#include <algorithm>

#include <Adafruit_GFX.h>
#include <Fonts/FreeMonoBold9pt7b.h>
#include <Font_din1451e.h>
#include <Fonts/Org_01.h>

#include "epaper.h"

static GxEPD2_DISPLAY_CLASS<GxEPD2_DRIVER_CLASS, MAX_HEIGHT(GxEPD2_DRIVER_CLASS)>
	display(GxEPD2_DRIVER_CLASS(/*CS=5*/ EPD_CS, /*DC=*/ 17, /*RST=*/ 16, /*BUSY=*/ 4));

void epaper_init(void)
{
    display.init();
}

void epaper_test(void)
{
  display.setRotation(0);
  display.setFont(&FreeMonoBold9pt7b);
  display.setTextColor(GxEPD_BLACK);
  int16_t tbx, tby; uint16_t tbw, tbh;
  display.getTextBounds("Hello World!", 0, 0, &tbx, &tby, &tbw, &tbh);
  // center the bounding box by transposition of the origin:
  uint16_t x = ((display.width() - tbw) / 2) - tbx;
  uint16_t y = ((display.height() - tbh) / 2) - tby;
  display.setFullWindow();
  display.firstPage();
  do
  {
    display.fillScreen(GxEPD_WHITE);
    display.setCursor(x, y);
    display.print("Hello World!");
    for(int i = -1; i <= 1; i++) {
      display.drawCircle(display.width()/2, display.height()/2, tbw*15/10/2+i, GxEPD_RED);
    }
  }
  while (display.nextPage());

  Serial.println(F("Init done. Display going to powersave…"));

  display.hibernate();
}

void epaper_draw_and_hibernate(epaper_callback cb)
{
  display.setRotation(0);
  display.setFullWindow();
  display.firstPage();

  do {
    cb(&display);
  } while(display.nextPage());

  display.hibernate();
}

#if 0
// find minimum and maximum values in a vector. NaN is ignored.
template<typename T>
void minmax(const std::vector<T> &vec, T *min, T *max)
{
  bool first = true;

  // fallback values: will be used if the vector is empty or only consists of NaNs
  *min = 0;
  *max = 1;

  for(auto &v: vec) {
    if(isnan(v)) {
      continue;
    }

    if(first) {
      *min = *max = v;
      first = false;
      continue;
    }

    if(v < *min) {
      *min = v;
    }

    if(v > *max) {
      *max = v;
    }
  }
}

void epaper_plot(uint16_t x, uint16_t y, uint16_t w, uint16_t h, timeseries_t *timeseries, uint32_t time_tick_interval)
{
  char s[32];

  uint32_t trange = timeseries->tend - timeseries->tstart;
  uint32_t tstep = timeseries->interval;

  if(trange == 0) {
    trange = 3600;
  }

  float vmin, vmax;
  minmax(timeseries->data, &vmin, &vmax);

  float vrange = vmax - vmin;

  Serial.print(F("Value range: "));
  Serial.print(vrange);
  Serial.print(F(" – Min: "));
  Serial.print(vmin);
  Serial.print(F(" – Max: "));
  Serial.println(vmax);

  if(vrange == 0.0f) {
    vrange = 1.0f;
  }

  // add some margin
  vmax += vrange * 0.05f;
  vmin -= vrange * 0.05f;
  vrange = vmax - vmin;

  bool firstpoint = true;
  uint16_t last_x;
  uint16_t last_y;

  // set font for axis labels
  display.setFont(&Org_01);
  display.setTextColor(GxEPD_BLACK);
  int16_t tbx, tby; uint16_t tbw, tbh;
  display.getTextBounds("20:48", 0, 0, &tbx, &tby, &tbw, &tbh);

  uint16_t label_height = tbh;

  // actual graph area
  uint16_t plot_x = x + 150;
  uint16_t plot_y = y;
  uint16_t plot_w = w - 150;
  uint16_t plot_h = h - label_height - 5;

  // determine vertical tick interval
  uint16_t max_vert_tick_count = plot_h / (label_height + 5);
  float min_vert_tick_step = vrange / (float)max_vert_tick_count;

  static const PROGMEM float TEST_FACTORS[] = {1.0f, 0.5f, 0.25f, 0.1f};

  float scale = 1e3f;
  float accepted_scale = scale;
  bool scale_found = false;

  while((scale > 1e-3f) && !scale_found) {
    float tmp_scale;

    for(auto factor: TEST_FACTORS) {
      tmp_scale = scale * factor;
      if(tmp_scale < min_vert_tick_step) {
        scale_found = true;
        break;
      }
      accepted_scale = tmp_scale;
    }
    scale = tmp_scale;
  }

