package com.opencsv.validators;

import com.opencsv.exceptions.CsvValidationException;

import java.util.function.Function;

This validator is best used to validate a specific property of the row - either about a specific
element or information about the array itself.
An empty or null first row is considered invalid.
As with all row validators the assumption is you have control of the data and have skipped any initial
empty lines AND that your validator checks the size or handles the IndexOutOfBoundsException.
There are several examples coded in the RowFunctionValidatorTest but here are a couple to give you the
idea of the flexibility this validator offers.

    private static final String[] GOOD_ROW = {"8675309", "Firstname", "M", "Lastname", "Dec 06, 1951"};
    private static final String[] BAD_ROW = {"not a number", "not capitialized", "not an initial", "Not Single word", "12/06/51"};
    private static final String[] LONG_ROW = {"8675309", "Firstname", "M", "Lastname", "Dec 06, 1951", "More data"};
    private static final String[] SHORT_ROW = {"8675309", "Firstname", "Lastname", "Dec 06, 1951"};
    private static final Function<String[], Boolean> THIRD_ELEMENT_IS_MIDDLE_INITIAL = (x) -> {
        return x.length > 2 && x[2].matches("^[A-Z]$");
    };
    private static final Function<String[], Boolean> ROW_MUST_HAVE_FIVE_ELEMENTS = (x) -> {
        return (x.length == 5);
    };
    @Test    @DisplayName("Simple test to show checking an middle initial")    public void thirdElementIsMiddleInitial() {
        validator = new RowFunctionValidator(THIRD_ELEMENT_IS_MIDDLE_INITIAL, "The third element must be the middle initial.");
        assertTrue(validator.isValid(GOOD_ROW));
        assertFalse(validator.isValid(BAD_ROW));
    }
    @Test    @DisplayName("The row must have a specific number of elements in order to be valid.")    public void numberOfElementsInARow() {
        validator = new RowFunctionValidator(ROW_MUST_HAVE_FIVE_ELEMENTS, "A Row can have only five elements.");
        assertTrue(validator.isValid(GOOD_ROW));
        assertFalse(validator.isValid(LONG_ROW));
        assertFalse(validator.isValid(SHORT_ROW));
    }

Author:
Scott Conway
Since:
5.0/**
 * This validator is best used to validate a specific property of the row - either about a specific
 * element or information about the array itself.
 * <p>An empty or null first row is considered invalid.</p>
 * <p>As with all row validators the assumption is you have control of the data and have skipped any initial
 * empty lines AND that your validator checks the size or handles the IndexOutOfBoundsException.</p>
 * <p>There are several examples coded in the RowFunctionValidatorTest but here are a couple to give you the
 * idea of the flexibility this validator offers.</p>
 *
 * <pre>{@code
 *     private static final String[] GOOD_ROW = {"8675309", "Firstname", "M", "Lastname", "Dec 06, 1951"};
 *     private static final String[] BAD_ROW = {"not a number", "not capitialized", "not an initial", "Not Single word", "12/06/51"};
 *     private static final String[] LONG_ROW = {"8675309", "Firstname", "M", "Lastname", "Dec 06, 1951", "More data"};
 *     private static final String[] SHORT_ROW = {"8675309", "Firstname", "Lastname", "Dec 06, 1951"};
 *
 *     private static final Function<String[], Boolean> THIRD_ELEMENT_IS_MIDDLE_INITIAL = (x) -> {
 *         return x.length > 2 && x[2].matches("^[A-Z]$");
 *     };
 *
 *     private static final Function<String[], Boolean> ROW_MUST_HAVE_FIVE_ELEMENTS = (x) -> {
 *         return (x.length == 5);
 *     };
 * }
 * {@code    @Test}
 * {@code    @DisplayName("Simple test to show checking an middle initial")}
 * {@code    public void thirdElementIsMiddleInitial() {
 *         validator = new RowFunctionValidator(THIRD_ELEMENT_IS_MIDDLE_INITIAL, "The third element must be the middle initial.");
 *
 *         assertTrue(validator.isValid(GOOD_ROW));
 *         assertFalse(validator.isValid(BAD_ROW));
 *     }
 * }
 * {@code    @Test}
 * {@code    @DisplayName("The row must have a specific number of elements in order to be valid.")}
 * {@code    public void numberOfElementsInARow() {
 *         validator = new RowFunctionValidator(ROW_MUST_HAVE_FIVE_ELEMENTS, "A Row can have only five elements.");
 *
 *         assertTrue(validator.isValid(GOOD_ROW));
 *         assertFalse(validator.isValid(LONG_ROW));
 *         assertFalse(validator.isValid(SHORT_ROW));
 *     }
 * }</pre>
 *
 * @author Scott Conway
 * @since 5.0
 */

public class RowFunctionValidator implements RowValidator {
    private Function<String[], Boolean> testFunction;
    private String failureMessage;

    
Default Constructor.
Params:
testFunction –   - function to run against the Array of Strings.
failureMessage – - message to be included in the CsvValidationException error message./**
     * Default Constructor.
     *
     * @param testFunction   - function to run against the Array of Strings.
     * @param failureMessage - message to be included in the CsvValidationException error message.
     */
    public RowFunctionValidator(Function<String[], Boolean> testFunction, String failureMessage) {
        this.testFunction = testFunction;
        this.failureMessage = failureMessage;
    }

    @Override
    public boolean isValid(String[] row) {
        if (row == null || row.length == 0) {
            return false;
        }
        return testFunction.apply(row);
    }

    @Override
    public void validate(String[] row) throws CsvValidationException {
        if (!isValid(row)) {
            throw new CsvValidationException(failureMessage);
        }
    }
}