Epub improvements (#160)

* Improved navigation and search result highlighting in the EPUB reader

* refactor: implement JIT chunk restoration for robust navigation

- Fixes search and bookmark navigation failing in same-chapter transitions.
- Introduced JIT (Just-in-Time) HTML restoration in `epub_reader.js` to
  re-populate virtualized chunks before CFI resolution or search scrolling.
- Synchronized search highlighting and user highlights within
  newly-restored chunk segments.
- Improved search navigation accuracy by mapping occurrences to
  relative chunk indices.

* Implemented a custom text selection engine for the paginated EPUB reader to support cross-page selection and improved handle interaction.

* Implemented management of external file behavior and improved library filtering.

* Added support for toolbar customization in the EPUB reader.

* Added support for toolbar customization in the PDF reader.

* fix: rendering during auto-scroll and navigation on long pages

* Added a "Scroll to Top" feature to the auto-scroll controls in both EPUB and PDF readers.

app/src/main/java/com/aryan/reader/pdf/PdfPageComposable.kt

@@ -123,7 +123,7 @@ import kotlinx.coroutines.Dispatchers
 import kotlinx.coroutines.NonCancellable
 import kotlinx.coroutines.channels.Channel
 import kotlinx.coroutines.coroutineScope
-import kotlinx.coroutines.flow.collectLatest
+import kotlinx.coroutines.flow.conflate
 import kotlinx.coroutines.isActive
 import kotlinx.coroutines.launch
 import kotlinx.coroutines.withContext
@@ -1104,12 +1104,12 @@ internal fun PdfPageComposable(
         try {
             page = withContext(Dispatchers.IO) { pdfDocumentItem.openPage(pdfPageIndex) }
 
-            snapshotFlow { visibleScreenRect() }.collectLatest { currentVisibleRect ->
+            snapshotFlow { visibleScreenRect() }.conflate().collect { currentVisibleRect ->
                 val tileCalcStart = System.nanoTime()
-                if (!isActive) return@collectLatest
+                if (!isActive) return@collect
 
                 if (isScrolling && effectiveScale > 1f) {
-                    return@collectLatest
+                    return@collect
                 }
 
                 val pxTl: Float
@@ -1131,7 +1131,7 @@ internal fun PdfPageComposable(
                                 oldTiles.forEach { PdfBitmapPool.recycle(it.bitmap) }
                             }
                         }
-                        return@collectLatest
+                        return@collect
                     }
                 } else {
                     val pivotX = screenWidth / 2f

app/src/main/java/com/aryan/reader/pdf/PdfVerticalReader.kt

@@ -139,6 +139,8 @@ class VerticalPdfReaderState {
     internal var scrollToPageHandler: (suspend (Int) -> Unit)? = null
     internal var snapToPageHandler: (suspend (Int) -> Unit)? = null
     internal var scrollByHandler: (suspend (Float) -> Unit)? = null
+    internal var scrollToTopHandler: (suspend () -> Unit)? = null
+    internal var scrollToBottomHandler: (suspend () -> Unit)? = null
 
     suspend fun scrollToPage(pageIndex: Int) {
         scrollToPageHandler?.invoke(pageIndex)
@@ -151,6 +153,14 @@ class VerticalPdfReaderState {
     suspend fun scrollBy(delta: Float) {
         scrollByHandler?.invoke(delta)
     }
+
+    suspend fun scrollToTop() {
+        scrollToTopHandler?.invoke()
+    }
+
+    suspend fun scrollToBottom() {
+        scrollToBottomHandler?.invoke()
+    }
 }
 
 @Composable
@@ -244,6 +254,8 @@ internal fun PdfVerticalReader(
             state.scrollToPageHandler = null
             state.snapToPageHandler = null
             state.scrollByHandler = null
+            state.scrollToTopHandler = null
+            state.scrollToBottomHandler = null
         }
     }
     var globalEraserPosition by remember { mutableStateOf<Offset?>(null) }
@@ -527,6 +539,23 @@ internal fun PdfVerticalReader(
                     )
                 }
             }
+
+            state.scrollToTopHandler = {
+                panYAnimatable.animateTo(
+                    targetValue = headerHeightPx,
+                    animationSpec = tween(durationMillis = 500, easing = FastOutSlowInEasing)
+                )
+            }
+
+            state.scrollToBottomHandler = {
+                val currentZoom = zoomAnimatable.value
+                val zoomedDocHeight = totalDocHeight * currentZoom
+                val minPanY = (screenHeight - footerHeightPx - zoomedDocHeight).coerceAtMost(headerHeightPx)
+                panYAnimatable.animateTo(
+                    targetValue = minPanY,
+                    animationSpec = tween(durationMillis = 500, easing = FastOutSlowInEasing)
+                )
+            }
         }
 
         var selectionClearTrigger by remember { mutableLongStateOf(0L) }

app/src/main/java/com/aryan/reader/pdf/RichTextSystem.kt

@@ -420,7 +420,7 @@ class PdfRichTextRepository(private val context: Context) {
                             isItalic = sObj.optBoolean("i"),
                             isUnderline = sObj.optBoolean("u"),
                             isStrikethrough = sObj.optBoolean("st"),
-                            fontPath = sObj.optString("fp", null),
+                            fontPath = sObj.optString("fp"),
                         )
                     )
                 }

app/src/main/java/com/aryan/reader/pdf/data/PdfAnnotationData.kt

@@ -200,8 +200,8 @@ object TextBoxSerializer {
                         isItalic = obj.optBoolean("isItalic", false),
                         isUnderline = obj.optBoolean("isUnderline", false),
                         isStrikeThrough = obj.optBoolean("isStrikeThrough", false),
-                        fontPath = obj.optString("fontPath", null).takeIf { !it.isNullOrBlank() },
-                        fontName = obj.optString("fontName", null).takeIf { !it.isNullOrBlank() }
+                        fontPath = obj.optString("fontPath").takeIf { !it.isNullOrBlank() },
+                        fontName = obj.optString("fontName").takeIf { !it.isNullOrBlank() }
                     )
                 )
             }
@@ -269,7 +269,7 @@ object HighlightSerializer {
                         color = try { PdfHighlightColor.valueOf(obj.getString("color")) } catch(_: Exception) { PdfHighlightColor.YELLOW },
                         text = obj.optString("text", ""),
                         range = Pair(obj.optInt("rangeStart", 0), obj.optInt("rangeEnd", 0)),
-                        note = obj.optString("note", null).takeIf { !it.isNullOrBlank() }
+                        note = obj.optString("note").takeIf { !it.isNullOrBlank() }
                     )
                 )
             }