Coverage Summary for Class: SurferPaneSceneStrategy (com.georgeci.moneysurfer.navigation)

 package com.georgeci.moneysurfer.navigation
 
 import androidx.compose.foundation.layout.Box
 import androidx.compose.foundation.layout.WindowInsets
 import androidx.compose.foundation.layout.WindowInsetsSides
 import androidx.compose.foundation.layout.only
 import androidx.compose.foundation.layout.safeDrawing
 import androidx.compose.foundation.layout.windowInsetsPadding
 import androidx.compose.material3.adaptive.ExperimentalMaterial3AdaptiveApi
 import androidx.compose.material3.adaptive.currentWindowAdaptiveInfoV2
 import androidx.compose.material3.adaptive.layout.ThreePaneScaffoldScope
 import androidx.compose.material3.adaptive.layout.calculatePaneScaffoldDirective
 import androidx.compose.material3.adaptive.navigation3.ListDetailSceneStrategy
 import androidx.compose.material3.adaptive.navigation3.rememberListDetailSceneStrategy
 import androidx.compose.runtime.Composable
 import androidx.compose.runtime.CompositionLocalProvider
 import androidx.compose.runtime.Immutable
 import androidx.compose.runtime.remember
 import androidx.compose.ui.Modifier
 import androidx.compose.ui.unit.Dp
 import androidx.compose.ui.unit.dp
 import androidx.navigation3.runtime.NavEntry
 import androidx.navigation3.scene.Scene
 import androidx.navigation3.scene.SceneStrategy
 import androidx.navigation3.scene.SceneStrategyScope
 import com.georgeci.moneysurfer.uikit.window.LocalSurferPane
 import com.georgeci.moneysurfer.uikit.window.SurferPane
 import com.georgeci.moneysurfer.uikit.window.SurferPaneRole
 import com.georgeci.moneysurfer.uikit.window.SurferWindowSize
 import com.georgeci.moneysurfer.uikit.window.currentSurferWindowSize
 
 /** Horizontal partitions the scaffold is allowed when the inline panel is on screen. */
 private const val InlinePanelPartitions = 3
 
 /**
  * Creates and remembers the app's [SurferPaneSceneStrategy].
  *
  * Two delegates rather than one: the Material directive derived from the window caps the scaffold
  * at two horizontal partitions (its default breakpoint set stops at Expanded, so the third
  * partition it would grant a Large window never materialises), and raising that cap unconditionally
  * would hand every section a third column it has nothing to put in. The wider directive is
  * therefore used only for the scenes that actually carry an inline panel.
  */
 @OptIn(ExperimentalMaterial3AdaptiveApi::class)
 @Composable
 fun <T : Any> rememberSurferPaneSceneStrategy(): SurferPaneSceneStrategy<T> {
     val directive = calculatePaneScaffoldDirective(currentWindowAdaptiveInfoV2())
     val delegate = rememberListDetailSceneStrategy<T>(directive = directive)
     val inlinePanelDelegate = rememberListDetailSceneStrategy<T>(
         directive = directive.copy(maxHorizontalPartitions = InlinePanelPartitions),
     )
     val inlinePanelSupported = currentSurferWindowSize() >= SurferWindowSize.Large
     return remember(delegate, inlinePanelDelegate, inlinePanelSupported) {
         SurferPaneSceneStrategy(
             delegate = delegate,
             inlinePanelDelegate = inlinePanelDelegate,
             inlinePanelSupported = inlinePanelSupported,
         )
     }
 }
 
 /**
  * The app's list-detail pane host: [ListDetailSceneStrategy] plus the two things the screens
  * inside it cannot work out for themselves (issue #388).
  *
  * 1. It tells every entry which pane it landed in, through [LocalSurferPane], so the detail pane
  *    stops drawing a second top app bar, a second back arrow and a second FAB next to the list
  *    pane that already draws all three.
  * 2. It pads the horizontal `safeDrawing` insets once, around the whole scaffold, and thereby
  *    consumes them for both panes. Applied per pane — which is what `surferSafeInsets()` used to
  *    do — the list pane padded its right edge and the detail pane its left, interior edges with
  *    no system inset behind them.
  *
  * Below the two-pane breakpoint the delegate declines the scene (it is constructed with
  * `shouldHandleSinglePaneLayout = false`), this strategy declines with it, and nothing above is
  * applied — compact-width behaviour is untouched, down to the composition local's default.
  *
  * @param inlinePanelDelegate the delegate used for scenes carrying an [extraPane] entry, which
  *   needs a third horizontal partition the plain [delegate] does not grant.
  * @param inlinePanelSupported whether the window is wide enough for that third column. Below it an
  *   [extraPane] entry makes this strategy decline the whole scene, so the panel falls through to
  *   the next strategy and renders as the full-screen route it is on a phone.
  */
 @OptIn(ExperimentalMaterial3AdaptiveApi::class)
 class SurferPaneSceneStrategy<T : Any>(
     private val delegate: ListDetailSceneStrategy<T>,
     private val inlinePanelDelegate: ListDetailSceneStrategy<T> = delegate,
     private val inlinePanelSupported: Boolean = false,
 ) : SceneStrategy<T> {
 
