c-ai-conversation/deepgram_client.c

#include "deepgram_client.h"
#include <string.h>

// Returns string that caller must free
static char *dg_find_transcript(char *json_response) {
  printf("Parsing response: %s \n", json_response);
  char *start = strstr(json_response, "\"transcript\":\"");
  if (!start)
    return NULL;

  start += 14;                    // Skip past "transcript":"
  char *end = strchr(start, '"'); // Find closing quote
  // Copy substring between start and end
  size_t len = end - start;
  char *result = malloc(len + 1);
  strncpy(result, start, len);
  result[len] = '\0';
  return result;
}

char *dg_transcribe(FILE *audio_file) {
  CURL *curl;
  CURLcode res;
  struct curl_slist *headers = NULL;

  // Initialize response buffer
  struct curl_response_data response = {0};
  response.data = malloc(1);
  response.size = 0;

  // Get file size
  fseek(audio_file, 0, SEEK_END);
  long file_size = ftell(audio_file);
  fseek(audio_file, 0, SEEK_SET);

  struct curl_file_data data;
  data.file = audio_file;
  data.size = file_size;

  curl = curl_easy_init();
  if (curl) {
    // Set headers for Deepgram API
    char *deepgram_api_key = getenv("DEEPGRAM_API_KEY");
    if (!deepgram_api_key) {
      fprintf(stderr, "DEEPGRAM_API_KEY environment variable not set\n");
      free(response.data);
      curl_easy_cleanup(curl);
      return NULL;
    }

    char auth_header[256];
    snprintf(auth_header, sizeof(auth_header), "Authorization: Token %s", deepgram_api_key);
    headers = curl_slist_append(headers, auth_header);

    curl_easy_setopt(curl, CURLOPT_URL,
                     "https://api.deepgram.com/v1/"
                     "listen?encoding=linear16&sample_rate=48000&channels=1");
    curl_easy_setopt(curl, CURLOPT_HTTPHEADER, headers);
    curl_easy_setopt(curl, CURLOPT_POST, 1L);
    curl_easy_setopt(curl, CURLOPT_READFUNCTION, curl_read_callback_file);
    curl_easy_setopt(curl, CURLOPT_READDATA, &data);
    curl_easy_setopt(curl, CURLOPT_POSTFIELDSIZE, file_size);
    curl_easy_setopt(curl, CURLOPT_WRITEFUNCTION, curl_write_callback_response);
    curl_easy_setopt(curl, CURLOPT_WRITEDATA, &response);

    res = curl_easy_perform(curl);
    if (res != CURLE_OK) {
      fprintf(stderr, "curl failed: %s\n", curl_easy_strerror(res));
      free(response.data);
      curl_slist_free_all(headers);
      curl_easy_cleanup(curl);
      return NULL;
    }

    printf("done performing curl\n");

    curl_slist_free_all(headers);
    curl_easy_cleanup(curl);
  }

  // Parse transcript from complete response
  char *transcript = dg_find_transcript(response.data);
  free(response.data);

  return transcript;
}

struct curl_response_data *dg_text_to_speech(char *text) {
  CURL *curl;
  CURLcode res;
  struct curl_slist *headers = NULL;

  // Create JSON payload - need to escape the text properly
  // Worst case: every char needs escaping, so allocate 2x + overhead
  size_t text_len = strlen(text);
  size_t payload_size = text_len * 2 + 100;
  char *json_payload = malloc(payload_size);

  // Simple approach: replace problematic chars with spaces
  char *escaped_text = malloc(text_len + 1);
  strcpy(escaped_text, text);
  for (int i = 0; escaped_text[i]; i++) {
    if (escaped_text[i] == '"' || escaped_text[i] == '\n' ||
        escaped_text[i] == '\r' || escaped_text[i] == '\t') {
      escaped_text[i] = ' ';
    }
  }

  snprintf(json_payload, payload_size,
           "{"
           "\"text\":\"%s\""
           "}",
           escaped_text);

  free(escaped_text);

  // Initialize response buffer
  struct curl_response_data *response =
      malloc(sizeof(struct curl_response_data));
  response->data = malloc(1);
  response->size = 0;

  curl = curl_easy_init();
  if (curl) {
    char *deepgram_api_key = getenv("DEEPGRAM_API_KEY");
    if (!deepgram_api_key) {
      fprintf(stderr, "DEEPGRAM_API_KEY environment variable not set\n");
      free(response->data);
      curl_easy_cleanup(curl);
      return NULL;
    }

    char auth_header[256];
    snprintf(auth_header, sizeof(auth_header), "Authorization: Token %s", deepgram_api_key);
    headers = curl_slist_append(headers, auth_header);
    headers = curl_slist_append(headers, "Content-Type: application/json");

    curl_easy_setopt(curl, CURLOPT_URL,
                     "https://api.deepgram.com/v1/"
                     "speak?encoding=linear16&sample_rate=48000");
    curl_easy_setopt(curl, CURLOPT_HTTPHEADER, headers);
    curl_easy_setopt(curl, CURLOPT_POST, 1L);
    curl_easy_setopt(curl, CURLOPT_POSTFIELDS, json_payload);
    curl_easy_setopt(curl, CURLOPT_WRITEFUNCTION, curl_write_callback_response);
    curl_easy_setopt(curl, CURLOPT_WRITEDATA, response);

    res = curl_easy_perform(curl);
    if (res != CURLE_OK) {
      fprintf(stderr, "curl failed: %s\n", curl_easy_strerror(res));
      free(response->data);
      free(response);
      curl_slist_free_all(headers);
      curl_easy_cleanup(curl);
      return NULL;
    }

    curl_slist_free_all(headers);
    curl_easy_cleanup(curl);
  }

  printf("received audio of %d length for tts\n", (int)response->size);

  // Debug: print first 100 chars to see if it's audio or error message
  printf("First 100 chars: %.100s\n", response->data);

  free(json_payload);
  return response;
}