Added missing chapters count in MangaInfoHeader (#9184)

* Added missing chapters count in MangaInfoHeader

* Added "Might be missing chapters"

* Added missing chapters to MangaAndSourceTitlesLarge function

* Removed comments

* Reworked getMissingChapters to countMissingChapters, moved -1 check

* Attempting detecting sub-chapters

* Moved MissingChapters to ChapterHeader; Adapted design to fit in

* Fixed block comment in one-line-element

* Fixed critical missing-chapter counting bug

* Undid unintentional & unnecessary changes

* Moved & refactored countMissingChapters

* Fixed import order; Mapping chapter object to chapterNumber

* Optimized "No (valid) chapters" detection

---------

Co-authored-by: arkon <arkon@users.noreply.github.com>

domain/src/main/java/tachiyomi/domain/chapter/service/MissingChapters.kt

@@ -0,0 +1,37 @@
+package tachiyomi.domain.chapter.service
+
+import kotlin.math.floor
+
+fun countMissingChapters(chaptersInput: List<Float>): Int? {
+    if (chaptersInput.isEmpty()) {
+        return 0
+    }
+
+    val chapters = chaptersInput
+        // Remove any invalid chapters
+        .filter { it != -1f }
+        // Convert to integers, as we cannot check if 16.5 is missing
+        .map { floor(it.toDouble()).toInt() }
+        // Only keep unique chapters so that -1 or 16 are not counted multiple times
+        .distinct()
+        .sortedBy { it }
+
+    if (chapters.isEmpty()) {
+        return null
+    }
+
+    var missingChaptersCount = 0
+    var previousChapter = 0 // The actual chapter number, not the array index
+
+    // We go from 0 to lastChapter - Make sure to use the current index instead of the value
+    for (i in chapters.indices) {
+        val currentChapter = chapters[i]
+        if (currentChapter > previousChapter + 1) {
+            // Add the amount of missing chapters
+            missingChaptersCount += currentChapter - previousChapter - 1
+        }
+        previousChapter = currentChapter
+    }
+
+    return missingChaptersCount
+}