Ajajha

Fun.java

package com.dkc.pp.util;

import android.support.annotation.NonNull;

import java.util.ArrayList;
import java.util.List;
import java.util.Map;

public class BooleanPredicateProcessor {
    private boolean isNumeric(String text) {
        for (int i = 0; i < text.length(); i++) {
            char c = text.charAt(i);

            if (c < '0' || c > '9') {
               return false;
            }
        }

        return true;
    }

    String[] processArithmetic(String[] pieces) {
        for (int i = 2; i < pieces.length; i++) {

            if (pieces[i-1].equals("+")) {
                int left = Integer.parseInt(pieces[i-2]);
                int right = Integer.parseInt(pieces[i]);

                pieces[i] = Integer.toString(left + right);
                pieces[i-1] = null;
                pieces[i-2] = null;
            }
            else if (pieces[i-1].equals("-")) {
                int left = Integer.parseInt(pieces[i-2]);
                int right = Integer.parseInt(pieces[i]);

                pieces[i] = Integer.toString(left - right);
                pieces[i-1] = null;
                pieces[i-2] = null;
            }
        }

        List<String> withoutNulls = new ArrayList<>(pieces.length);

        for (String piece : pieces) {
            if (piece != null) withoutNulls.add(piece);
        }

        return withoutNulls.toArray(new String[0]);
    }

    public boolean processPredicate(String predicate, Map<String, Integer> variables) {
        String[] pieces = resolveVariables(predicate, variables);
        pieces = processArithmetic(pieces);


        String operation = pieces[1];
        int leftOperand = Integer.parseInt(pieces[0]);
        int rightOperand = Integer.parseInt(pieces[2]);

        switch (operation) {
            case "<":
                return leftOperand < rightOperand;
            case ">":
                return leftOperand > rightOperand;
            case ">=":
                return leftOperand >= rightOperand;
            case "<=":
                return leftOperand <= rightOperand;
            case "==":
                return leftOperand == rightOperand;
            default:
                throw new RuntimeException(String.format("Listen you mother fucker, I'm not interested in that operation. Take your %s and fuck off!", operation));
        }
    }

    @NonNull
    private String[] resolveVariables(String predicate, Map<String, Integer> variables) {
        String[] pieces = predicate.split(" ");

        for (int i = 0; i < pieces.length; i++) {
            if (variables.containsKey(pieces[i])) {
                pieces[i] = variables.get(pieces[i]).toString();
            }
            else if (!isNumeric(pieces[i]) && !isAnOperator(pieces[i])) {
                throw new RuntimeException(String.format("Unable to resolve variable for string = '%s'", pieces[i]));
            }
        }
        return pieces;
    }

    private boolean isAnOperator(String piece) {
       switch (piece) {
           case "<":
           case ">":
           case ">=":
           case "<=":
           case "==":
           case "+":
           case "-":
               return true;

           default:
               return false;
       }
    }
}