#include <stdlib.h>
#include <arpa/inet.h>
#include <unistd.h>
#include <fcntl.h>
#include <errno.h>
#include <assert.h>

#include <event2/event.h>
#include <event2/bufferevent.h>

#include "render_internal.h"    // for render_cmd_build
#include "render_remote.h"
#include "common.h"

struct remote_render_ctx {
    struct event *ev_conn;
    struct bufferevent *data_bev;

    #pragma pack(push)
    #pragma pack(1)

    struct {
        u_int8_t    mode;

        u_int32_t   img_w;
        u_int32_t   img_h;

        double      x1;
        double      y1;
        double      x2;
        double      y2;
    } render_cmd;

    #pragma pack(pop)
    
    // has cb_done/cb_fail already been called?
    int alive;

    void (*cb_sent)(void *arg);
    void (*cb_data)(struct evbuffer *buf, void *arg);
    void (*cb_done)(void *arg);
    void (*cb_fail)(void *arg);

    void *cb_arg;
};

static void _remote_render_free (struct remote_render_ctx *ctx) {
    // free the data_bev
    if (ctx->data_bev) {
        bufferevent_free(ctx->data_bev);
        ctx->data_bev = NULL;
    }
    
    // close the socket (ctx->ev_conn remains valid even after we're done with it...)
    close(event_get_fd(ctx->ev_conn));

    // and the event
    event_free(ctx->ev_conn);
    
    // free the context structure
    free(ctx);
}

static void _remote_render_done (struct remote_render_ctx *ctx) {
    assert(ctx->alive);
    
    ctx->alive = 0;

    ctx->cb_done(ctx->cb_arg);

    _remote_render_free(ctx);
}

static void _remote_render_fail (struct remote_render_ctx *ctx) {
    assert(ctx->alive);
    
    ctx->alive = 0;

    ctx->cb_fail(ctx->cb_arg);
    
    _remote_render_free(ctx);
}

static void _remote_write (struct bufferevent *bev, void *arg) {
    struct remote_render_ctx *ctx = arg;

    // the write buffer was drained, so the render command was sent
    ctx->cb_sent(ctx->cb_arg);
    
    // we don't care about EV_WRITE anymore
    if (bufferevent_disable(ctx->data_bev, EV_WRITE))
        ERROR("bufferevent_disable");

    // start receiving data
    if (bufferevent_enable(ctx->data_bev, EV_READ))
        ERROR("bufferevent_enable");
    
    return;
error:
    _remote_render_fail(ctx);
}

static void _remote_read (struct bufferevent *bev, void *arg) {
    struct remote_render_ctx *ctx = arg;
    
    // pass the bufferevent's input buffer to our callback - libevent doesn't provide any function to access this, but hopefully this works correctly
    ctx->cb_data(EVBUFFER_INPUT(bev), ctx->cb_arg);
}

static void _remote_error (struct bufferevent *bev, short what, void *arg) {
    struct remote_render_ctx *ctx = arg;

    // OH NOES; WHAT DO WE DO!?
    
    if (what & EVBUFFER_EOF) {
        // great!
        
        // send any remaining-chunk data
        if (EVBUFFER_LENGTH(EVBUFFER_INPUT(bev)) > 0)
            ctx->cb_data(EVBUFFER_INPUT(bev), ctx->cb_arg);

        // signal completion
        _remote_render_done(ctx);

        return;

    } else if (what & EVBUFFER_ERROR) {
        // crap.
        PWARNING("EVBUFFER_ERROR");

    } else if (what & EVBUFFER_TIMEOUT) {
        // ah well
        WARNING("render_remote: timeout");

    } else {
        FATAL("weird bufferevent error code: 0x%02X", what);
    }
    
    // cb_fail + free
    _remote_render_fail(ctx);
}

static void _remote_connected (int fd, short event, void *arg) {
    struct remote_render_ctx *ctx = arg;

