// Smolhershey example program producing HP-GL output.  Copyright
// 02024 Kragen Javier Sitaker.  See smolhershey.md for license.
//
// Mostly the same as smolhersheyexample.c, but in some ways it is a
// more complete example, showing how to use userdata.
//
// hp2xx from the hp2xx package can be used to visualize the output
// (./smolhersheyhpgl | hp2xx -), and hp2xx -m png can convert it to a
// PNG.  It looks better with a wider pen (-p 5); I did some
// brute-force antialiasing with hp2xx -p 5 -d 600 -m png and using
// ImageMagick to reduce the resolution with convert -geometry
// 596x596, then cleaned it up with optipng, and checked in the result
// as smolhersheyhpgl.png.

#include <stdio.h>
#include <stdlib.h>
#include <errno.h>
#include <math.h>
#include "smolhershey.h"

// Context data for our HP-GL output.  This is an example of how to
// use userdata.
typedef struct {
  FILE *output;

  // http://cmp.felk.cvut.cz/cmp/courses/ROB/labsmaterial/other/hpgl.html says:
  // “One irritant to HPGL is that there are two different coordinate
  // systems in use. Small-format plotters, including A- and B-size
  // plotters, locate the origin at the lower-left corner;
  // large-format plotters, including D- and E-size plotters, located
  // the origin at the center of the media.”
  float x_origin, y_origin,     // Starting point.
    scale,                      // In 25μm units, 1016 per inch.
    angle;                      // In radians.
  sh_point last;   // Last point visited, to avoid redundant commands.
  int valid;       // Boolean indicating whether last is valid.
} hpgl_context;

static inline sh_point hpgl_xform(hpgl_context *ctx, sh_point p)
{
  // Note that because Hershey fonts have Y increasing down, rather
  // than up, we reverse the signs on the Y coordinates from p.
  double s = sin(ctx->angle), c = cos(ctx->angle);
  return (sh_point) {
    .x = ctx->x_origin + ctx->scale * (c * p.x + s * p.y),
    .y = ctx->y_origin + ctx->scale * (s * p.x - c * p.y),
  };
}

static void hpgl_draw_line(sh_point start, sh_point end, void *userdata)
{
  hpgl_context *ctx = userdata;
  // Do we need to lift the pen?
  int lift_pen = (!ctx->valid ||
                  start.x != ctx->last.x ||
                  start.y != ctx->last.y);
  ctx->valid = 1;
  ctx->last = end;

  start = hpgl_xform(ctx, start);
  end = hpgl_xform(ctx, end);

  if (lift_pen) {
    fprintf(ctx->output, "PU;PA%d,%d;PD;\n", start.x, start.y);
  }
  // Plot relative within each path, which delta-compresses so that
  // the output isn’t so bulky.
  fprintf(ctx->output, " PR%d,%d;\n", end.x - start.x, end.y - start.y);
}

// Read an entire text file into malloced memory.
int slurp_file(u8 **buf, int *buflen, const char *name)
{
  FILE *font_file = fopen(name, "r");
  if (!font_file) return 0;

  // Get file size.
  fseek(font_file, 0L, SEEK_END);
  *buflen = ftell(font_file);
  rewind(font_file);

  // Allocate memory for font data.
  *buf = malloc(*buflen);

  if (!*buf) {
    fclose(font_file);
    return 0;
  }
     
  // Read font data into memory.
  fread(*buf, 1, *buflen, font_file);
  fclose(font_file);

  return 1;
}

int main(int argc, char **argv)
{
  // Load Hershey font data from a file.
  char *font_file_path = "/usr/share/hershey-fonts/cursive.jhf";
  u8 *font_data;
  int font_data_length;
  if (!slurp_file(&font_data, &font_data_length, font_file_path)) {
    int err = errno;
    perror(font_file_path);
    if (err == ENOENT) {
      fprintf(stderr,
              "Maybe: sudo apt install hershey-fonts-data  # or equivalent\n");
    }

    return 1;
  }

  // Allocate space for glyph pointers (assuming 96 glyphs + EOF).
  u8 *glyph_pointers[97]; // One extra for EOF

  // Initialize sh_font structure with one extra slot for EOF.
  sh_font my_font = { .lines = glyph_pointers, .n = 97 };

  int num_glyphs = sh_load_font(&my_font, font_data, font_data_length);

  if (num_glyphs > my_font.n) { 
    fprintf(stderr, "Font allocation wasn’t big enough.\n");
    free(font_data); 
    return 1; 
  }

  hpgl_context ctx = {
    .output = stdout,
    .scale = 14,
    .x_origin = 1016, .y_origin = 1016, // 1", 1"
    .angle = 3.14159 / 3,       // 60°
  };

