1 files changed, 88 insertions, 0 deletions
diff --git a/src/database/index.cpp b/src/database/index.cpp
new file mode 100644
index 00000000..a828578d
--- /dev/null
+++ b/src/database/index.cpp
@@ -0,0 +1,88 @@
+/*
+ * Copyright 2023 jacqueline <me@jacqueline.id.au>
+ *
+ * SPDX-License-Identifier: GPL-3.0-only
+ */
+
+#include "index.hpp"
+#include <stdint.h>
+#include <variant>
+#include "komihash.h"
+#include "leveldb/write_batch.h"
+#include "records.hpp"
+
+namespace database {
+
+const IndexInfo kAlbumsByArtist{
+    .id = 1,
+    .name = "Albums by Artist",
+    .components = {Tag::kArtist, Tag::kAlbum, Tag::kAlbumTrack},
+};
+
+const IndexInfo kTracksByGenre{
+    .id = 2,
+    .name = "Tracks by Genre",
+    .components = {Tag::kGenre, Tag::kTitle},
+};
+
+const IndexInfo kAllTracks{
+    .id = 3,
+    .name = "All Tracks",
+    .components = {Tag::kTitle},
+};
+
+auto Index(const IndexInfo& info, const Track& t, leveldb::WriteBatch* batch)
+    -> bool {
+  IndexKey key{
+      .header{
+          .id = info.id,
+          .depth = 0,
+          .components_hash = 0,
+      },
+      .item = {},
+      .track = {},
+  };
+
+  for (std::uint8_t i = 0; i < info.components.size(); i++) {
+    // Fill in the text for this depth.
+    auto text = t.tags().at(info.components.at(i));
+    if (text) {
+      key.item = *text;
+    } else {
+      key.item = {};
+    }
+
+    // If this is the last component, then we should also fill in the track id.
+    if (i == info.components.size() - 1) {
+      key.track = t.data().id();
+    } else {
+      key.track = {};
+    }
+
+    auto encoded = EncodeIndexKey(key);
+    batch->Put(encoded.slice, leveldb::Slice{});
+
+    // If there are more components after this, then we need to finish by
+    // narrowing the header with the current title.
+    if (i < info.components.size() - 1) {
+      key.header = ExpandHeader(key.header, key.item);
+    }
+  }
+  return true;
+}
+
+auto ExpandHeader(const IndexKey::Header& header,
+                  const std::optional<std::string>& component)
+    -> IndexKey::Header {
+  IndexKey::Header ret{header};
+  ret.depth++;
+  if (component) {
+    ret.components_hash =
+        komihash(component->data(), component->size(), ret.components_hash);
+  } else {
+    ret.components_hash = komihash(NULL, 0, ret.components_hash);
+  }
+  return ret;
+}
+
+}  // namespace database