#include <curl/curl.h>
#include <curl/easy.h>
#include <stdint.h>
#include <stdio.h>
#include <yyjson.h>

#define API_LEN 256
#define URL_LEN 512
#define TEXT_LEN 4096

typedef struct tgbot {
  CURL *curl;
  char api[API_LEN];
  int64_t offset;
} tgbot;

typedef struct tgmessage {
  int64_t chat_id;
  const char *text;
} tgmessage;

void send_message(tgbot *bot, tgmessage *message) {
  char url[512];
  char *encoded_text = curl_easy_escape(bot->curl, message->text, 0);
  snprintf(url, sizeof(url), "%ssendMessage?chat_id=%ld&text=%s", bot->api,
           message->chat_id, encoded_text);

  curl_easy_setopt(bot->curl, CURLOPT_URL, url);
  curl_easy_perform(bot->curl);

  curl_free(encoded_text);
}

size_t write_cb(void *ptr, size_t size, size_t nmemb, char *data) {
  strncat(data, ptr, size * nmemb);
  return size * nmemb;
}

int handle_updates(tgbot *bot) {
  /* Prepare our update */
  char url[URL_LEN] = {0};
  char response[TEXT_LEN] = {0};
  snprintf(url, sizeof(url), "%sgetUpdates?timeout=30&offset=%ld", bot->api,
           bot->offset + 1);

  /* A little bit higher than 30s polling */
  curl_easy_setopt(bot->curl, CURLOPT_TIMEOUT, 35L);
  curl_easy_setopt(bot->curl, CURLOPT_URL, url);
  curl_easy_setopt(bot->curl, CURLOPT_WRITEFUNCTION, write_cb);
  curl_easy_setopt(bot->curl, CURLOPT_WRITEDATA, response);

  int res = curl_easy_perform(bot->curl);
  if (res != CURLE_OK) {
    return -1;
  }

  /* Print json response */
  fprintf(stdout, "%s\n", response);

  /* Let's parse json */
  yyjson_doc *doc = yyjson_read(response, strlen(response), 0);
  yyjson_val *root = yyjson_doc_get_root(doc);

  yyjson_val *ok = yyjson_obj_get(root, "ok");
  if (yyjson_get_bool(ok) != true) {
    yyjson_doc_free(doc);
    return -1;
  }

  /* Parse result */
  yyjson_val *result = yyjson_obj_get(root, "result");
  /* result is an array, so iterate over it */
  yyjson_val *a_result;
  size_t idx, max;
  yyjson_arr_foreach(result, idx, max, a_result) {
    /* Update offset */
    yyjson_val *update_id = yyjson_obj_get(a_result, "update_id");
    bot->offset = yyjson_get_sint(update_id);

    /* Get message */
    yyjson_val *message = yyjson_obj_get(a_result, "message");
    yyjson_val *text = yyjson_obj_get(message, "text");
    yyjson_val *chat = yyjson_obj_get(message, "chat");
    yyjson_val *id = yyjson_obj_get(chat, "id");

    /* Echo message */
    tgmessage msg = {
        .chat_id = yyjson_get_sint(id),
        .text = yyjson_get_str(text),
    };
    send_message(bot, &msg);
  }

  return 0;
}

int main(int argc, char **argv) {
  if (argc < 2) {
    fprintf(stderr, "Usage: %s <token>", argv[0]);
    return -1;
  }

  /* Initialize curl */
  curl_global_init(CURL_GLOBAL_ALL);

  /* Initialize our bot struct */
  tgbot bot = {
      .offset = 0,
      .curl = curl_easy_init(),
  };

  /* Retrieve bot token from args */
  snprintf(bot.api, sizeof(bot.api), "https://api.telegram.org/bot%s/",
           argv[1]);

  /* Bot loop */
  int err = 0;
  while (!err) {
    /* Find a better way to deal with CTRL-C, etc... and cleanup */
    err = handle_updates(&bot);
  }

  /* Cleanup */
  curl_easy_cleanup(bot.curl);
  curl_global_cleanup();
}