/*
 * ===========================================================================
 *  04_Voice_Assistant  —  MaTouch AI ESP32-S3 2.8" TFT ST7789V
 * ===========================================================================
 *
 *  ---------------------------------------------------------------------------
 *  VIDEO AND WRITTEN INSTRUCTIONS
 *
 *      Watch the video : https://youtu.be/Px3FT47RV2M
 *      Full article    : https://robojax.com/RTJ851
 *                        ("AI Voice Assistant" - wiring, settings, screenshots
 *                         and answers to the common problems)
 *
 *  Watching the video first will save you time - it shows the Arduino IDE
 *  settings and the library versions being set up step by step.
 *  ---------------------------------------------------------------------------
 *
 *  A complete voice assistant on a $40 board:
 *
 *      hold SPEAK  ->  both INMP441 microphones record you
 *                  ->  Azure Speech turns the audio into text
 *                  ->  DeepSeek v4-flash thinks of an answer
 *                  ->  Azure Speech turns the answer into audio
 *                  ->  the MAX98357 speaker says it out loud
 *
 *  and the whole conversation is drawn as chat bubbles on the touchscreen.
 *
 *  WHY THIS COMBINATION OF SERVICES (each is used where it is best):
 *   - Azure STT accepts a plain WAV in a plain POST with one header. OpenAI's
 *     transcription endpoint wants multipart/form-data - miserable on an MCU.
 *   - Azure TTS can return RAW 16 kHz PCM ("riff-16khz-16bit-mono-pcm"),
 *     which streams straight into the I2S speaker with NO MP3 decoder at all.
 *   - DeepSeek v4-flash is fast and nearly free per reply. NOTE: the old
 *     model names deepseek-chat / deepseek-reasoner were RETIRED in July 2026.
 *     Most tutorials online still use them and are broken. See secrets.h.
 *
 *  A detail the vendor examples get wrong: this board has TWO microphones on
 *  one I2S bus (left + right), but every Makerfabs demo records left-only and
 *  throws one away. This sketch records both and averages them.
 *
 *  ---------------------------------------------------------------------------
 *  *** WHICH USB PORT - THIS MATTERS ***
 *  The speaker shares IO19/IO20 with the NATIVE USB port. Upload and power
 *  through the CH340K UART USB-C port, and set USB CDC On Boot = Disabled.
 *  If you use the wrong port the audio will be garbage or uploads will fail.
 *  ---------------------------------------------------------------------------
 *
 *  FILL IN secrets.h BEFORE FLASHING (WiFi + all three API keys).
 *
 *  BOARD SETTINGS (Tools menu - EVERY line matters, wrong = black screen
 *  or compile errors. These reset when you switch cores - recheck them!)
 *
 *      Board            : ESP32S3 Dev Module
 *      ESP32 core       : 2.0.17
 *      PSRAM            : OPI PSRAM        <-- required, audio buffer lives there
 *      Flash Size       : 16MB (128Mb)
 *      Partition Scheme : 16M Flash (3MB APP/9.9MB FATFS)
 *      USB CDC On Boot  : Disabled         <-- required, see USB note above
 *      Upload Speed     : 921600
 *      Port             : the CH340K USB-C port (the one near RESET)
 *
 *  LIBRARIES
 *      GFX Library for Arduino   v1.5.6   (NOT 1.6.x - that pairs with core 3)
 *      bb_captouch               v1.3.1
 *      ArduinoJson               v7.x
 *      Adafruit NeoPixel         any recent
 *
 *  ---------------------------------------------------------------------------
 *  FUNCTIONS IN THIS SKETCH
 *      led(r,g,b) + LED_* macros   RGB status colours (blue/amber/green/red)
 *      getTouch(&x,&y)      read the touch panel, mapped to screen coordinates
 *      speakButtonHeld()    true while a finger is on the SPEAK button
 *      bubbleLines(t)       how many lines a message wraps to
 *      drawOneBubble(m,y)   draw a single chat bubble
 *      redrawChat()         rebuild the chat area from history, newest at bottom
 *      clearChat()          wipe the chat history (CLEAR button)
 *      chatBubble(t,user)   add a message to history and redraw
 *      drawWifi()           WiFi signal bars + dBm readout
 *      drawBar(label,col)   bottom bar: SPEAK button + CLEAR + WiFi meter
 *      micInit()            I2S input - BOTH INMP441 mics, stereo
 *      spkInit()            I2S output - MAX98357 speaker
 *      recordWhileHeld()    record while SPEAK held, downmix stereo->mono
 *      writeWavHeader(...)  prepend the 44-byte RIFF/WAVE header
 *      dumpWavToSD(...)     save the exact upload to SD (/stt_debug.wav)
 *      readHttpResponse()   read an HTTPS reply, de-chunking it properly
 *      azureSTT(...)        chunked upload of the WAV -> recognised text
 *      deepseekChat(...)    question -> deepseek-v4-flash -> answer text
 *      azureTTSSpeak(text)  answer -> Azure voice -> PSRAM -> speaker
 *      setup() / loop()     boot + WiFi / one conversation turn per press
 *
 *  Robojax.com
 * ===========================================================================
 */

#include <Arduino_GFX_Library.h>
#include <bb_captouch.h>
#include <Adafruit_NeoPixel.h>
#include <ArduinoJson.h>
#include <WiFi.h>
#include <WiFiClientSecure.h>
#include <HTTPClient.h>
#include <SPI.h>
#include <SD.h>
#include "driver/i2s.h"
#include "pins.h"
#include "secrets.h"

/* --- audio geometry ------------------------------------------------------- */
#define SAMPLE_RATE     16000
#define RECORD_MAX_S    6                       // hard cap on one question
#define WAV_HEADER_LEN  44
#define REC_BUF_BYTES   (SAMPLE_RATE * RECORD_MAX_S * 2)   // 16-bit mono

