#define _GNU_SOURCE
#include <iostream>
#include <cstdarg>
#include <cstdlib>
#include <cstring>
#include <cassert>
#include <unistd.h>
#include "screenbuffer.h"

using namespace std;


static void initTerminal(){
	cout<<"\x1B[?1049h"  // start alternate screen
	      "\x1B[2J"  // clear screen
	      "\x1B[H"  // move to top left
	    <<flush;
}

static void deinitTerminal(){
	cout<<"\x1B[?1049l"  // end alternate screen
	    <<flush;
}


ScreenBuffer::ScreenBuffer(int W,int H)
		:W(W),H(H){
	screen=new char[W*H];
	prevscreen=new char[W*H];
	memset(screen,' ',W*H);
	memset(prevscreen,' ',W*H);
	initTerminal();
}

ScreenBuffer::~ScreenBuffer(){
	delete[] screen;
	delete[] prevscreen;
	deinitTerminal();
}

void ScreenBuffer::moveto(int x,int y){
	assert(x>=0&&x<W&&y>=0&&y<H);
	curx=x;
	cury=y;
}

void ScreenBuffer::printstr(const char *buf){
	int basex=curx;
	for(int i=0;buf[i];i++){
		if(buf[i]!='\n'){
			if(curx==W){
				if(cury==H-1){
					curx--;
					break;
				}
				curx=basex;
				cury++;
			}
			screen[W*cury+curx]=buf[i];
			curx++;
		} else {
			if(cury==H-1)break;
			curx=basex;
		}
	}

	if(curx==W){
		if(cury==H-1){
			curx--;
		} else {
			curx=basex;
			cury++;
		}
	}
}

int ScreenBuffer::printf_varargs(const char *format,va_list ap){
	char *buf;
	int ret=vasprintf(&buf,format,ap);
	assert(buf);
	printstr(buf);
	free(buf);
	return ret;
}

__attribute__((format (printf, 2, 3)))
int ScreenBuffer::printf(const char *format,...){
	va_list ap;
	va_start(ap,format);
	int ret=printf_varargs(format,ap);
	va_end(ap);
	return ret;
}

__attribute__((format (printf, 4, 5)))
int ScreenBuffer::mvprintf(int x,int y,const char *format,...){
	moveto(x,y);

	va_list ap;
	va_start(ap,format);
	int ret=printf_varargs(format,ap);
	va_end(ap);
	return ret;
}

void ScreenBuffer::draw(){
	bool changed[W*H];
	for(int i=0;i<W*H;i++){
		changed[i]=screen[i]!=prevscreen[i];
	}
	for(int y=0;y<H;y++){
		for(int x=1;x<W-1;x++){
			changed[W*y+x]|=changed[W*y+x-1]&changed[W*y+x+1];
		}
	}

	bool prepped=false;

	for(int y=0;y<H;y++){
		bool needtomove=true;
		for(int x=0;x<W;x++){
			if(!changed[W*y+x]){
				needtomove=true;
				continue;
			}
			if(!prepped){
				cout<<"\x1B[?25l";  // invisible cursor
				prepped=true;
			}
			if(needtomove){
				cout<<"\x1B["<<y+1<<';'<<x+1<<'H';
				needtomove=false;
			}
			cout.put(screen[W*y+x]);
		}
	}
	if(prepped){
		cout<<"\x1B[?12;25h"  // visible cursor
		    <<"\x1B["<<H<<';'<<W<<'H'  // move past screen
		    <<flush;
	}

	memcpy(prevscreen,screen,W*H);
}

void ScreenBuffer::emergencyDeinit(){
	static const char *str="\n\x1B[?1049l\x1B[12;25h^C\n";
	write(1,str,strlen(str));
}