// This file is part of www.nand2tetris.org
// and the book "The Elements of Computing Systems"
// by Nisan and Schocken, MIT Press.
// File name: projects/12/String.jack

/**
 * Represents character strings. In addition for constructing and disposing
 * strings, the class features methods for getting and setting individual
 * characters of the string, for erasing the string's last character,
 * for appending a character to the string's end, and more typical
 * string-oriented operations.
 */
class String { 
    field Array str;
    field int length;
    field int strLength;

    /** constructs a new empty string with a mavalimum length of mavalLength
     *  and initial length of 0. */
    constructor String new(int mavalLength) {
        if (mavalLength > 0){
            let str = Array.new(mavalLength);
        }
        let strLength = mavalLength;
        let length = 0;
        return this;
    }

    /** Disposes this string. */
    method void dispose() {
        if(length > 0){
            do str.dispose();
        }
        do Memory.deAlloc(this);
        return;
    }

    /** Returns the current length of this string. */
    method int length() {
        return length;
    }

    /** Returns the character at the j-th location of this string. */
    method char charAt(int j) {
        if(j > length){
            do Sys.error(7);
        }
        return str[j];          
    }

    /** Sets the character at the j-th location of this string to c. */
    method void setCharAt(int j, char c) {
        if(j > length){
            do Sys.error(7);
        }
        let str[j] = c;
        return;
    }

    /** Appends c to this string's end and returns this string. */
    method String appendChar(char c) {
        if(strLength = length){
            do Sys.error(7);
        }
        let str[length] = c;
        let length = length + 1;
        return this;
    }

    /** Erases the last character from this string. */
    method void eraseLastChar() {
        if (length = 0){
            do Sys.error(7);
        }
        let str[length] = 0;
        let length = length - 1;
        return;
    }

    /** Returns the integer value of this string, 
     *  until a non-digit character is detected. */
    method int intValue() {
        var int d, sum, i;
        var bool f;
        while(i < length){
            let d = str[i];
            if ((d > 47) & (d < 58)){
                let sum = (sum * 10) + (d - 48);
            }
            else{
                if((i = 0) & (d = 45)){
                    let f = true;
                }
                else{
                    let i = length;
                }
            }
            let i = i + 1;
        }
        if (f){
            return -sum;
        }
        return sum;
    }

    /** Sets this string to hold a representation of the given value. */
    method void setInt(int val) {
        var Array c;
        var int d, b, a;
        let c = Array.new(6);
        if (val < 0){
            let d = ~0;
            let val = -val;
        }
        let b = val;
        while(b > 0){
            let b = val / 10;
            let c[a] = 48 + val - (b * 10);
            let a = a + 1;
            let val = b;
        }
        if (d){
            let c[a] = 45;
            let a = a + 1;
        }
        if (a = 0){
            let str[0] = 48;
            let length = 1;
        }
        else{
            let length = 0;
            while (length < a){
                let str[length] = c[a - 1 - length];
                let length = length + 1;
            }
        }
        do Array.dispose(c);
        return;
    }
    /** Returns the new line character. */
    function char newLine() {
        return 128;
    }

    /** Returns the backspace character. */
    function char backSpace() {
        return 129;
    }

    /** Returns the double quote (") character. */
    function char doubleQuote() {
        return 34;
    }
}