/* Software gain applied to the recording. The INMP441 capture is quiet at
 * 16-bit depth; if the serial monitor reports "mic peak" under ~10% while you
 * speak normally, raise this (6 -> 10 -> 16). If it reports clipping (100%),
 * lower it. */
#define MIC_GAIN        6

/* 1 = read BOTH microphones (stereo bus) and average them - better SNR.
 * 0 = vendor-style single left mic. Use 0 as a fallback if recordings come
 *     back silent or garbled in stereo mode. */
#define USE_BOTH_MICS   1

/* Status LED brightness, 0-255. The WS2812 runs from the power rail and is
 * uncomfortably bright at full power - 25 is plenty visible on camera. */
#define LED_BRIGHTNESS  25

/* HWSPI (not ESP32SPI): the debug WAV dump writes to the SD card, which
 * shares these pins - both must go through the same SPI driver. */
Arduino_HWSPI *bus = new Arduino_HWSPI(
    TFT_DC, TFT_CS, TFT_SCLK, TFT_MOSI, TFT_MISO, &SPI, true);
Arduino_GFX *gfx = new Arduino_ST7789(bus, TFT_RES, 1, true);

BBCapTouch bbct;
Adafruit_NeoPixel rgb(RGB_LED_NUM, RGB_LED_PIN, NEO_GRB + NEO_KHZ800);

/* --- big buffers live in PSRAM, allocated once at boot -------------------- */
uint8_t *wav_buf = nullptr;      // WAV_HEADER_LEN + up to REC_BUF_BYTES

/* --- state ---------------------------------------------------------------- */
enum State { ST_IDLE, ST_RECORDING, ST_STT, ST_LLM, ST_TTS, ST_ERROR };
State state = ST_IDLE;

/* --- diagnostics: shown ON SCREEN so the serial monitor is optional -------- */
bool  ok_sd = false;
float g_mic_peak_pct = 0;          // last recording's raw peak, % of full scale
char  g_stt_err[64] = "";          // last STT failure cause, verbatim
char  g_llm_err[64] = "";          // last DeepSeek failure cause, verbatim

/* --- layout --------------------------------------------------------------- */
#define CHAT_H     200              // chat area: y 0..199
#define BAR_Y      202              // button bar below it
#define BTN_SPEAK_X   4
#define BTN_SPEAK_W 160
#define BTN_CLEAR_X 170
#define BTN_CLEAR_W  58
#define WIFI_X      236             // signal indicator, right end of the bar
#define BTN_H        36

/* --- chat history: last 8 messages, redrawn newest-at-bottom like a phone.
 * This is what prevents new text printing over old - the whole area is
 * rebuilt from history on every message, older lines scroll up and out. */
#define CHAT_HISTORY 8
struct ChatMsg { char text[160]; bool from_user; };
ChatMsg chat_hist[CHAT_HISTORY];
int     chat_count = 0;

/* --- LED status colours: visible from across the room --------------------- */
void led(uint8_t r, uint8_t g, uint8_t b) {
  rgb.setPixelColor(0, rgb.Color(r, g, b));
  rgb.show();
}
#define LED_IDLE()    led(0, 0, 0)
#define LED_LISTEN()  led(0, 60, 255)     // blue   - recording
#define LED_THINK()   led(255, 120, 0)    // amber  - waiting on the cloud
#define LED_SPEAK()   led(0, 255, 40)     // green  - talking
#define LED_ERROR()   led(255, 0, 0)      // red


/* ===========================================================================
 *  Touch
 * =========================================================================== */
bool getTouch(uint16_t *x, uint16_t *y) {
  TOUCHINFO ti;
  if (!bbct.getSamples(&ti)) return false;
  if (ti.count < 1) return false;
  *x = ti.y[0];
  *y = (ti.x[0] > 240) ? 0 : (240 - ti.x[0]);
  return true;
}

bool speakButtonHeld() {
  uint16_t x, y;
  if (!getTouch(&x, &y)) return false;
  return (x >= BTN_SPEAK_X && x < BTN_SPEAK_X + BTN_SPEAK_W && y >= BAR_Y);
}


/* ===========================================================================
 *  Chat UI  —  word-wrapped bubbles, user right/blue, assistant left/grey
 * =========================================================================== */
#define CHAT_CHARS 42                          // chars per line at textsize 1

static int bubbleLines(const char *t) {
  int l = ((int)strlen(t) + CHAT_CHARS - 1) / CHAT_CHARS;
  return l < 1 ? 1 : l;
}

void drawOneBubble(const ChatMsg &m, int y) {
  int len = strlen(m.text);
  int lines = bubbleLines(m.text);
  int h = lines * 10 + 8;
  uint16_t bg = m.from_user ? gfx->color565(0, 70, 140) : gfx->color565(50, 50, 55);
  int w = (len > CHAT_CHARS ? CHAT_CHARS : len) * 6 + 10;
  if (w < 30) w = 30;
  int x = m.from_user ? (316 - w) : 4;

  gfx->fillRoundRect(x, y, w, h, 5, bg);
  gfx->setTextSize(1);
  gfx->setTextColor(WHITE);
  for (int i = 0; i < lines; i++) {
    char line[CHAT_CHARS + 1] = {0};
    strncpy(line, m.text + i * CHAT_CHARS, CHAT_CHARS);
    gfx->setCursor(x + 5, y + 5 + i * 10);
    gfx->print(line);
  }
}

