1 files changed, 118 insertions, 0 deletions
diff --git a/src/tangara/database/track_finder.cpp b/src/tangara/database/track_finder.cpp
new file mode 100644
index 00000000..21a44339
--- /dev/null
+++ b/src/tangara/database/track_finder.cpp
@@ -0,0 +1,118 @@
+/*
+ * Copyright 2023 jacqueline <me@jacqueline.id.au>
+ *
+ * SPDX-License-Identifier: GPL-3.0-only
+ */
+
+#include "database/track_finder.hpp"
+
+#include <deque>
+#include <functional>
+#include <memory>
+#include <mutex>
+#include <sstream>
+#include <string>
+#include <string_view>
+
+#include "database/track_finder.hpp"
+#include "ff.h"
+
+#include "drivers/spi.hpp"
+#include "memory_resource.hpp"
+
+namespace database {
+
+static_assert(sizeof(TCHAR) == sizeof(char), "TCHAR must be CHAR");
+
+CandidateIterator::CandidateIterator(std::string_view root)
+    : to_explore_(&memory::kSpiRamResource) {
+  to_explore_.push_back({root.data(), root.size()});
+}
+
+auto CandidateIterator::next(FILINFO& info) -> std::optional<std::string> {
+  std::scoped_lock<std::mutex> lock{mut_};
+  while (!to_explore_.empty() || current_) {
+    if (!current_) {
+      current_.emplace();
+
+      // Get the next directory to iterate through.
+      current_->first = to_explore_.front();
+      to_explore_.pop_front();
+      const TCHAR* next_path =
+          static_cast<const TCHAR*>(current_->first.data());
+
+      // Open it for iterating.
+      FRESULT res = f_opendir(&current_->second, next_path);
+      if (res != FR_OK) {
+        current_.reset();
+        continue;
+      }
+    }
+
+    FRESULT res = f_readdir(&current_->second, &info);
+    if (res != FR_OK || info.fname[0] == 0) {
+      // No more files in the directory.
+      f_closedir(&current_->second);
+      current_.reset();
+      continue;
+    } else if (info.fattrib & (AM_HID | AM_SYS) || info.fname[0] == '.') {
+      // System or hidden file. Ignore it and move on.
+      continue;
+    } else {
+      // A valid file or folder.
+      std::pmr::string full_path{&memory::kSpiRamResource};
+      full_path += current_->first;
+      full_path += "/";
+      full_path += info.fname;
+
+      if (info.fattrib & AM_DIR) {
+        // This is a directory. Add it to the explore queue.
+        to_explore_.push_back(full_path);
+      } else {
+        // This is a file! We can return now.
+        return {{full_path.data(), full_path.size()}};
+      }
+    }
+  }
+
+  // Out of paths to explore.
+  return {};
+}
+
+TrackFinder::TrackFinder(
+    tasks::WorkerPool& pool,
+    size_t parallelism,
+    std::function<void(FILINFO&, std::string_view)> processor,
+    std::function<void()> complete_cb)
+    : pool_{pool},
+      parallelism_(parallelism),
+      processor_(processor),
+      complete_cb_(complete_cb) {}
+
+auto TrackFinder::launch(std::string_view root) -> void {
+  iterator_ = std::make_unique<CandidateIterator>(root);
+  num_workers_ = parallelism_;
+  for (size_t i = 0; i < parallelism_; i++) {
+    schedule();
+  }
+}
+
+auto TrackFinder::schedule() -> void {
+  pool_.Dispatch<void>([&]() {
+    FILINFO info;
+    auto next = iterator_->next(info);
+    if (next) {
+      std::invoke(processor_, info, *next);
+      schedule();
+    } else {
+      std::scoped_lock<std::mutex> lock{workers_mutex_};
+      num_workers_ -= 1;
+      if (num_workers_ == 0) {
+        iterator_.reset();
+        std::invoke(complete_cb_);
+      }
+    }
+  });
+}
+
+}  // namespace database