager(this, LinearLayoutManager.HORIZONTAL, false)
+        rvEventAttendees.adapter = UserChipAdapter(emptyList())
+
+        btnBack.setOnClickListener { finish() }
+    }
+
+    /**
+     * Populate the individual UI items with actual content about the event.
+     *
+     * This can only be called once all of the necessary data is fetched.
+     */
+    private fun setEventDetails() {
+        // Set basic event details
+        tvEventTitle.text = event.title
+        tvEventStartTime.text = getString(R.string.event_start_time, formatDateTime(event.start_time.toLocalDateTime()))
+        tvEventEndTime.text = getString(R.string.event_end_time, formatDateTime(event.end_time.toLocalDateTime()))
+        tvEventDescription.text = event.description
+        tvEventCreatedAt.text = getString(R.string.event_created_at, formatDateTime(event.created_at.toLocalDateTime()))
+
+        val userId = (application as MyApplication).tokenManager.userId
+
+        // Set categories or show the placeholder
+        val categoryList = event.category_ids.mapNotNull { categories[it] }
+        rvEventCategories.adapter = CategoryChipAdapter(categoryList, isRemovable = false)
+        tvNoCategories.visibility = if (categoryList.isEmpty()) View.VISIBLE else View.GONE
+        if (event.owner_user_id == userId) {
+            tvNoCategories.text = getString(R.string.no_categories_placeholder)
+        } else {
+            tvNoCategories.text = getString(R.string.no_invited_categories_placeholder)
+        }
+
+
+        // Set attendees or show the placeholder
+        val attendeeList = event.attendee_ids.mapNotNull { users[it] }
+        rvEventAttendees.adapter = UserChipAdapter(attendeeList)
+        tvNoAttendees.visibility = if (attendeeList.isEmpty()) View.VISIBLE else View.GONE
+        tvNoAttendees.text = getString(R.string.no_attendees_placeholder)
+
+        // Show the owner section only if this event isn't owned by the logged user
+        if (event.owner_user_id != userId) {
+            val owner = users[event.owner_user_id]
+            if (owner == null) throw IllegalStateException("Event owner wasn't fetched")
+            tvEventOwner.visibility = View.VISIBLE
+            chipEventOwner.visibility = View.VISIBLE
+            chipEventOwner.text = owner.username
+        } else {
+            tvEventOwner.visibility = View.GONE
+            chipEventOwner.visibility = View.GONE
+        }
+    }
+
+    /**
+     * Determines whether event categories need to be fetched.
+     *
+     * Categories will be fetched if:
+     * - They weren't already set
+     * - One (or more) of the event categories wasn't found in the list of existing categories.
+     *   Note that this case will also produce a warning.
+     *
+     * Categories won't be fetched if the currently logged in user isn't also the event owner,
+     * as they don't have the rights to access the invitor's categories.
+     *
+     * This will return back a Deferred object, being obtained in an already started coroutine.
+     */
+    private fun determineCategoryFetchTask(): Deferred<Map<String, CategoryResponse>>? {
+        val userId = (application as MyApplication).tokenManager.userId
+
+        if (userId != event.owner_user_id) return null
+
+        return if (categories.isEmpty()) {
+            lifecycleScope.async { fetchEventCategories(event.id) }
+        } else if (categories.keys.intersect(event.category_ids).size != event.category_ids.size) {
+            Log.w(
+                "EventDetailsActivity",
+                "One or more of the event categories wasn't found in the list of categories. Categories will be re-fetched."
+            )
+            lifecycleScope.async { fetchEventCategories(event.id) }
+        } else null
+    }
+
+    /**
+     * Determines which users need to be fetched and creates a fetch task if necessary.
+     *
+     * This will fetch all the users that are attending the event and the event's user id,
+     * skipping any users that are already fetched. Note that if any of the event attendees
+     * aren't already in the users list, yet the list isn't empty, a warning will be produced.
+     *
+     * This will return back a Deferred object, being obtained in an already started coroutine.
+     */
+    private fun determineUserFetchTask(): Deferred<Map<String, UserResponse>>? {
+        val userIdsToFetch = mutableSetOf<String>().apply {
+            if (users.isEmpty()) {
+                addAll(event.attendee_ids)
+                add(event.owner_user_id)
+            } else {
+                if (!users.containsKey(event.owner_user_id)) add(event.owner_user_id)
+
+                // Check for missing attendees and log a warning for each
+                val missingAttendees = event.attendee_ids.filter { !users.containsKey(it) }
+                if (missingAttendees.isNotEmpty()) {
+                    missingAttendees.forEach { attendeeId ->
+                        Log.w(
+                            "EventDetailsActivity",
+                            "Missing attendee ID: $attendeeId in the provided users list. Will fetch it additionally."
+                        )
+                    }
+                    addAll(missingAttendees)
+                }
+            }
+        }
+
+        return if (userIdsToFetch.isNotEmpty()) {
+            lifecycleScope.async { fetchUsers(userIdsToFetch.toList()) }
+        } else null
+    }
+
+    /**
+     * Fetch all the categories of given event.
+     *
+     * This will return a hash map, with the category IDs as keys.
+     */
+    private suspend fun fetchEventCategories(eventId: String): Map<String, CategoryResponse> {
+        val fetchedCategories = withContext(Dispatchers.IO) {
+            RetrofitClient.categoryService.eventCategories(eventId)
+        }
+
+        return fetchedCategories.associateBy { it.id }
+    }
+
+    /**
+     * Fetch all the requested users (by IDs).
+     *
+     * This will return a hash map, with the user IDs as keys.
+     *
+     * Note that this will make an API request for each requested user ID.
+     * These requests will be made in parallel.
+     */
+    private suspend fun fetchUsers(userIds: List<String>): Map<String, UserResponse> {
+        val fetchedUsers = withContext(Dispatchers.IO) {
+            val usersDeferred = userIds.map { async { RetrofitClient.usersService.getUser(it) }}
+            usersDeferred.map { it.await() }
+
+        }
+
+        return fetchedUsers.associateBy { it.user_id }
+    }
+
+    /**
+     * Format a date time object into a string.
+     *
+     * This is used to format the datetime shown for the event start, end & creation times.
+     */
+    private fun formatDateTime(dateTime: java.time.LocalDateTime): String {
+        return dateTime.format(DateTimeFormatter.ofPattern("yyyy-MM-dd HH:mm"))
+    }
+}

