From adfeee063faccbfaa248571e9fd8ab8d2f712796 Mon Sep 17 00:00:00 2001
From: IFAKA <99131130+IFAKA@users.noreply.github.com>
Date: Fri, 19 Dec 2025 13:28:36 +0100
Subject: [PATCH] Handle empty spine in getBookSize() and calculateProgress()
 (#67)

## Problem
- `getBookSize()` calls `getCumulativeSpineItemSize(getSpineItemsCount()
- 1)` which passes -1 when spine is empty
- `calculateProgress()` then divides by zero when book size is 0

## Fix
- Return 0 from `getBookSize()` if spine is empty
- Return 0 from `calculateProgress()` if book size is 0

## Testing
- Builds successfully with `pio run`
- Affects: `lib/Epub/Epub.cpp`
---
 lib/Epub/Epub.cpp | 12 ++++++++++--
 1 file changed, 10 insertions(+), 2 deletions(-)

diff --git a/lib/Epub/Epub.cpp b/lib/Epub/Epub.cpp
index 408ebf8..a3edac8 100644
--- a/lib/Epub/Epub.cpp
+++ b/lib/Epub/Epub.cpp
@@ -358,13 +358,21 @@ int Epub::getTocIndexForSpineIndex(const int spineIndex) const {
   return -1;
 }
 
-size_t Epub::getBookSize() const { return getCumulativeSpineItemSize(getSpineItemsCount() - 1); }
+size_t Epub::getBookSize() const {
+  if (spine.empty()) {
+    return 0;
+  }
+  return getCumulativeSpineItemSize(getSpineItemsCount() - 1);
+}
 
 // Calculate progress in book
 uint8_t Epub::calculateProgress(const int currentSpineIndex, const float currentSpineRead) {
+  size_t bookSize = getBookSize();
+  if (bookSize == 0) {
+    return 0;
+  }
   size_t prevChapterSize = (currentSpineIndex >= 1) ? getCumulativeSpineItemSize(currentSpineIndex - 1) : 0;
   size_t curChapterSize = getCumulativeSpineItemSize(currentSpineIndex) - prevChapterSize;
-  size_t bookSize = getBookSize();
   size_t sectionProgSize = currentSpineRead * curChapterSize;
   return round(static_cast<float>(prevChapterSize + sectionProgSize) / bookSize * 100.0);
 }