// Example program for Smolhershey font library.  Copyright 02024
// Kragen Javier Sitaker.  See smolhershey.md for license.
// 
// Render Times Roman text in ASCII art with Hershey fonts.
//
// The program’s output is in a comment at the end of the file.
//
// Cleaned-up and enhanced GPT-4 output.
//
// See also smolhersheyhpgl.c for a more elaborate example.

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

enum {
  CANVAS_WIDTH = 210,
  CANVAS_HEIGHT = 30,
};

// Canvas for ASCII art.
char canvas[CANVAS_HEIGHT][CANVAS_WIDTH];

void init_canvas()
{
  memset(canvas, ' ', sizeof canvas);
}

void print_canvas()
{
  for (int y = 0; y < CANVAS_HEIGHT; y++) {
    fwrite(canvas[y], CANVAS_WIDTH, 1, stdout);
    putchar('\n');
  }
}

// Bresenham’s line algorithm implementation for ASCII drawing.
void ascii_draw_line(sh_point start, sh_point end, void *userdata)
{
  int dx = abs(end.x - start.x), sx = start.x < end.x ? 1 : -1;
  int dy = -abs(end.y - start.y), sy = start.y < end.y ? 1 : -1;
  int err = dx + dy;
  for (;;) {
    if (start.x >= 0 && start.x < CANVAS_WIDTH &&
        start.y >= 0 && start.y < CANVAS_HEIGHT) {
      canvas[start.y][start.x] = '#'; // Draw point at current position
    }

    if (start.x == end.x && start.y == end.y) break;

    int e2 = 2 * err;

    if (e2 >= dy) {
      err += dy;
      start.x += sx;
    }

    if (e2 <= dx) {
      err += dx;
      start.y += sy;
    }
  }
}

// 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/timesr.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; 
  }

  // Initialize graphics context.
  sh_gc gc = {
    .font = &my_font,
    .cp = {0, 12},              // Starting at {0, 12}
    .draw_line = ascii_draw_line,
  };

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

  for (char *p = text_to_render; *p; p++) {
    sh_show(&gc, *p - ' ');
  }

  print_canvas();

  free(font_data); 

  return 0; 
}

/* The program outputs:
  ########     ########                      #####      #####                                                 ########   ##   #######                                       #####                #####         #  
     ##           ##                            ##         ##                                                    ##      ##      #                                             ##                   ##        ##  
     ##           ##                            ##         ##                                                    ##      ##      #                                             ##                   ##        ### 
     ##           ##                            ##         ##                                                     ##    # ##    #                                              ##                   ##        ### 
     ##           ##                            ##         ##                                                     ##    # ##    #                                              ##                   ##        ### 
     ##           ##                            ##         ##                                                     ##    # ##    #                                              ##                   ##        ### 
     ##           ##                            ##         ##                                                     ##    # ##    #                                              ##                   ##        ### 
     ##           ##            ######          ##         ##            #####                                    ##    # ##    #            #####         #####   #####       ##            #####  ##        ### 
     ##           ##          ###     #         ##         ##          ###    ##                                   ##  #   ##  #           ###    ##          ##  #    ##      ##          ###    # ##         ## 
     ##           ##         ##       ##        ##         ##         ##       ##                                  ##  #   ##  #          ##       ##         ## #    # #      ##         ##       ###         #  
     ###############        ##         #        ##         ##        ##         ##                                 ##  #   ##  #         ##         ##        ###      #       ##        ##         ##         #  
     ##           ##        ##         ##       ##         ##        ##         ##                                 ##  #   ##  #         ##         ##        ###              ##        ##         ##         #  
     ##           ##       ##          ##       ##         ##       ##           ##                                ##  #   ##  #        ##           ##       ##               ##       ##          ##         #  
     ##           ##       ##############       ##         ##       ##           ##                                ##  #   ##  #        ##           ##       ##               ##       ##          ##         #  
     ##           ##       ##                   ##         ##       ##           ##                                 ###     ###         ##           ##       ##               ##       ##          ##         #  
     ##           ##       ##                   ##         ##       ##           ##                                 ###     ###         ##           ##       ##               ##       ##          ##            
     ##           ##       ##                   ##         ##       ##           ##      #                          ###     ###         ##           ##       ##               ##       ##          ##            
     ##           ##        ##                  ##         ##        ##         ##      # #                         # #     # #          ##         ##        ##               ##        ##         ##            
     ##           ##        ##          #       ##         ##        ##         ##       ##                         # #     # #          ##         ##        ##               ##        ##         ##            
     ##           ##         ##        #        ##         ##         ##       ##         #                          #       #            ##       ##         ##               ##         ##       ###         #  
     ##           ##          ##     ##         ##         ##          ##    ###         #                           #       #             ##    ###          ##               ##          ##    ## ##        # # 
  ########     ########         #####        ########   ########         #####          #                            #       #               #####         ########         ########         ####   #####      #  
*/