#include<stdio.h>
#include<string.h>
#include<stdlib.h>
// Function to search for a label in the symbol table
int searchSymtab(char label[]){
    char symbol[10];
    //It uses a file (symtab) to read symbol-value pairs.
    FILE *symtab;
    int value;
    symtab=fopen("symtab.txt","r");
    //reads the file until end of the file
    while(!feof(symtab)){
        fscanf(symtab,"%s %d",symbol,&value);
        //If any of the strings are found it returns 1
        if(!strcmp(label,symbol)){
			fclose(symtab);
            return 1;
        }
    }
	fclose(symtab);
	
    return 0;
}
// Function to search for an opcode in the opcode table
int searchOpcode(char opcode[]){
	//uses a file to read opcodes
	FILE *optab;
	char op[10];
	optab = fopen("optab.txt","r");
	//reads the file until end of the file
	while(!feof(optab)){
		fscanf(optab,"%s",op);
		//If any of the strings are found it returns 1
		if(!strcmp(op,opcode)){
			fclose(optab);
			return 1;
		}
	}
	fclose(optab);
	return 0;
}
int main(){
	//declares pointers
	FILE *in,*out,*sym;
	//Starting address Location Counter op..intiger
	int sA,locctr,op;
	char label[10],opcode[10],operand[10];
	in = fopen("input.txt","r");
	out = fopen("intermediate.txt","w");
	sym = fopen("symtab.txt","w");
	fclose(sym);
	if(!feof(in)){
		fscanf(in,"%s%s%d",label,opcode,&op);
		if(!strcmp(opcode,"START")){
			sA=op;
			locctr=op;
			fprintf(out,"%s %s %s %d\n"," - ",label,opcode,op);
			
		}
		else{
			locctr=0;
			sA=0;
		}
	}
	while(!feof(in)){
		
		fscanf(in,"%s%s%s",label,opcode,operand);
		
		fprintf(out,"%d %s %s %s\n",locctr,label,opcode,operand);
		if(!strcmp(label,"**")){
			if(!strcmp(opcode,"END")){
				break;
				}
			locctr+=3;
			
		}
		else{
			if(searchSymtab(label)){
				printf("Symbol Error\n");
			}else{
				if(searchOpcode(opcode)){
					locctr+=3;
				}
				else if(!strcmp(opcode,"WORD")){
					sym = fopen("symtab.txt","a");
					fprintf(sym,"%s %d\n",label,locctr);
					fclose(sym);
					locctr+=3;
					
				}
				else if(!strcmp(opcode,"RESW")){
					sym = fopen("symtab.txt","a");
					fprintf(sym,"%s %d\n",label,locctr);
					fclose(sym);
					op=	atoi(operand);
					op*=3;
					locctr+=op;
					
				}
				else if(!strcmp(opcode,"BYTE")){
					sym = fopen("symtab.txt","a");
					fprintf(sym,"%s %d\n",label,locctr);
					fclose(sym);
					locctr+=(strlen(operand)-3);
				}
				
				else{
					printf("opcode error");
				}
			}
		}
		
	}
	printf("length = %d\n",locctr-sA);
	fclose(in);
	fclose(out);
	return 0;
			
}