4 files changed, 23 insertions, 3 deletions
diff --git a/src/database/CMakeLists.txt b/src/database/CMakeLists.txt
index 04e1d5d8..c5cc59cb 100644
--- a/src/database/CMakeLists.txt
+++ b/src/database/CMakeLists.txt
@@ -5,7 +5,7 @@
 idf_component_register(
   SRCS "env_esp.cpp" "database.cpp" "track.cpp" "records.cpp" "file_gatherer.cpp" "tag_parser.cpp" "index.cpp"
   INCLUDE_DIRS "include"
-  REQUIRES "result" "span" "esp_psram" "fatfs" "libtags" "komihash" "cbor" "tasks" "shared_string")
+  REQUIRES "result" "span" "esp_psram" "fatfs" "libtags" "komihash" "cbor" "tasks" "shared_string" "util")
 
 target_compile_options(${COMPONENT_LIB} PRIVATE ${EXTRA_WARNINGS})
 
diff --git a/src/database/include/tag_parser.hpp b/src/database/include/tag_parser.hpp
index 4be5ad16..b0e9a151 100644
--- a/src/database/include/tag_parser.hpp
+++ b/src/database/include/tag_parser.hpp
@@ -8,6 +8,7 @@
 
 #include <string>
 
+#include "lru_cache.hpp"
 #include "track.hpp"
 
 namespace database {
@@ -21,8 +22,19 @@ class ITagParser {
 
 class TagParserImpl : public ITagParser {
  public:
-  virtual auto ReadAndParseTags(const std::string& path, TrackTags* out)
+  auto ReadAndParseTags(const std::string& path, TrackTags* out)
       -> bool override;
+
+ private:
+  /*
+   * Cache of tags that have already been extracted from files. Ideally this
+   * cache should be slightly larger than any page sizes in the UI.
+   */
+  util::LruCache<16, std::string, TrackTags> cache_;
+
+  // We could also consider keeping caches of artist name -> shared_string and
+  // similar. This hasn't been done yet, as this isn't a common workload in any
+  // of our UI.
 };
 
 }  // namespace database
diff --git a/src/database/include/track.hpp b/src/database/include/track.hpp
index 620fc59e..78f973ac 100644
--- a/src/database/include/track.hpp
+++ b/src/database/include/track.hpp
@@ -12,6 +12,7 @@
 #include <memory>
 #include <optional>
 #include <string>
+#include <unordered_map>
 #include <utility>
 
 #include "leveldb/db.h"
@@ -88,7 +89,7 @@ class TrackTags {
 
  private:
   Encoding encoding_;
-  std::map<Tag, shared_string> tags_;
+  std::unordered_map<Tag, shared_string> tags_;
 };
 
 /*
diff --git a/src/database/tag_parser.cpp b/src/database/tag_parser.cpp
index 2b784ea5..06d8a8c9 100644
--- a/src/database/tag_parser.cpp
+++ b/src/database/tag_parser.cpp
@@ -97,6 +97,12 @@ static const char* kTag = "TAGS";
 
 auto TagParserImpl::ReadAndParseTags(const std::string& path, TrackTags* out)
     -> bool {
+  std::optional<TrackTags> cached = cache_.Get(path);
+  if (cached) {
+    *out = *cached;
+    return true;
+  }
+
   if (path.ends_with(".m4a")) {
     // TODO(jacqueline): Re-enabled once libtags is fixed.
     ESP_LOGW(kTag, "skipping m4a %s", path.c_str());
@@ -160,6 +166,7 @@ auto TagParserImpl::ReadAndParseTags(const std::string& path, TrackTags* out)
     out->duration = ctx.duration;
   }
 
+  cache_.Put(path, *out);
   return true;
 }