package programming.set9.dna;

import java.util.Arrays;
import java.util.HashMap;

public class DNAMatcher {

    private static final String[] bases = { "A", "C", "G", "T" };
    private static final HashMap<Character, Character> baseCombinations = new HashMap<Character, Character>();

    private final String dnaString;

    public DNAMatcher(String base) {

        baseCombinations.put('A', 'T');
        baseCombinations.put('T', 'A');
        baseCombinations.put('C', 'G');
        baseCombinations.put('G', 'C');

        if (base.equals(null) || !validateDNA(base)) {
            throw new IllegalArgumentException("YOU HAVE TO ENTER A VALID DNA STRING");
        }
        this.dnaString = base.toUpperCase();
    }

    /**
     * Returns the index of the first position in the base DNA string where
     * candidateDNA can bind, if any.
     *
     * @param candidateDNA the DNA string to try to bind to the base DNA.
     * @return index of the first binding position or {@code -1} if the candidate
     *         DNA string cannot bind to the base string.
     * @throws IllegalArgumentException if {@code candidateDNA} is {@code null},
     *                                  empty, or contains characters other than A,
     *                                  C, G, and T.
     */
    public int findFirstBindingPosition(String candidateDNA) {

        if (candidateDNA.equals(null) || !validateDNA(candidateDNA)) {
            throw new IllegalArgumentException("YOU HAVE TO ENTER A VALID DNA STRING");
        }
        candidateDNA = candidateDNA.toUpperCase();
        for (int i = 0; i < dnaString.length(); i++) {
            for (int j = 0; true; j++) {
                if (i + j >= dnaString.length()) {
                    break;
                } else {
                    if (baseCombinations.get(dnaString.charAt(i + j)) == candidateDNA.charAt(j)) {
                        if (j == candidateDNA.length() - 1)
                            return i;
                    } else {
                        break;
                    }
                }

            }

        }
        return -1;
    }

    private boolean validateDNA(String dnaString) {
        for (int i = 0; i < dnaString.length(); i++) {
            if (Arrays.stream(bases).anyMatch(String.valueOf(dnaString.charAt(i))::equals)) {
            } else {
                return false;
            }
        }
        return true;
    }
}