/*
 * -----------------------------------------------------
 * CS2S03/SE2S03, October 2011
 * Assignment 4, Question 2
 * File: PE0615.cpp
 * -----------------------------------------------------
 * This program draws a stylized representation 
 * of a tree by using recursive decomposition.
 * -----------------------------------------------------
 */ 
 
#include <iostream>
#include <cmath>
#include "simpio.h"
#include "graphics.h"
#include "genlib.h"
#include "random.h"

using namespace std;

/* Constants Declaration*/
const double PI = 3.1415926535;
const double RATIO = 0.8;
const double ANGLE = 45;     // angle between two neighboring branches
const int MAX_LEVEL = 15;    // max level of recursion
const int MIN_LEVEL = 3;     // min level of recursion

/* Private function prototype */
void DrawTree(double x, double y, double theta, double len, int order);

/* Main program */
int main() 
{
    Randomize();
	InitGraphics();
	cout << "Program to draw a tree" << endl;
	// root position
	double x0 = GetWindowWidth() / 2;
	double y0 = 0.2;
	// trunk length
	double trunkLen = GetWindowHeight() * (1 - RATIO);
	DrawTree(x0, y0, 90, trunkLen, 0);

	return 0;
}

/*
 * Function: DrawTree
 * Usage: DrawTree(x, y, theta, len, order);
 * ---------------------------------------------------------------------------------
 *
 * The function draws a tree at root position (x, y) with trunk length *len* at the
 * angle *theta* (degrees) with the horizontal line.
 * 
 * The decision to branch is made randomly at each step of the process, so the tree is
 * asymmetric, like trees in the nature. It branches at least MIN_LEVEL times and at
 * most MAX_LEVEL times.
 * ---------------------------------------------------------------------------------
 */

void DrawTree(double x, double y, double theta, double len, int order) {
	
	// draw the trunk
	MovePen(x, y);
    double radian = (theta / 180) * PI;
    double dx = len * cos(radian);
    double dy = len * sin(radian);
    DrawLine(dx, dy);

	if (order > RandomInteger(MIN_LEVEL, MAX_LEVEL)) return;
	
    // trunk length for subtrees
	double subLen = len * RATIO;
	// draw two subtrees at the top the trunk
	DrawTree(x + dx, y + dy, theta + ANGLE / 2.0, subLen, order + 1);
	DrawTree(x + dx, y + dy, theta - ANGLE / 2.0, subLen, order + 1);
}