     override fun SceneStrategyScope<T>.calculateScene(entries: List<NavEntry<T>>): Scene<T>? {
         val roles = entries.surferPaneGroup().mapNotNull { it.declaredPaneRole() }
         val hasInlinePanel = SurferPaneRole.Extra in roles
         // The panel is the third column of a list + detail + panel layout. Anything less — a
         // narrow window, or a panel opened without both of the others behind it — has no place to
         // put it, and it is better off as the full-screen form it already is everywhere else.
         val panelFits = inlinePanelSupported &&
             SurferPaneRole.List in roles &&
             SurferPaneRole.Detail in roles
         if (hasInlinePanel && !panelFits) return null
 
         val panes = entries.calculateSurferPanes()
         val decorated = entries.map { entry ->
             val pane = panes[entry.contentKey] ?: return@map entry
             NavEntry(navEntry = entry) {
                 CompositionLocalProvider(LocalSurferPane provides pane) { entry.Content() }
             }
         }
         val strategy = if (hasInlinePanel) inlinePanelDelegate else delegate
         val scene = calculateScene(strategy, decorated) ?: return null
         return SurferPaneScene(delegate = scene, originals = entries.associateBy { it.contentKey })
     }
 
     companion object {
         /**
          * Preferred width of a list pane, pinned to the design's 270–320 dp range (wireframe 270,
          * hi-fi 300, direction D 320) instead of the 360 dp the Material directive defaults to.
          */
         val ListPanePreferredWidth: Dp = 300.dp
 
         /** Preferred width of an [extraPane], from the design's 300–340 dp add-panel column. */
         val InlinePanelPreferredWidth: Dp = 340.dp
 
         /**
          * Marks a [NavEntry] as the list pane of a list-detail layout, showing [detailPlaceholder]
          * beside it while nothing is selected.
          */
         @OptIn(ExperimentalMaterial3AdaptiveApi::class)
         fun listPane(
             detailPlaceholder: @Composable ThreePaneScaffoldScope.() -> Unit = {},
         ): Map<String, Any> =
             ListDetailSceneStrategy.listPane(detailPlaceholder = detailPlaceholder) +
                 ListDetailSceneStrategy.preferredPaneSize(width = ListPanePreferredWidth) +
                 (PaneRoleKey to SurferPaneRole.List)
 
         /** Marks a [NavEntry] as a detail pane of a list-detail layout. */
         @OptIn(ExperimentalMaterial3AdaptiveApi::class)
         fun detailPane(): Map<String, Any> =
             ListDetailSceneStrategy.detailPane() + (PaneRoleKey to SurferPaneRole.Detail)
 
         /**
          * Marks a [NavEntry] as the inline panel displayed beside the detail pane it was opened
          * from — the design's "inline add panel (no modal)" (issue #391).
          *
          * Only honoured on a window wide enough for three columns, and only on top of a full list
          * plus detail stack; everywhere else the entry is presented as an ordinary route.
          */
         @OptIn(ExperimentalMaterial3AdaptiveApi::class)
         fun extraPane(): Map<String, Any> =
             ListDetailSceneStrategy.extraPane() +
                 ListDetailSceneStrategy.preferredPaneSize(width = InlinePanelPreferredWidth) +
                 (PaneRoleKey to SurferPaneRole.Extra)
 
         /**
          * Our own copy of the pane role. The delegate's metadata carries the same information, but
          * in `internal` classes this module cannot read.
          */
         internal const val PaneRoleKey = "com.georgeci.moneysurfer.navigation.SurferPaneRole"
     }
 }
 
