#include "usb_descriptors.h"

#include <string.h>
#include <stdio.h>

#include "esp_mac.h"

namespace esphome {
namespace grub_boot_switch {

// USB constants we need without dragging in <tusb.h> from this header
constexpr uint8_t USB_DESC_DEVICE = 0x01;
constexpr uint8_t USB_DESC_CONFIGURATION = 0x02;
constexpr uint8_t USB_DESC_INTERFACE = 0x04;
constexpr uint8_t USB_DESC_ENDPOINT = 0x05;

constexpr uint8_t USB_CLASS_MSC = 0x08;
constexpr uint8_t USB_MSC_SUBCLASS_SCSI = 0x06;
constexpr uint8_t USB_MSC_PROTOCOL_BBB = 0x50;

constexpr uint8_t EP_BULK = 0x02;

// Mirrors the layout in reference/src/usb.c so the host sees the same shape
// as the original STM32 firmware.
constexpr uint8_t MSC_EP_IN = 0x81;
constexpr uint8_t MSC_EP_OUT = 0x01;
constexpr uint16_t MSC_EP_SIZE = 64;  // Full-speed bulk

static void put16le(uint8_t *p, uint16_t v) {
  p[0] = v & 0xFF;
  p[1] = (v >> 8) & 0xFF;
}

void usb_descriptors_build(UsbDescriptorBundle *b, uint16_t vid, uint16_t pid,
                           const char *manufacturer, const char *product,
                           const char *serial_override) {
  // ---- Device descriptor ----
  uint8_t *d = b->device;
  d[0] = 18;                          // bLength
  d[1] = USB_DESC_DEVICE;             // bDescriptorType
  put16le(d + 2, 0x0200);             // bcdUSB
  d[4] = 0x00;                        // bDeviceClass (defined in interface)
  d[5] = 0x00;                        // bDeviceSubClass
  d[6] = 0x00;                        // bDeviceProtocol
  d[7] = 64;                          // bMaxPacketSize0
  put16le(d + 8, vid);
  put16le(d + 10, pid);
  put16le(d + 12, 0x0200);            // bcdDevice
  d[14] = 1;                          // iManufacturer (string index)
  d[15] = 2;                          // iProduct
  d[16] = 3;                          // iSerialNumber
  d[17] = 1;                          // bNumConfigurations

  // ---- Configuration descriptor (config + interface + 2 endpoints) ----
  uint8_t *c = b->config;
  // Configuration
  c[0] = 9;
  c[1] = USB_DESC_CONFIGURATION;
  put16le(c + 2, 32);                 // wTotalLength
  c[4] = 1;                           // bNumInterfaces
  c[5] = 1;                           // bConfigurationValue
  c[6] = 0;                           // iConfiguration
  c[7] = 0x80;                        // bmAttributes (bus powered)
  c[8] = 50;                          // bMaxPower (100mA)
  // Interface
  c[9] = 9;
  c[10] = USB_DESC_INTERFACE;
  c[11] = 0;                          // bInterfaceNumber
  c[12] = 0;                          // bAlternateSetting
  c[13] = 2;                          // bNumEndpoints
  c[14] = USB_CLASS_MSC;
  c[15] = USB_MSC_SUBCLASS_SCSI;
  c[16] = USB_MSC_PROTOCOL_BBB;
  c[17] = 0;                          // iInterface
  // Endpoint OUT
  c[18] = 7;
  c[19] = USB_DESC_ENDPOINT;
  c[20] = MSC_EP_OUT;
  c[21] = EP_BULK;
  put16le(c + 22, MSC_EP_SIZE);
  c[24] = 0;
  // Endpoint IN
  c[25] = 7;
  c[26] = USB_DESC_ENDPOINT;
  c[27] = MSC_EP_IN;
  c[28] = EP_BULK;
  put16le(c + 29, MSC_EP_SIZE);
  c[31] = 0;

  // ---- Strings ----
  // Index 0: language ID (English, US) — esp_tinyusb expects index 0 to be the
  // language; it builds the actual descriptor from a static "0x0409" string.
  static const char kLang[] = {0x09, 0x04, 0};
  b->strings[0] = kLang;
  b->strings[1] = manufacturer;
  b->strings[2] = product;

  if (serial_override && serial_override[0] != '\0') {
    snprintf(b->serial_buf, sizeof(b->serial_buf), "%s", serial_override);
  } else {
    uint8_t mac[6] = {};
    esp_read_mac(mac, ESP_MAC_WIFI_STA);
    snprintf(b->serial_buf, sizeof(b->serial_buf), "%02X%02X%02X%02X%02X%02X", mac[0],
             mac[1], mac[2], mac[3], mac[4], mac[5]);
  }
  b->strings[3] = b->serial_buf;
}

}  // namespace grub_boot_switch
}  // namespace esphome