Standardize File handling with FsHelpers (#110)

## Summary

* Standardize File handling with FsHelpers
* Better central place to manage to logic of if files exist/open for
reading/writing

lib/FsHelpers/FsHelpers.cpp

@@ -0,0 +1,112 @@
+#include "FsHelpers.h"
+
+#include <SD.h>
+
+#include <vector>
+
+bool FsHelpers::openFileForRead(const char* moduleName, const char* path, File& file) {
+  if (!SD.exists(path)) {
+    return false;
+  }
+
+  file = SD.open(path, FILE_READ);
+  if (!file) {
+    Serial.printf("[%lu] [%s] Failed to open file for reading: %s\n", millis(), moduleName, path);
+    return false;
+  }
+  return true;
+}
+
+bool FsHelpers::openFileForRead(const char* moduleName, const std::string& path, File& file) {
+  return openFileForRead(moduleName, path.c_str(), file);
+}
+
+bool FsHelpers::openFileForRead(const char* moduleName, const String& path, File& file) {
+  return openFileForRead(moduleName, path.c_str(), file);
+}
+
+bool FsHelpers::openFileForWrite(const char* moduleName, const char* path, File& file) {
+  file = SD.open(path, FILE_WRITE, true);
+  if (!file) {
+    Serial.printf("[%lu] [%s] Failed to open file for writing: %s\n", millis(), moduleName, path);
+    return false;
+  }
+  return true;
+}
+
+bool FsHelpers::openFileForWrite(const char* moduleName, const std::string& path, File& file) {
+  return openFileForWrite(moduleName, path.c_str(), file);
+}
+
+bool FsHelpers::openFileForWrite(const char* moduleName, const String& path, File& file) {
+  return openFileForWrite(moduleName, path.c_str(), file);
+}
+
+bool FsHelpers::removeDir(const char* path) {
+  // 1. Open the directory
+  File dir = SD.open(path);
+  if (!dir) {
+    return false;
+  }
+  if (!dir.isDirectory()) {
+    return false;
+  }
+
+  File file = dir.openNextFile();
+  while (file) {
+    String filePath = path;
+    if (!filePath.endsWith("/")) {
+      filePath += "/";
+    }
+    filePath += file.name();
+
+    if (file.isDirectory()) {
+      if (!removeDir(filePath.c_str())) {
+        return false;
+      }
+    } else {
+      if (!SD.remove(filePath.c_str())) {
+        return false;
+      }
+    }
+    file = dir.openNextFile();
+  }
+
+  return SD.rmdir(path);
+}
+
+std::string FsHelpers::normalisePath(const std::string& path) {
+  std::vector<std::string> components;
+  std::string component;
+
+  for (const auto c : path) {
+    if (c == '/') {
+      if (!component.empty()) {
+        if (component == "..") {
+          if (!components.empty()) {
+            components.pop_back();
+          }
+        } else {
+          components.push_back(component);
+        }
+        component.clear();
+      }
+    } else {
+      component += c;
+    }
+  }
+
+  if (!component.empty()) {
+    components.push_back(component);
+  }
+
+  std::string result;
+  for (const auto& c : components) {
+    if (!result.empty()) {
+      result += "/";
+    }
+    result += c;
+  }
+
+  return result;
+}