// GET /api/devices/screen.bin?mac=XX — Render and return a raw 2bpp grayscale
// bitmap for the device's current screen.
// Uses LVGL to render the device's XML layout, quantizes to 4 grayscale levels,
// and packs into 2 bits per pixel (96,000 bytes for 800×480).

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

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

internal const char *kTagDeviceScreenBitmap = "API_DEV_SCREEN_BMP";

internal esp_err_t api_devices_screen_bitmap_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, "application/octet-stream");

  // 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(kTagDeviceScreenBitmap, "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);

  // Setup the MAC address subject so the XML can bind to it
  static lv_subject_t mac_subject;
  static char mac_buf[18];
  static char mac_prev_buf[18];

  strncpy(mac_buf, mac, sizeof(mac_buf));
  strncpy(mac_prev_buf, mac, sizeof(mac_prev_buf));

  lv_subject_init_string(&mac_subject, mac_buf, mac_prev_buf, sizeof(mac_buf),
                         mac);

  // Register the subject in the global XML scope under the name "device_mac"
  lv_xml_component_scope_t *global_scope =
      lv_xml_component_get_scope("globals");
  if (global_scope)
  {
    lv_xml_register_subject(global_scope, "device_mac", &mac_subject);
    ESP_LOGI(kTagDeviceScreenBitmap,
             "Registered subject 'device_mac' with value: %s", mac);
  }

  bool render_success = false;

  // 1. Prepare the XML payload
  const char *xml_to_register = NULL;

  if (dev->xml_layout[0] == '\0')
  {
    ESP_LOGI(kTagDeviceScreenBitmap, "Device %s has no layout xml.", mac);
    xSemaphoreGive(g_LvglMutex);
    httpd_resp_send_err(req, HTTPD_404_NOT_FOUND, "No layout configured");
    return ESP_FAIL;
  }

  if (strstr(dev->xml_layout, "<screen") != NULL)
  {
    xml_to_register = dev->xml_layout;
    ESP_LOGI(kTagDeviceScreenBitmap,
             "XML already contains <screen>, passing directly to parser.");
  }

  // 2. Register the XML payload as a component
  lv_result_t res =
      lv_xml_register_component_from_data("current_device", xml_to_register);

  if (res == LV_RESULT_OK)
  {
    ESP_LOGI(kTagDeviceScreenBitmap,
             "Successfully registered XML for device %s", mac);

    lv_obj_t *new_scr = lv_xml_create_screen("current_device");

    if (new_scr)
    {
      lv_screen_load(new_scr);
      scr = new_scr;
      render_success = true;
    }
    else
    {
      ESP_LOGE(kTagDeviceScreenBitmap,
               "lv_xml_create_screen failed for device %s", mac);
    }
  }
  else
  {
    ESP_LOGE(kTagDeviceScreenBitmap,
             "lv_xml_register_component_from_data failed for device %s", mac);
  }

  // 3. Fallback if LVGL XML parsing or creation failed
  if (!render_success)
  {
    ESP_LOGW(kTagDeviceScreenBitmap,
             "XML render failed, falling back to raw text layout");
    lv_obj_t *label = lv_label_create(scr);
    lv_label_set_text(label, "XML Parsing Error\nSee serial log");
    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(kTagDeviceScreenBitmap, "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;

  // Output: 2 bits per pixel, 4 pixels per byte → width*height/4 bytes
  constexpr uint32_t kBitmapSize = 96000; // 800 * 480 / 4
  uint8_t *bitmap = (uint8_t *)heap_caps_malloc(kBitmapSize, MALLOC_CAP_SPIRAM);
  if (!bitmap)
  {
    bitmap = (uint8_t *)malloc(kBitmapSize);
    if (!bitmap)
    {
      xSemaphoreGive(g_LvglMutex);
      ESP_LOGE(kTagDeviceScreenBitmap, "Failed to allocate bitmap buffer");
      httpd_resp_send_err(req, HTTPD_500_INTERNAL_SERVER_ERROR,
                          "Out of memory");
      return ESP_FAIL;
    }
  }

  // LVGL renders into RGB565 (2 bytes per pixel).
  // Quantize to 4 grayscale levels and pack 4 pixels per byte (2bpp).
  // Pixel encoding (MSB first):
  //   0b00 = BLACK   (lum 0)
  //   0b01 = DARK_GRAY  (lum 85)
  //   0b10 = LIGHT_GRAY (lum 170)
  //   0b11 = WHITE   (lum 255)
  uint32_t bitmap_idx = 0;
  for (uint32_t y = 0; y < height; ++y)
  {
    const uint16_t *src_row =
        (const uint16_t *)((const uint8_t *)draw_buf->data +
                           (y * draw_buf->header.stride));

    for (uint32_t x = 0; x < width; x += 4)
    {
      uint8_t packed = 0;
      for (int p = 0; p < 4; ++p)
      {
        uint16_t c = src_row[x + p];
        // Expand 5/6/5 components
        uint8_t r_5 = (c >> 11) & 0x1F;
        uint8_t g_6 = (c >> 5) & 0x3F;
        uint8_t b_5 = c & 0x1F;

        // Unpack to 8-bit
        uint8_t r = (r_5 << 3) | (r_5 >> 2);
        uint8_t g = (g_6 << 2) | (g_6 >> 4);
        uint8_t b = (b_5 << 3) | (b_5 >> 2);

        // Luminance → 2-bit quantized level (0..3)
        uint8_t lum = (r * 77 + g * 150 + b * 29) >> 8;
        uint8_t level = lum >> 6; // 0,1,2,3

        packed |= (level << (6 - p * 2));
      }
      bitmap[bitmap_idx++] = packed;
    }
  }

  xSemaphoreGive(g_LvglMutex);

  ESP_LOGI(kTagDeviceScreenBitmap, "Bitmap ready: %lu bytes. Sending...",
           (unsigned long)bitmap_idx);
  esp_err_t sendRes = httpd_resp_send(req, (const char *)bitmap, bitmap_idx);

  free(bitmap);

  return sendRes;
}

internal const httpd_uri_t api_devices_screen_bitmap_uri = {
    .uri = "/api/devices/screen.bin",
    .method = HTTP_GET,
    .handler = api_devices_screen_bitmap_handler,
    .user_ctx = NULL};