// Ti-Pote — Audio I/O via a single full-duplex I2S bus.
//
// I2S_NUM_0 is configured as MASTER in RX+TX mode. BCLK and WS are
// shared between the INMP441 microphone (RX) and the MAX98357A
// amplifier (TX), which is the standard I2S bus layout — exactly
// what was working on the Raspberry Pi side.
//
// Pin map (single shared I2S bus):
//   BCLK         = GPIO 32   shared mic SCK + speaker BCLK
//   LRCLK / WS   = GPIO 33   shared mic WS  + speaker LRC
//   Mic data in  = GPIO 34   INMP441 SD (input-only pin, perfect)
//   Speaker DOUT = GPIO 22   MAX98357A DIN
//
// Mic L/R stays tied to GND → talks on the LEFT slot of the I2S frame.
//
// Format exchanged with the Pi on the UART:
//   PCM signed 16-bit little-endian, mono, 16 kHz.
//
// Internally the bus runs at 32-bit stereo slots (INMP441 requires it).
// readMicChunk() converts the 32-bit left slot down to S16 mono.
// writeSpeakerChunk() expands S16 mono to 32-bit stereo frames before
// handing them to i2s_write().

#pragma once

#include <Arduino.h>
#include <stdint.h>
#include <stddef.h>

namespace tipote {

class Audio {
public:
    static constexpr int       SAMPLE_RATE      = 16000;
    static constexpr int       CHANNELS         = 1;
    static constexpr int       BYTES_PER_SAMPLE = 2;  // S16

    // Initialise both I2S ports. Safe to call exactly once from setup().
    bool begin();

    // Pull whatever the mic DMA has ready. Writes S16 mono little-endian
    // bytes into `out`, up to `outCapacity` bytes, and returns the number
    // of bytes actually written (always even, possibly zero).
    //
    // Non-blocking (timeout = 0).
    size_t readMicChunk(uint8_t* out, size_t outCapacity);

    // Push S16 mono little-endian PCM to the speaker DMA. Blocks up to
    // ~50 ms waiting for room. Returns bytes actually accepted.
    size_t writeSpeakerChunk(const uint8_t* data, size_t len);

    // Drop anything pending in the speaker DMA. Used on shutdown / reset.
    void flushSpeaker();

    // ─── Debug / bring-up ────────────────────────────────────────
    //
    // Stats updated on every readMicChunk() call, covering *this last
    // batch only*. Handy to confirm the mic is actually clocking data
    // into the ESP32 without blowing up the main audio path.
    struct MicStats {
        int32_t leftRawMin;     // raw int32 sample on left I2S slot
        int32_t leftRawMax;
        int32_t rightRawMin;    // raw int32 sample on right I2S slot
        int32_t rightRawMax;
        int16_t s16Min;         // post-shift S16 sample (output channel)
        int16_t s16Max;
        size_t  samples;        // sample pairs in the batch
    };
    const MicStats& lastMicStats() const { return lastStats_; }

    // Which I2S slot to route into the S16 output. Flip at runtime if
    // the mic's L/R pin doesn't land where we expect.
    enum class MicChannel { Left, Right };
    void setMicChannel(MicChannel ch) { micChannel_ = ch; }
    MicChannel micChannel() const { return micChannel_; }

private:
    bool        micStarted_ = false;
    bool        spkStarted_ = false;
    MicChannel  micChannel_ = MicChannel::Left;
    MicStats    lastStats_  = {0, 0, 0, 0, 0, 0, 0};
};

}  // namespace tipote