/*

  Shennong_IL9341.ino
  
  Scroll through Chinese Short Story
  "The Farmer God Shen Nong Tastes All the Plants" 

  U8g2_for_Adafruit_GFX:
    - Use U8g2 fonts with Adafruit GFX
    - Support for UTF-8 in print statement
    - 90, 180 and 270 degree text direction
  
  List of all U8g2 fonts: https://github.com/olikraus/u8g2/wiki/fntlistall


  English translation:
  The Farmer God Shen Nong Tastes All the Plants 

  Source:
  http://chinesereadingpractice.com/2012/08/22/the-farmer-god-shen-nong-tastes-all-the-plants/

  All his life, Shen Nong had a crystal abdomen, and one could 
  clearly see all of his internal organs. At that time, humans were 
  often getting sick and even dying because they ate things 
  indiscriminately [not knowing if they were good or bad]. Shen 
  Nong determinedly tasted everything everywhere; the 
  good-tasting things he put in a bag on his left side, those were 
  for people to eat; the bad-tasting things he put in a bag on his 
  right side, and those were used for medicine.

  The first time, Shen Nong tasted a small fresh leaf. As this leaf 
  fell into his stomach, it cleaned every inch of his insides so that 
  every organ top and bottom was fresh and cool, as if [the leaf] 
  was somehow on patrol [making the rounds], so Shen Nong 
  called it “chá” [to investigate / check], and later generations of 
  men called it “chá” [tea]. Shen Nong put it in the bag on the 
  right. The second time, Shen Nong tasted a little light red flower 
  that looked like a butterfly, which was sweet and delicious, with 
  an exotic smell that filled his nostrils, so he called it “licorice”. He 
  put it in the bag on the left. In this way, Shen Nong diligently 
  tasted all manner of flora, and every time he was poisoned, he 
  used tea to rescue himself. Before long, the bag on his left 
  contained 47,000 kinds of flowers, grasses, roots and leaves, 
  and the right side had 398,000 kinds.

  But one day, Shen Nong tasted “heartbreak grass”, and this 
  poison was too terrible, so there wasn’t enough time to eat the 
  tea leaves to detoxify and he died. He sacrificed himself to save 
  humanity, so people call him the “Bodhisattva of Medicine”, and 
  people forever commemorate him through this story. 


*/
#include "SPI.h"
#include "Adafruit_GFX.h"
#include "Adafruit_ILI9341.h"
#include "U8g2_for_Adafruit_GFX.h"

#define TFT_DC 9
#define TFT_CS 10

Adafruit_ILI9341 display = Adafruit_ILI9341(TFT_CS, TFT_DC);

U8G2_FOR_ADAFRUIT_GFX u8g2_for_adafruit_gfx;


// To read the short story with all glyphs you need at least a font with _gb2312b postfix
// However, a font with _gb2312b postfix is very large and will not always fit on
// the target controller. For testing you can use _chinese1 extenstion, but then
// many gylphs are skipped and not visible.
//
// wqy fonts are available in different sizes, here are only wqy12, wqy14 and wqy16 listed

//#define FONT u8g2_font_wqy12_t_chinese1
//#define FONT u8g2_font_wqy12_t_gb2312b

//#define FONT u8g2_font_wqy14_t_chinese1
//#define FONT u8g2_font_wqy14_t_gb2312b

//#define FONT u8g2_font_wqy16_t_chinese1
#define FONT u8g2_font_wqy16_t_gb2312b

// The next two macros define the scroll speed of the short story
#define SCROLL_DELTA 4
#define SCROLL_DELAY 100


// Chinese Short Story
// The Farmer God Shen Nong Tastes All the Plants 
// Please excause wrong line breaks

const char c_str[] = 
"Shen Nong\n\n"
"神农一生下来就是\n"
"个水晶肚子，五脏\n"
"六腑全都能看得一\n"
"清二楚。那时侯，\n"
"人们经常因为乱吃\n"
"东西而生病，甚至\n"
"丧命。神农决心尝\n"
"遍所有的东西，好\n"
"吃的放在身边左边\n"
"的袋子里，给人吃\n"
"；\n"
"不好吃的就放在身\n"
"子右边的袋子里，\n"
"作药用。\n"
"第一次，神农尝了\n"
"一片小嫩叶。这叶\n"
"片一落进肚里，就\n"
"上上下下地把里面\n"
"各器官擦洗得清清\n"
"爽爽，\n"
"象巡查似的，\n"
"神农把它叫做\n"
"“查”，\n"
"就是后人所称的\n"
"“茶”。\n"
"神农将它放进右边\n"
"袋子里。第二次，\n"
"神农尝了朵蝴蝶样\n"
"的淡红小花，甜津\n"
"津的，香味扑鼻，\n"
"这是“甘草”。他把\n"
"它放进了左边袋子\n"
"里。就这样，神农\n"
"辛苦地尝遍百草，\n"
"每次中毒，都靠茶\n"
"来解救。后来，\n"
"他左边的袋子里花\n"
"草根叶有四万七千\n"
"种，右边有三十九\n"
"万八千种。\n"
"但有一天，神农尝\n"
"到了“断肠草”，这\n"
"种毒草太厉害了，\n"
"他还来不及吃茶解\n"
"毒就死了。\n"
"他是为了拯救人们\n"
"而牺牲的，人们称\n"
"他为“药王菩萨”，\n"
"人间以这个神话故\n"
"事永远地纪念他。\n";


