/* ===========================================================================
 *  01_Web_Camera  —  Seeed Studio XIAO ESP32S3 Sense
 * ===========================================================================

SHORT DESCRIPTION

Turns the Seeed Studio XIAO ESP32-S3 Sense into a Wi-Fi camera you watch in
any browser. The board creates its own Wi-Fi network, so no router and no
internet are needed: join it from your phone, open the page, and you get
live video at up to 28 frames per second, three preview resolutions, a full
3 megapixel snapshot, time-lapse recording, and rotate and full-screen
controls. Photos are held in the board's memory and saved to your phone
with one tap. Needs nothing but the board and a USB-C cable, and it runs on
any ESP32 core version.

 *
 *  ---------------------------------------------------------------------------
 *  ROBOJAX.COM  -  XIAO ESP32S3 Sense project series
 *
 *    WATCH THE VIDEO
 *        https://youtu.be/PuuTazJDKgA
 *
 *    PROJECT RESOURCE PAGES - full write-up, photos, wiring and downloads
 *        1 Web camera................ https://robojax.com/RTJ853
 *        2 Offline face recognition.. https://robojax.com/RTJ854
 *        3 What is this part?........ https://robojax.com/RTJ003
 *        4 Making it talk............ https://robojax.com/RTJ004
 *        5 The AI watcher............ https://robojax.com/RTJ005
 *
 *    THE BOARD
 *        https://www.seeedstudio.com/XIAO-ESP32S3-Sense-p-5639.html?sensecap_affiliate=Vac9tOl&referring_service=link
 *        Bought at my own cost - this series is not sponsored.
 *
 *    ARDUINO IDE SETTINGS - identical for every sketch in this series
 *
 *        Board            : XIAO_ESP32S3      (Tools > Board > esp32)
 *        ESP32 core       : 2.0.17            <-- REQUIRED, see note below
 *        PSRAM            : OPI PSRAM         <-- required, nothing works without
 *        Flash Size       : 8MB (64Mb)
 *        Partition Scheme : Default with spiffs (3MB APP/1.5MB SPIFFS)
 *        USB CDC On Boot  : Enabled           <-- the XIAO has ONE native USB
 *                                                 port; Disabled = no Serial
 *        Upload Speed     : 921600
 *
 *        Erase All Flash Contents Before Sketch Upload : DISABLED
 *            Enabled wipes the flash where saved names live, on every upload.
 *
 *    WHY CORE 2.0.17 AND NOT 3.x
 *        Espressif REMOVED the on-device face detection models in core 3, so
 *        the face project will not compile there. 2.0.17 is the last 2.x and
 *        the only version that has both those models and the XIAO_ESP32S3
 *        board definition, which was added in 2.0.8. One setting, whole series.
 *
 *    LIBRARIES
 *        None to install. Camera, face models, LittleFS, Preferences and the
 *        web server all ship with the ESP32 core itself.
 *
 *  All of this code is free. If it helped you, a subscribe on YouTube is
 *  the best way to support more of it.
 *  ---------------------------------------------------------------------------
 *
 *  A web camera with no screen, no SD card and no cloud account. The board
 *  makes its own Wi-Fi network, your phone or laptop joins it and opens a web
 *  page: live video, a 3 megapixel SNAP button, time-lapse, and photos you
 *  save straight to the device you are watching on.
 *
 *  Nothing here needs the internet, and there is no router in the loop at all
 *  - which means it works in a shed, in a field, or at a show with no Wi-Fi.
 *
 *  IT RUNS ON ANY ESP32 CORE. There is no face detection in this sketch, so
 *  none of the version pinning the later projects need applies here. If you
 *  only ever build this one, install the newest ESP32 core and ignore the
 *  2.0.17 note in the block above.
 *
 *  THE ONE THING TO UNDERSTAND
 *  ---------------------------
 *  Photos live in PSRAM, which is memory - not a card. It is fast and it needs
 *  no extra hardware, but it is VOLATILE: reset the board and every photo is
 *  gone. Measured on this board, 8 MB of PSRAM holds roughly:
 *
 *        2,600 preview frames at 320x240   (3.7 KB each)
 *          550 frames at 800x600           (14.9 KB each)
 *           24 photos at 2048x1536         (337.8 KB each)
 *
 *  So: take the shot, then SAVE it to your phone. That is the whole workflow,
 *  and it is why this sketch puts the save button next to every picture.
 *
 *  WHY THE PREVIEW FREEZES WHEN YOU PRESS SNAP
 *  -------------------------------------------
 *  The camera driver allocates its frame buffers when it starts, sized for
 *  whatever resolution it started at, and they cannot grow. To take a picture
 *  bigger than the preview, the driver has to be shut down and restarted at
 *  the new size - about a second, during which there is no video.
 *
 *  This is not a bug and it is not worth hiding. Every ESP32 camera does it.
 *  (We measured the alternative: calling set_framesize() to move up in size
 *  works *sometimes*, which is far worse than never.)
 *
 *  HOW TO USE
 *  ----------
 *  1. Upload, then open the Serial Monitor at 115200. It prints what to do.
 *  2. On your phone, join the Wi-Fi network "Robojax-XIAO"
 *     (password in secrets.h), then open  http://192.168.4.1
 *
 *     >> If the page TIMES OUT, turn off mobile data (or tap "stay
 *     >> connected" when the phone warns there is no internet). Phones
 *     >> route around a no-internet network, and the board's address
 *     >> only exists on the Wi-Fi side. This is the #1 gotcha of every
 *     >> access-point project. The 'wifi' serial command shows it live:
 *     >> "devices connected: 1, page requests served: 0" = exactly this.
 *
 *  3. Tap SNAP for a full 3 MP photo, or start a time-lapse.
 *  4. Tap SAVE under any photo to keep it on your phone.
 *  5. On the video itself: ROTATE turns the view in 90-degree steps (the
 *     angle is remembered on that phone), FULL fills the screen with just
 *     the video - tap EXIT or press Esc to come back. Rotation happens in
 *     the browser: the sensor cannot rotate 90 degrees, so saved photos
 *     keep the sensor's own orientation.
 *
 *  Serial commands:
 *      snap             take a 3 MP photo
 *      lapse <sec>      start a time-lapse, one frame every <sec> seconds
 *      stop             stop the time-lapse
 *      list             list the photos in memory
 *      free             show free PSRAM
 *      wipe             delete all photos
 *      help             this list
 *
 *  ---------------------------------------------------------------------------
 *  WIRING:  none. The board and a USB-C cable, nothing else.
 *  ---------------------------------------------------------------------------
 *  FUNCTIONS IN THIS SKETCH
 *      camStart(size,n)   (re)start the camera driver at a given resolution
 *      previewName()      human-readable name of the current preview size
 *      psFreeKB()         free PSRAM in KB
 *      photoStore(fb)     copy a captured frame into the gallery in PSRAM
 *      photoFree(i)       release one photo
 *      photoWipe()        release all photos
 *      doSnap()           restart at 3 MP, capture, store, restart preview
 *      doTimelapse()      capture at the preview size on a timer
 *      publishFrame()     copy the newest preview frame for the stream server
 *      handleRoot/Status/Stream/Snap/Photo/Delete/Wipe/Size/Lapse   HTTP
 *      startWiFi()        access point (default) or join your network
 *      startServers()     page/control server (80) and stream server (81)
 *      pollSerial()       the serial command set
 *      setup() / loop()   boot, then run the camera forever
 *
 *  Robojax.com
 * ===========================================================================
 */

