/*

     File: fetch_service.c 

 Abstract: XPC service that downloads remote files using libcurl.

  Version: 1.0

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 MAKES NO WARRANTIES, EXPRESS OR IMPLIED, INCLUDING WITHOUT LIMITATION

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 OPERATION ALONE OR IN COMBINATION WITH YOUR PRODUCTS.

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 */

#include <asl.h>

#include <assert.h>

#include <errno.h>

#include <stdio.h>

#include <curl/curl.h>

#include <xpc/xpc.h>

typedef struct {

    xpc_connection_t connection;

    int stop_download;

} fetch_progress_ctx_t;

static size_t

fetch_write_callback(void *ptr, size_t size, size_t nmemb, FILE *stream)

{

    return fwrite(ptr, size, nmemb, stream);

}

static int

fetch_progress_callback(fetch_progress_ctx_t *ctx, double t, double d,

                        __unused double ultotal, __unused double ulnow)

{

    if (ctx->stop_download) {

        // Transfer has been aborted.

        return (TRUE);

    }

    // Compute the precentage transferred and send a message to UI.

    if (t != 0.0) {

        xpc_object_t message = xpc_dictionary_create(NULL, NULL, 0);

        xpc_dictionary_set_double(message, "progressValue", d*100.0/t);

        xpc_connection_send_message(ctx->connection, message);

        xpc_release(message);

    }

    return (FALSE);

}

// Download file using libcurl.

//

// Returns CURLE_OK on success.  Also, returns a pointer to a error message

// with errmsg, if provided.

static int

fetch_download_file(const char *url, int fd, fetch_progress_ctx_t *ctx,

                    const char **errmsg)

{

    CURL *curl = NULL;

    CURLcode err = CURLE_OK;

    FILE *fp = NULL;

    if (errmsg)

        *errmsg = NULL;

    // Convert file descriptor to file pointer

    if ((fp = fdopen(dup(fd), "r+")) == NULL) {

        err = CURLE_WRITE_ERROR;

        if (errmsg)

            *errmsg = strerror(errno);

        goto errout;

    }

    // Initialize libcurl.

    if ((curl = curl_easy_init()) == NULL) {

        err = CURLE_FAILED_INIT;

        goto errout;

    }

    // Set the URI of the remote file to be saved into the file.

    if ((err = curl_easy_setopt(curl, CURLOPT_URL, url)) != CURLE_OK)

        goto errout;

    // Set the file pointer as the output for the HTTP server response.

    if ((err = curl_easy_setopt(curl, CURLOPT_WRITEDATA, fp)) != CURLE_OK)

        goto errout;

    // Set read/write callbacks.

    if ((err = curl_easy_setopt(curl, CURLOPT_WRITEFUNCTION, 

                                fetch_write_callback)) != CURLE_OK)

        goto errout;

    if ((err = curl_easy_setopt(curl, CURLOPT_PROGRESSDATA, ctx)) != CURLE_OK)

        goto errout;

    if ((err = curl_easy_setopt(curl, CURLOPT_PROGRESSFUNCTION,

                                fetch_progress_callback)) != CURLE_OK)

        goto errout;

    if ((err = curl_easy_setopt(curl, CURLOPT_NOPROGRESS, 0L)) != CURLE_OK)

        goto errout;

    // Perform file transfer.

    err = curl_easy_perform(curl);

    if (CURLE_ABORTED_BY_CALLBACK == err) {

        if (errmsg)

            *errmsg = "Download Canceled";

    }

errout:

    if (fp)

        fclose(fp);

    if (curl)

        curl_easy_cleanup(curl);

    if (errmsg && *errmsg == NULL) {

        if (err != CURLE_OK)

            *errmsg = curl_easy_strerror(err);

        else

            *errmsg = NULL;

    }

    return (err);

}

// Process the XPC request, create a temporary file to hold downloaded,

// data, and build/return XPC reply.

static void

fetch_process_request(xpc_object_t request, xpc_object_t reply)

{

    // Get the URL and XPC connection from the XPC request

    const char *url = xpc_dictionary_get_string(request, "url");

    xpc_connection_t conn =

        xpc_dictionary_create_connection(request, "connection");

    int ret_fd = -1;

    char *tempname;

    int errcode = 0;

    const char *errmsg = NULL;

    __block fetch_progress_ctx_t ctx = { conn, FALSE };

    // Check URL to make sure it is valid. Only support HTTP.

    if (NULL == url || strncasecmp("http://", url, 7)) {

        errcode = EINVAL;

        errmsg = "Invalid URL";

        goto errout;

    }

    // Check XPC Connection

    if (conn == NULL) {

        errcode = EINVAL;

        errmsg = "Invalid XPC connection";

        goto errout;

    }

    // Set up XPC connection endpoint for sending progress reports and receiving

    // cancel notification.

