#include <stdio.h>
#include <assert.h>
#include <gd.h>
#include <math.h>

#include "GdCharts.h"

void createChart(std::string filename, ChartPrices const &prices,
		 int width, int height)
{
  assert(width >= 1);
  assert(height >= 1);
  gdImagePtr im = gdImageCreate(width, height);
  assert(im);
  /*int background =*/ gdImageColorAllocate(im, 0, 0, 0);
  const int count = std::min((int)prices.size(), width);
  if (count)
    {
      const double newest = prices[0];
      const double oldest = prices[count - 1];
      double lowest = newest;
      double highest = newest;
      for (int i = 1; i < count; i++)
	{
	  double current = prices[i];
	  lowest = std::min(lowest, current);
	  highest = std::max(highest, current);
	}
      if (lowest == highest)
	{
	  highest = highest + 1;
	  lowest = lowest - 1;
	  // Technically this could still fail for large numbers!
	}
      int topColor;
      int bodyColor;
      if (oldest > newest)
	{ // Red
	  topColor = gdImageColorAllocate(im, 0xff, 0, 0);
	  bodyColor = gdImageColorAllocate(im, 0x80, 0x14, 0x14);
	}
      else if (oldest < newest)
	{ // Green
	  topColor = gdImageColorAllocate(im, 0, 0xff, 0);
	  bodyColor = gdImageColorAllocate(im, 0, 0x80, 0);
	}
      else
	{ // Grey
	  topColor = gdImageColorAllocate(im, 0xc0, 0xc0, 0xc0);
	  bodyColor = gdImageColorAllocate(im, 0x60, 0x60, 0x60);
	}
      for (int i = 0; i < count; i++)
	{
	  int lineTop = 
	    (int)((highest - prices[i]) / (highest - lowest) * height);
	  // Ideally we don't need this, but there might be a round off
	  // error.
	  if (lineTop < 0)
	    lineTop = 0;
	  else if (lineTop >= height)
	    lineTop = height - 1;
	  const int imageX = width - i - 1;
	  gdImageSetPixel(im, imageX, lineTop, topColor);
	  gdImageLine(im, imageX, lineTop + 1, imageX, height, bodyColor);
	}
    }
  FILE *file = fopen(filename.c_str(), "wb");
  assert(file);
  gdImageGif(im, file);
  fclose(file);
  gdImageDestroy(im);
};

#ifdef GD_CHARTS_UNIT_TEST

// Build with g++ -DGD_CHARTS_UNIT_TEST -lgd GdCharts.C

int main(int, char **)
{
  ChartPrices prices;
  for (int i = 0; i < 19; i++)
    prices.push_back(sin(i * 0.314159));
  prices.push_back(prices[0]);
  createChart("full_sine_wave.gif", prices, 20);
  createChart("quarter_sine_wave.gif", prices, 5);
  createChart("three_quarter_sine_wave.gif", prices, 15);
  createChart("extra_space.gif", prices, 30);
}

#endif