#define MAX_PHOTOS        24      // the 3 MP ceiling; smaller shots use fewer bytes
#define PSRAM_RESERVE_KB  1800    // never let the gallery starve the camera driver
#define PREVIEW_JPEG_Q    12      // 10 = better picture, 20 = smaller and faster
#define SNAP_JPEG_Q       10      // the 3 MP shot deserves the good setting

#include <WiFi.h>
#include <esp_http_server.h>
#include <esp_log.h>
#include "esp_camera.h"
#include "camera_pins.h"
#include "secrets.h"

/* --- the gallery, entirely in PSRAM --------------------------------------- */
struct Photo {
  uint8_t *buf;
  size_t   len;
  uint16_t w, h;
  uint32_t at;          // millis() when it was taken
};
Photo  gallery[MAX_PHOTOS];
int    photo_count = 0;
uint32_t shutter_no = 0;          // running count, for filenames

/* --- preview state -------------------------------------------------------- */
framesize_t preview_size = FRAMESIZE_VGA;   // nice on a phone, still quick
volatile bool req_snap   = false;
volatile int  req_size   = -1;               // a framesize_t, or -1 for nothing
volatile bool req_wipe   = false;

uint32_t lapse_every_ms = 0;                 // 0 = time-lapse off
uint32_t lapse_next     = 0;
uint32_t lapse_taken    = 0;

float st_fps = 0;
bool  cam_up = false;
char  st_note[64] = "";

/* Diagnostics: counts every request that actually reaches the board. If the
 * page times out on the phone but this number never moves, the requests are
 * dying on the network side; if it moves, the board side is alive. */
volatile uint32_t http_hits = 0;

/* --- the shared preview frame the stream server hands out ----------------- */
static uint8_t          *g_jpg = NULL;
static size_t            g_jpg_len = 0;
static volatile uint32_t g_frame_no = 0;
static SemaphoreHandle_t g_jpg_mux = NULL;

httpd_handle_t srv_page = NULL, srv_stream = NULL;

char ser_line[48];
int  ser_len = 0;


/* ===========================================================================
 *  Camera
 * =========================================================================== */
bool camStart(framesize_t fs, int fb_count, int quality) {
  if (cam_up) { esp_camera_deinit(); cam_up = false; delay(120); }

  camera_config_t c = {};
  c.ledc_channel = LEDC_CHANNEL_0;
  c.ledc_timer   = LEDC_TIMER_0;
  c.pin_d0 = Y2_GPIO_NUM;  c.pin_d1 = Y3_GPIO_NUM;
  c.pin_d2 = Y4_GPIO_NUM;  c.pin_d3 = Y5_GPIO_NUM;
  c.pin_d4 = Y6_GPIO_NUM;  c.pin_d5 = Y7_GPIO_NUM;
  c.pin_d6 = Y8_GPIO_NUM;  c.pin_d7 = Y9_GPIO_NUM;
  c.pin_xclk  = XCLK_GPIO_NUM;
  c.pin_pclk  = PCLK_GPIO_NUM;
  c.pin_vsync = VSYNC_GPIO_NUM;
  c.pin_href  = HREF_GPIO_NUM;
  c.pin_sscb_sda = SIOD_GPIO_NUM;    // core 2.x spelling ("sscb" is their typo)
  c.pin_sscb_scl = SIOC_GPIO_NUM;
  c.pin_pwdn  = PWDN_GPIO_NUM;
  c.pin_reset = RESET_GPIO_NUM;
  c.xclk_freq_hz = 20000000;
  c.pixel_format = PIXFORMAT_JPEG;   // no image processing here, so straight to JPEG
  c.frame_size   = fs;
  c.jpeg_quality = quality;
  c.fb_count     = fb_count;
  c.fb_location  = CAMERA_FB_IN_PSRAM;
  c.grab_mode    = CAMERA_GRAB_LATEST;

