import { AbstractParseTreeVisitor } from 'antlr4ts/tree/AbstractParseTreeVisitor';
import { LoopStmtContext, ProgramContext } from '../../client/src/generated/bfParser';
import { bfVisitor } from '../../client/src/generated/bfVisitor';
import {getTree} from './bfGrammar';
import { DiagnosticSeverity } from 'vscode-languageserver-types';

/**
 * Run BF code
 * @param text 
 * @param fn 
 * @param input 
 * @returns 
 */
export async function runBF(text:string,fn:string,input:string){
	//get tree and issues
	const {tree,issues} = getTree(text,fn);

	//get only errors
	const x = issues.filter(e=>e.type===DiagnosticSeverity.Error);
	//if any error, drop
	if(x.length>0) {
		throw Error('Errors exist');
	}
	// make visitor
	const vis = new BFExecutor(input);
	
	//visit the tree
	vis.visit(tree);

	//get output
	return vis.outputStr;
}


class BFExecutor
	extends AbstractParseTreeVisitor<void>
	implements bfVisitor<void> {

	/**
	 * 
	 * @param input Input string
	 * @param inputPtr Input pointer to start from
	 */
	constructor(protected input: string='', protected inputPtr: number = 0) {
		super();
	}
	/**
	 * The memory cells (Can work with negative cells this way)
	 */
    protected cells: Map<number, number> = new Map();
    /**
	 * Pointer
	 */
	protected ptr: number = 0;
	/** Output string */
	protected outputStrArray:string[]=[];

	/**
	 * Output string (Available only after visiting)
	 */
	public get outputStr(){
		return this.outputStrArray.join('');
	}


	defaultResult() {}

	visitLoopStmt(ctx:LoopStmtContext){
		while((this.cells.get(this.ptr)??0)!==0){
			this.visitChildren(ctx);
		}
	}
	visitPtrLeft() {
		
		--this.ptr;
	}
	visitPtrRight() {
		++this.ptr;
	}
	visitPtrIncr() {

    	const val = this.cells.get(this.ptr);
    	if (val === undefined) {
    		this.cells.set(this.ptr, 1);
		} else if(val===255){
			this.cells.delete(this.ptr);
		}else{
    		this.cells.set(this.ptr, val + 1);
    	}
	}
	visitPtrDecr() {
		// console.log('down',this.ptr,this.cells);

    	const val = this.cells.get(this.ptr);
    	if (val === undefined || val === 0) {
    		this.cells.set(this.ptr, 255);
    	} else if(val===1){
			this.cells.delete(this.ptr);
		}else{
    		this.cells.set(this.ptr, val - 1);
    	}
	}
	visitOutputStmt() {
		const val = this.cells.get(this.ptr)??0;
		const str = String.fromCharCode(val);
		// console.log('op',str);
		this.outputStrArray.push(str);
	}

	visitInputStmt(){
		//get char
		const char = this.input.charCodeAt(this.inputPtr)??0;
		//increment the input pointer after this
		this.inputPtr++;
		this.cells.set(this.ptr,char);
	}
}