#include <M5StickC.h>
#include "Kernel.h"
#include "UI.h"
#include "Util.h"

int voltage_to_percent(float voltage);
void Battery_draw(int hwnd, int x, int y, int width, int height);

#define BATTERY_BARS                  4
#define BATTERY_TERMINAL_HEIGHT_PCNT 20
#define BATTERY_TERMINAL_WIDTH_PCNT   5
#define BATTERY_PADDING_PCNT          5

#define BATTERY_COLOUR                0x999999
#define BATTERY_LOW_COLOUR            0xAA0000
#define BATTERY_BAR_COLOUR            0xAAAAAA
#define BATTERY_BAR_LOW_COLOUR        0xFF0000

int battery_bars = -1;

int Battery(int pid, unsigned int signal)
{
  if (signal & SIGNAL_START)
  {
    Kernel_signal_mask(pid, SIGNAL_START | SIGNAL_STOP | SIGNAL_TICK);
    UI_create_window(&Battery_draw, 1);
  }
  if (signal & SIGNAL_STOP)
  {
    return 255;
  }
  if (signal & SIGNAL_TICK)
  {
    float vbat = M5.Axp.GetVbatData() * 1.1 / 1000;
    int percent = voltage_to_percent(vbat);
    int bars = floor((percent / (100.0 / BATTERY_BARS)) + 0.5);
    if (battery_bars != bars)
    {
      battery_bars = bars;
      Kernel_signal(SIGNAL_REDRAW);
    }
  }

  return 0;
}

void Battery_draw(int hwnd, int wnd_x, int wnd_y, int wnd_width, int wnd_height)
{
  // Draw terminal
  int terminal_width = wnd_width * (BATTERY_TERMINAL_WIDTH_PCNT / 100.0);
  int terminal_height = wnd_height * (BATTERY_TERMINAL_HEIGHT_PCNT / 100.0);
  M5.Lcd.fillRect(
    wnd_x,
    wnd_y + (wnd_height / 2) - (terminal_height / 2),
    terminal_width,
    terminal_height,
    battery_bars == 0 ? rgb_to_colour(BATTERY_LOW_COLOUR) : rgb_to_colour(BATTERY_COLOUR)
    );

  // Draw battery shell
  M5.Lcd.fillRect(
    wnd_x + terminal_width,
    wnd_y,
    wnd_width - terminal_width,
    wnd_height,
    battery_bars == 0 ? rgb_to_colour(BATTERY_LOW_COLOUR) : rgb_to_colour(BATTERY_COLOUR)
    );

  // Do some math
  int padding_horizontal = wnd_width * (BATTERY_PADDING_PCNT / 100.0);
  int padding_vertical = wnd_height * (BATTERY_PADDING_PCNT / 100.0);
  
  int bar_width = (wnd_width - terminal_width - 2 - (padding_horizontal * (BATTERY_BARS + 1))) / BATTERY_BARS;
  int bar_height = wnd_height - (padding_vertical * 2) - 2;

  int bar_x = wnd_x + wnd_width - 1 - padding_horizontal - bar_width;
  int bar_y = wnd_y + 1 + padding_vertical;

  // Draw battery bars
  int bars = battery_bars;
  Serial.printf("Drawing %d bars\n", bars);
  while (bars > 0)
  {
    M5.Lcd.fillRect(
      bar_x,
      bar_y,
      bar_width,
      bar_height,
      battery_bars == 0 ? rgb_to_colour(BATTERY_BAR_LOW_COLOUR) : rgb_to_colour(BATTERY_BAR_COLOUR)
      );
    bar_x -= (bar_width + padding_horizontal);
    bars--;
  }
}

int voltage_to_percent(float voltage)
{
  /*
    4.2 volts 100%
    4.1 about 90%
    4.0 about 80%
    3.9 about 60%
    3.8 about 40%
    3.7 about 20%
    3.6 empty for practical purposes
   */
  return ((voltage - 3.6) / (4.2-3.6)) * 100;
}