#include "ps_graph.h"

#define GRAPH_SIZE 400
#define HALF_GRAPH_SIZE (GRAPH_SIZE / 2)
#define GRID_STEP (GRAPH_SIZE / 10)

void ps_export_graph(FILE *file, const struct expr_node *node, const struct graph_range *range) {
    int i;
    double x;
    int first = 1;

    fprintf(file,
        "306 500 translate\n"
        "2 setlinewidth\n"
        "/gridline {\n"
        "   .5 setlinewidth\n"
        "   .5 setgray\n"
        "   [3 3] 0 setdash\n"
        "   newpath\n"
        "   moveto\n"
        "   rlineto\n"
        "   stroke\n"
        "} def\n"
        "\n"
    );

    /* mrizka */
    for (i = -HALF_GRAPH_SIZE + GRID_STEP; i < HALF_GRAPH_SIZE; i += GRID_STEP) {
        fprintf(file, "%5d     0 %5d %5d gridline\n", GRAPH_SIZE, -HALF_GRAPH_SIZE, i);
        fprintf(file, "    0 %5d %5d %5d gridline\n", GRAPH_SIZE, i, -HALF_GRAPH_SIZE);
    }

    /* popisky */
    fprintf(file,
        "/Arial findfont\n"
        "12 scalefont\n"
        "setfont\n"
    );

    for (i = -HALF_GRAPH_SIZE; i <= HALF_GRAPH_SIZE; i += GRID_STEP) {
        double inorm = (double)i / (double)GRAPH_SIZE + 0.5;
        double xval = range->xmax * inorm + range->xmin * (1.0 - inorm); 
        double yval = range->ymax * inorm + range->ymin * (1.0 - inorm); 
        
        fprintf(file,
            "newpath\n"
            "%d %d moveto\n"
            "(%.2f) dup\n"
            "stringwidth pop neg\n"
            "0 rmoveto\n"
            "-10 -3 rmoveto\n"
            "show\n"
            "\n",
            -HALF_GRAPH_SIZE, i, yval
        );

        fprintf(file,
            "newpath\n"
            "%d %d moveto\n"
            "(%.2f) dup\n"
            "stringwidth pop\n"
            "2 div neg\n"
            "-20 rmoveto\n"
            "show\n"
            "\n",
            i, -HALF_GRAPH_SIZE, xval
        );

    }

    fprintf(file,
        "[] 0 setdash\n"
        "newpath\n"
        "%d %d moveto\n"
        "%d 0 rlineto\n"
        "0 %d rlineto\n"
        "%d 0 rlineto\n"
        "closepath\n"
        "gsave\n"
        "clip\n",
        -HALF_GRAPH_SIZE, -HALF_GRAPH_SIZE, GRAPH_SIZE, GRAPH_SIZE, -GRAPH_SIZE 
    );

    fprintf(file,
        "2 setlinewidth\n"
        "0 .3 .7 setrgbcolor\n"
        "newpath\n"
    );

    for (x = range->xmin; x <= range->xmax; x += range->step) {
        const char *cmd = "lineto";
        double xpos, ypos;
        double y = node_eval(node, x);
       
        if (y != y) {
            first = 1;
            continue;
        }

        xpos = (double)(-HALF_GRAPH_SIZE) + (x - range->xmin) / (range->xmax - range->xmin) * (double)GRAPH_SIZE;
        ypos = (double)(-HALF_GRAPH_SIZE) + (y - range->ymin) / (range->ymax - range->ymin) * (double)GRAPH_SIZE;
        
        if (first) {
            cmd = "moveto";
            first = 0;
        }
        fprintf(file, "%.2f %.2f %s\n", xpos, ypos, cmd);
    }

    fprintf(file,
        "stroke\n"
    );

    fprintf(file,
        "grestore\n"
        "2 setlinewidth\n"
        "0 0 0 setrgbcolor\n"
        "stroke\n"
    );


}