/* Rebuild the whole chat area from history: newest message anchored at the
 * bottom, older ones stacked upward until the area is full. */
void redrawChat() {
  gfx->fillRect(0, 0, 320, CHAT_H, BLACK);
  int shown = min(chat_count, CHAT_HISTORY);
  int y = CHAT_H - 2;
  for (int i = 0; i < shown; i++) {
    ChatMsg &m = chat_hist[(chat_count - 1 - i) % CHAT_HISTORY];
    int h = bubbleLines(m.text) * 10 + 8;
    y -= h;
    if (y < 0) break;                          // area full - older ones drop off
    drawOneBubble(m, y);
    y -= 4;
  }
}

void clearChat() {
  chat_count = 0;
  redrawChat();
}

void chatBubble(const char *text, bool from_user) {
  ChatMsg &m = chat_hist[chat_count % CHAT_HISTORY];
  strncpy(m.text, text, sizeof(m.text) - 1);
  m.text[sizeof(m.text) - 1] = 0;
  m.from_user = from_user;
  chat_count++;
  redrawChat();
}

/* WiFi bars + dBm, right end of the button bar. Refreshed from the loop. */
void drawWifi() {
  gfx->fillRect(WIFI_X, BAR_Y, 320 - WIFI_X, BTN_H, BLACK);
  bool up = (WiFi.status() == WL_CONNECTED);
  long rssi = up ? WiFi.RSSI() : -100;
  // -55 dBm or better = full bars; each 10 dB drops one
  int bars = rssi > -55 ? 4 : rssi > -65 ? 3 : rssi > -75 ? 2 : rssi > -85 ? 1 : 0;

  for (int b = 0; b < 4; b++) {
    int bh = 6 + b * 6;                       // heights 6,12,18,24
    uint16_t col = (b < bars) ? GREEN : gfx->color565(60, 60, 60);
    gfx->fillRect(WIFI_X + 2 + b * 8, BAR_Y + 28 - bh, 6, bh, col);
  }
  gfx->setTextSize(1);
  gfx->setCursor(WIFI_X + 38, BAR_Y + 6);
  if (up) {
    gfx->setTextColor(CYAN);
    gfx->printf("%lddBm", rssi);
  } else {
    gfx->setTextColor(RED);
    gfx->print("DOWN");
  }
  gfx->setCursor(WIFI_X + 38, BAR_Y + 18);
  gfx->setTextColor(gfx->color565(120, 120, 120));
  gfx->print("WiFi");
}

void drawBar(const char *label, uint16_t colour) {
  gfx->fillRect(0, BAR_Y, 320, 240 - BAR_Y, BLACK);
  gfx->fillRoundRect(BTN_SPEAK_X, BAR_Y, BTN_SPEAK_W, BTN_H, 6, colour);
  gfx->drawRoundRect(BTN_SPEAK_X, BAR_Y, BTN_SPEAK_W, BTN_H, 6, WHITE);
  gfx->setTextSize(2);
  gfx->setTextColor(WHITE);
  gfx->setCursor(BTN_SPEAK_X + 10, BAR_Y + 10);
  gfx->print(label);

  // CLEAR wipes the chat history
  gfx->fillRoundRect(BTN_CLEAR_X, BAR_Y, BTN_CLEAR_W, BTN_H, 6, gfx->color565(110, 35, 35));
  gfx->drawRoundRect(BTN_CLEAR_X, BAR_Y, BTN_CLEAR_W, BTN_H, 6, WHITE);
  gfx->setTextSize(1);
  gfx->setTextColor(WHITE);
  gfx->setCursor(BTN_CLEAR_X + 14, BAR_Y + 15);
  gfx->print("CLEAR");

  drawWifi();
}


/* ===========================================================================
 *  I2S  —  microphones on port 0, speaker on port 1. Separate hardware
 *  ports, so recording and playback can never fight over a bus.
 * =========================================================================== */
void micInit() {
  i2s_config_t cfg = {
    .mode = (i2s_mode_t)(I2S_MODE_MASTER | I2S_MODE_RX),
    .sample_rate = SAMPLE_RATE,
    .bits_per_sample = I2S_BITS_PER_SAMPLE_16BIT,
    /* BOTH channels - this is the two-microphone fix. The vendor examples
     * use ONLY_LEFT here and waste the second microphone. USE_BOTH_MICS 0
     * falls back to the vendor-proven single-mic configuration. */
#if USE_BOTH_MICS
    .channel_format = I2S_CHANNEL_FMT_RIGHT_LEFT,
#else
    .channel_format = I2S_CHANNEL_FMT_ONLY_LEFT,
#endif
    .communication_format = I2S_COMM_FORMAT_STAND_I2S,
    .intr_alloc_flags = ESP_INTR_FLAG_LEVEL1,
    .dma_buf_count = 8,
    .dma_buf_len = 256,
    .use_apll = false,
    .tx_desc_auto_clear = false,
    .fixed_mclk = 0
  };
  i2s_pin_config_t pins = {
    .mck_io_num = I2S_PIN_NO_CHANGE,
    .bck_io_num = I2S_MIC_SCK,
    .ws_io_num = I2S_MIC_WS,
    .data_out_num = I2S_PIN_NO_CHANGE,
    .data_in_num = I2S_MIC_SD
  };
  i2s_driver_install(I2S_MIC_PORT, &cfg, 0, NULL);
  i2s_set_pin(I2S_MIC_PORT, &pins);
}

void spkInit() {
  i2s_config_t cfg = {
    .mode = (i2s_mode_t)(I2S_MODE_MASTER | I2S_MODE_TX),
    .sample_rate = SAMPLE_RATE,
    .bits_per_sample = I2S_BITS_PER_SAMPLE_16BIT,
    .channel_format = I2S_CHANNEL_FMT_ONLY_LEFT,   // mono - the amp downmixes anyway
    .communication_format = I2S_COMM_FORMAT_STAND_I2S,
    .intr_alloc_flags = ESP_INTR_FLAG_LEVEL1,
    .dma_buf_count = 8,
    .dma_buf_len = 256,
    .use_apll = false,
    .tx_desc_auto_clear = true,
    .fixed_mclk = 0
  };
  i2s_pin_config_t pins = {
    .mck_io_num = I2S_PIN_NO_CHANGE,
    .bck_io_num = I2S_SPK_BCLK,
    .ws_io_num = I2S_SPK_LRC,
    .data_out_num = I2S_SPK_DOUT,
    .data_in_num = I2S_PIN_NO_CHANGE
  };
  i2s_driver_install(I2S_SPK_PORT, &cfg, 0, NULL);
  i2s_set_pin(I2S_SPK_PORT, &pins);
  i2s_zero_dma_buffer(I2S_SPK_PORT);
}


