package de.brudaswen.util.format;

import android.text.Editable;
import android.text.TextWatcher;

/**
 * Format input inside {@link android.widget.EditText} and make character blocks.
 * <p>
 * <p>
 * IBAN: <code>XXXX XXXX XXXX XXXX XXXX XXXX XXXX XXXX XXXX</code>
 * <p>
 * Credit card: <code>XXXX XXXX XXXX XXXX</code>
 *
 * @author Sven Obser (sven@brudaswen.de)
 */
public class NumberBlockWatcher implements TextWatcher {

    private static final int NO_MAX_CHARS = -1;

    /**
     * Create default IBAN text watch:
     * <p>
     * Style: <code>XXXX XXXX XXXX XXXX XXXX XXXX XXXX XXXX XXXX</code>
     */
    public static NumberBlockWatcher getIbanNumberBlockWatcher() {
        return new NumberBlockWatcher(4, ' ', true, 36);
    }

    /**
     * Create default credit card text watch:
     * <p>
     * Style: <code>XXXX XXXX XXXX XXXX</code>
     */
    public static NumberBlockWatcher getCreditCardNumberBlockWatcher() {
        return new NumberBlockWatcher(4, ' ', false, 16);
    }

    private final int size;
    private final char space;
    private final boolean toUpper;
    private final int maxChars;

    /**
     * Create Iban text watcher with custom properties.
     *
     * @param size     Size of the character blocks.
     * @param space    Spacing character between blocks.
     * @param toUpper  Change characters to uppercase.
     * @param maxChars Max number of chars (excluding space) or {@link #NO_MAX_CHARS} to disable.
     */
    public NumberBlockWatcher(int size, char space, boolean toUpper, int maxChars) {
        this.size = size + 1;
        this.space = space;
        this.toUpper = toUpper;

        if (maxChars > NO_MAX_CHARS) {
            this.maxChars = maxChars + maxChars / size - 1;
        } else {
            this.maxChars = NO_MAX_CHARS;
        }
    }

    @Override
    public void onTextChanged(CharSequence s, int start, int before, int count) {
    }

    @Override
    public void beforeTextChanged(CharSequence s, int start, int count, int after) {
    }

    @Override
    public void afterTextChanged(Editable s) {
        for (int i = 0; i < s.length(); ) {
            final char c = s.charAt(i);

            if (isSpacePosition(i) && c != space) {
                // Insert missing space
                s.insert(i, String.valueOf(space));
                i++;
            } else if (!isSpacePosition(i) && c == space) {
                // Delete wrongly placed space and check position again
                s.delete(i, i + 1);
            } else if (toUpper && !isSpacePosition(i) && Character.isLowerCase(c)) {
                s.replace(i, i + 1, String.valueOf(Character.toUpperCase(c)));
            } else {
                // Everything all right
                i++;
            }
        }

        if (maxChars > NO_MAX_CHARS && s.length() > maxChars) {
            s.delete(maxChars, s.length());
        }
    }

    private boolean isSpacePosition(int i) {
        return (i + 1) % size == 0;
    }
}