// Smolhershey font library.  Copyright 02024 Kragen Javier Sitaker.
// See smolhershey.md for license.

#include "smolhershey.h"

int sh_load_font(sh_font *f, u8 *p, int n)
{
  int m = 0;                    // Number of lines read.
  u8 *e = p + n;                // End of buffer.
  for (;;) {
    if (m < f->n) f->lines[m] = p; // Add line pointer to array if possible
    m++;
    if (p == e) break;
    while (p != e) {
      if (*p++ == '\n') break;
    }
  }
  if (m < f->n) f->n = m;       // Update glyph array length if possible.
  return m;
}

static inline sh_point displace(sh_point a, sh_point b)
{
  return (sh_point){ a.x + b.x, a.y + b.y };
}

void sh_show(sh_gc *gc, unsigned glyph_index)
{
  // An example line from a JHF file is
  // 12345 14G\KFK[ RKFTFWGXHYJYMXOWPTQKQ\n
  // 0123456789 123456789 123456789 123456  <- byte offset

  // This means glyph 12345 has 14 points, with left boundary at G,
  // right boundary at \, first line from KF to K[, followed by
  // lifting the pen, a line from KF to TF, a line from TF to WG, etc.
  // Each character represents a coordinate in offset-'R' form; 'R' is
  // 0, 'S' is 1, 'T' is 2, 'Q' is -1, 'P' is -2, etc, so to get the
  // numeric value we subtract 'R'.  So KF is (-7, -12), K[ is (-7,
  // 9), G is -11, \ is 10, etc.  As a special case, the " R" escape
  // means to lift the pen.

  // For our purposes we don’t care about the glyph number, and we can
  // infer the number of points from the line length (because Kamal
  // Mostafa has joined the lines of text originally broken at 72
  // columns).  We only care about the left and right boundaries and
  // the points.

  // Bias current point by JHF bias value 'R' to decode the bytes.
  // The x-bias is implicit in the later cp.x -= line[8] step.
  sh_point cp = displace(gc->cp, (sh_point){0, -'R'});
  if (glyph_index + 1 >= gc->font->n) return; // Out of bounds!
  u8 **lines = gc->font->lines,
    *line = lines[glyph_index],
    *end = lines[glyph_index+1] - 1;

  cp.x -= line[8];     // Move to center of glyph by adding left width

  for (u8 *p = &line[12]; p < end; p += 2) {
    if (p[-2] == ' ' || p[0] == ' ') continue;
    gc->draw_line(displace(cp, (sh_point){ p[-2], p[-1] }),
                  displace(cp, (sh_point){ p[0], p[1] }),
                  gc->userdata);
  }

  cp.x += line[9] - 'R'; // Move to right edge of glyph by adding right width

  gc->cp = displace(cp, (sh_point){'R', 'R'});
}