#include<iostream>
#include<cmath>
#include<thread>
#include<vector>
#include<chrono>
using namespace std;

float *table;
const int values_per_degree = 100000;
const int tablesize = values_per_degree * 360;

void partial_init(size_t start, size_t stop){
	for(unsigned int i = start; i < stop; i++){
		float degrees = (float)i / values_per_degree;
		table[i] = sinf(degrees / (180.0 / M_PI));
	}	
}

void fastmath_init(){
	// Make the actual table
	table = new float[tablesize];
	int threads = 8;

	vector<thread*> threadlist;
	for(int i = 0; i < threads; i++){
		threadlist.push_back(new thread(partial_init, i * (tablesize/8), (i+1) * (tablesize/8)));
	}
	for(auto t : threadlist)
		t->join();

	// Wait for all those threads to finish!
}


float fast_sin(float degrees){
	while(degrees < 0)
		degrees += 360.0;
	return table[(int)(degrees * values_per_degree) % tablesize];  // table lookup goes here
}

float fast_cos(float degrees){
	return fast_sin(degrees + 90);
}

void fastmath_cleanup(){
	delete [] table;
}	


/* Minimal bar-making function
 * 	bar is a null-terminated string of 100 asterisks
 * 	Since it's null-terminated, a pointer partway through the string will be a 
 * 	pointer to a valid shorter null-terminated string of asterisks.  Kinda like
 * 	if you want to watch a half-hour movie, you could start watching a 2-hour
 * 	movie starting 1.5 hours in, and in half an hour you'd reach the end.
 */
const char* mkbar(int len){
	static const char *bar = "***************************************************************************************************";
	return bar + (100 - len);
}

int main(){
	/* Uncomment this next call once you have fastmath_init working */
	fastmath_init();
	/* 
	 * Uncomment this next loop once you have fast_sin working
	 * If it's working right, you should see a sin wave printed from this line */
	
	for(int i = -360; i < 720; i += 10)
		cout <<  mkbar(fast_sin(i) * 30 + 30) << "  " << fast_sin(i) << endl;
	

	/* This is a speed benchmark */

	float *testvals = new float[10000];
	for(int i = 0; i < 10000; i++)
		testvals[i] = (random() % 360000) / 1000.0;
	
	/*
	using namespace chrono;
	system_clock::time_point start = system_clock::now();
	float r;
	for(int i = 0; i < 100000; i++)
		for(int j = 0; j < 10000; j++)
			r += fast_sin(testvals[j] + i);	// Replace sinf with fast_sin once it works
	system_clock::time_point end = system_clock::now();
	duration<double> time_taken = end - start;
	cout << "Time taken:  " << time_taken.count() << " seconds" << endl;
	cout << r << endl;
	delete [] testvals;
	*/

	/* Uncomment this next loop once you've written fast_cos, to compare values with cosf */
	
	for(int i = 0; i < 360; i+= 15){
		cout << i << " " << cosf(i / (180.0 / M_PI)) << "\t" << fast_cos(i) << endl;
	}
	

	/* Uncomment this next call once you have fastmath_cleanup working */
	fastmath_cleanup();
	return 0;
}