  // Initialize graphics context.
  sh_gc gc = {
    .font = &my_font,
    .draw_line = hpgl_draw_line,
    .userdata = &ctx,
  };

  char *text_to_render = argc == 1 ? "Hello, World!" : argv[1];

  for (char *p = text_to_render; *p; p++) {
    sh_show(&gc, *p - ' ');
    ctx.valid = 0;              // ensure PU before next glyph
  }

  free(font_data); 

  return 0; 
}

/* The program’s output, which hp2xx at least renders reasonably, is:
PU;PA1004,1135;PD;
 PR-26,-17;
 PR-31,2;
 PR-13,7;
 PR-17,26;
 PR2,31;
 PR7,12;
 PR26,18;
 PR31,-2;
 PR25,-14;
 PR41,-40;
 PR59,-67;
 PR34,-52;
 PR11,-38;
 PR-14,-24;
 PR-20,-5;
 PR-24,14;
PU;PA1065,1100;PD;
 PR26,130;
 PR2,32;
 PR-3,50;
 PR-10,38;
 PR-18,26;
 PR-12,7;
 PR-19,-5;
 PR-7,-12;
 PR10,-38;
 PR35,-52;
 PR59,-67;
 PR53,-47;
 PR36,-21;
 PR20,5;
 PR7,13;
 PR1,31;
 PR-5,19;
 PR-22,45;
PU;PA1275,1270;PD;
 PR2,31;
 PR-5,19;
 PR-17,26;
 PR-24,14;
 PR-19,-5;
 PR-7,-12;
 PR-2,-31;
 PR17,-27;
 PR36,-21;
 PR31,-1;
 PR27,17;
 PR14,24;
 PR1,31;
 PR-5,19;
 PR-22,46;
 PR-22,45;
 PR-40,71;
 PR-17,26;
 PR-30,34;
 PR-24,14;
 PR-19,-6;
 PR-2,-31;
 PR17,-26;
 PR42,-40;
 PR78,-61;
 PR72,-42;
 PR20,5;
 PR7,12;
 PR1,31;
 PR-5,19;
 PR-22,46;
 PR-22,45;
 PR-40,71;
 PR-17,26;
 PR-30,34;
 PR-24,14;
 PR-19,-6;
 PR-2,-31;
 PR17,-26;
 PR42,-40;
 PR78,-61;
 PR72,-42;
 PR20,5;
 PR7,12;
 PR1,31;
 PR-5,19;
 PR-22,46;
PU;PA1408,1694;PD;
 PR-14,-24;
 PR-2,-31;
 PR5,-19;
 PR17,-26;
 PR24,-14;
 PR31,-2;
 PR27,17;
 PR14,24;
 PR1,32;
 PR-5,19;
 PR-17,26;
 PR-24,14;
 PR-31,2;
 PR-26,-18;
 PR5,-19;
 PR24,-14;
 PR31,-2;
 PR26,18;
 PR21,36;
 PR2,31;
 PR-5,19;
PU;PA1559,1817;PD;
 PR5,-19;
 PR-19,-5;
 PR-5,19;
 PR19,5;
 PR24,-14;
 PR11,-38;
PU;PA1606,2178;PD;
 PR-26,-17;
 PR-31,2;
 PR-13,7;
 PR-17,26;
 PR2,31;
 PR7,12;
 PR26,17;
 PR31,-1;
 PR37,-21;
 PR175,-118;
PU;PA1612,2385;PD;
 PR185,-269;
PU;PA1612,2385;PD;
 PR241,-172;
PU;PA1696,2530;PD;
 PR-2,-31;
 PR16,-57;
 PR27,-65;
 PR52,-78;
 PR64,-86;
PU;PA1870,2495;PD;
 PR-14,-25;
 PR-2,-31;
 PR5,-19;
 PR17,-26;
 PR24,-14;
 PR31,-2;
 PR27,17;
 PR14,25;
 PR1,31;
 PR-5,19;
 PR-17,26;
 PR-24,14;
 PR-31,2;
 PR-26,-17;
 PR5,-19;
 PR24,-14;
 PR31,-2;
 PR26,17;
 PR21,36;
 PR2,32;
 PR-5,19;
 PR-22,45;
 PR-18,26;
 PR25,-14;
 PR21,36;
 PR19,6;
 PR24,-14;
 PR29,-34;
 PR12,-7;
 PR20,6;
 PR7,12;
 PR1,31;
 PR-5,19;
 PR-22,45;
 PR-22,46;
 PR-40,71;
 PR-17,26;
 PR-30,33;
 PR-24,14;
 PR-19,-5;
 PR-2,-31;
 PR17,-26;
 PR42,-40;
 PR78,-62;
 PR72,-42;
 PR20,6;
 PR7,12;
 PR1,31;
 PR-5,19;
 PR-22,45;
PU;PA2172,2934;PD;
 PR-31,2;
 PR-26,-17;
 PR-14,-24;
 PR-2,-31;
 PR5,-20;
 PR17,-26;
 PR24,-14;
 PR31,-2;
 PR27,18;
 PR14,24;
 PR1,31;
 PR-17,26;
 PR-176,199;
PU;PA2143,2968;PD;
 PR53,-48;
 PR36,-21;
 PR20,6;
 PR7,12;
 PR1,31;
 PR-5,19;
 PR-22,45;
PU;PA2074,3185;PD;
 PR170,-98;
PU;PA2304,3052;PD;
 PR5,-19;
 PR20,5;
 PR-6,19;
 PR-19,-5;
*/