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

@@ -11,12 +11,14 @@ import com.p_vacho.neat_calendar.api.models.CategoryResponse
 
 class CategoryAdapter(
     private val categories: MutableList<CategoryResponse>,
-    private val onDeleteClick: (CategoryResponse, Int) -> Unit
+    private val onDeleteClick: (CategoryResponse, Int) -> Unit,
+    private val onEditClick: (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 editButton: ImageButton = view.findViewById(R.id.btnEditCategory)
         val deleteButton: ImageButton = view.findViewById(R.id.btnDeleteCategory)
     }
 
@@ -33,10 +35,9 @@ class CategoryAdapter(
         holder.colorIndicator.setBackgroundColor(category.color.toArgb())
         holder.categoryName.text = category.name
 
-        // Set click listener for the delete button
+        // Set click listeners for the buttons
-        holder.deleteButton.setOnClickListener {
+        holder.deleteButton.setOnClickListener { onDeleteClick(category, position) }
-            onDeleteClick(category, position)
+        holder.editButton.setOnClickListener { onEditClick(category, position) }
-        }
     }
 
     override fun getItemCount(): Int = categories.size
@@ -64,4 +65,15 @@ class CategoryAdapter(
         categories.add(category)
         notifyItemInserted(categories.size)
     }
+
+    /**
+     * Edit an existing category, updating it in the UI.
+     *
+     * Call this after the onEditClick callback edits the category from the backend API.
+     */
+    fun editCategory(category: CategoryResponse) {
+        val position = categories.indexOfFirst { it.id == category.id }
+        categories[position] = category
+        notifyItemChanged(position)
+    }
 }