/* ===========================================================================
 *  Recording  —  runs while the SPEAK button is held (up to RECORD_MAX_S).
 *  Reads stereo pairs, averages L+R into one mono stream, applies a little
 *  software gain, and fills wav_buf after the 44-byte header slot.
 *  Returns the number of audio bytes recorded.
 * =========================================================================== */
size_t recordWhileHeld() {
  int16_t *mono = (int16_t *)(wav_buf + WAV_HEADER_LEN);
  size_t   mono_samples = 0;
  const size_t max_samples = SAMPLE_RATE * RECORD_MAX_S;

  int16_t chunk[512];
  uint32_t last_touch_ok = millis();
  int32_t  peak = 0;                        // loudest raw sample - mic health check

  i2s_zero_dma_buffer(I2S_MIC_PORT);

  while (mono_samples < max_samples) {
    size_t got = 0;
    i2s_read(I2S_MIC_PORT, chunk, sizeof(chunk), &got, 80 / portTICK_PERIOD_MS);

#if USE_BOTH_MICS
    size_t n = got / 4;                     // 4 bytes = one L+R pair
    for (size_t i = 0; i < n && mono_samples < max_samples; i++) {
      int32_t raw = ((int32_t)chunk[i * 2] + (int32_t)chunk[i * 2 + 1]) / 2;
#else
    size_t n = got / 2;                     // 2 bytes = one mono sample
    for (size_t i = 0; i < n && mono_samples < max_samples; i++) {
      int32_t raw = chunk[i];
#endif
      if (abs(raw) > peak) peak = abs(raw);
      int32_t mixed = raw * MIC_GAIN;
      if (mixed >  32767) mixed =  32767;
      if (mixed < -32768) mixed = -32768;
      mono[mono_samples++] = (int16_t)mixed;
    }

    /* The GT911 is polled between I2S reads. A 250 ms grace period stops a
     * momentary missed touch sample from cutting the recording short. */
    if (speakButtonHeld()) last_touch_ok = millis();
    else if (millis() - last_touch_ok > 250) break;

    // live progress on the button
    static uint32_t last_draw = 0;
    if (millis() - last_draw > 200) {
      last_draw = millis();
      gfx->fillRect(BTN_SPEAK_X + 2, BAR_Y + BTN_H - 6,
                    (int)((BTN_SPEAK_W - 4) * mono_samples / max_samples), 4, WHITE);
    }
  }

  /* Mic health line: peak as % of full scale BEFORE gain.
   *   0%       = the mic is not being read at all (config/pin problem)
   *   under 3% = too quiet - speak closer or raise MIC_GAIN
   *   3-40%    = healthy speech level
   */
  g_mic_peak_pct = peak * 100.0 / 32768.0;
  Serial.printf("mic peak: %.1f%% of full scale (gain x%d applied%s)\n",
                g_mic_peak_pct, MIC_GAIN,
                peak == 0 ? " - MIC IS SILENT, check USE_BOTH_MICS" : "");

  return mono_samples * 2;
}

/* Dump the exact WAV we are about to POST onto the SD card, so it can be
 * played on a PC - you hear exactly what Azure hears. Overwritten each time. */
void dumpWavToSD(size_t audio_bytes) {
  if (!ok_sd) return;
  SD.remove("/stt_debug.wav");
  File f = SD.open("/stt_debug.wav", FILE_WRITE);
  if (!f) return;
  f.write(wav_buf, WAV_HEADER_LEN + audio_bytes);
  f.close();
  Serial.println("debug copy saved to SD as /stt_debug.wav");
}

/* Standard 44-byte RIFF/WAVE header for 16 kHz 16-bit mono PCM. */
void writeWavHeader(uint8_t *h, uint32_t data_bytes) {
  uint32_t file_len = data_bytes + 36;
  uint32_t byte_rate = SAMPLE_RATE * 2;
  memcpy(h, "RIFF", 4);           memcpy(h + 4, &file_len, 4);
  memcpy(h + 8, "WAVEfmt ", 8);
  uint32_t fmt_len = 16;          memcpy(h + 16, &fmt_len, 4);
  uint16_t fmt = 1, ch = 1;       memcpy(h + 20, &fmt, 2);   memcpy(h + 22, &ch, 2);
  uint32_t rate = SAMPLE_RATE;    memcpy(h + 24, &rate, 4);  memcpy(h + 28, &byte_rate, 4);
  uint16_t align = 2, bits = 16;  memcpy(h + 32, &align, 2); memcpy(h + 34, &bits, 2);
  memcpy(h + 36, "data", 4);      memcpy(h + 40, &data_bytes, 4);
}


