#include <assert.h>

#include <stdio.h>

#include <stdlib.h>

#include <uv.h>

#include <curl/curl.h>

uv_loop_t *loop;

CURLM *curl_handle;

uv_timer_t timeout;

typedef struct curl_context_s {

    uv_poll_t poll_handle;

    curl_socket_t sockfd;

} curl_context_t;

curl_context_t *create_curl_context(curl_socket_t sockfd) {

    curl_context_t *context;

    context = (curl_context_t*) malloc(sizeof *context);

    context->sockfd = sockfd;

    int r = uv_poll_init_socket(loop, &context->poll_handle, sockfd);

    assert(r == 0);

    context->poll_handle.data = context;

    return context;

}

void curl_close_cb(uv_handle_t *handle) {

    curl_context_t *context = (curl_context_t*) handle->data;

    free(context);

}

void destroy_curl_context(curl_context_t *context) {

    uv_close((uv_handle_t*) &context->poll_handle, curl_close_cb);

}

void add_download(const char *url, int num) {

    char filename[50];

    sprintf(filename, "%d.download", num);

    FILE *file;

    file = fopen(filename, "w");

    if (file == NULL) {

        fprintf(stderr, "Error opening %s\n", filename);

        return;

    }

    CURL *handle = curl_easy_init();

    curl_easy_setopt(handle, CURLOPT_WRITEDATA, file);

    curl_easy_setopt(handle, CURLOPT_URL, url);

    curl_multi_add_handle(curl_handle, handle);

    fprintf(stderr, "Added download %s -> %s\n", url, filename);

}

void check_multi_info(void) {

    char *done_url;

    CURLMsg *message;

    int pending;

    while ((message = curl_multi_info_read(curl_handle, &pending))) {

        switch (message->msg) {

        case CURLMSG_DONE:

            curl_easy_getinfo(message->easy_handle, CURLINFO_EFFECTIVE_URL,

                            &done_url);

            printf("%s DONE\n", done_url);

            curl_multi_remove_handle(curl_handle, message->easy_handle);

            curl_easy_cleanup(message->easy_handle);

            break;

        default:

            fprintf(stderr, "CURLMSG default\n");

            abort();

        }

    }

}

void curl_perform(uv_poll_t *req, int status, int events) {

    uv_timer_stop(&timeout);

    int running_handles;

    int flags = 0;

    if (status < 0)                      flags = CURL_CSELECT_ERR;

    if (!status && events & UV_READABLE) flags |= CURL_CSELECT_IN;

    if (!status && events & UV_WRITABLE) flags |= CURL_CSELECT_OUT;

    curl_context_t *context;

    context = (curl_context_t*)req;

    curl_multi_socket_action(curl_handle, context->sockfd, flags, &running_handles);

    check_multi_info();   

}

void on_timeout(uv_timer_t *req) {

    int running_handles;

    curl_multi_socket_action(curl_handle, CURL_SOCKET_TIMEOUT, 0, &running_handles);

    check_multi_info();

}

void start_timeout(CURLM *multi, long timeout_ms, void *userp) {

    if (timeout_ms <= 0)

        timeout_ms = 1; /* 0 means directly call socket_action, but we'll do it in a bit */

    uv_timer_start(&timeout, on_timeout, timeout_ms, 0);

}

int handle_socket(CURL *easy, curl_socket_t s, int action, void *userp, void *socketp) {

    curl_context_t *curl_context;

    if (action == CURL_POLL_IN || action == CURL_POLL_OUT) {

        if (socketp) {

            curl_context = (curl_context_t*) socketp;

        }

        else {

            curl_context = create_curl_context(s);

            curl_multi_assign(curl_handle, s, (void *) curl_context);

        }

    }

    switch (action) {

        case CURL_POLL_IN:

            uv_poll_start(&curl_context->poll_handle, UV_READABLE, curl_perform);

            break;

        case CURL_POLL_OUT:

            uv_poll_start(&curl_context->poll_handle, UV_WRITABLE, curl_perform);

            break;

        case CURL_POLL_REMOVE:

            if (socketp) {

                uv_poll_stop(&((curl_context_t*)socketp)->poll_handle);

                destroy_curl_context((curl_context_t*) socketp);                

                curl_multi_assign(curl_handle, s, NULL);

            }

            break;

        default:

            abort();

    }

    return 0;

}

int main(int argc, char **argv) {

    loop = uv_default_loop();

    if (argc <= 1)

        return 0;

    if (curl_global_init(CURL_GLOBAL_ALL)) {

        fprintf(stderr, "Could not init cURL\n");

        return 1;

    }

    uv_timer_init(loop, &timeout);

    curl_handle = curl_multi_init();

    curl_multi_setopt(curl_handle, CURLMOPT_SOCKETFUNCTION, handle_socket);

    curl_multi_setopt(curl_handle, CURLMOPT_TIMERFUNCTION, start_timeout);

    while (argc-- > 1) {

        add_download(argv[argc], argc);

    }

    uv_run(loop, UV_RUN_DEFAULT);

    curl_multi_cleanup(curl_handle);

    return 0;

}