feat: [#25] drag & drop dans la vue liste du projet (long-press handle, reorderTasks)

app/src/main/java/com/planify/mobile/ui/components/DragHandle.kt

@@ -0,0 +1,109 @@
+package com.planify.mobile.ui.components
+
+import androidx.compose.foundation.gestures.detectDragGesturesAfterLongPress
+import androidx.compose.foundation.layout.Box
+import androidx.compose.foundation.lazy.LazyListItemInfo
+import androidx.compose.foundation.lazy.LazyListState
+import androidx.compose.material.icons.Icons
+import androidx.compose.material.icons.outlined.DragHandle
+import androidx.compose.material3.Icon
+import androidx.compose.material3.MaterialTheme
+import androidx.compose.runtime.Composable
+import androidx.compose.runtime.getValue
+import androidx.compose.runtime.mutableFloatStateOf
+import androidx.compose.runtime.mutableIntStateOf
+import androidx.compose.runtime.mutableStateOf
+import androidx.compose.runtime.remember
+import androidx.compose.runtime.rememberCoroutineScope
+import androidx.compose.runtime.setValue
+import androidx.compose.ui.Modifier
+import androidx.compose.ui.graphics.graphicsLayer
+import androidx.compose.ui.input.pointer.pointerInput
+import androidx.compose.ui.zIndex
+import kotlinx.coroutines.launch
+
+/** State for a reorderable LazyColumn. */
+class ReorderState {
+    var draggedIndex by mutableStateOf<Int?>(null)
+    var dragOffsetY by mutableFloatStateOf(0f)
+    var overIndex by mutableIntStateOf(-1)
+
+    fun isDragged(index: Int) = draggedIndex == index
+    fun isOver(index: Int) = overIndex == index
+}
+
+@Composable
+fun rememberReorderState() = remember { ReorderState() }
+
+/**
+ * Modifier for a drag handle icon that drives a [ReorderState].
+ * Call [onReorder] when the drag ends with the new list order.
+ */
+@Composable
+fun <T> Modifier.reorderDragHandle(
+    item: T,
+    index: Int,
+    items: List<T>,
+    state: ReorderState,
+    listState: LazyListState,
+    onReorder: (List<T>) -> Unit,
+): Modifier {
+    val scope = rememberCoroutineScope()
+    return this.pointerInput(item, items) {
+        detectDragGesturesAfterLongPress(
+            onDragStart = {
+                state.draggedIndex = index
+                state.dragOffsetY = 0f
+                state.overIndex = index
+            },
+            onDrag = { change, dragAmount ->
+                change.consume()
+                state.dragOffsetY += dragAmount.y
+                val currentInfo: LazyListItemInfo? = listState.layoutInfo.visibleItemsInfo
+                    .firstOrNull { it.index == (state.draggedIndex ?: -1) }
+                if (currentInfo != null) {
+                    val currentCenter = currentInfo.offset + currentInfo.size / 2 + state.dragOffsetY.toInt()
+                    val newOver = listState.layoutInfo.visibleItemsInfo
+                        .minByOrNull { kotlin.math.abs(it.offset + it.size / 2 - currentCenter) }
+                        ?.index ?: state.overIndex
+                    state.overIndex = newOver
+                }
+            },
+            onDragEnd = {
+                val from = state.draggedIndex ?: return@detectDragGesturesAfterLongPress
+                val to = state.overIndex
+                if (from != to && to >= 0 && to < items.size) {
+                    val mutable = items.toMutableList()
+                    val moved = mutable.removeAt(from)
+                    mutable.add(to, moved)
+                    scope.launch { onReorder(mutable) }
+                }
+                state.draggedIndex = null
+                state.dragOffsetY = 0f
+                state.overIndex = -1
+            },
+            onDragCancel = {
+                state.draggedIndex = null
+                state.dragOffsetY = 0f
+                state.overIndex = -1
+            },
+        )
+    }
+}
+
+/** Modifier to apply drag visual feedback (elevation + offset) to a dragged item. */
+fun Modifier.draggedItemModifier(isDragged: Boolean, offsetY: Float): Modifier =
+    if (isDragged) this
+        .zIndex(1f)
+        .graphicsLayer { translationY = offsetY; shadowElevation = 8f }
+    else this
+
+@Composable
+fun DragHandleIcon(modifier: Modifier = Modifier) {
+    Icon(
+        imageVector = Icons.Outlined.DragHandle,
+        contentDescription = "Réordonner",
+        tint = MaterialTheme.colorScheme.onSurfaceVariant,
+        modifier = modifier,
+    )
+}