  esp_err_t err = esp_camera_init(&c);
  cam_up = (err == ESP_OK);
  if (!cam_up) Serial.printf("camera init failed at that size, error 0x%x\n", err);
  else {
    sensor_t *s = esp_camera_sensor_get();
    if (s) { s->set_hmirror(s, 1); s->set_vflip(s, 1); }
  }
  return cam_up;
}

const char *sizeName(framesize_t fs) {
  switch (fs) {
    case FRAMESIZE_QVGA: return "320x240";
    case FRAMESIZE_VGA:  return "640x480";
    case FRAMESIZE_SVGA: return "800x600";
    case FRAMESIZE_QXGA: return "2048x1536";
    default:             return "?";
  }
}
uint32_t psFreeKB() { return ESP.getFreePsram() / 1024; }


/* ===========================================================================
 *  The gallery
 * =========================================================================== */
bool photoStore(camera_fb_t *fb) {
  if (photo_count >= MAX_PHOTOS) {
    snprintf(st_note, sizeof(st_note), "memory full - save and delete some photos");
    return false;
  }
  if ((int)(psFreeKB() - (fb->len / 1024)) < PSRAM_RESERVE_KB) {
    snprintf(st_note, sizeof(st_note), "not enough PSRAM left - delete some photos");
    return false;
  }
  uint8_t *copy = (uint8_t *)ps_malloc(fb->len);
  if (!copy) { snprintf(st_note, sizeof(st_note), "PSRAM allocation failed"); return false; }

  memcpy(copy, fb->buf, fb->len);
  gallery[photo_count] = { copy, fb->len, fb->width, fb->height, millis() };
  photo_count++;
  shutter_no++;
  Serial.printf("photo %d stored: %ux%u, %.1f KB  (PSRAM free %lu KB)\n",
                photo_count, fb->width, fb->height, fb->len / 1024.0, psFreeKB());
  return true;
}

void photoFree(int i) {
  if (i < 0 || i >= photo_count) return;
  free(gallery[i].buf);
  for (int k = i; k < photo_count - 1; k++) gallery[k] = gallery[k + 1];
  photo_count--;
}

void photoWipe() {
  for (int i = 0; i < photo_count; i++) free(gallery[i].buf);
  photo_count = 0;
  Serial.printf("gallery wiped, PSRAM free %lu KB\n", psFreeKB());
}


/* ===========================================================================
 *  SNAP  —  full 3 MP, which means restarting the driver twice
 * =========================================================================== */
void doSnap() {
  snprintf(st_note, sizeof(st_note), "taking a 3 MP photo...");
  Serial.println(F("SNAP: restarting the driver at 2048x1536"));
  uint32_t t0 = millis();

  if (!camStart(FRAMESIZE_QXGA, 1, SNAP_JPEG_Q)) {
    snprintf(st_note, sizeof(st_note), "could not start the camera at 3 MP");
    camStart(preview_size, 2, PREVIEW_JPEG_Q);
    return;
  }

  /* The sensor needs a moment to settle its exposure at the new size, and the
   * first frame after a restart is usually badly exposed. Throw two away. */
  delay(300);
  for (int i = 0; i < 2; i++) {
    camera_fb_t *warm = esp_camera_fb_get();
    if (warm) esp_camera_fb_return(warm);
  }

  uint32_t tc = millis();
  camera_fb_t *fb = esp_camera_fb_get();
  uint32_t capture_ms = millis() - tc;

  if (fb) {
    photoStore(fb);
    esp_camera_fb_return(fb);
    snprintf(st_note, sizeof(st_note), "3 MP photo captured in %lu ms", capture_ms);
  } else {
    snprintf(st_note, sizeof(st_note), "the 3 MP capture failed");
  }

  camStart(preview_size, 2, PREVIEW_JPEG_Q);
  Serial.printf("SNAP done, preview back after %lu ms total\n", millis() - t0);
}


/* ===========================================================================
 *  Time-lapse  —  at the PREVIEW size, so no driver restart and no gap
 * =========================================================================== */
void doTimelapse() {
  if (!lapse_every_ms || millis() < lapse_next) return;
  lapse_next = millis() + lapse_every_ms;

  camera_fb_t *fb = esp_camera_fb_get();
  if (!fb) return;
  bool ok = photoStore(fb);
  esp_camera_fb_return(fb);

  if (ok) {
    lapse_taken++;
    snprintf(st_note, sizeof(st_note), "time-lapse: %lu frames", (unsigned long)lapse_taken);
  } else {
    lapse_every_ms = 0;                  // out of room - stop rather than spam
    Serial.println(F("time-lapse stopped: out of memory"));
  }
}


