From 51a4faddd4b2c7a625998ab913a3b803bcd4d13d Mon Sep 17 00:00:00 2001
From: Daniel <danielchelling@gmail.com>
Date: Tue, 20 Jan 2026 20:41:27 -0800
Subject: [PATCH] fix: remove OOM-causing hrefToSpineIndex map from TOC pass

The unordered_map with 2768 string keys (~100KB+) was causing OOM crashes
at beginTocPass() on ESP32-C3's limited ~380KB RAM.

Reverted createTocEntry() to use original O(n) spine file scan instead.
Kept the safe spineToTocIndex vector in buildBookBin() (only ~5.5KB).
---
 lib/Epub/Epub/BookMetadataCache.cpp | 24 +++++++++---------------
 lib/Epub/Epub/BookMetadataCache.h   |  3 ---
 2 files changed, 9 insertions(+), 18 deletions(-)

diff --git a/lib/Epub/Epub/BookMetadataCache.cpp b/lib/Epub/Epub/BookMetadataCache.cpp
index 517d59d..98f86c1 100644
--- a/lib/Epub/Epub/BookMetadataCache.cpp
+++ b/lib/Epub/Epub/BookMetadataCache.cpp
@@ -49,23 +49,12 @@ bool BookMetadataCache::beginTocPass() {
     return false;
   }
 
-  // Build href->spineIndex lookup map for O(1) access during TOC creation
-  hrefToSpineIndex.clear();
-  hrefToSpineIndex.reserve(spineCount);
-  spineFile.seek(0);
-  for (int i = 0; i < spineCount; i++) {
-    auto entry = readSpineEntry(spineFile);
-    hrefToSpineIndex[entry.href] = static_cast<int16_t>(i);
-  }
-  spineFile.seek(0);
-
   return true;
 }
 
 bool BookMetadataCache::endTocPass() {
   tocFile.close();
   spineFile.close();
-  hrefToSpineIndex.clear();
   return true;
 }
 
@@ -271,10 +260,15 @@ void BookMetadataCache::createTocEntry(const std::string& title, const std::stri
   }
 
   int16_t spineIndex = -1;
-  auto it = hrefToSpineIndex.find(href);
-  if (it != hrefToSpineIndex.end()) {
-    spineIndex = it->second;
-  } else {
+  spineFile.seek(0);
+  for (int i = 0; i < spineCount; i++) {
+    auto spineEntry = readSpineEntry(spineFile);
+    if (spineEntry.href == href) {
+      spineIndex = static_cast<int16_t>(i);
+      break;
+    }
+  }
+  if (spineIndex == -1) {
     Serial.printf("[%lu] [BMC] addTocEntry: Could not find spine item for TOC href %s\n", millis(), href.c_str());
   }
 
diff --git a/lib/Epub/Epub/BookMetadataCache.h b/lib/Epub/Epub/BookMetadataCache.h
index e0efc36..c7e9590 100644
--- a/lib/Epub/Epub/BookMetadataCache.h
+++ b/lib/Epub/Epub/BookMetadataCache.h
@@ -3,7 +3,6 @@
 #include <SDCardManager.h>
 
 #include <string>
-#include <unordered_map>
 #include <vector>
 
 class BookMetadataCache {
@@ -55,8 +54,6 @@ class BookMetadataCache {
   // Temp file handles during build
   FsFile spineFile;
   FsFile tocFile;
-  // Lookup cache for O(1) href->spineIndex during TOC pass
-  std::unordered_map<std::string, int16_t> hrefToSpineIndex;
 
   uint32_t writeSpineEntry(FsFile& file, const SpineEntry& entry) const;
   uint32_t writeTocEntry(FsFile& file, const TocEntry& entry) const;