#include <algorithm>
#include <fstream>
#include <stdexcept>
#include <cassert>
#include <cmath>
#include <cinttypes>
#include <termio.h>

#include "buffer.h"
#include "manager.h"
#include "throw.h"

using namespace std;


Buffer::Buffer(Manager *manager)
	:manager(manager){}

Buffer::Buffer(Manager *manager,bool singleLineMode)
	:manager(manager),singleLineMode(singleLineMode){}

void Buffer::handleCommand(const Command &cmd){
	//TODO: optimise the relayoutScreen's in this function

	if(cmd[0]=="open_file"){
		const string &fname=cmd[1];
		filename=fname;
		ifstream file(fname);
		if(!file){
			manager->receive({"error","Cannot open file '"+fname+"'"});
			return;
		}
		i64 nread=tb.read(file);
		cursor.line=0;
		cursor.x=0;
		screen.clear();
		dirty=false;
		manager->receive({"info","Opened, read "+to_string(nread)+" characters"});
	} else if(cmd[0]=="save_file"){
		if(filename.size()==0){
			manager->receive({"save_prompt"});
			return;
		}
		ofstream file(filename);
		if(!file){
			manager->receive({"error","Cannot open file '"+filename+"' for writing"});
			return;
		}
		i64 nwritten=tb.write(file);
		dirty=false;
		manager->receive({"info","Saved, written "+to_string(nwritten)+" characters"});
	} else if(cmd[0]=="insert_char"){
		char c=cmd[1][0];
		assert(c!='\n');
		tb.insert(cursor.line,cursor.x,cmd[1][0]);
		dirty=true;
		cursor.x++;
		relayoutScreen();
		if(findCursorInScreen().x==-1){
			screen.erase(screen.begin());
			relayoutScreen();
		}
	} else if(cmd[0]=="insert_newline"){
		tb.insert(cursor.line,cursor.x,'\n');
		dirty=true;
		cursor.x=0;
		cursor.line++;
		relayoutScreen();
		if(findCursorInScreen().x==-1){
			screen.erase(screen.begin());
			relayoutScreen();
		}
	} else if(cmd[0]=="delete_backward"){
		if(cursor.x==0&&cursor.line==0){
			bel();
			return;
		}
		if(cursor.x>0){
			cursor.x--;
			tb.erase(cursor.line,cursor.x);
		} else {
			cursor.line--;
			cursor.x=tb.lineLen(cursor.line);
			tb.erase(cursor.line,cursor.x);
		}
		dirty=true;
		relayoutScreen();
		if(findCursorInScreen().x==-1){
			scrollUp();
		} else {
			relayoutScreen();
		}
	} else if(cmd[0]=="delete_forward"){
		if(cursor.line==tb.numLines()-1&&cursor.x==tb.lineLen(cursor.line)){
			bel();
			return;
		}
		tb.erase(cursor.line,cursor.x);
		dirty=true;
		relayoutScreen();
	} else if(cmd[0]=="move_forward"){
		if(cursor.line==tb.numLines()-1&&cursor.x==tb.lineLen(cursor.line)){
			bel();
			return;
		}
		if(cursor.x==tb.lineLen(cursor.line)){
			cursor.x=0;
			cursor.line++;
		} else {
			cursor.x++;
		}
		if(findCursorInScreen().x==-1){
			screen.erase(screen.begin());
			relayoutScreen();
		}
	} else if(cmd[0]=="move_backward"){
		if(cursor.line==0&&cursor.x==0){
			bel();
			return;
		}
		if(cursor.x==0){
			cursor.line--;
			cursor.x=tb.lineLen(cursor.line);
		} else {
			cursor.x--;
		}
		if(findCursorInScreen().x==-1){
			scrollUp();
		}
	} else if(cmd[0]=="move_downward"){
		Screenpos sp=findCursorInScreen();
		if(sp.x==-1){
			bel();
			return;
		}
		if(sp.y==(i64)screen.size()-1){
			if(screen[sp.y].line==tb.numLines()-1&&
			   (screen[sp.y].cells.size()==0
					?tb.lineLen(screen[sp.y].line)==0
					:screen[sp.y].cells.back().linex==tb.lineLen(screen[sp.y].line)-1)){
				//so screen[sp.y] contains the end of that logical line
				if(cursor.x==tb.lineLen(screen[sp.y].line)){
					bel();
				} else {
					cursor.x=tb.lineLen(screen[sp.y].line);
				}
				return;
			}
			screen.erase(screen.begin());
			relayoutScreen();
		} else {
			sp.y++;
		}
		cursor.line=screen[sp.y].line;
		if(sp.x>=(i64)screen[sp.y].cells.size()){
			if(screen[sp.y].cells.size()==0)cursor.x=0;
			else {
				cursor.x=screen[sp.y].cells.back().linex;
				//Now if we would've landed *after* the end of the line, go there.
				if(cursor.x==tb.lineLen(cursor.line)-1)cursor.x++;
			}
		} else {
			cursor.x=screen[sp.y].cells[sp.x].linex;
		}
	} else if(cmd[0]=="move_upward"){
		Screenpos sp=findCursorInScreen();
		if(sp.x==-1){
			bel();
			return;
		}
		if(sp.y==0){
			if(screen[sp.y].line==0&&screen[sp.y].part==0){
				if(cursor.x==0)bel();
				else cursor.x=0;
				return;
			}
			scrollUp();
		} else {
			sp.y--;
		}
		cursor.line=screen[sp.y].line;
		if(sp.x>=(i64)screen[sp.y].cells.size()){
			if(screen[sp.y].cells.size()==0)cursor.x=0;
			else {
				cursor.x=screen[sp.y].cells.back().linex;
				//Now if we would've landed *after* the end of the line, go there.
				if(cursor.x==tb.lineLen(cursor.line)-1)cursor.x++;
			}
		} else {
			cursor.x=screen[sp.y].cells[sp.x].linex;
		}
	} else if(cmd[0]=="move_pagedown"){
		Screenpos sp=findCursorInScreen();
		if(sp.x==-1||screen.size()==0){
			bel();
			return;
		}
		i64 lastLine=screen.back().line;
		i64 lastX=screen.back().cells.size()==0 ? screen.back().fromx : screen.back().cells.back().linex+1;
		i64 newTopLine,newTopPart;
		if(lastX>=tb.lineLen(lastLine)){
			if(lastLine==tb.numLines()-1){
				cursor.line=lastLine;
				cursor.x=lastX;
				return;
			}
			newTopLine=lastLine+1;
			newTopPart=0;
		} else {
			newTopLine=lastLine;
			newTopPart=screen.back().part+1;
		}
		vector<ScreenLine> screenCopy=screen;
		renewLayout(newTopLine,newTopPart,lastWidth,lastHeight);
		if((i64)screen.size()<lastHeight){
			i64 gap=lastHeight-screen.size();
			screen.insert(screen.begin(),screenCopy.begin()+(screenCopy.size()-gap),screenCopy.end());
			cursor.line=screen.back().line;
			if(screen.back().cells.size()==0)cursor.x=screen.back().fromx;
			else cursor.x=screen.back().cells.back().linex+1;
		} else {
			cursor.line=screen[sp.y].line;
			if((i64)screen[sp.y].cells.size()<sp.x){
				if(screen[sp.y].cells.size()==0)cursor.x=screen[sp.y].fromx;
				else cursor.x=screen[sp.y].cells.back().linex+1;
			}
		}
	} else if(cmd[0]=="cancel"){
		bel(); //nothing to cancel, apparently
	} else {
		cerr<<"Unknown command: "<<cmd[0]<<endl;
		bel();
	}
}