/* ===========================================================================
 *  Preview  —  publish the newest frame for the stream server
 * =========================================================================== */
void publishFrame() {
  uint32_t t0 = millis();
  camera_fb_t *fb = esp_camera_fb_get();
  if (!fb) { delay(5); return; }

  xSemaphoreTake(g_jpg_mux, portMAX_DELAY);
  uint8_t *nb = (uint8_t *)ps_realloc(g_jpg, fb->len);
  if (nb) {
    g_jpg = nb;
    memcpy(g_jpg, fb->buf, fb->len);
    g_jpg_len = fb->len;
    g_frame_no++;
  }
  xSemaphoreGive(g_jpg_mux);
  esp_camera_fb_return(fb);

  uint32_t dt = millis() - t0;
  if (dt < 1) dt = 1;
  st_fps = st_fps * 0.85f + (1000.0f / dt) * 0.15f;
}


/* ===========================================================================
 *  Web page
 * =========================================================================== */
static const char PAGE_HTML[] PROGMEM = R"HTML(<!doctype html><html><head>
<meta charset="utf-8"><meta name="viewport" content="width=device-width,initial-scale=1">
<title>Robojax - XIAO Wi-Fi Camera</title><style>
:root{--bg:#0f1115;--card:#181b22;--line:#2a2f3a;--tx:#e8eaf0;--dim:#98a0b0;--cy:#22d3ee}
*{box-sizing:border-box}body{margin:0;background:var(--bg);color:var(--tx);
font:16px/1.5 system-ui,-apple-system,Segoe UI,Roboto,sans-serif}
.wrap{max-width:520px;margin:0 auto;padding:12px}
h1{font-size:17px;margin:0 0 2px}.sub{color:var(--dim);font-size:13px;margin-bottom:10px}
.badge{display:inline-block;background:#0b3;color:#031;font-weight:700;font-size:11px;
padding:2px 7px;border-radius:99px;vertical-align:middle;margin-left:6px}
.view{position:relative;background:#000;border:1px solid var(--line);border-radius:12px;overflow:hidden}
.view img{display:block;position:absolute;left:50%;top:50%;transform-origin:center}
.view.fs{position:fixed;inset:0;z-index:50;border-radius:0;border:0}
.vbtns{position:absolute;top:8px;right:8px;z-index:2;display:flex;gap:6px}
.vbtn{flex:0 0 auto;padding:7px 11px;font-size:11px;font-weight:700;border:0;border-radius:99px;
color:#fff;background:rgba(15,17,21,.6)}
.strip{margin-top:10px;padding:9px 12px;border-radius:10px;background:var(--card);
border:1px solid var(--line);font-size:14px;min-height:40px;display:flex;align-items:center}
.row{display:flex;gap:8px;margin-top:10px}
button{flex:1;padding:15px 10px;font-size:15px;font-weight:700;border:0;border-radius:11px;
color:#fff;background:#2563eb}
button.sec{background:#334155}button.warn{background:#7f1d1d}button:active{filter:brightness(.85)}
.mini{padding:7px 10px;font-size:12px;font-weight:600;border-radius:7px;background:#334155;flex:0 0 auto}
.stats{display:flex;gap:14px;margin-top:10px;color:var(--dim);font-size:12.5px;flex-wrap:wrap}
.stats b{color:var(--tx)}
details{margin-top:12px;background:var(--card);border:1px solid var(--line);
border-radius:10px;padding:10px 12px}
summary{cursor:pointer;font-weight:600;font-size:14px}
input{width:70px;padding:8px;border-radius:7px;border:1px solid var(--line);
background:#0c0e13;color:var(--tx);font-size:14px}
.ph{display:flex;gap:10px;align-items:center;padding:8px 0;border-bottom:1px solid var(--line)}
.ph img{width:74px;border-radius:6px;background:#000;flex:0 0 auto}
.ph .meta{flex:1;font-size:12.5px;color:var(--dim);line-height:1.35}
.ph .meta b{color:var(--tx);display:block;font-size:13.5px}
.note{color:var(--dim);font-size:12px;margin-top:8px}
a.save{display:inline-block;padding:7px 10px;font-size:12px;font-weight:600;
border-radius:7px;background:#2563eb;color:#fff;text-decoration:none}
</style></head><body><div class="wrap">
<h1>Wi-Fi Camera<span class="badge">NO INTERNET</span></h1>
<div class="sub">XIAO ESP32S3 Sense &middot; Robojax.com</div>

<div class="view" id="view">
  <img id="cam" src="">
  <div class="vbtns">
    <button class="vbtn" onclick="rotate()">ROTATE</button>
    <button class="vbtn" id="fsb" onclick="fs()">FULL</button>
  </div>
</div>
<div class="strip" id="strip">starting...</div>

<div class="row">
  <button onclick="go('/snap')">SNAP &middot; 3 MP</button>
  <button class="sec" onclick="document.getElementById('lp').scrollIntoView()">Time-lapse</button>
</div>

<div class="stats">
  <span>preview <b id="sz">-</b></span>
  <span>FPS <b id="fps">0</b></span>
  <span>photos <b id="n">0</b></span>
  <span>PSRAM free <b id="ps">-</b> KB</span>
</div>

<div class="row">
  <button class="mini" style="flex:1" onclick="go('/size?v=0')">320x240</button>
  <button class="mini" style="flex:1" onclick="go('/size?v=1')">640x480</button>
  <button class="mini" style="flex:1" onclick="go('/size?v=2')">800x600</button>
</div>

