Implemented LaunchId and FileSelection, updated Notes (#281)

- Implemented `LaunchId` to keep track of the apps that are started
- Implemented `FileSelection` app to select existing and/or new files.
- Moved some re-usable file functionality to `tt::file::`
- Renamed `Files` app to `FileBrowser`
- Updated `Notes` app to use new `FileSelection` functionality, and cleaned it up a bit.
- General code cleanliness improvements

TactilityCore/Include/Tactility/file/File.h

@@ -3,10 +3,34 @@
 #include "Tactility/TactilityCore.h"
 
 #include <cstdio>
+#include <dirent.h>
 #include <sys/stat.h>
+#include <vector>
 
 namespace tt::file {
 
+/** File types for `dirent`'s `d_type`. */
+enum {
+    TT_DT_UNKNOWN = 0,
+#define TT_DT_UNKNOWN TT_DT_UNKNOWN // Unknown type
+    TT_DT_FIFO = 1,
+#define TT_DT_FIFO TT_DT_FIFO // Named pipe or FIFO
+    TT_DT_CHR = 2,
+#define TT_DT_CHR TT_DT_CHR // Character device
+    TT_DT_DIR = 4,
+#define TT_DT_DIR TT_DT_DIR // Directory
+    TT_DT_BLK = 6,
+#define TT_DT_BLK TT_DT_BLK // Block device
+    TT_DT_REG = 8,
+#define TT_DT_REG TT_DT_REG // Regular file
+    TT_DT_LNK = 10,
+#define TT_DT_LNK TT_DT_LNK // Symbolic link
+    TT_DT_SOCK = 12,
+#define TT_DT_SOCK TT_DT_SOCK // Local-domain socket
+    TT_DT_WHT = 14
+#define TT_DT_WHT TT_DT_WHT // Whiteout inodes
+};
+
 #ifdef _WIN32
 constexpr char SEPARATOR = '\\';
 #else
@@ -36,6 +60,13 @@ std::unique_ptr<uint8_t[]> readBinary(const std::string& filepath, size_t& outSi
  */
 std::unique_ptr<uint8_t[]> readString(const std::string& filepath);
 
+/** Write text to a file
+ * @param[in] path file path to write to
+ * @param[in] content file content to write
+ * @return true when operation is successful
+ */
+bool writeString(const std::string& filepath, const std::string& content);
+
 /** Ensure a directory path exists.
  * @param[in] path the directory path to find, or to create recursively
  * @param[in] mode the mode to use when creating directories
@@ -43,4 +74,41 @@ std::unique_ptr<uint8_t[]> readString(const std::string& filepath);
  */
 bool findOrCreateDirectory(std::string path, mode_t mode);
 
+/**
+ * Concatenate a child path with a parent path, ensuring proper slash inbetween
+ * @param basePath an absolute path with or without trailing "/"
+ * @param childPath the name of the child path (e.g. subfolder or file)
+ * @return the concatenated path
+ */
+std::string getChildPath(const std::string& basePath, const std::string& childPath);
+
+typedef int (*ScandirFilter)(const dirent*);
+
+typedef bool (*ScandirSort)(const dirent&, const dirent&);
+
+/** Used for sorting by alphanumeric value and file type */
+bool direntSortAlphaAndType(const dirent& left, const dirent& right);
+
+/** A filter for filtering out "." and ".." */
+int direntFilterDotEntries(const dirent* entry);
+
+/**
+ * A scandir()-like implementation that works on ESP32.
+ * It does not return "." and ".." items but otherwise functions the same.
+ * It returns an allocated output array with allocated dirent instances.
+ * The caller is responsible for free-ing the memory of these.
+ *
+ * @param[in] path path the scan for files and directories
+ * @param[out] outList a pointer to vector of dirent
+ * @param[in] filter an optional filter to filter out specific items
+ * @param[in] sort an optional sorting function
+ * @return the amount of items that were stored in "output" or -1 when an error occurred
+ */
+int scandir(
+    const std::string& path,
+    std::vector<dirent>& outList,
+    ScandirFilter _Nullable filter,
+    ScandirSort _Nullable sort
+);
+
 }