void Buffer::receive(const Command &cmd){
	handleCommand(cmd);
	// cerr<<"New cursor is (line="<<cursor.line<<", x="<<cursor.x<<")"<<endl;
}

static string showChar(char c){
	if(c>=32&&c<127)return {c};
	return {'\\','x',
	        "0123456789abcdef"[(unsigned char)c/16],
	        "0123456789abcdef"[(unsigned char)c%16]};
}

vector<Buffer::ScreenLine> Buffer::layoutLine(const string &line,i64 linenum,i64 width){
	assert(width>=5); //5 == (maximum char repr width) + 1, where the 1 is an extra column on the right
	if(line.size()==0){
		return {{linenum,0,0,{}}};
	}
	vector<ScreenLine> layout;
	vector<Cell> cur;
	i64 x=0;
	i64 linepart=0,fromx=0;
	for(i64 i=0;i<(i64)line.size();i++){
		char c=line[i];
		string repr;
		bool special=false;
		if(c=='\t'){
			repr=string(4-cur.size()%4,' ');
		} else {
			repr=showChar(c);
			special=repr.size()>1;
		}
		assert(repr.size()>0);
		if(x+(i64)repr.size()>=width){
			layout.push_back({linenum,linepart,fromx,move(cur)});
			cur.clear();
			linepart++;
			fromx=i;
			x=0;
		}
		Cell cell={'\0',special,i};
		for(char rc : repr){
			cell.c=rc;
			cur.push_back(cell);
			x++;
		}
	}
	if(cur.size()>0)layout.push_back({linenum,linepart,fromx,move(cur)});
	return layout;
}