<details id="lp" open><summary>Time-lapse</summary>
  <div class="row">
    <span style="flex:1;font-size:14px;align-self:center">every
      <input id="iv" type="number" value="10" min="1"> seconds</span>
    <button class="mini" onclick="lapse()">START</button>
    <button class="mini" onclick="go('/lapse?s=0')">STOP</button>
  </div>
  <div class="note">Time-lapse frames are taken at the preview size, so there is no
  pause and no driver restart. Pick a smaller preview to fit far more frames.</div>
</details>

<details open><summary>Photos <span id="n2" style="color:#98a0b0"></span></summary>
  <div id="gal"></div>
  <div class="row"><button class="warn" onclick="if(confirm('Delete every photo?'))go('/wipe')">DELETE ALL</button></div>
  <div class="note"><b>Photos live in memory, not on a card.</b> Reset or unplug the
  board and they are gone. Tap SAVE to keep one on your phone. Saved photos are exactly
  what the sensor captured &mdash; the ROTATE button turns the live view only.</div>
</details>

<div class="note">The camera, the web page and the Wi-Fi network all come from the
board itself. There is no router and no internet connection involved.</div>
</div><script>
var view=document.getElementById('view'),cam=document.getElementById('cam');
cam.src='http://'+location.hostname+':81/stream';

/* --- rotate + fullscreen -------------------------------------------------
   Rotation is done here in the browser (the sensor can only flip 180, not
   90), so it turns the live view; saved photos are untouched. The chosen
   angle is remembered on this phone. Fullscreen uses the real Fullscreen
   API where the browser has one, and falls back to a fixed overlay where
   it does not (iPhones). */
var rot=+(localStorage.getItem('rot')||0);
function isFs(){return document.fullscreenElement===view||view.classList.contains('fs')}
function layout(){
  var bw,bh,odd=(rot%180)!==0;
  if(isFs()){view.style.height='';bw=window.innerWidth;bh=window.innerHeight;}
  else{bw=view.clientWidth;bh=odd?bw*4/3:bw*3/4;view.style.height=bh+'px';}
  var L=odd?Math.min(bh,bw/0.75):Math.min(bw,bh/0.75);   // stream is 4:3
  cam.style.width=L+'px';
  cam.style.transform='translate(-50%,-50%) rotate('+rot+'deg)';
}
function rotate(){rot=(rot+90)%360;localStorage.setItem('rot',rot);layout()}
function fsUi(){document.getElementById('fsb').textContent=isFs()?'EXIT':'FULL';layout()}
function fs(){
  if(isFs()){
    if(document.fullscreenElement)document.exitFullscreen();
    view.classList.remove('fs');
  }else if(view.requestFullscreen){
    view.requestFullscreen().catch(function(){view.classList.add('fs')});
  }else view.classList.add('fs');
  setTimeout(fsUi,120);
}
document.addEventListener('fullscreenchange',fsUi);
window.addEventListener('resize',layout);
layout();

function go(u){fetch(u).then(tick)}
function lapse(){go('/lapse?s='+document.getElementById('iv').value)}
function del(i){go('/delete?i='+i)}
function ago(ms){var s=Math.round(ms/1000);if(s<60)return s+'s ago';
  var m=Math.round(s/60);if(m<60)return m+'m ago';return Math.round(m/60)+'h ago'}
function tick(){
  fetch('/status').then(r=>r.json()).then(s=>{
    document.getElementById('fps').textContent=s.fps.toFixed(1);
    document.getElementById('sz').textContent=s.size;
    document.getElementById('n').textContent=s.n;
    document.getElementById('n2').textContent='('+s.n+' of '+s.max+')';
    document.getElementById('ps').textContent=s.psram;
    document.getElementById('strip').textContent=s.note||'ready';
    var h='';
    for(var i=0;i<s.photos.length;i++){var p=s.photos[i];
      h+='<div class="ph"><img src="/photo?i='+i+'" loading="lazy">'+
         '<div class="meta"><b>'+p.w+'x'+p.h+'</b>'+(p.kb).toFixed(1)+' KB &middot; '+ago(p.age)+'</div>'+
         '<a class="save" href="/photo?i='+i+'&dl=1" download="robojax_'+p.w+'x'+p.h+'_'+i+'.jpg">SAVE</a>'+
         '<button class="mini" onclick="del('+i+')">X</button></div>';
    }
    document.getElementById('gal').innerHTML=h||'<div class="note">No photos yet.</div>';
  }).catch(()=>{});
}
setInterval(tick,1000);tick();
</script></body></html>)HTML";


/* ===========================================================================
 *  HTTP handlers
 * =========================================================================== */
static esp_err_t handleRoot(httpd_req_t *req) {
  http_hits++;
  Serial.println(F("http: page requested"));
  httpd_resp_set_type(req, "text/html");
  return httpd_resp_send(req, PAGE_HTML, HTTPD_RESP_USE_STRLEN);
}

static esp_err_t handleStatus(httpd_req_t *req) {
  http_hits++;
  char json[1600];
  int n = snprintf(json, sizeof(json),
      "{\"fps\":%.1f,\"size\":\"%s\",\"n\":%d,\"max\":%d,\"psram\":%lu,"
      "\"lapse\":%lu,\"note\":\"%s\",\"photos\":[",
      st_fps, sizeName(preview_size), photo_count, MAX_PHOTOS,
      (unsigned long)psFreeKB(), (unsigned long)(lapse_every_ms / 1000), st_note);