/* ===========================================================================
 *  HTTP response reader  —  shared by all three cloud calls.
 *  Returns the status code and fills body_out. Handles chunked transfer
 *  encoding PROPERLY: the chunk-size markers must be stripped, or they end
 *  up embedded inside the JSON body and the parse fails on long replies.
 * =========================================================================== */
/* Block until the connection has data (or the budget runs out). Returns false
 * on timeout / closed-and-empty. Every read below goes through this, because
 * a reasoning model can think for many seconds between the response headers
 * and the first byte of the body - and a bare read() would just time out. */
static bool waitData(WiFiClientSecure &c, uint32_t ms) {
  uint32_t t0 = millis();
  while (!c.available()) {
    if (!c.connected()) return false;
    if (millis() - t0 > ms) return false;
    delay(10);
  }
  return true;
}

static int readHttpResponse(WiFiClientSecure &client, String &body_out, uint32_t idle_ms) {
  body_out = "";

  if (!waitData(client, idle_ms)) { Serial.println("HTTP: no response at all"); return 0; }
  String status_line = client.readStringUntil('\n');
  int code = 0;
  sscanf(status_line.c_str(), "HTTP/%*s %d", &code);

  bool chunked = false;
  while (waitData(client, idle_ms)) {
    String h = client.readStringUntil('\n');
    if (h == "\r" || h.length() <= 1) break;         // blank line = end of headers
    h.toLowerCase();
    if (h.startsWith("transfer-encoding:") && h.indexOf("chunked") >= 0) chunked = true;
  }

  if (chunked) {
    int blanks = 0;
    while (true) {
      /* The chunk-size line may not arrive for a long time while the model
       * reasons. Waiting here - instead of letting read() time out - is the
       * whole fix: a timed-out read looks exactly like "0" (final chunk),
       * which silently truncated the body to nothing. */
      if (!waitData(client, idle_ms)) {
        Serial.println("HTTP: timed out waiting for the next chunk");
        break;
      }
      String szline = client.readStringUntil('\n');
      szline.trim();
      if (szline.length() == 0) {                    // stray blank line
        if (++blanks > 4) break;
        continue;
      }
      blanks = 0;

      long sz = strtol(szline.c_str(), NULL, 16);
      if (sz <= 0) break;                            // genuine final chunk

      long got = 0;
      while (got < sz) {
        if (!waitData(client, idle_ms)) break;
        while (client.available() && got < sz) { body_out += (char)client.read(); got++; }
      }
      if (waitData(client, 3000)) client.readStringUntil('\n');   // CRLF after chunk
      if (got < sz) { Serial.println("HTTP: short chunk"); break; }
    }
  } else {
    while (waitData(client, idle_ms))
      while (client.available()) body_out += (char)client.read();
  }
  return code;
}


/* ===========================================================================
 *  CLOUD CALL 1  —  Azure speech-to-text
 *  One POST, one header, plain WAV body. This is why Azure does the ears.
 * =========================================================================== */
bool azureSTT(size_t audio_bytes, String &text_out) {
  /* HTTPClient's one-shot POST fails on bodies this large (it attempts one
   * giant TLS write and dies with error -3 SEND_PAYLOAD_FAILED). So this
   * function speaks HTTP directly and streams the WAV up in 4 KB chunks -
   * reliable, and if it ever stalls we know the exact byte it stopped at. */
  WiFiClientSecure client;
  client.setInsecure();                    // no cert bundle on-device; see notes
  client.setTimeout(15);                   // seconds, for reads

  writeWavHeader(wav_buf, audio_bytes);
  dumpWavToSD(audio_bytes);                // PC-playable copy of what we send
  size_t total = WAV_HEADER_LEN + audio_bytes;

  if (!client.connect(AZURE_STT_HOST, 443)) {
    snprintf(g_stt_err, sizeof(g_stt_err), "TLS connect failed");
    Serial.println("STT: TLS connect failed");
    return false;
  }

  /* Two valid host forms use DIFFERENT URL paths - detect which one is in
   * secrets.h:  <resource>.cognitiveservices.azure.com -> /stt/speech/...
   *             <region>.stt.speech.microsoft.com      -> /speech/...     */
  bool custom_subdomain = (strstr(AZURE_STT_HOST, ".cognitiveservices.azure.com") != NULL);
  String req = String("POST ") + (custom_subdomain ? "/stt" : "") +
               "/speech/recognition/conversation/cognitiveservices/v1"
               "?language=" AZURE_STT_LANG "&format=simple HTTP/1.1\r\n"
               "Host: " AZURE_STT_HOST "\r\n"
               "Ocp-Apim-Subscription-Key: " AZURE_SPEECH_KEY "\r\n"
               "Content-Type: audio/wav; codecs=audio/pcm; samplerate=16000\r\n"
               "Accept: application/json\r\n"
               "Connection: close\r\n"
               "Content-Length: " + String(total) + "\r\n\r\n";
  client.print(req);

  /* body, 4 KB at a time */
  size_t sent = 0;
  while (sent < total) {
    size_t n = min((size_t)4096, total - sent);
    size_t w = client.write(wav_buf + sent, n);
    if (w == 0) {
      delay(50);                           // brief stall - retry once
      w = client.write(wav_buf + sent, n);
      if (w == 0) {
        snprintf(g_stt_err, sizeof(g_stt_err), "upload stalled at %uKB",
                 (unsigned)(sent / 1024));
        Serial.printf("STT: upload stalled at %u/%u bytes\n",
                      (unsigned)sent, (unsigned)total);
        client.stop();
        return false;
      }
    }
    sent += w;
    yield();
  }
  Serial.printf("STT: uploaded %u bytes\n", (unsigned)sent);

  /* read the reply with proper de-chunking */
  String resp;
  int code = readHttpResponse(client, resp, 10000);
  client.stop();

  if (code != 200) {
    snprintf(g_stt_err, sizeof(g_stt_err), "HTTP %d", code);
    Serial.printf("STT HTTP %d: %s\n", code, resp.c_str());
    return false;
  }