  /* Start drawing */

  display.drawRect(plot_x, plot_y, plot_w, plot_h, GxEPD_BLACK);

  // draw vertical grid lines
  for(uint64_t reltime = ((timeseries->tstart / time_tick_interval) + 1) * time_tick_interval - timeseries->tstart;
      reltime < trange;
      reltime += time_tick_interval) {
      uint16_t px = plot_x + plot_w * reltime / trange;
      uint16_t py = plot_y;
      uint16_t ph = plot_h + 2;

      display.drawFastVLine(px, py, ph, GxEPD_BLACK);

      time_t t = reltime + timeseries->tstart;
      tm *gmt = gmtime(&t);
      if(t % 86400 == 0) {
        strftime(s, sizeof(s), "%d.%m.", gmt);
      } else {
        strftime(s, sizeof(s), "%H:%M", gmt);
      }

      display.getTextBounds(s, 0, 0, &tbx, &tby, &tbw, &tbh);

      display.setCursor(px - tbw/2, y+h + tby);
      display.print(s);
  }

  // draw horizontal grid lines
  for(float tick_val = (float)((int)(vmin / accepted_scale) + 1) * accepted_scale;
      tick_val < vmax;
      tick_val += accepted_scale) {

    uint16_t py = plot_y - (float)plot_h * (tick_val - vmax) / vrange;
    uint16_t px = plot_x - 3;
    uint16_t pw = plot_w + 3;

    display.drawFastHLine(px, py, pw, GxEPD_BLACK);

    snprintf(s, sizeof(s), timeseries->format, tick_val);

    display.getTextBounds(s, 0, 0, &tbx, &tby, &tbw, &tbh);

    display.setCursor(px - tbw - 2, py + tby + tbh);
    display.print(s);
  }

  size_t i = 0;
  for(uint32_t reltime = 0; reltime < trange; reltime += tstep) {
    if(i >= timeseries->data.size()) {
      Serial.println(F("Index out of range! Time range does not match data points."));
      break;
    }

    /*Serial.print(F("Processing data point at dt="));
    Serial.print(reltime);
    Serial.print(F("… "));*/

    float val = timeseries->data[i++];
    if(isnan(val)) {
      //Serial.println(F("Skipping NaN!"));

      firstpoint = true;
      continue;
    }

    uint16_t px = plot_x + plot_w * reltime / trange;
    uint16_t py = plot_y - (float)plot_h * (val - vmax) / vrange;

    if(!firstpoint) {
      /*Serial.print(F("Line from ("));
      Serial.print(last_x);
      Serial.print(F(","));
      Serial.print(last_y);
      Serial.print(F(") to ("));
      Serial.print(px);
      Serial.print(F(","));
      Serial.print(py);
      Serial.println(F(")."));*/

      display.drawLine(last_x, last_y, px, py, GxEPD_RED);

      // draw it again, 1px below, to give it more weight
      display.drawLine(last_x, last_y+1, px, py+1, GxEPD_RED);
    } else {
      //Serial.println(F("First point, not drawn."));
      firstpoint = false;
    }

    last_x = px;
    last_y = py;
  }

  /* Draw large current value + unit */

  size_t cur_val_idx = timeseries->data.size() - 1;
  while((cur_val_idx > 0) && isnan(timeseries->data[cur_val_idx])) {
    cur_val_idx--;
  }

  float current_value = timeseries->data[cur_val_idx];

  display.setFont(&din1451e24pt7b);
  display.setTextColor(GxEPD_RED);

  char fmt[16];

  snprintf(fmt, sizeof(fmt), "%s %%s", timeseries->format);
  snprintf(s, sizeof(s), fmt, current_value, timeseries->unit);

  display.getTextBounds(s, 0, 0, &tbx, &tby, &tbw, &tbh);

  display.setCursor(plot_x - tbw - 35, plot_y + plot_h/2 - tby - tbh/2 - 5);
  display.print(s);

  uint16_t large_text_height = tbh;

  time_t t = timeseries->tstart + trange * cur_val_idx / timeseries->data.size();
  tm *gmt = gmtime(&t);
  strftime(s, sizeof(s), "%Y-%m-%d %H:%M", gmt);

  display.setFont(&Org_01);

  display.getTextBounds(s, 0, 0, &tbx, &tby, &tbw, &tbh);

  display.setCursor(plot_x - tbw - 35, plot_y + plot_h/2 - tby + large_text_height/2 + 5);
  display.print(s);
}
#endif