Fixes wav files written with WavWriter.h to be complete (#663)

* Fixes wav files written with WavWriter.h to be complete

Before the transfer buffer was not flushed so wav header files would say the file was a certain size but actually it would be smaller because the full data was not written to the wav file. This would result in perfect loops being recalled imperfectly. See https://github.com/willemOH/daisy_looper/tree/main commits for debugging which proves this behavior.

* Improves reliability of multiple consecutive writes

before, the first write would be exact, but subsequent writes would introduce artifacts or inaccuracies to the wav file as compared to recording into a buffer. Powercycling would solve this but not ideal. Now, after 5 writes, there is usually not artefacts or differences between wav file and equivalent buffer. Although occasionally this isn't true so this isn't a complete fix and the issue should be looked into by someone who knows more about this class and fatfs than I.

Author: willemOH

src/util/WavWriter.h

@@ -143,12 +143,30 @@ class WavWriter
     {
         unsigned int bw = 0;
         recording_      = false;
-        // We _should_ flush whatever's left in the transfer buff
-        // TODO: that.
+
+        // Flush remaining data in the transfer buffer
+        if (wptr_ > 0) // Check if there is unwritten data in the buffer
+        {
+            uint32_t remaining_size = wptr_ * (cfg_.bitspersample / 8);
+            // Ensure remaining_size does not exceed the buffer size
+            if (remaining_size > sizeof(transfer_buff))
+            {
+                remaining_size = sizeof(transfer_buff);
+            }
+            f_write(&fp_, transfer_buff, remaining_size, &bw);
+        }
+        
         wavheader_.FileSize = CalcFileSize();
         f_lseek(&fp_, 0);
         f_write(&fp_, &wavheader_, sizeof(wavheader_), &bw);
         f_close(&fp_);
+
+        // Clear the transfer buffer and reset the buffer state
+        memset(transfer_buff, 0, sizeof(transfer_buff));
+        bstate_ = BufferState::IDLE;
+        wptr_ = 0; // Reset the write pointer
+        num_samps_ = 0; // Reset the number of samples
+        recording_ = false;          // Ensure recording is inactive  
     }
 
     /** Opens a file for writing. Writes the initial WAV Header, and gets ready for stream-based recording. */