  JsonDocument doc;
  DeserializationError err = deserializeJson(doc, resp);
  if (err) {
    snprintf(g_stt_err, sizeof(g_stt_err), "bad JSON reply");
    Serial.printf("STT parse error, raw response: %s\n", resp.c_str());
    return false;
  }

  const char *status = doc["RecognitionStatus"];
  if (!status || strcmp(status, "Success") != 0) {
    /* The status names the exact failure:
     *   InitialSilenceTimeout = Azure heard silence (mic level too low)
     *   NoMatch               = heard sound but no recognisable words
     *   BabbleTimeout         = heard only noise                       */
    snprintf(g_stt_err, sizeof(g_stt_err), "%s", status ? status : "no status");
    Serial.printf("STT status: %s\nraw: %s\n", status ? status : "null", resp.c_str());
    return false;
  }
  text_out = doc["DisplayText"].as<String>();
  if (text_out.length() == 0) snprintf(g_stt_err, sizeof(g_stt_err), "empty text");
  return text_out.length() > 0;
}


/* ===========================================================================
 *  CLOUD CALL 2  —  DeepSeek chat completion
 *  OpenAI-compatible format. Model name is deepseek-v4-flash - the old
 *  deepseek-chat name is dead, see secrets.h.
 * =========================================================================== */
bool deepseekChat(const String &question, String &answer_out) {
  /* Manual HTTP, same as azureSTT: HTTPClient truncates larger TLS response
   * bodies (long answers + the model's hidden reasoning), which shows up as
   * "bad JSON reply". Reading until the server closes the connection is
   * reliable regardless of reply length. */
  JsonDocument req;
  req["model"] = DEEPSEEK_MODEL;
  req["max_tokens"] = LLM_MAX_TOKENS;
  JsonArray msgs = req["messages"].to<JsonArray>();
  JsonObject sys = msgs.add<JsonObject>();
  sys["role"] = "system";  sys["content"] = SYSTEM_PROMPT;
  JsonObject usr = msgs.add<JsonObject>();
  usr["role"] = "user";    usr["content"] = question;

  String body;
  serializeJson(req, body);

  WiFiClientSecure client;
  client.setInsecure();
  /* 60 s: deepseek-v4-flash is a REASONING model. Easy questions answer in
   * ~2 s, but anything that needs actual working-out (an Ohm's law problem,
   * say) can think for 10-30 s before sending a single byte. */
  client.setTimeout(60);

  if (!client.connect(DEEPSEEK_HOST, 443)) {
    snprintf(g_llm_err, sizeof(g_llm_err), "TLS connect failed");
    Serial.println("LLM: TLS connect failed");
    return false;
  }

  client.print(String("POST /chat/completions HTTP/1.1\r\n"
               "Host: " DEEPSEEK_HOST "\r\n"
               "Authorization: Bearer " DEEPSEEK_KEY "\r\n"
               "Content-Type: application/json\r\n"
               "Connection: close\r\n"
               "Content-Length: ") + String(body.length()) + "\r\n\r\n");
  client.print(body);

  /* read the reply with proper de-chunking; generous window - long
   * questions make the model think for a while before it responds */
  String resp;
  int code = readHttpResponse(client, resp, 60000);
  client.stop();

  if (code != 200) {
    snprintf(g_llm_err, sizeof(g_llm_err), "HTTP %d", code);
    Serial.printf("LLM HTTP %d: %s\n", code, resp.c_str());
    return false;
  }

  JsonDocument doc;
  DeserializationError err = deserializeJson(doc, resp);
  if (err) {
    snprintf(g_llm_err, sizeof(g_llm_err), "bad JSON reply");
    Serial.printf("LLM parse error, raw: %s\n", resp.c_str());
    return false;
  }

  const char *content = doc["choices"][0]["message"]["content"];
  const char *finish  = doc["choices"][0]["finish_reason"];
  if (!content || !content[0]) {
    /* v4-flash is a reasoning model: if finish_reason is "length", the whole
     * token budget went to internal reasoning - raise LLM_MAX_TOKENS. */
    if (finish && strcmp(finish, "length") == 0)
      snprintf(g_llm_err, sizeof(g_llm_err), "empty - raise LLM_MAX_TOKENS");
    else
      snprintf(g_llm_err, sizeof(g_llm_err), "empty content");
    Serial.printf("LLM empty content, raw: %s\n", resp.c_str());
    return false;
  }
  answer_out = String(content);
  answer_out.trim();
  if (answer_out.length() == 0) snprintf(g_llm_err, sizeof(g_llm_err), "blank answer");
  return answer_out.length() > 0;
}


/* ===========================================================================
 *  CLOUD CALL 3  —  Azure text-to-speech, streamed straight to the speaker
 *  We ask for riff-16khz-16bit-mono-pcm: a WAV whose payload is exactly what
 *  the I2S peripheral eats. Skip the 44-byte header, forward the rest.
 *  No MP3 decoder, no audio library, no buffering the whole reply.
 * =========================================================================== */
/* Read exactly n bytes from a client (or until timeout). */
static size_t readExact(WiFiClientSecure &c, uint8_t *dst, size_t n) {
  size_t got = 0;
  uint32_t t0 = millis();
  while (got < n && millis() - t0 < 10000) {
    int r = c.read(dst + got, n - got);
    if (r > 0) { got += r; t0 = millis(); }
    else if (!c.connected() && !c.available()) break;
    else delay(2);
  }
  return got;
}

bool azureTTSSpeak(const String &text) {
  // Escape the XML special characters for the SSML body
  String safe = text;
  safe.replace("&", "&amp;");
  safe.replace("<", "&lt;");
  safe.replace(">", "&gt;");

  String ssml = "<speak version='1.0' xml:lang='" AZURE_TTS_LANG "'>"
                "<voice name='" AZURE_TTS_VOICE "'>" + safe + "</voice></speak>";

