BestWayToWriteMethodTest

import static org.junit.Assert.*;

import com.google.common.jimfs.Configuration;
import com.google.common.jimfs.Jimfs;

import java.io.IOException;
import java.nio.charset.StandardCharsets;
import java.nio.file.*;
import java.util.Arrays;

import junit.framework.AssertionFailedError;
import org.junit.Before;
import org.junit.Test;

// uses https://github.com/google/jimfs

public class BestWayToWriteMethodTest {

    private static final String TEST_FILE_NAME = "/testFileName.txt";

    private Path _rootPath;
    private BestWayToWriteMethod _bestWay;

    @Before
    public void before() {
        final FileSystem mockFileSystem = Jimfs.newFileSystem(Configuration.unix());
        _rootPath = mockFileSystem.getPath("/");

        _bestWay = new BestWayToWriteMethod(mockFileSystem);
    }

    @Test
    public void zeroDataLines() throws IOException {
        writeTestFileContents(TEST_FILE_NAME,
                "01 header",
                "99 trailer  000000000");

        _bestWay.processFile(TEST_FILE_NAME);
    }

    @Test
    public void simpleOneLineValidFile() throws IOException {
        writeTestFileContents(TEST_FILE_NAME,
                "01 header",
                "02 data",
                "99 trailer  000000001");

        _bestWay.processFile(TEST_FILE_NAME);
    }

    @Test
    public void simpleTwoLineValidFile() throws IOException {
        writeTestFileContents(TEST_FILE_NAME,
                "01 header",
                "02 line 1",
                "02 line 2",
                "99 trailer  000000002");

        _bestWay.processFile(TEST_FILE_NAME);
    }

    @Test
    public void firstLineNotHeader() throws IOException {
        writeTestFileContents(TEST_FILE_NAME,
                "NO Header");

        processFileExpectingAssertionFailedError(TEST_FILE_NAME,
                "First record must be a header record. Found record type 'NO' instead. Line #1 = NO Header");
    }

    @Test
    public void trailerCountWrong() throws IOException {
        writeTestFileContents(TEST_FILE_NAME,
                "01 header",
                "99 trailer  000123456");

        processFileExpectingAssertionFailedError(TEST_FILE_NAME,
                "Trailer record has incorrect record count. Trailer record has 123456. Actual detail record count 0.");
    }

    @Test
    public void trailerCountWrongWithDetails() throws IOException {
        writeTestFileContents(TEST_FILE_NAME,
                "01 header",
                "02 detail 1",
                "02 detail 2",
                "02 detail 3",
                "99 trailer  123456789");

        processFileExpectingAssertionFailedError(TEST_FILE_NAME,
                "Trailer record has incorrect record count. Trailer record has 123456789. Actual detail record count 3.");
    }

    @Test
    public void dataAfterTrailer() throws IOException {
        writeTestFileContents(TEST_FILE_NAME,
                "01 header",
                "02 detail 1",
                "99 trailer  000000001",
                "02 out of place detail record");

        processFileExpectingAssertionFailedError(TEST_FILE_NAME,
                "Invalid record after trailer on line 4: 02 out of place detail record");
    }

    @Test
    public void dataAfterTrailerWithDifferentCounts() throws IOException {
        writeTestFileContents(TEST_FILE_NAME,
                "01 header",
                "02 detail 1",
                "02 detail 2",
                "02 detail 3",
                "02 detail 4",
                "02 detail 5",
                "99 trailer  000000005",
                "02 another out of place record");

        processFileExpectingAssertionFailedError(TEST_FILE_NAME,
                "Invalid record after trailer on line 8: 02 another out of place record");
    }

    @Test
    public void outOfPlaceHeaderRecord() throws IOException {
        writeTestFileContents(TEST_FILE_NAME,
                "01 header",
                "02 detail 1",
                "01 out of place",
                "02 detail 2",
                "99 trailer  000000002");

        processFileExpectingAssertionFailedError(TEST_FILE_NAME,
                "Duplicate header record found at line 3: 01 out of place");
    }

    @Test
    public void invalidRecordType() throws IOException {
        writeTestFileContents(TEST_FILE_NAME,
                "01 header",
                "02 detail 1",
                "86 bad record type",
                "02 detail 2",
                "99 trailer  000000002");

        processFileExpectingAssertionFailedError(TEST_FILE_NAME,
                "Unrecognized record type '86' found at line 3: 86 bad record type");
    }

    private void writeTestFileContents(final String fileName, final String... lines) throws IOException {
        Files.write(_rootPath.resolve(fileName), Arrays.asList(lines), StandardCharsets.UTF_8);
    }

    private void processFileExpectingAssertionFailedError(final String fileName, final String expectedExceptionMessage) throws IOException {
        try {
            _bestWay.processFile(fileName);
            throw new IllegalStateException("Expected AssertionFailedError, with message '" + expectedExceptionMessage + "'.");
        } catch (final AssertionFailedError afe) {
            assertEquals(expectedExceptionMessage, afe.getMessage());
        }
    }

}