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

@@ -2,11 +2,9 @@ package com.p_vacho.neat_calendar.adapters
 
 import android.content.res.ColorStateList
 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.google.android.material.chip.Chip
 import com.p_vacho.neat_calendar.R
 import com.p_vacho.neat_calendar.api.models.CategoryResponse
 
@@ -14,47 +12,37 @@ class CategoryChipAdapter(
     private val categories: List<CategoryResponse>,
     private val isRemovable: Boolean = false,
     private val onRemoveCategory: ((CategoryResponse, Int) -> Unit)? = null
-) : RecyclerView.Adapter<RecyclerView.ViewHolder>() {
+) : RecyclerView.Adapter<CategoryChipAdapter.CategoryChipViewHolder>() {
 
-    inner class CategoryViewHolder(val textView: TextView) : RecyclerView.ViewHolder(textView)
+    inner class CategoryChipViewHolder(val chip: Chip) : RecyclerView.ViewHolder(chip)
-
-    inner class RemovableCategoryViewHolder(view: View) : RecyclerView.ViewHolder(view) {
-        val textView: TextView = view.findViewById(R.id.chipText)
-        val removeButton: ImageButton = view.findViewById(R.id.removeButton)
-    }
 
     override fun getItemViewType(position: Int): Int {
         return if (isRemovable) 1 else 0
     }
 
-    override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): RecyclerView.ViewHolder {
+    override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): CategoryChipViewHolder {
-        return if (viewType == 1) {
+        val layoutResId = if (viewType == 1) {
-            val view = LayoutInflater.from(parent.context)
+            R.layout.item_removable_category_chip
-                .inflate(R.layout.item_removable_category_chip, parent, false)
-            RemovableCategoryViewHolder(view)
         } else {
-            val view = LayoutInflater.from(parent.context)
+            R.layout.item_category_chip
-                .inflate(R.layout.item_category_chip, parent, false) as TextView
-            CategoryViewHolder(view)
         }
+
+        val chip = LayoutInflater.from(parent.context)
+            .inflate(layoutResId, parent, false) as Chip
+        return CategoryChipViewHolder(chip)
     }
 
-    override fun onBindViewHolder(holder: RecyclerView.ViewHolder, position: Int) {
+    override fun onBindViewHolder(holder: CategoryChipViewHolder, position: Int) {
         val category = categories[position]
+        val chip = holder.chip
 
-        if (holder is CategoryViewHolder) {
+        // Set the chip's text and background color
-            // Regular category chip
+        chip.text = category.name
-            holder.textView.text = category.name
+        chip.chipStrokeColor = ColorStateList.valueOf(category.color.toArgb())
-            holder.textView.backgroundTintList = ColorStateList.valueOf(category.color.toArgb())
-        } else if (holder is RemovableCategoryViewHolder) {
-            // Removable category chip
-            holder.textView.text = category.name
 
-            // Apply background tint to the LinearLayout (container)
+        if (isRemovable) {
-            holder.itemView.backgroundTintList = ColorStateList.valueOf(category.color.toArgb())
+            // Set close icon click listener for removable chips
-
+            chip.setOnCloseIconClickListener {
-            // Set up the remove button's click listener
-            holder.removeButton.setOnClickListener {
                 onRemoveCategory?.invoke(category, position)
             }
         }

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

@@ -80,7 +80,7 @@ class EventCardAdapter(
         // Initialize empty state for categories
         holder.rvCategories.layoutManager =
             LinearLayoutManager(holder.itemView.context, LinearLayoutManager.HORIZONTAL, false)
-        holder.rvCategories.adapter = CategoryChipAdapter(emptyList())
+        holder.rvCategories.adapter = CategoryChipAdapter(emptyList(), isRemovable = false)
 
         // Events list might contain events that are owned by others (invited events)
         // we can't show the categories & edit / delete buttons for these, as we don't
@@ -138,7 +138,7 @@ class EventCardAdapter(
             }
 
             // Update the RecyclerView adapter on the main thread
-            holder.rvCategories.adapter = CategoryChipAdapter(categories)
+            holder.rvCategories.adapter = CategoryChipAdapter(categories, isRemovable = false)
         }
     }
 }