  /* Manual HTTP like the other two cloud calls - and for a hard reason:
   * Azure sends this audio with CHUNKED transfer encoding, and HTTPClient's
   * raw stream hands over the chunk framing (ASCII "2000\r\n" lines) mixed
   * into the PCM. Played as sound, every chunk boundary is an audible KNOCK.
   * Here we parse the framing properly and keep only clean audio bytes. */
  WiFiClientSecure client;
  client.setInsecure();
  client.setTimeout(20);

  const char *host = AZURE_REGION ".tts.speech.microsoft.com";
  if (!client.connect(host, 443)) {
    Serial.println("TTS: TLS connect failed");
    return false;
  }

  client.print(String("POST /cognitiveservices/v1 HTTP/1.1\r\n"
               "Host: ") + host + "\r\n"
               "Ocp-Apim-Subscription-Key: " AZURE_SPEECH_KEY "\r\n"
               "Content-Type: application/ssml+xml\r\n"
               "X-Microsoft-OutputFormat: riff-16khz-16bit-mono-pcm\r\n"
               "User-Agent: MaTouchRobojax\r\n"
               "Connection: close\r\n"
               "Content-Length: " + String(ssml.length()) + "\r\n\r\n");
  client.print(ssml);

  /* status + headers; note whether the body is chunked */
  String status_line = client.readStringUntil('\n');
  int code = 0;
  sscanf(status_line.c_str(), "HTTP/%*s %d", &code);
  bool chunked = false;
  long content_len = -1;
  while (client.connected() || client.available()) {
    String h = client.readStringUntil('\n');
    if (h == "\r" || h.length() <= 1) break;
    h.toLowerCase();
    if (h.startsWith("transfer-encoding:") && h.indexOf("chunked") >= 0) chunked = true;
    if (h.startsWith("content-length:")) content_len = h.substring(15).toInt();
  }
  if (code != 200) {
    Serial.printf("TTS HTTP %d\n", code);
    client.stop();
    return false;
  }

  const size_t AUDIO_CAP = 1200 * 1024;    // ~37 s of speech
  uint8_t *audio = (uint8_t *)ps_malloc(AUDIO_CAP);
  if (!audio) { client.stop(); return false; }
  size_t alen = 0;

  if (chunked) {
    /* chunked: <hex size>\r\n <bytes> \r\n ... 0\r\n\r\n */
    while (true) {
      String szline = client.readStringUntil('\n');
      long sz = strtol(szline.c_str(), NULL, 16);
      if (sz <= 0) break;
      if (alen + sz > AUDIO_CAP) break;
      size_t got = readExact(client, audio + alen, sz);
      alen += got;
      client.readStringUntil('\n');        // trailing CRLF after each chunk
      if (got < (size_t)sz) break;
    }
  } else if (content_len > 0) {
    alen = readExact(client, audio, min((size_t)content_len, AUDIO_CAP));
  } else {
    /* no framing info: read until the server closes */
    uint32_t idle = millis();
    while ((client.connected() || client.available()) && millis() - idle < 5000) {
      int r = client.read(audio + alen, min((size_t)2048, AUDIO_CAP - alen));
      if (r > 0) { alen += r; idle = millis(); }
      else delay(5);
    }
  }
  client.stop();
  Serial.printf("TTS: %u KB clean audio (%s), playing\n",
                (unsigned)(alen / 1024), chunked ? "de-chunked" : "plain");

  bool ok = (alen > WAV_HEADER_LEN);
  if (ok) {
    /* NOW the audio actually starts - this is the honest moment to go green */
    LED_SPEAK();
    drawBar("SPEAKING...", gfx->color565(0, 130, 40));

    /* skip the RIFF header; a silence pre-roll softens the amp wake-up pop */
    static const uint8_t lead_in[640] = {0};             // 20 ms of silence
    size_t w = 0;
    i2s_write(I2S_SPK_PORT, lead_in, sizeof(lead_in), &w, portMAX_DELAY);
    i2s_write(I2S_SPK_PORT, audio + WAV_HEADER_LEN, alen - WAV_HEADER_LEN, &w, portMAX_DELAY);
    i2s_write(I2S_SPK_PORT, lead_in, sizeof(lead_in), &w, portMAX_DELAY);
  }
  free(audio);

  // let the DMA buffers drain so the last word is not cut off
  delay(150);
  i2s_zero_dma_buffer(I2S_SPK_PORT);
  return ok;
}


/* ===========================================================================
 *  SETUP
 * =========================================================================== */
void setup() {
  Serial.begin(115200);
  delay(400);
  Serial.println("\n=== 04 Voice Assistant  |  Robojax.com ===");
  Serial.println("Mics -> Azure STT -> DeepSeek -> Azure TTS -> speaker");

  pinMode(TFT_BLK, OUTPUT);
  digitalWrite(TFT_BLK, LOW);
  pinMode(SD_CS, OUTPUT);
  digitalWrite(SD_CS, HIGH);

  // one shared SPI bus for TFT + SD (started before either device)
  SPI.begin(TFT_SCLK, TFT_MISO, TFT_MOSI);

  gfx->begin();
  gfx->fillScreen(BLACK);
  digitalWrite(TFT_BLK, HIGH);

  // SD is optional here - it only stores the /stt_debug.wav diagnostic copy
  ok_sd = SD.begin(SD_CS, SPI, 20000000);
  digitalWrite(SD_CS, HIGH);
  Serial.println(ok_sd ? "SD ok - will save /stt_debug.wav after each recording"
                       : "SD not found - debug WAV dump disabled (not fatal)");

  bbct.init(TOUCH_SDA, TOUCH_SCL, TOUCH_RST, TOUCH_INT);
  delay(50);

  rgb.begin();
  rgb.setBrightness(LED_BRIGHTNESS);
  LED_IDLE();

  /* One recording buffer for the whole session, in PSRAM. This is the 8 MB
   * that makes the board worth buying. */
  wav_buf = (uint8_t *)ps_malloc(WAV_HEADER_LEN + REC_BUF_BYTES);
  if (!wav_buf) {
    gfx->setTextColor(RED);
    gfx->setTextSize(2);
    gfx->setCursor(10, 100);
    gfx->print("PSRAM alloc failed!");
    gfx->setTextSize(1);
    gfx->setCursor(10, 130);
    gfx->print("Tools > PSRAM > OPI PSRAM must be set.");
    while (1) delay(1000);
  }

  micInit();
  spkInit();

  gfx->setTextSize(1);
  gfx->setTextColor(YELLOW);
  gfx->setCursor(4, 4);
  gfx->printf("Connecting to %s ...", WIFI_SSID);
  Serial.printf("Connecting to %s ", WIFI_SSID);