//Takes width without gutter
void Buffer::performInitialLayout(i64 width,i64 height){
	assert(width>0&&height>0);
	const i64 targetCursorScreenY=height/2;

	screen.clear();
	if(tb.numLines()==0){
		screen.push_back({0,0,0,{}});
		return;
	}

	assert(cursor.line>=0&&cursor.x>=0&&
	       cursor.line<tb.numLines()&&cursor.x<=tb.lineLen(cursor.line));

	//Layout the line the cursor is on.
	screen=layoutLine(tb[cursor.line],cursor.line,width);
	i64 cursorScreenY=0;
	while(cursorScreenY+1<(i64)screen.size()&&screen[cursorScreenY+1].fromx<=cursor.x){
		cursorScreenY++;
	}

	//First, layout lines above the cursor line until the cursor is at or past halfway
	//the screen, or the buffer is exhausted.
	i64 topLine=cursor.line-1; //logical line
	while(topLine>=0&&cursorScreenY<targetCursorScreenY){
		vector<ScreenLine> layout=layoutLine(tb[topLine],topLine,width);
		screen.insert(screen.begin(),layout.begin(),layout.end());
		cursorScreenY+=layout.size();
		topLine--;
	}

	//Remove any lines from the top until the cursor is exactly halfway the screen.
	//Store the removed lines in `spliced`.
	vector<ScreenLine> spliced;
	if(cursorScreenY>targetCursorScreenY){
		for(i64 i=0;i<cursorScreenY-targetCursorScreenY;i++){
			spliced.push_back(move(screen[i]));
		}
		screen.erase(screen.begin(),screen.begin()+(cursorScreenY-targetCursorScreenY));
	}

	//Then, layout lines *under* the cursor line until the screen is full, or the buffer is
	//exhausted.
	i64 bottomLine=cursor.line+1; //logical line
	while(bottomLine<tb.numLines()&&(i64)screen.size()<height){
		vector<ScreenLine> layout=layoutLine(tb[bottomLine],bottomLine,width);
		screen.insert(screen.end(),layout.begin(),layout.end());
		// cerr<<"Added bottomLine="<<bottomLine<<" (tb.numLines()="<<tb.numLines()<<")"<<endl;
		bottomLine++;
	}
	if((i64)screen.size()>height){
		//Oops, we overran a bit. Prune the end so that we fill the screen exactly.
		screen.resize(height);
	} else if((i64)screen.size()<height){
		//We didn't even manage to fill the whole screen. Try to fill up the gap, first with the
		//lines in `spliced`, and then with extra logical lines from the textblob.
		i64 endgap=height-screen.size();
		if(endgap<=(i64)spliced.size()){
			//`spliced` contains enough lines to fill the gap.
			screen.insert(screen.begin(),spliced.begin()+(spliced.size()-endgap),spliced.end());
		} else {
			//We'll have to pull in some more lines from the textblob.
			screen.insert(screen.begin(),spliced.begin(),spliced.end());
			while(topLine>=0&&(i64)screen.size()<height){
				vector<ScreenLine> layout=layoutLine(tb[topLine],topLine,width);
				screen.insert(screen.begin(),layout.begin(),layout.end());
				topLine--;
			}
			if((i64)screen.size()>height){
				//Oops, we overran a bit. Prune the end so that we fill the screen exactly.
				screen.resize(height);
			}
		}
	}
}

//Takes width without gutter
void Buffer::renewLayout(i64 topLine,i64 topPart,i64 width,i64 height){
	assert(width>0&&height>0);
	assert(topLine>=0&&topPart>=0);

	screen.clear();
	if(tb.numLines()==0){
		screen.push_back({0,0,0,{}});
		return;
	}

	screen=layoutLine(tb.getLine(topLine),topLine,width);
	if(topPart>0)screen.erase(screen.begin(),screen.begin()+topPart);

	i64 bottomLine=topLine+1;
	while(bottomLine<tb.numLines()&&(i64)screen.size()<height){
		vector<ScreenLine> layout=layoutLine(tb[bottomLine],bottomLine,width);
		screen.insert(screen.end(),layout.begin(),layout.end());
		bottomLine++;
	}

	if((i64)screen.size()>height){
		screen.resize(height);
	}
}

void Buffer::relayoutScreen(){
	renewLayout(screen[0].line,screen[0].part,lastWidth,lastHeight);
}

void Buffer::scrollUp(){
	assert(screen.size()!=0);
	if(screen[0].part>0){
		renewLayout(screen[0].line,screen[0].part-1,lastWidth,lastHeight);
		return;
	}
	if(screen[0].line==0){
		bel();
		return;
	}

	i64 topLine=screen[0].line-1;
	screen=layoutLine(tb.getLine(topLine),topLine,lastWidth);
	renewLayout(screen.back().line,screen.back().part,lastWidth,lastHeight);
}