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

@@ -0,0 +1,30 @@
+package com.p_vacho.neat_calendar.adapters
+
+import android.view.LayoutInflater
+import android.view.ViewGroup
+import androidx.recyclerview.widget.RecyclerView
+import com.google.android.material.chip.Chip
+import com.p_vacho.neat_calendar.R
+import com.p_vacho.neat_calendar.api.models.UserResponse
+
+class UserChipAdapter(
+    private val users: List<UserResponse>
+) : RecyclerView.Adapter<UserChipAdapter.UserChipViewHolder>() {
+
+    inner class UserChipViewHolder(val chip: Chip) : RecyclerView.ViewHolder(chip)
+
+    override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): UserChipViewHolder {
+        val chip = LayoutInflater.from(parent.context)
+            .inflate(R.layout.item_user_chip, parent, false) as Chip
+        return UserChipViewHolder(chip)
+    }
+
+    override fun onBindViewHolder(holder: UserChipViewHolder, position: Int) {
+        val user = users[position]
+        val chip = holder.chip
+
+        chip.text = user.username
+    }
+
+    override fun getItemCount(): Int = users.size
+}

app/src/main/java/com/p_vacho/neat_calendar/api/models/UserModels.kt

@@ -1,13 +1,16 @@
 package com.p_vacho.neat_calendar.api.models
 
+import android.os.Parcelable
+import kotlinx.parcelize.Parcelize
 import java.time.OffsetDateTime
 
+@Parcelize
 data class UserResponse(
     val user_id: String,
     val username: String,
     val email: String,
     val created_at: OffsetDateTime,
-)
+) : Parcelable
 
 data class PartialUserRequest(
     val username: String?,

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

@@ -24,7 +24,7 @@ interface CategoryService {
     suspend fun createCategory(@Body categoryData: CategoryRequest): CategoryResponse
 
     @PATCH("/categories/{category_id}")
-    suspend fun createCategory(@Path("category_id") categoryId: String, @Body categoryData: PartialCategoryRequest): CategoryResponse
+    suspend fun updateCategory(@Path("category_id") categoryId: String, @Body categoryData: PartialCategoryRequest): CategoryResponse
 
     @DELETE("/categories/{category_id}")
     suspend fun deleteCategory(@Path("category_id") categoryId: String): Unit

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

@@ -46,7 +46,7 @@
                 android:layout_marginTop="16dp"
                 android:text="@string/select_color"
                 app:icon="@drawable/ic_circle"
-                app:iconTint="@android:color/holo_blue_dark"
+                app:iconTint="@color/category_indicator_color"
                 app:cornerRadius="8dp"
                 style="@style/Widget.MaterialComponents.Button.OutlinedButton" />
 

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

@@ -121,7 +121,7 @@
                 android:textSize="14sp"
                 android:textColor="?android:attr/textColorPrimary"
                 android:textStyle="bold"
-                tools:text="Categories:" />
+                android:text="@string/categories_section" />
 
             <androidx.recyclerview.widget.RecyclerView
                 android:id="@+id/rvEventCategories"
@@ -133,6 +133,18 @@
                 tools:layoutManager="androidx.recyclerview.widget.LinearLayoutManager"
                 tools:orientation="horizontal" />
 
+            <!-- Placeholder for empty categories -->
+            <TextView
+                android:id="@+id/tvNoCategories"
+                android:layout_width="match_parent"
+                android:layout_height="wrap_content"
+                android:layout_marginTop="8dp"
+                android:gravity="center"
+                android:text="@string/no_categories_placeholder"
+                android:textSize="14sp"
+                android:textColor="?android:attr/textColorSecondary"
+                android:visibility="gone" />
+
             <!-- Attendees Section -->
             <TextView
                 android:id="@+id/tvEventAttendees"
@@ -142,18 +154,48 @@
                 android:textSize="14sp"
                 android:textColor="?android:attr/textColorPrimary"
                 android:textStyle="bold"
-                tools:text="Attendees:" />
+                android:text="@string/attendees_section" />
 
