export function validateString(input: string, index: number): boolean {
  const validator = new BracketsValidator();
  
  for (let i = index; i < input.length; i++) {
    const char = input[i];
    
   if (!validator.isValidChar(char)) {
     return false;
   }
  }
  
  return true;
}



class BracketsValidator {
  private readonly bracketPairs: Record<string, string> = {
    '{': '}',
    '[': ']',
    '(': ')',
  };
  private readonly openBrackets: Set<string> = new Set(Object.keys(this.bracketPairs));
  private readonly closingBrackets: Set<string> = new Set(Object.values(this.bracketPairs));
  private stack: string[] = [];
  
  public isValidChar(char: string): boolean {
    if (this.isNotBracket(char)) {
      return true;
    }
    
    if (this.isOpeningBracket(char)) {
      this.push(char);
      return true;
    }
    
    if (this.hasMatchFor(char)) {
      this.pop();
      return true;
    }
    
    return false;
  }
  
  private push(bracket: string): void {
    this.stack.push(bracket);
  } 
  
  private pop(): string|undefined {
    return this.stack.pop();
  }
  
  private lastFromStack(): string|undefined {
    return this.stack.slice(-1)[0];
  }
  
  private hasMatchFor(bracket: string): boolean {
    const previousBracket: string|undefined = this.lastFromStack();
    
    if (undefined === previousBracket) {
      return false;
    }
    
    const match = this.matchFor(bracket);
    
    if (previousBracket !== match) {
      return false;
    }
    
    return true;
  }
  
  private isOpeningBracket(char: string): boolean {
    if (this.openBrackets.has(char)) {
      return true;
    }

    return false;
  }
  
  private isClosingBracket(char: string): boolean {
    if (this.closingBrackets.has(char)) {
      return true;
    }

    return false;
  }
  
  private isNotBracket(char: string): boolean {
    if (this.isOpeningBracket(char)) {
      return false;
    }
    
    if (this.isClosingBracket(char)) {
      return false;
    }
    
    return true;
  }
  
  private matchFor(bracket: string): string {
    const index: number = Object.values(this.bracketPairs).indexOf(bracket);
    return Object.keys(this.bracketPairs)[index];
  }
}