char buf[48];      // there are at most 8 chinese glyphs per line, max buf size is 8*3 = 24 
 
uint8_t total_lines;    // the total number of lines in the story
uint8_t i;        // loop variable for the lines
uint8_t line_cnt;   // number of lines to draw, usually equal to lines_per_draw
uint8_t start_line;   // topmost visible line, derived from top_window_pos
uint8_t lines_per_draw; // how many lines to draw on the screen, derived from font and display height
uint16_t glyph_height;  // height of the glyphs
uint16_t glyph_width;

uint16_t top_window_pos;    // defines the display position in pixel within the text
uint16_t total_height;      // total height in pixel, derived from font height and total_lines
uint16_t top_offset;     // offset between the first visible line and the display


uint8_t u8x8_GetStringLineCnt(const char *str)
{
  char e;
  uint8_t line_cnt = 1;
  if ( str == NULL )
    return 0;
  for(;;)
  {
    e = *str;
    if ( e == '\0' )
      break;
    str++;
    if ( e == '\n' )
      line_cnt++;
  }
  return line_cnt;
}

/*
    Assumes strings, separated by '\n' in "str".
    Returns the string at index "line_idx". First strng has line_idx = 0
    Example:
      Returns "xyz" for line_idx = 1 with str = "abc\nxyz"
    Support both UTF8 and normal strings.
*/
const char *u8x8_GetStringLineStart(uint8_t line_idx, const char *str )
{
  char e;
  uint8_t line_cnt = 1;
  
  if ( line_idx == 0 )
    return str;

  for(;;)
  {
    e = *str;
    if ( e == '\0' )
      break;
    str++;
    if ( e == '\n' )
    {
      if ( line_cnt == line_idx )
  return str;
      line_cnt++;
    }
  }
  return NULL;  /* line not found */
}

/* copy until first '\n' or '\0' in str */
/* Important: There is no string overflow check, ensure */
/* that the destination buffer is large enough */
void u8x8_CopyStringLine(char *dest, uint8_t line_idx, const char *str)
{
  if ( dest == NULL )
    return;
  str = u8x8_GetStringLineStart( line_idx, str );
  if ( str != NULL )
  {
    for(;;)
    {
      if ( *str == '\n' || *str == '\0' )
  break;
      *dest = *str;
      dest++;
      str++;
    }
  }
  *dest = '\0';
}


void setup() {
  display.begin();
  display.setRotation(0);
  display.fillScreen(ILI9341_BLACK);
  u8g2_for_adafruit_gfx.begin(display);                 // connect u8g2 procedures to Adafruit GFX

  u8g2_for_adafruit_gfx.setFont(FONT);
  u8g2_for_adafruit_gfx.setForegroundColor(ILI9341_WHITE);      // apply Adafruit GFX color
  
  /* calculate the length of the text in lines */
  total_lines = u8x8_GetStringLineCnt(c_str);
  
  /* get the height of the glyphs */
  //glyph_height = u8g2_for_adafruit_gfx.getMaxCharHeight();
  glyph_height = u8g2_for_adafruit_gfx.u8g2.font_info.max_char_height;
  glyph_width = u8g2_for_adafruit_gfx.u8g2.font_info.max_char_width;

  /* calculate the height of the text in pixel */
  total_height = (uint16_t)total_lines * (uint16_t)glyph_height;
  

  /* calculate how many lines must be drawn on the screen */
  lines_per_draw = display.height() / glyph_height;
  lines_per_draw += 2;

  /* start at the top of the text */
  top_window_pos = 0;
  
}

void loop() {  

  start_line = top_window_pos / glyph_height;
  top_offset = top_window_pos % glyph_height;
  
  line_cnt = total_lines - start_line;
  if ( line_cnt > lines_per_draw )
    line_cnt = lines_per_draw;

  //display.clearDisplay();                               // clear the graphcis buffer  
  
  for( i = 0; i < line_cnt; i++ )
  {
    /* copy a line of the text to the local buffer */
    u8x8_CopyStringLine(buf, i+start_line, c_str);
    
    /* draw the content of the local buffer */
    display.fillRect(0, i*glyph_height-top_offset, line_cnt*glyph_width, glyph_height, ILI9341_BLACK);
    u8g2_for_adafruit_gfx.drawUTF8(0, i*glyph_height-top_offset +glyph_height, buf);

    
  }
  
  //display.display();                                    // make everything visible
  delay(SCROLL_DELAY);
  top_window_pos += SCROLL_DELTA;  
}