  for (int i = 0; i < photo_count && n < (int)sizeof(json) - 120; i++)
    n += snprintf(json + n, sizeof(json) - n,
                  "%s{\"w\":%u,\"h\":%u,\"kb\":%.1f,\"age\":%lu}",
                  i ? "," : "", gallery[i].w, gallery[i].h,
                  gallery[i].len / 1024.0, (unsigned long)(millis() - gallery[i].at));

  snprintf(json + n, sizeof(json) - n, "]}");
  httpd_resp_set_type(req, "application/json");
  return httpd_resp_sendstr(req, json);
}

static int queryInt(httpd_req_t *req, const char *key, int fallback) {
  char q[96], v[24];
  if (httpd_req_get_url_query_str(req, q, sizeof(q)) != ESP_OK) return fallback;
  if (httpd_query_key_value(q, key, v, sizeof(v)) != ESP_OK) return fallback;
  return atoi(v);
}

static esp_err_t handleSnap(httpd_req_t *req) {
  req_snap = true;
  return httpd_resp_sendstr(req, "ok");
}

static esp_err_t handleSize(httpd_req_t *req) {
  req_size = queryInt(req, "v", -1);
  return httpd_resp_sendstr(req, "ok");
}

static esp_err_t handleLapse(httpd_req_t *req) {
  int s = queryInt(req, "s", 0);
  if (s <= 0) {
    lapse_every_ms = 0;
    snprintf(st_note, sizeof(st_note), "time-lapse stopped after %lu frames",
             (unsigned long)lapse_taken);
  } else {
    lapse_every_ms = (uint32_t)s * 1000UL;
    lapse_next = millis();
    lapse_taken = 0;
    snprintf(st_note, sizeof(st_note), "time-lapse running, every %d s", s);
  }
  return httpd_resp_sendstr(req, "ok");
}

static esp_err_t handleDelete(httpd_req_t *req) {
  photoFree(queryInt(req, "i", -1));
  snprintf(st_note, sizeof(st_note), "photo deleted");
  return httpd_resp_sendstr(req, "ok");
}

static esp_err_t handleWipe(httpd_req_t *req) {
  req_wipe = true;
  return httpd_resp_sendstr(req, "ok");
}

/* Serve one photo. With &dl=1 the browser saves it instead of showing it,
 * which on a phone means straight into the camera roll / Downloads. */
static esp_err_t handlePhoto(httpd_req_t *req) {
  int i  = queryInt(req, "i", -1);
  int dl = queryInt(req, "dl", 0);
  if (i < 0 || i >= photo_count) {
    httpd_resp_set_status(req, "404 Not Found");
    return httpd_resp_sendstr(req, "no such photo");
  }
  httpd_resp_set_type(req, "image/jpeg");
  if (dl) {
    char cd[96];
    snprintf(cd, sizeof(cd), "attachment; filename=\"robojax_%ux%u_%d.jpg\"",
             gallery[i].w, gallery[i].h, i);
    httpd_resp_set_hdr(req, "Content-Disposition", cd);
  }
  return httpd_resp_send(req, (const char *)gallery[i].buf, gallery[i].len);
}

/* --- MJPEG stream --------------------------------------------------------
 * Serves whatever loop() published last. The frame is copied out under the
 * lock and sent afterwards, so a slow phone can never stall the camera - which
 * matters because a running time-lapse must not miss frames just because
 * somebody is watching the preview on a weak signal. */
#define BOUNDARY "robojaxframe"
static const char *STREAM_TYPE = "multipart/x-mixed-replace;boundary=" BOUNDARY;
static const char *STREAM_PART = "\r\n--" BOUNDARY "\r\nContent-Type: image/jpeg\r\nContent-Length: %u\r\n\r\n";

static esp_err_t handleStream(httpd_req_t *req) {
  if (httpd_resp_set_type(req, STREAM_TYPE) != ESP_OK) return ESP_FAIL;
  httpd_resp_set_hdr(req, "Access-Control-Allow-Origin", "*");

  uint8_t *copy = NULL;
  size_t   cap = 0;
  uint32_t seen = 0;
  char     part[80];
  esp_err_t res = ESP_OK;

  while (res == ESP_OK) {
    while (g_frame_no == seen) vTaskDelay(pdMS_TO_TICKS(5));

    xSemaphoreTake(g_jpg_mux, portMAX_DELAY);
    seen = g_frame_no;
    size_t len = g_jpg_len;
    if (len > cap) {
      uint8_t *nb = (uint8_t *)ps_realloc(copy, len);
      if (!nb) { xSemaphoreGive(g_jpg_mux); break; }
      copy = nb; cap = len;
    }
    if (g_jpg && len) memcpy(copy, g_jpg, len);
    xSemaphoreGive(g_jpg_mux);

    if (!len) continue;
    size_t hl = snprintf(part, sizeof(part), STREAM_PART, (unsigned)len);
    res = httpd_resp_send_chunk(req, part, hl);
    if (res == ESP_OK) res = httpd_resp_send_chunk(req, (const char *)copy, len);
  }

  if (copy) free(copy);
  return res;
}

void startServers() {
  httpd_config_t cfg = HTTPD_DEFAULT_CONFIG();
  cfg.server_port = 80;
  cfg.ctrl_port   = 32768;
  cfg.max_uri_handlers = 12;

  httpd_uri_t u[] = {
    { "/",       HTTP_GET, handleRoot,   NULL },
    { "/status", HTTP_GET, handleStatus, NULL },
    { "/snap",   HTTP_GET, handleSnap,   NULL },
    { "/size",   HTTP_GET, handleSize,   NULL },
    { "/lapse",  HTTP_GET, handleLapse,  NULL },
    { "/photo",  HTTP_GET, handlePhoto,  NULL },
    { "/delete", HTTP_GET, handleDelete, NULL },
    { "/wipe",   HTTP_GET, handleWipe,   NULL },
  };
  if (httpd_start(&srv_page, &cfg) == ESP_OK)
    for (auto &h : u) httpd_register_uri_handler(srv_page, &h);