//Returns {-1,-1} if not found
Buffer::Screenpos Buffer::findCursorInScreen() const {
	if(screen.size()==0)return {-1,-1};
	if(cursor.x>tb.lineLen(cursor.line)){
		THROW("Invalid cursor position: past end of line");
	}
	auto lineit=lower_bound(screen.begin(),screen.end(),cursor.line,[this](const ScreenLine &sl,i64 line){
		return sl.line<line||(sl.line==line&&sl.fromx<=cursor.x);
	});
	if(lineit==screen.begin())return {-1,-1};

	const i64 y=lineit==screen.end()?screen.size()-1:distance(screen.begin(),lineit)-1;
	if(screen[y].line!=cursor.line)return {-1,-1}; //cursor is below screen on a new line
	const vector<Cell> &cells=screen[y].cells;
	auto chrit=lower_bound(cells.begin(),cells.end(),cursor.x,[](const Cell &cell,i64 x){
		return cell.linex<x;
	});
	const i64 x=distance(cells.begin(),chrit);
	assert(x<=(i64)cells.size());
	if(x<(i64)cells.size())return {y,x};
	if(cells.size()==0){
		return {y,0};
	}
	if(cells.back().linex==cursor.x-1&&cursor.x==tb.lineLen(cursor.line)){
		return {y,x};
	} else {
		return {-1,-1};
	}
}

static i64 numberWidth(i64 number){
	if(number<0)return 1+numberWidth(-number);
	if(number==0)return 1;
	return (i64)log10(number)+1;
}

void Buffer::show(i64 atx,i64 aty,i64 width,i64 height){
	static const Style gutterStyle={3,9,false,false};
	static const Style gutterContinuationStyle={1,9,false,true};
	static const Style textStyle={9,9,false,false};
	static const Style specialStyle={5,9,false,false};

	i64 gutterWidth=singleLineMode ? 0 : numberWidth(tb.numLines())+2;
	i64 newWidth=width-gutterWidth;
	if(newWidth!=lastWidth||height!=lastHeight||screen.size()==0){
		if(lastWidth==-1)performInitialLayout(newWidth,height);
		else renewLayout(screen[0].line,screen[0].part,newWidth,height);
		lastWidth=newWidth;
		lastHeight=height;
	}

	setstyle(&textStyle);
	fillrect(atx,aty,width,height,' ');

	pushcursor();
	i64 y;
	i64 curScreenX=-1,curScreenY=-1;
	// cerr<<"Buffer::show: screen.size()="<<screen.size()<<endl;
	for(y=0;y<(i64)screen.size();y++){
		if(!singleLineMode){
			if(screen[y].fromx==0){
				setstyle(&gutterStyle);
				moveto(atx+gutterWidth-1-numberWidth(screen[y].line+1),aty+y);
				tprintf("%" PRIi64,screen[y].line+1);
			} else if(y==0){
				setstyle(&gutterContinuationStyle);
				moveto(atx+gutterWidth-2-numberWidth(screen[y].line+1),aty+y);
				tprintf("^%" PRIi64,screen[y].line+1);
			}
		}

		moveto(atx+gutterWidth,aty+y);

		i64 screenX=atx+gutterWidth;
		setstyle(&textStyle);
		for(const Cell &cell : screen[y].cells){
			if(cell.special)setstyle(&specialStyle);
			else setstyle(&textStyle);
			tputc(cell.c);
			if(curScreenX==-1&&cell.linex==cursor.x&&screen[y].line==cursor.line){
				curScreenX=screenX;
				curScreenY=aty+y;
			}
			screenX++;
		}

		//Maybe the cursor should be positioned AFTER this line
		if(curScreenX==-1&&screen[y].line==cursor.line&&cursor.x==tb.lineLen(cursor.line)&&
		   (y==(i64)screen.size()-1||screen[y+1].line>cursor.line)){
			if(screenX==atx+width)curScreenX=screenX-1;
			else curScreenX=screenX;
			curScreenY=aty+y;
		}
	}
	setstyle(&textStyle);
	if(y<height)fillrect(atx,aty+y,width,height-y,' ');
	popcursor();
	if(curScreenX!=-1){
		moveto(curScreenX,curScreenY);
	}
}

string Buffer::getText() const {
	if(singleLineMode){
		string line=tb.fullText();
		line.pop_back();
		return line;
	} else {
		return tb.fullText();
	}
}

bool Buffer::isDirty() const {
	return dirty;
}