    // set up the read/write bufferevent
    if ((ctx->data_bev = bufferevent_new(fd, &_remote_read, &_remote_write, &_remote_error, ctx)) == NULL)
        ERROR("bufferevent_new");

    // write the render command
    if (bufferevent_write(ctx->data_bev, &ctx->render_cmd, sizeof(ctx->render_cmd)))
        ERROR("bufferevent_write");

    // wait for it to be written out
    if (bufferevent_enable(ctx->data_bev, EV_WRITE))
        ERROR("bufferevent_enable");
    
    return;

error:
    _remote_render_fail(ctx);
}

static void render_cmd_build (struct render *render, struct remote_render_ctx *ctx) {
    // just copy over the render params to the render_cmd
    ctx->render_cmd.mode = render->mode;
    ctx->render_cmd.img_w = htonl(render->img_w);
    ctx->render_cmd.img_h = htonl(render->img_h);
    ctx->render_cmd.x1 = render->x1;
    ctx->render_cmd.y1 = render->y1;
    ctx->render_cmd.x2 = render->x2;
    ctx->render_cmd.y2 = render->y2;
}

struct remote_render_ctx *render_remote (
        struct render *render,
        struct remote_node *remote_node,
        void (*cb_sent)(void *arg),
        void (*cb_data)(struct evbuffer *buf, void *arg),
        void (*cb_done)(void *arg),
        void (*cb_fail)(void *arg),
        void *cb_arg
) {    
    struct remote_render_ctx *ctx;
    int sock;

    printf("remote_node render load: %d/%d\n", remote_node->current_load, remote_node->parallel_renders);

    // alloc the remote render ctx
    if (!(ctx = calloc(1, sizeof(struct remote_render_ctx))))
        ERROR("calloc");
    
    // store the provided callback functions
    ctx->cb_sent = cb_sent;
    ctx->cb_data = cb_data;
    ctx->cb_done = cb_done;
    ctx->cb_fail = cb_fail;
    ctx->cb_arg = cb_arg;
    
    // copy the relevant stuff from the render_ctx
    render_cmd_build(render, ctx);
    
    // create the socket
    if ((sock = socket(remote_node->addr.ss_family, SOCK_STREAM, 0)) < 0)
        PERROR("socket");

    // mark it as nonblocking
    if (fcntl(sock, F_SETFL, O_NONBLOCK) == -1)
        PERROR("fcntl");
    
    // initiate the connect
    int err = connect(sock, (struct sockaddr *) &remote_node->addr, sizeof(remote_node->addr));

    if (err != -1 || errno != EINPROGRESS)
        PERROR("connect");

    // do the libevent dance
    if (!(ctx->ev_conn = event_new(NULL, sock, EV_WRITE, &_remote_connected, ctx)))
        ERROR("event_new");

    if (event_add(ctx->ev_conn, NULL))
        ERROR("event_add");
    
    // we are now alive
    ctx->alive = 1;

    // success
    return ctx;

error:
    free(ctx);

    if (sock > 0)
        close(sock);

    return NULL;
}

int render_remote_set_recv (struct remote_render_ctx *ctx, size_t recv_threshold, size_t unread_buffer) {
    if (ctx->data_bev == NULL)
        return -1;

    bufferevent_setwatermark(ctx->data_bev, EV_READ, recv_threshold, recv_threshold + unread_buffer);

    return 0;
}

int render_remote_shake (struct remote_render_ctx *ctx) {
    if (ctx->data_bev == NULL)
        return -1;

    ctx->cb_data(EVBUFFER_INPUT(ctx->data_bev), ctx->cb_arg);

    return 0;
}

void render_remote_cancel (struct remote_render_ctx *ctx) {
    // we must be alive for this..
    assert(ctx->alive);

    // if it's still just connecting, cancel that
    if (event_pending(ctx->ev_conn, EV_WRITE, NULL))
        event_del(ctx->ev_conn);
    
    // this takes care of the rest
    _remote_render_free (ctx);
}