  /* The stream handler never returns, so it gets its own server - otherwise
   * it would block every button on the page. */
  cfg.server_port = 81;
  cfg.ctrl_port   = 32769;
  httpd_uri_t s = { "/stream", HTTP_GET, handleStream, NULL };
  if (httpd_start(&srv_stream, &cfg) == ESP_OK)
    httpd_register_uri_handler(srv_stream, &s);

  /* Say so if either server failed - a quiet failure here looks identical to
   * a network problem from the phone's side. */
  Serial.printf("web page server (port 80) ....... %s\n", srv_page   ? "OK" : "FAILED");
  Serial.printf("video stream server (port 81) ... %s\n", srv_stream ? "OK" : "FAILED");
  Serial.printf("free heap after servers ......... %u bytes\n", ESP.getFreeHeap());
}


/* ===========================================================================
 *  Wi-Fi
 * =========================================================================== */
void startWiFi() {
#if USE_ACCESS_POINT
  /* Narrate what the access point sees, so "the phone says connected" can be
   * checked from this side. A healthy join prints TWO lines: first the radio
   * association, then the IP hand-out. Association without an IP line means
   * the phone joined the network but never asked for an address - and then
   * 192.168.4.1 times out exactly as if the server were down. */
  WiFi.onEvent([](WiFiEvent_t e, WiFiEventInfo_t) {
    if (e == ARDUINO_EVENT_WIFI_AP_STACONNECTED)
      Serial.println(F("wifi: a device joined the network"));
    else if (e == ARDUINO_EVENT_WIFI_AP_STADISCONNECTED)
      Serial.println(F("wifi: a device LEFT the network"));
    else if (e == ARDUINO_EVENT_WIFI_AP_STAIPASSIGNED)
      Serial.println(F("wifi: the device was given an IP address - it can reach the page now"));
  });

  WiFi.mode(WIFI_AP);
  WiFi.softAP(AP_SSID, AP_PASSWORD);
  delay(300);
  Serial.println(F("\n---------------------------------------------"));
  Serial.printf("  Join Wi-Fi network : %s\n", AP_SSID);
  Serial.printf("  Password           : %s\n", AP_PASSWORD);
  Serial.printf("  Then open          : http://%s\n", WiFi.softAPIP().toString().c_str());
  Serial.println(F("  No router, no internet, nothing leaves the board."));
  Serial.println(F(""));
  Serial.println(F("  IF THE PAGE TIMES OUT: turn OFF mobile data on the"));
  Serial.println(F("  phone (or tap 'stay connected' when it warns about"));
  Serial.println(F("  no internet). Phones route around a no-internet"));
  Serial.println(F("  network, and then this address is unreachable."));
  Serial.println(F("  Type 'wifi' here to see devices and requests live."));
  Serial.println(F("---------------------------------------------\n"));
#else
  WiFi.mode(WIFI_STA);
  WiFi.begin(WIFI_SSID, WIFI_PASSWORD);
  Serial.print(F("joining Wi-Fi"));
  uint32_t t0 = millis();
  while (WiFi.status() != WL_CONNECTED && millis() - t0 < 20000) { delay(400); Serial.print('.'); }
  Serial.println();
  if (WiFi.status() == WL_CONNECTED)
    Serial.printf("  Open: http://%s\n\n", WiFi.localIP().toString().c_str());
  else {
    Serial.println(F("  FAILED. The ESP32-S3 is 2.4 GHz only - it cannot see a"));
    Serial.println(F("  5 GHz network. Check secrets.h.\n"));
  }
#endif
}


/* ===========================================================================
 *  Serial commands
 * =========================================================================== */
void printHelp() {
  Serial.println(F("\nCommands:"));
  Serial.println(F("  snap             take a 3 MP photo"));
  Serial.println(F("  lapse <sec>      start a time-lapse, one frame every <sec> seconds"));
  Serial.println(F("  stop             stop the time-lapse"));
  Serial.println(F("  list             list the photos in memory"));
  Serial.println(F("  free             show free PSRAM"));
  Serial.println(F("  wifi             network status: devices connected, requests served"));
  Serial.println(F("  wipe             delete all photos"));
  Serial.println(F("  help             this list\n"));
}

