#include <stdio.h>
#include <stdlib.h>
#include <string.h>  //strdup
#include <curl/curl.h>
#include <cjson/cJSON.h>
#include "auth.h"

char* get_token(const char* ak, const char* sk)
{
    char* token = NULL;

    //保存响应报文，写入文件流时会自动分配内存空间
    char* respdata = NULL;
    size_t respsize = 0;
    FILE* fp = open_memstream(&respdata, &respsize);
    if (!fp)
    {
        perror("open_memstream");
        return NULL;
    }

    CURL* client = curl_easy_init();
    if (!client)
    {
        perror("curl_easy_init");
        fclose(fp);
        return NULL;
    }

    //设置URL
    char* url = NULL;
    asprintf(&url, "https://aip.baidubce.com/oauth/2.0/token?grant_type=client_credentials&client_id=%s&client_secret=%s&", ak, sk);
    curl_easy_setopt(client, CURLOPT_URL, url);

    //将服务器返回的响应报文保存到文件流中
    curl_easy_setopt(client, CURLOPT_WRITEDATA, fp);

    //发送请求报文
    CURLcode error = curl_easy_perform(client);
    if (error != CURLE_OK)
    {
        fprintf(stderr, "curl_easy_perform: %s\n", curl_easy_strerror(error));
        fclose(fp);
        free(url);
        curl_easy_cleanup(client);
        return NULL;
    }

    //关闭文件流之后才能访问内存中的数据
    fclose(fp);
    free(url);
    curl_easy_cleanup(client);

    //解析响应报文
    cJSON* root = cJSON_Parse(respdata);
    if (!root)
    {
        const char *error_ptr = cJSON_GetErrorPtr();
        if (error_ptr != NULL)
        {
            fprintf(stderr, "Error before: %s\n", error_ptr);
        }

        free(respdata);
        return NULL;
    }

    cJSON* access_token = cJSON_GetObjectItem(root, "access_token");
    if (!access_token)
    {
        fprintf(stderr, "access_token attribute not found\n");
        free(respdata);
        cJSON_Delete(root);
        return NULL;
    }

    if (!cJSON_IsString(access_token))
    {
        fprintf(stderr, "access_token attribute format error\n");
        free(respdata);
        cJSON_Delete(root);
        return NULL;
    }

    token = strdup(access_token->valuestring);

    // 释放响应报文占用的内存
    free(respdata);
    // 删除解析后对象占用的内存
    cJSON_Delete(root);

    return token;
}