 /**
  * The [SurferPane] each entry belongs to, keyed by `contentKey`, for the entries
  * [ListDetailSceneStrategy] will group into one scaffold — mirroring its own grouping: walk back
  * from the top while entries keep declaring a pane, and stop at the first one that does not.
  *
  * Entries outside that group, and every entry of a group with no list pane in it (a creation form
  * pushed straight from the dashboard, say), are left out of the map and keep the default
  * [SurferPane] — a detail pane with nothing beside it still needs its own chrome to be usable.
  */
 internal fun <T : Any> List<NavEntry<T>>.calculateSurferPanes(): Map<Any, SurferPane> {
     val group = surferPaneGroup()
     if (group.none { it.declaredPaneRole() == SurferPaneRole.List }) return emptyMap()
     var detailSeen = false
     return group.mapIndexed { index, entry ->
         val role = requireNotNull(entry.declaredPaneRole())
         val hasBackStack = when (role) {
             // Dismissing the panel leaves the list and the detail it was opened from on screen,
             // so its affordance always goes somewhere.
             SurferPaneRole.Extra -> true
             // A detail pane gives up its back affordance when popping would do nothing but swap
             // it for the placeholder. It keeps one if there is an earlier detail to return to, or
             // an entry stacked above it that displaced its own list — a list route can be pushed
             // from a detail (Accounts' "See all" pushes the transactions list), which leaves the
             // detail beside a list that is not its own, and that still needs a way out. An inline
             // panel stacked above it does not displace anything and does not count.
             SurferPaneRole.Detail -> detailSeen || group.displacesFrom(index)
             SurferPaneRole.List, SurferPaneRole.Single -> false
         }
         if (role == SurferPaneRole.Detail) detailSeen = true
         entry.contentKey to SurferPane(role = role, hasPaneBackStack = hasBackStack)
     }.toMap()
 }
 
 /** The entries [ListDetailSceneStrategy] will group into one scaffold, oldest first. */
 private fun <T : Any> List<NavEntry<T>>.surferPaneGroup(): List<NavEntry<T>> =
     takeLastWhile { it.declaredPaneRole() != null }
 
 /** Whether any entry above [index] takes the place of the pane at [index]. */
 private fun <T : Any> List<NavEntry<T>>.displacesFrom(index: Int): Boolean =
     (index + 1..lastIndex).any { this[it].declaredPaneRole() != SurferPaneRole.Extra }
 
 private fun NavEntry<*>.declaredPaneRole(): SurferPaneRole? =
     metadata[SurferPaneSceneStrategy.PaneRoleKey] as? SurferPaneRole
 
 /**
  * Calls [strategy]'s scene calculation from inside another strategy's, naming the delegate
  * explicitly — a plain `with(strategy) { calculateScene(entries) }` inside the caller would have
  * two implicit dispatch receivers carrying that member extension, and the wrong one recurses.
  */
 private fun <T : Any> SceneStrategyScope<T>.calculateScene(
     strategy: SceneStrategy<T>,
     entries: List<NavEntry<T>>,
 ): Scene<T>? = with(strategy) { calculateScene(entries) }
 
 /**
  * Wraps a list-detail [Scene] to pad the horizontal `safeDrawing` insets once, around both panes.
  *
  * [windowInsetsPadding] also *consumes* what it applies, so the per-screen `surferSafeInsets()`
  * inside each pane contributes nothing horizontally — no change needed in the screens, and no
  * padding on the edge where the two panes meet.
  *
  * @param originals the undecorated entries by `contentKey`. [previousEntries] is fed back through
  *   the strategy chain to build the predictive-back scene; handing back the decorated entries
  *   would wrap them a second time and the stale inner value would win.
  */
 @Immutable
 private class SurferPaneScene<T : Any>(
     private val delegate: Scene<T>,
     private val originals: Map<Any, NavEntry<T>>,
 ) : Scene<T> {
 
     override val key: Any get() = delegate.key
 
     override val entries: List<NavEntry<T>> get() = delegate.entries
 
     override val previousEntries: List<NavEntry<T>>
         get() = delegate.previousEntries.map { originals[it.contentKey] ?: it }
 
     override val metadata: Map<String, Any> get() = delegate.metadata
 
     override val content: @Composable () -> Unit = {
         Box(
             modifier = Modifier.windowInsetsPadding(
                 WindowInsets.safeDrawing.only(WindowInsetsSides.Horizontal),
             ),
         ) {
             delegate.content()
         }
     }
 
     override fun equals(other: Any?): Boolean =
         this === other || (other is SurferPaneScene<*> && delegate == other.delegate)
 
     override fun hashCode(): Int = delegate.hashCode()
 }