             <androidx.recyclerview.widget.RecyclerView
                 android:id="@+id/rvEventAttendees"
                 android:layout_width="match_parent"
                 android:layout_height="wrap_content"
                 android:layout_marginTop="8dp"
-                tools:listitem="@layout/item_attendee_chip"
+                tools:listitem="@layout/item_user_chip"
                 tools:itemCount="3"
                 tools:layoutManager="androidx.recyclerview.widget.LinearLayoutManager"
                 tools:orientation="horizontal" />
 
+            <!-- Placeholder for empty attendees -->
+            <TextView
+                android:id="@+id/tvNoAttendees"
+                android:layout_width="match_parent"
+                android:layout_height="wrap_content"
+                android:layout_marginTop="8dp"
+                android:gravity="center"
+                android:text="@string/no_attendees_placeholder"
+                android:textSize="14sp"
+                android:textColor="?android:attr/textColorSecondary"
+                android:visibility="gone" />
+
+            <!-- Event Owner Section -->
+            <TextView
+                android:id="@+id/tvEventOwner"
+                android:layout_width="match_parent"
+                android:layout_height="wrap_content"
+                android:layout_marginTop="12dp"
+                android:textSize="14sp"
+                android:textColor="?android:attr/textColorPrimary"
+                android:textStyle="bold"
+                android:text="@string/event_owner_section" />
+
+            <include
+                android:id="@+id/chipEventOwner"
+                layout="@layout/item_user_chip"
+                android:layout_width="wrap_content"
+                android:layout_height="wrap_content"
+                android:layout_marginTop="8dp" />
+
             <!-- Created At -->
             <TextView
                 android:id="@+id/tvEventCreatedAt"
@@ -166,5 +208,4 @@
 
         </LinearLayout>
     </androidx.cardview.widget.CardView>
-
 </androidx.constraintlayout.widget.ConstraintLayout>

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

@@ -20,7 +20,7 @@
             android:id="@+id/colorIndicator"
             android:layout_width="8dp"
             android:layout_height="0dp"
-            android:background="@android:color/holo_blue_dark"
+            android:background="@color/category_indicator_color"
             app:layout_constraintTop_toTopOf="parent"
             app:layout_constraintBottom_toBottomOf="parent"
             app:layout_constraintStart_toStartOf="parent" />
@@ -40,20 +40,39 @@
             app:layout_constraintTop_toTopOf="parent"
             app:layout_constraintBottom_toBottomOf="parent"
             app:layout_constraintStart_toEndOf="@id/colorIndicator"
-            app:layout_constraintEnd_toStartOf="@id/btnDeleteCategory" />
+            app:layout_constraintEnd_toStartOf="@id/buttonContainer" />
 
-        <!-- Delete Button -->
+        <!-- Button Container -->
-        <ImageButton
+        <LinearLayout
-            android:id="@+id/btnDeleteCategory"
+            android:id="@+id/buttonContainer"
-            android:layout_width="40dp"
+            android:layout_width="wrap_content"
-            android:layout_height="40dp"
+            android:layout_height="wrap_content"
-            android:background="?attr/selectableItemBackgroundBorderless"
+            android:orientation="horizontal"
-            android:src="@drawable/ic_trashbin"
+            android:gravity="center"
-            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" />
+            app:layout_constraintEnd_toEndOf="parent">
+
+            <!-- Edit Button -->
+            <ImageButton
+                android:id="@+id/btnEditCategory"
+                android:layout_width="40dp"
+                android:layout_height="40dp"
+                android:background="?attr/selectableItemBackgroundBorderless"
+                android:src="@drawable/ic_pencil"
+                android:contentDescription="@string/edit_category"
+                app:tint="?android:attr/textColorSecondary" />
+
+            <!-- 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" />
+        </LinearLayout>
 
     </androidx.constraintlayout.widget.ConstraintLayout>
 </androidx.cardview.widget.CardView>

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

@@ -17,6 +17,6 @@
     app:chipIconTint="?android:attr/textColorSecondary"
     app:chipBackgroundColor="@android:color/transparent"
     app:chipSurfaceColor="@android:color/transparent"
-    app:chipStrokeColor="@android:color/holo_blue_dark"
+    app:chipStrokeColor="@color/category_indicator_color"
     app:closeIconEnabled="false"
     tools:text="Work" />