void handleSerialLine(char *l) {
  while (*l == ' ') l++;
  if      (!strncmp(l, "snap", 4))  req_snap = true;
  else if (!strncmp(l, "wipe", 4))  req_wipe = true;
  else if (!strncmp(l, "stop", 4)) { lapse_every_ms = 0; Serial.println(F("time-lapse stopped")); }
  else if (!strncmp(l, "free", 4))  Serial.printf("PSRAM free %lu KB, heap %u\n", psFreeKB(), ESP.getFreeHeap());
  else if (!strncmp(l, "wifi", 4)) {
#if USE_ACCESS_POINT
    Serial.printf("\nAP \"%s\"  at  http://%s\n", AP_SSID, WiFi.softAPIP().toString().c_str());
    Serial.printf("devices connected ........ %d\n", WiFi.softAPgetStationNum());
#else
    Serial.printf("\njoined \"%s\"  at  http://%s  (%d dBm)\n", WIFI_SSID,
                  WiFi.localIP().toString().c_str(), WiFi.RSSI());
#endif
    Serial.printf("page requests served ..... %lu\n", (unsigned long)http_hits);
    Serial.printf("servers .................. page %s, stream %s\n\n",
                  srv_page ? "OK" : "FAILED", srv_stream ? "OK" : "FAILED");
  }
  else if (!strncmp(l, "lapse ", 6)) {
    int s = atoi(l + 6);
    if (s > 0) { lapse_every_ms = (uint32_t)s * 1000UL; lapse_next = millis(); lapse_taken = 0;
                 Serial.printf("time-lapse every %d s\n", s); }
    else Serial.println(F("usage: lapse <seconds>"));
  }
  else if (!strncmp(l, "list", 4)) {
    Serial.printf("\n%d photo(s), PSRAM free %lu KB\n", photo_count, psFreeKB());
    for (int i = 0; i < photo_count; i++)
      Serial.printf("  %2d  %ux%-9u %7.1f KB   %lus ago\n", i, gallery[i].w, gallery[i].h,
                    gallery[i].len / 1024.0, (unsigned long)((millis() - gallery[i].at) / 1000));
    Serial.println();
  }
  else printHelp();
}

void pollSerial() {
  while (Serial.available()) {
    char c = Serial.read();
    if (c == '\n' || c == '\r') {
      if (ser_len > 0) { ser_line[ser_len] = 0; handleSerialLine(ser_line); ser_len = 0; }
    } else if (ser_len < (int)sizeof(ser_line) - 1) ser_line[ser_len++] = c;
  }
}


/* ===========================================================================
 *  SETUP / LOOP
 * =========================================================================== */
void setup() {
  Serial.begin(115200);
  uint32_t t0 = millis();
  while (!Serial && millis() - t0 < 2500) delay(10);
  delay(200);

  /* Silence the harmless "gdma: no peripheral is connected to the channel"
   * error that the DMA layer prints every time the camera driver is stopped.
   * It is red and it looks like a fault, and this sketch restarts the driver
   * on purpose every time you press SNAP. */
  esp_log_level_set("gdma", ESP_LOG_NONE);

  Serial.println(F("\n=== 01 Web Camera  |  Robojax.com ==="));

  if (!psramFound()) {
    /* Stop with the answer on screen rather than failing confusingly later:
     * the camera buffers and every stored photo live in PSRAM. */
    pinMode(LED_BUILTIN, OUTPUT);
    while (true) {
      Serial.println();
      Serial.println(F("###########################################################"));
      Serial.println(F("#  STOPPED: PSRAM IS NOT ENABLED                          #"));
      Serial.println(F("###########################################################"));
      Serial.println(F("  Fix it in one menu:   Tools > PSRAM > \"OPI PSRAM\""));
      Serial.println(F("  then upload again."));
      Serial.println();
      Serial.println(F("  WHY THIS HAPPENS: the XIAO_ESP32S3 board entry defaults"));
      Serial.println(F("  PSRAM to \"Disabled\", and switching boards resets every"));
      Serial.println(F("  Tools option to that board's defaults - silently."));
      Serial.println();
      Serial.println(F("  The camera buffers and every photo live in PSRAM."));
      for (int i = 0; i < 20; i++) {
        digitalWrite(LED_BUILTIN, !digitalRead(LED_BUILTIN));
        delay(100);
      }
    }
  }
  g_jpg_mux = xSemaphoreCreateMutex();

  if (!camStart(preview_size, 2, PREVIEW_JPEG_Q)) {
    Serial.println(F("\nCAMERA FAILED."));
    Serial.println(F("  - reseat the camera ribbon cable"));
    Serial.println(F("  - check Tools > PSRAM is OPI"));
    Serial.println(F("  - the sensor has no reset line: POWER CYCLE, do not just"));
    Serial.println(F("    press RESET"));
    while (1) delay(1000);
  }
  Serial.printf("preview running at %s, PSRAM free %lu KB\n",
                sizeName(preview_size), psFreeKB());

  startWiFi();
  startServers();
  printHelp();
}

void loop() {
  pollSerial();

  /* Requests from the web page are handled here, never inside an HTTP task -
   * only one place is allowed to own the camera. */
  if (req_wipe) { req_wipe = false; photoWipe(); snprintf(st_note, sizeof(st_note), "all photos deleted"); }
  if (req_snap) { req_snap = false; doSnap(); }
  if (req_size >= 0) {
    framesize_t want = req_size == 0 ? FRAMESIZE_QVGA
                     : req_size == 1 ? FRAMESIZE_VGA : FRAMESIZE_SVGA;
    req_size = -1;
    if (want != preview_size) {
      preview_size = want;
      camStart(preview_size, 2, PREVIEW_JPEG_Q);
      snprintf(st_note, sizeof(st_note), "preview now %s", sizeName(preview_size));
    }
  }

  doTimelapse();
  publishFrame();
}