Calendink/Provider/main/api/devices/screen_image.cpp

// GET /api/devices/screen.png?mac=XX — Render and return a PNG for the device's current screen
// Uses LVGL to render the device's XML layout (or a fallback label) then encodes to PNG via lodepng.

#include "lv_setup.hpp"
#include "lodepng/lodepng.h"
#include "esp_http_server.h"
#include "esp_log.h"
#include "esp_heap_caps.h"
#include "lvgl.h"
#include <string.h>
#include "lodepng_alloc.hpp"

#include "types.hpp"
#include "device.hpp"

internal const char *kTagDeviceScreenImage = "API_DEV_SCREEN_IMG";

internal esp_err_t api_devices_screen_image_handler(httpd_req_t *req)
{
  httpd_resp_set_hdr(req, "Access-Control-Allow-Origin", "*");
  httpd_resp_set_hdr(req, "Cache-Control", "no-cache, no-store, must-revalidate");
  httpd_resp_set_type(req, "image/png");

  // Extract mac query parameter
  char mac[18] = {};
  size_t buf_len = httpd_req_get_url_query_len(req) + 1;
  if (buf_len > 1)
  {
    char query[64] = {};
    if (httpd_req_get_url_query_str(req, query, sizeof(query)) == ESP_OK)
    {
      httpd_query_key_value(query, "mac", mac, sizeof(mac));
    }
  }

  if (mac[0] == '\0')
  {
    httpd_resp_send_err(req, HTTPD_400_BAD_REQUEST, "Missing 'mac' query param");
    return ESP_FAIL;
  }

  device_t *dev = find_device(mac);
  if (!dev)
  {
    httpd_resp_send_err(req, HTTPD_404_NOT_FOUND, "Device not registered");
    return ESP_FAIL;
  }

  // --- LVGL rendering (mutex-protected) ---
  if (xSemaphoreTake(g_LvglMutex, pdMS_TO_TICKS(5000)) != pdTRUE)
  {
    ESP_LOGE(kTagDeviceScreenImage, "Failed to get LVGL mutex");
    httpd_resp_send_err(req, HTTPD_500_INTERNAL_SERVER_ERROR, "LVGL busy");
    return ESP_FAIL;
  }

  lv_obj_t *scr = lv_screen_active();

  // Clear all children from the active screen
  lv_obj_clean(scr);

  // White background for grayscale
  lv_obj_set_style_bg_color(scr, lv_color_white(), LV_PART_MAIN);

  if (dev->xml_layout[0] != '\0')
  {
    // TODO: Use lv_xml_create() when LVGL XML runtime is verified working.
    // For now, show the XML as text to prove the pipeline works end to end.
    // Once we confirm LV_USE_XML compiles, we'll swap this for the real XML parser.
    lv_obj_t *label = lv_label_create(scr);
    lv_label_set_text(label, dev->xml_layout);
    lv_obj_set_style_text_color(label, lv_color_black(), LV_PART_MAIN);
    lv_obj_align(label, LV_ALIGN_TOP_LEFT, 10, 10);
  }
  else
  {
    // Fallback: render "Hello <mac>"
    lv_obj_t *label = lv_label_create(scr);
    char text[48];
    snprintf(text, sizeof(text), "Hello %s", mac);
    lv_label_set_text(label, text);
    lv_obj_set_style_text_color(label, lv_color_black(), LV_PART_MAIN);
    lv_obj_align(label, LV_ALIGN_CENTER, 0, 0);
  }

  // Force LVGL to fully render the screen
  lv_refr_now(g_LvglDisplay);

  lv_draw_buf_t *draw_buf = lv_display_get_buf_active(g_LvglDisplay);
  if (!draw_buf)
  {
    xSemaphoreGive(g_LvglMutex);
    ESP_LOGE(kTagDeviceScreenImage, "No active draw buffer");
    httpd_resp_send_err(req, HTTPD_500_INTERNAL_SERVER_ERROR, "Display uninitialized");
    return ESP_FAIL;
  }

  uint32_t width = CONFIG_CALENDINK_DISPLAY_WIDTH;
  uint32_t height = CONFIG_CALENDINK_DISPLAY_HEIGHT;

  // Handle stride != width
  uint8_t *packed_data = (uint8_t *)draw_buf->data;
  bool needs_free = false;

  if (draw_buf->header.stride != width)
  {
    packed_data = (uint8_t *)heap_caps_malloc(width * height, MALLOC_CAP_SPIRAM);
    if (!packed_data)
    {
      xSemaphoreGive(g_LvglMutex);
      ESP_LOGE(kTagDeviceScreenImage, "Failed to allocate packed buffer");
      httpd_resp_send_err(req, HTTPD_500_INTERNAL_SERVER_ERROR, "Out of memory");
      return ESP_FAIL;
    }
    needs_free = true;
    for (uint32_t y = 0; y < height; ++y)
    {
      memcpy(packed_data + (y * width),
             (uint8_t *)draw_buf->data + (y * draw_buf->header.stride), width);
    }
  }

  // Encode to PNG
  unsigned char *png = nullptr;
  size_t pngsize = 0;

  lodepng_allocator_reset();

  ESP_LOGI(kTagDeviceScreenImage, "Encoding %lux%lu PNG for device %s", width, height, mac);
  unsigned error = lodepng_encode_memory(&png, &pngsize, packed_data, width, height, LCT_GREY, 8);

  if (needs_free)
  {
    free(packed_data);
  }

  xSemaphoreGive(g_LvglMutex);

  if (error)
  {
    ESP_LOGE(kTagDeviceScreenImage, "PNG encoding error %u: %s", error, lodepng_error_text(error));
    httpd_resp_send_err(req, HTTPD_500_INTERNAL_SERVER_ERROR, "PNG generation failed");
    return ESP_FAIL;
  }

  ESP_LOGI(kTagDeviceScreenImage, "PNG ready: %zu bytes. Sending...", pngsize);
  esp_err_t res = httpd_resp_send(req, (const char *)png, pngsize);

  return res;
}

internal const httpd_uri_t api_devices_screen_image_uri = {
    .uri = "/api/devices/screen.png",
    .method = HTTP_GET,
    .handler = api_devices_screen_image_handler,
    .user_ctx = NULL};