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

@@ -1,37 +1,24 @@
-<?xml version="1.0" encoding="utf-8"?>
+<com.google.android.material.chip.Chip
-<LinearLayout
     xmlns:android="http://schemas.android.com/apk/res/android"
-    xmlns:tools="http://schemas.android.com/tools"
     xmlns:app="http://schemas.android.com/apk/res-auto"
+    xmlns:tools="http://schemas.android.com/tools"
+    android:id="@+id/removableChip"
     android:layout_width="wrap_content"
     android:layout_height="wrap_content"
-    android:orientation="horizontal"
-    android:gravity="center_vertical"
     android:layout_marginEnd="8dp"
-    android:background="@drawable/bg_category_chip"
-    android:backgroundTint="@android:color/holo_blue_dark"
     android:paddingStart="8dp"
-    android:paddingEnd="4dp"
+    android:paddingEnd="8dp"
     android:paddingTop="4dp"
-    android:paddingBottom="4dp">
+    android:paddingBottom="4dp"
-
+    android:textSize="12sp"
-    <!-- Text for the category -->
+    android:textColor="?android:attr/textColorPrimary"
-    <TextView
+    app:chipIcon="@drawable/ic_tag"
-        android:id="@+id/chipText"
+    app:chipIconTint="?android:attr/textColorSecondary"
-        android:layout_width="wrap_content"
+    app:chipBackgroundColor="@android:color/transparent"
-        android:layout_height="wrap_content"
+    app:chipSurfaceColor="@android:color/transparent"
-        android:textSize="12sp"
+    app:chipStrokeColor="@android:color/holo_blue_dark"
-        android:textColor="?android:attr/textColorPrimary"
+    app:chipStrokeWidth="1dp"
-        tools:text="Work" />
+    app:closeIconEnabled="true"
-
+    app:closeIcon="@drawable/ic_close"
-    <!-- X button to remove the category -->
+    app:closeIconTint="?android:attr/textColorSecondary"
-    <ImageButton
+    tools:text="Work" />
-        android:id="@+id/removeButton"
-        android:layout_width="20dp"
-        android:layout_height="20dp"
-        android:layout_marginStart="8dp"
-        android:background="?attr/selectableItemBackgroundBorderless"
-        android:contentDescription="@string/remove_category"
-        android:src="@drawable/ic_close"
-        app:tint="?android:attr/textColorPrimary" />
-</LinearLayout>

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

@@ -7,5 +7,6 @@
     <color name="splash_dark_background">#121212</color> <!-- Dark gray -->
 
     <color name="event_indicator_color">#0035D0</color>
+    <color name="category_indicator_color">#0035D0</color>
     <color name="unreadIndicator">#bb6633</color>
 </resources>

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

@@ -44,6 +44,7 @@
     <string name="remove_category">Remove the category</string>
     <string name="add_category">Add category</string>
     <string name="update_event">Update Event</string>
+    <string name="update_category">Update Category</string>
     <string name="leave_invited_event">Leave invited event</string>
     <string name="open_app_settings">Open Settings</string>
     <string name="open_notifications">Open Notifications</string>
@@ -87,4 +88,16 @@
     <string name="event_details">Event Details</string>
     <string name="category_name">Category Name</string>
     <string name="open_categories">Open category management</string>
+    <string name="event_start_time">"Start: %1$s"</string>
+    <string name="event_end_time">End: %1$s</string>
+    <string name="event_created_at">Created on: %1$s</string>
+    <string name="categories_section">Categories:</string>
+    <string name="attendees_section">Attendees:</string>
+    <string name="no_attendees_placeholder">This event has no attendees.</string>
+    <string name="no_categories_placeholder">This event has no categories.</string>
+    <string name="event_owner_section">Event owner:</string>
+    <string name="no_invited_categories_placeholder">You can\'t see categories for invited events</string>
+    <string name="edit_category">Edit category</string>
+    <string name="please_enter_a_category_name">Please enter a category name</string>
+    <string name="failed_to_save_category">Failed to save category: %1$s</string>
 </resources>