app/src/main/java/com/planify/mobile/ui/project/ProjectScreen.kt

@@ -2,6 +2,7 @@ package com.planify.mobile.ui.project
 
 import androidx.compose.foundation.layout.Column
 import androidx.compose.foundation.layout.PaddingValues
+import androidx.compose.foundation.layout.Row
 import androidx.compose.foundation.layout.fillMaxSize
 import androidx.compose.foundation.layout.fillMaxWidth
 import androidx.compose.foundation.layout.padding
@@ -9,6 +10,7 @@ import androidx.compose.foundation.lazy.LazyColumn
 import androidx.compose.foundation.lazy.LazyRow
 import androidx.compose.foundation.lazy.items
 import androidx.compose.foundation.lazy.itemsIndexed
+import androidx.compose.foundation.lazy.rememberLazyListState
 import androidx.compose.material.icons.Icons
 import androidx.compose.material.icons.outlined.FolderOpen
 import androidx.compose.material3.Card
@@ -21,14 +23,20 @@ import androidx.compose.runtime.collectAsState
 import androidx.compose.runtime.getValue
 import androidx.compose.runtime.mutableStateOf
 import androidx.compose.runtime.remember
+import androidx.compose.ui.Alignment
 import androidx.compose.ui.Modifier
 import androidx.compose.ui.unit.dp
 import androidx.hilt.navigation.compose.hiltViewModel
 import com.planify.mobile.domain.model.Task
 import com.planify.mobile.domain.model.ViewStyle
+import com.planify.mobile.ui.components.DragHandleIcon
 import com.planify.mobile.ui.components.EmptyState
+import com.planify.mobile.ui.components.ReorderState
 import com.planify.mobile.ui.components.SectionHeader
 import com.planify.mobile.ui.components.TaskRow
+import com.planify.mobile.ui.components.draggedItemModifier
+import com.planify.mobile.ui.components.reorderDragHandle
+import com.planify.mobile.ui.components.rememberReorderState
 
 @Composable
 fun ProjectScreen(
@@ -62,6 +70,7 @@ fun ProjectScreen(
             },
             onTaskClick = onTaskClick,
             onCheckedChange = { task -> viewModel.toggleTask(task) },
+            onReorder = { viewModel.reorderTasks(it) },
             modifier = modifier,
         )
         ViewStyle.BOARD -> ProjectBoardView(
@@ -80,9 +89,13 @@ private fun ProjectListView(
     onToggleSection: (String) -> Unit,
     onTaskClick: (Task) -> Unit,
     onCheckedChange: (Task) -> Unit,
+    onReorder: (List<Task>) -> Unit,
     modifier: Modifier = Modifier,
 ) {
-    LazyColumn(modifier = modifier.fillMaxSize()) {
+    val listState = rememberLazyListState()
+    val reorderState = rememberReorderState()
+
+    LazyColumn(state = listState, modifier = modifier.fillMaxSize()) {
         state.sections.forEach { group ->
             val key = group.section?.id ?: "unsectioned"
             val name = group.section?.name ?: "Sans section"
@@ -98,12 +111,33 @@ private fun ProjectListView(
             }
 
             if (key !in collapsedSections) {
-                items(group.tasks, key = { it.id }) { task ->
-                    TaskRow(
-                        task = task,
-                        onCheckedChange = { onCheckedChange(task) },
-                        onClick = { onTaskClick(task) },
-                    )
+                itemsIndexed(group.tasks, key = { _, t -> t.id }) { index, task ->
+                    Row(
+                        modifier = Modifier
+                            .fillMaxWidth()
+                            .draggedItemModifier(
+                                isDragged = reorderState.isDragged(index),
+                                offsetY = if (reorderState.isDragged(index)) reorderState.dragOffsetY else 0f,
+                            ),
+                        verticalAlignment = Alignment.CenterVertically,
+                    ) {
+                        DragHandleIcon(
+                            modifier = Modifier.reorderDragHandle(
+                                item = task,
+                                index = index,
+                                items = group.tasks,
+                                state = reorderState,
+                                listState = listState,
+                                onReorder = onReorder,
+                            )
+                        )
+                        TaskRow(
+                            task = task,
+                            onCheckedChange = { onCheckedChange(task) },
+                            onClick = { onTaskClick(task) },
+                            modifier = Modifier.weight(1f),
+                        )
+                    }
                 }
                 item { HorizontalDivider(Modifier.padding(horizontal = 16.dp)) }
             }

app/src/main/java/com/planify/mobile/ui/project/ProjectViewModel.kt

@@ -68,4 +68,8 @@ class ProjectViewModel @Inject constructor(
     fun toggleTask(task: Task) {
         viewModelScope.launch { taskRepository.checkTask(task.id, !task.checked) }
     }
+
+    fun reorderTasks(reordered: List<Task>) {
+        viewModelScope.launch { taskRepository.reorderTasks(reordered.map { it.id }) }
+    }
 }