#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <math.h>

#include <X11/Xlib.h>
#include <X11/Xatom.h>
#include <X11/Xutil.h>
#include <X11/extensions/Xdbe.h>

#include <cairo.h>
#include <cairo-xlib.h>

#include <hexagram/can.h>
#include <hexagram/window.h>

static void draw_needle(cairo_t *cr,
                        double x,
                        double y,
                        double r,
                        double min_angle,
                        double max_angle,
                        double value) {
    double angle = min_angle + ((max_angle - min_angle) * value) - (M_PI/2);

    cairo_move_to(cr, x, y);

    cairo_set_source_rgb(cr, 0, 0.25, 1.0);

    cairo_line_to(cr,
                  x + r * cos(angle),
                  y + r * sin(angle));

    cairo_stroke(cr);
}

static void draw_face_number(cairo_t *cr,
                             double x,
                             double y,
                             double r,
                             double min_angle,
                             double max_angle,
                             double value,
                             const char *text) {
    double angle = min_angle + ((max_angle - min_angle) * value) - 1.658;

    cairo_set_source_rgb(cr, 1, 1, 1);

    cairo_move_to(cr,
                  x + r * cos(angle),
                  y + r * sin(angle));

    cairo_save(cr);
    cairo_rotate(cr, angle + 1.658);
    cairo_show_text(cr, text);
    cairo_stroke(cr);
    cairo_restore(cr);
}

static void draw_tachometer_needle(cairo_t *cr,
                                   double x,
                                   double y,
                                   double r,
                                   double rpm) {
    if (rpm > 8000) {
        rpm = 8000;
    }

    /*
     * Draw a tiny boi circle
     */
    cairo_set_source_rgb(cr, 1, 1, 1);
    cairo_arc(cr, x, y, 0.08 * r, 0, 2*M_PI);
    cairo_fill(cr);

    draw_needle(cr, x, y,   0.77 * r,
                          232    * (M_PI/180),
                          488    * (M_PI/180),
                          rpm / 8000);
}

static void draw_tachometer(cairo_t *cr,
                            double x,
                            double y,
                            double r) {
    int i;

    cairo_select_font_face(cr, "Helvetica",
      CAIRO_FONT_SLANT_NORMAL,
      CAIRO_FONT_WEIGHT_NORMAL);

    cairo_set_font_size(cr, r * 0.125);

    cairo_set_source_rgb(cr, 1, 1, 1);
    cairo_arc(cr, x, y, r, 0, 2*M_PI);
    cairo_stroke(cr);

    /*
     * Draw face numbers
     */
    for (i=0; i<=80; i+=10) {
        char text[4];

        snprintf(text, 3, "%02d", i);

        draw_face_number(cr, x, y,
                                0.85 * r,
                                232 * (M_PI/180),
                                488 * (M_PI/180),
                                i / 80.0,
                                text);
    }
}

static void draw_speedometer(cairo_t *cr,
                             double x,
                             double y,
                             double r) {
    cairo_arc(cr, x, y, r, 0, 2*M_PI);
    cairo_stroke(cr);
}

static void draw_thermometer(cairo_t *cr,
                             double x,
                             double y,
                             double r) {
    cairo_arc(cr, x, y, r, 0, 2*M_PI);
    cairo_stroke(cr);
}

static void draw_fuel_gauge(cairo_t *cr,
                            double x,
                            double y,
                            double r) {
    cairo_arc(cr, x, y, r, 0, 2*M_PI);
    cairo_stroke(cr);
}

static void draw_mfd(cairo_t *cr,
                     double x,
                     double y,
                     double width,
                     double height) {
    cairo_set_source_rgb(cr, 0.75, 0, 0);
    cairo_move_to(cr, x,         y);
    cairo_line_to(cr, x + width, y);
    cairo_line_to(cr, x + width, y + height);
    cairo_line_to(cr, x,         y + height);
    cairo_line_to(cr, x,         y);
    cairo_fill(cr);

    cairo_set_source_rgb(cr, 1, 1, 1);
    cairo_move_to(cr, x,         y);
    cairo_line_to(cr, x + width, y);
    cairo_line_to(cr, x + width, y + height);
    cairo_line_to(cr, x,         y + height);
    cairo_line_to(cr, x,         y);
    cairo_stroke(cr);
}

static void draw_gauge_cluster_bg(hexagram_window *window,
                                  double width,
                                  double height) {
    cairo_t *cr;

    cr = hexagram_window_create_bg_context(window);