  WiFi.mode(WIFI_STA);
  WiFi.begin(WIFI_SSID, WIFI_PASS);
  uint32_t t0 = millis();
  while (WiFi.status() != WL_CONNECTED && millis() - t0 < 20000) {
    delay(300);
    Serial.print(".");
  }
  Serial.println();

  clearChat();
  if (WiFi.status() == WL_CONNECTED) {
    Serial.printf("Connected, IP %s\n", WiFi.localIP().toString().c_str());
    chatBubble("Hold SPEAK and ask me anything.", false);
  } else {
    chatBubble("WiFi failed. Remember: the ESP32 is 2.4GHz only. Check secrets.h, then press RESET.", false);
    LED_ERROR();
  }
  drawBar("HOLD+TALK", gfx->color565(0, 90, 160));
}


/* ===========================================================================
 *  LOOP  —  one full conversation turn per button press
 * =========================================================================== */
void loop() {
  /* CLEAR button: edge-detected so one tap wipes once. Reading the panel
   * twice per loop (here and in speakButtonHeld) is fine - the GT911 just
   * reports its current state. */
  static bool tap_latch = false;
  static uint8_t tap_release = 0;
  if (state == ST_IDLE) {
    uint16_t cx, cy;
    if (getTouch(&cx, &cy)) {
      tap_release = 0;
      if (!tap_latch) {
        tap_latch = true;
        if (cx >= BTN_CLEAR_X && cx < BTN_CLEAR_X + BTN_CLEAR_W && cy >= BAR_Y) {
          clearChat();
          chatBubble("Hold SPEAK and ask me anything.", false);
        }
      }
    } else if (tap_latch && ++tap_release >= 4) {
      tap_latch = false;
      tap_release = 0;
    }

    /* live WiFi signal indicator, refreshed every 2 s while idle */
    static uint32_t last_wifi = 0;
    if (millis() - last_wifi > 2000) {
      last_wifi = millis();
      drawWifi();
    }
  }

  if (state == ST_IDLE && speakButtonHeld()) {

    /* ---- record ---- */
    state = ST_RECORDING;
    LED_LISTEN();
    drawBar("LISTENING...", gfx->color565(0, 60, 200));
    uint32_t t_rec = millis();
    size_t audio_bytes = recordWhileHeld();
    t_rec = millis() - t_rec;
    Serial.printf("Recorded %u bytes (%.1f s)\n", (unsigned)audio_bytes, audio_bytes / 32000.0);

    if (audio_bytes < SAMPLE_RATE / 2) {   // under a quarter second - a tap
      drawBar("HOLD+TALK", gfx->color565(0, 90, 160));
      LED_IDLE();
      state = ST_IDLE;
      return;
    }

    /* ---- speech to text ---- */
    state = ST_STT;
    LED_THINK();
    drawBar("HEARD YOU...", gfx->color565(150, 90, 0));
    uint32_t t_stt = millis();
    String question;
    if (!azureSTT(audio_bytes, question)) {
      /* Show the REAL cause on screen - no serial monitor needed. */
      char diag[96];
      snprintf(diag, sizeof(diag), "STT failed: %s | mic peak %.1f%%%s",
               g_stt_err, g_mic_peak_pct,
               ok_sd ? " | saved /stt_debug.wav" : "");
      chatBubble(diag, false);
      drawBar("HOLD+TALK", gfx->color565(0, 90, 160));
      LED_IDLE();
      state = ST_IDLE;
      return;
    }
    t_stt = millis() - t_stt;
    chatBubble(question.c_str(), true);
    Serial.printf("STT (%lu ms): %s\n", (unsigned long)t_stt, question.c_str());

    /* ---- think ---- */
    state = ST_LLM;
    drawBar("THINKING...", gfx->color565(150, 90, 0));
    uint32_t t_llm = millis();
    String answer;
    if (!deepseekChat(question, answer)) {
      char diag[96];
      snprintf(diag, sizeof(diag), "DeepSeek failed: %s", g_llm_err);
      chatBubble(diag, false);
      drawBar("HOLD+TALK", gfx->color565(0, 90, 160));
      LED_IDLE();
      state = ST_IDLE;
      return;
    }
    t_llm = millis() - t_llm;
    chatBubble(answer.c_str(), false);
    Serial.printf("LLM (%lu ms): %s\n", (unsigned long)t_llm, answer.c_str());

    /* ---- speak ----
     * Still amber here: the voice has to be synthesised and downloaded first
     * (a few seconds). azureTTSSpeak() itself flips the bar and LED to green
     * at the exact moment audio starts coming out of the speaker. */
    state = ST_TTS;
    LED_THINK();
    drawBar("GETTING VOICE", gfx->color565(150, 90, 0));
    uint32_t t_tts = millis();
    bool spoke = azureTTSSpeak(answer);
    t_tts = millis() - t_tts;

    /* Timing summary on serial - this feeds the "honest numbers" segment. */
    Serial.printf("TIMINGS  rec %.1fs | stt %lums | llm %lums | tts %lums%s\n",
                  audio_bytes / 32000.0, (unsigned long)t_stt,
                  (unsigned long)t_llm, (unsigned long)t_tts,
                  spoke ? "" : "  (TTS FAILED)");

    drawBar("HOLD+TALK", gfx->color565(0, 90, 160));
    LED_IDLE();
    state = ST_IDLE;
  }

  delay(20);
}