    xpc_connection_set_event_handler(conn, ^(xpc_object_t event) {

        xpc_type_t type = xpc_get_type(event);

        // If the remote end of this connection has gone away then stop download

        if (XPC_TYPE_ERROR == type &&

            XPC_ERROR_CONNECTION_INTERRUPTED == event) {

            asl_log(NULL, NULL, ASL_LEVEL_NOTICE, "Stopping transfer\n");

            ctx.stop_download = TRUE;

        }

    });

    xpc_connection_resume(conn);

    // Open a temporary file in the temp directory of the container.

    if (asprintf(&tempname, "%sfetch.XXXXXXXX", getenv("TMPDIR")) < 0) {

        errcode = errno;

        errmsg = "Couldn't alloc temp filename";

        goto errout;

    }

    if ((ret_fd = mkstemp(tempname)) < 0) {

        free(tempname);

        errcode = errno;

        errmsg = "Couldn't open temp file";

        goto errout;

    }

    // Unlink the file so it is removed as soon as it is closed.

    (void)unlink(tempname);

    free(tempname);

    // Download file add file descriptor to reply

    if ((errcode = fetch_download_file(url, ret_fd, &ctx, &errmsg)) == 0) {

        (void)lseek(ret_fd, 0, SEEK_SET);

        xpc_dictionary_set_fd(reply, "fd", ret_fd);

    }

errout:

    // Clean up and add errcode/errmsg to reply

    if (conn) {

        xpc_connection_suspend(conn);

        xpc_release(conn);

    }

    if (errcode && ret_fd != -1)

        close(ret_fd);

    xpc_dictionary_set_int64(reply, "errcode", (int64_t)errcode);

    if (errmsg)

        xpc_dictionary_set_string(reply, "errmsg", errmsg);

}

static void

fetch_peer_event_handler(xpc_connection_t peer, xpc_object_t event)

{

    // Get the object type.

    xpc_type_t type = xpc_get_type(event);

    if (XPC_TYPE_ERROR == type) {

        // Handle an error.

        if (XPC_ERROR_CONNECTION_INVALID == event) {

            // The client process on the other end of the connection

            // has either crashed or cancelled the connection.

            asl_log(NULL, NULL, ASL_LEVEL_NOTICE, "peer(%d) received "

                "XPC_ERROR_CONNECTION_INVALID",

                xpc_connection_get_pid(peer));

            xpc_connection_cancel(peer);

        } else if (XPC_ERROR_TERMINATION_IMMINENT == event) {

            // Handle per-connection termination cleanup. This

            // service is about to exit.

            asl_log(NULL, NULL, ASL_LEVEL_NOTICE, "peer(%d) received "

                "XPC_ERROR_TERMINATION_IMMINENT",

                xpc_connection_get_pid(peer));

        }

    } else if (XPC_TYPE_DICTIONARY == type) {

        xpc_object_t requestMessage = event;

        char *messageDescription = xpc_copy_description(requestMessage);

        asl_log(NULL, NULL, ASL_LEVEL_NOTICE, "received message from "

            "peer(%d)\n:%s",xpc_connection_get_pid(peer), messageDescription);

        free(messageDescription);

        xpc_object_t replyMessage = xpc_dictionary_create_reply(requestMessage);

        assert(replyMessage != NULL);

        // Process request and build a reply message.

        fetch_process_request(requestMessage, replyMessage);

        messageDescription = xpc_copy_description(replyMessage);

        asl_log(NULL, NULL, ASL_LEVEL_NOTICE, "reply message to peer(%d)\n: %s",

                xpc_connection_get_pid(peer), messageDescription);

        free(messageDescription);

        xpc_connection_send_message(peer, replyMessage);

        xpc_release(replyMessage);

    }

}

static void

fetch_event_handler(xpc_connection_t peer)

{

    // Generate an unique name for the queue to handle messages from

    // this peer and create a new dispatch queue for it.

    char *queue_name = NULL;

    asprintf(&queue_name, "%s-peer-%d", "com.apple.SandboxedFetch.fetch",

             xpc_connection_get_pid(peer));

    dispatch_queue_t peer_event_queue =

        dispatch_queue_create(queue_name, DISPATCH_QUEUE_SERIAL);

    assert(peer_event_queue != NULL);

    free(queue_name);

    // Set the target queue for connection.

    xpc_connection_set_target_queue(peer, peer_event_queue);

    // Set the handler block for connection.

    xpc_connection_set_event_handler(peer, ^(xpc_object_t event) {

        fetch_peer_event_handler(peer, event);

    });

    // Enable the peer connection to receive messages.

    xpc_connection_resume(peer);

}

int

main(int argc, const char *argv[])

{

    xpc_main(fetch_event_handler);

    exit(EXIT_FAILURE);

}