    /*
     * Paint canvas black
     */
    cairo_set_source_rgb(cr, 0, 0, 0);
    cairo_paint(cr);

    draw_tachometer(cr,
                    width  * 0.2,
                    height * 0.5,
                    height * 0.4);

    draw_speedometer(cr,
                     width  * 0.8,
                     height * 0.5,
                     height * 0.4);

    draw_thermometer(cr,
                     width  * 0.43,
                     height * 0.76,
                     height * 0.13);

    draw_fuel_gauge(cr,
                    width  * 0.57,
                    height * 0.76,
                    height * 0.13);

    draw_mfd(cr,
             width  * 0.42,
             height * 0.1,
             width  * 0.16,
             height * 0.5);

    cairo_destroy(cr);
}

static void update_gauge_cluster(cairo_t *cr,
                               struct can_frame *frame,
                               double x,
                               double y,
                               double width,
                               double height) {
    static double rpm = 0;
    
    if (frame->can_id == 0x280) {
        rpm = 0.25 * (double)(frame->data[2] | (frame->data[3] << 8));
    } else {
        return;
    }

    draw_tachometer_needle(cr,
                           x + width  * 0.2,
                           y + height * 0.5,
                           height * 0.4,
                           rpm);
}

int main(int argc, char **argv) {
    Display *display;
    fd_set rfds, rready;

    hexagram_can_if *can_if;
    hexagram_window *window;

    int fd, fd2,
        width  = 1024,
        height = 480;

    cairo_surface_t *sfc;
    cairo_t *cr;

    if ((can_if = hexagram_can_if_open("vcan0")) == NULL)
        exit(1);

    if ((window = hexagram_window_new_x11(NULL, width, height)) == NULL)
        exit(1);

    display = window->display;

    fd  = hexagram_can_if_fd(can_if);
    fd2 = hexagram_window_display_fd(window);

    /*
     * Draw the background layer
     */
    draw_gauge_cluster_bg(window, width, height);

    hexagram_window_show(window);

    /*
     * Set up the foreground surface
     */
    sfc = window->surface_fg;

    cr = cairo_create(sfc);

    /*
     * Set up file descriptors to monitor
     */
    FD_ZERO(&rfds);

    FD_SET(fd, &rfds);
    FD_SET(fd2, &rfds);

    while (1) {
        int pending;

        while ((pending = XPending(display)) != 0) {
            XEvent e;

            XNextEvent(display, &e);

            switch (e.type) {
                case Expose:
                    fprintf(stderr, "Event %d\n", e.type);

                    hexagram_window_refresh_bg(window);

                    break;
                        
                case ButtonPress:
                case KeyPress:
                    break;

                default:
                    fprintf(stderr, "Dropping unhandled XEvent.type = %d.\n", e.type);
            }
        }

        memcpy(&rready, &rfds, sizeof(rfds));

        if (select(fd2, &rready, NULL, NULL, NULL) < 0) {
            break;
        }

        if (FD_ISSET(fd, &rready)) {
            struct can_frame frame;

            hexagram_can_if_read(can_if, &frame);

            if (frame.can_id == 0x280) {
                hexagram_window_refresh_bg(window);

                update_gauge_cluster(cr, &frame, 0, 0, width, height);

                hexagram_window_swap_buffer(window);
            }
        }
    }

    cairo_destroy(cr);

    cairo_surface_destroy(sfc);
    XCloseDisplay(display);

    return 0;
}