// © 2020 and later: Unicode, Inc. and others.
// License & terms of use: http://www.unicode.org/copyright.html
package com.ibm.icu.dev.test.impl;

import static org.junit.Assert.assertEquals;
import static org.junit.Assert.assertTrue;
import static org.junit.Assert.fail;

import java.io.BufferedReader;
import java.io.IOException;
import java.math.BigDecimal;
import java.math.MathContext;
import java.util.ArrayList;
import java.util.List;

import org.junit.Test;

import com.ibm.icu.dev.test.TestUtil;
import com.ibm.icu.impl.Pair;
import com.ibm.icu.impl.units.ComplexUnitsConverter;
import com.ibm.icu.impl.units.ConversionRates;
import com.ibm.icu.impl.units.MeasureUnitImpl;
import com.ibm.icu.impl.units.UnitConverter;
import com.ibm.icu.impl.units.UnitsRouter;
import com.ibm.icu.util.Measure;
import com.ibm.icu.util.MeasureUnit;


public class UnitsTest {

    public static boolean compareTwoBigDecimal(BigDecimal expected, BigDecimal actual, BigDecimal delta) {
        BigDecimal diff =
                expected.abs().compareTo(BigDecimal.ZERO) < 1 ?
                        expected.subtract(actual).abs() :
                        (expected.subtract(actual).divide(expected, MathContext.DECIMAL128)).abs();

        if (diff.compareTo(delta) == -1) return true;
        return false;
    }

    @Test
    public void testComplexUnitsConverter() {
        class TestCase {
            String input;
            String output;
            BigDecimal value;
            Measure[] expected;
            // For mixed units, accuracy of the smallest unit
            double accuracy;

            TestCase(String input, String output, BigDecimal value, Measure[] expected, double accuracy) {
                this.input = input;
                this.output = output;
                this.value = value;
                this.expected = expected;
                this.accuracy = accuracy;
            }
        }
        TestCase[] testCases = new TestCase[] {
            // Significantly less than 2.0.
            new TestCase(
                "foot", "foot-and-inch", BigDecimal.valueOf(1.9999),
                new Measure[] {new Measure(1, MeasureUnit.FOOT), new Measure(11.9988, MeasureUnit.INCH)},
                0),

            // A minimal nudge under 2.0, rounding up to 2.0 ft, 0 in.
            // TODO(icu-units#108): this matches double precision calculations
            // from C++, but BigDecimal is in use: do we want Java to be more
            // precise than C++?
            new TestCase(
                "foot", "foot-and-inch", BigDecimal.valueOf(2.0).subtract(ComplexUnitsConverter.EPSILON),
                new Measure[] {new Measure(2, MeasureUnit.FOOT), new Measure(0, MeasureUnit.INCH)}, 0),

            // A slightly bigger nudge under 2.0, *not* rounding up to 2.0 ft!
            new TestCase("foot", "foot-and-inch",
                         BigDecimal.valueOf(2.0).subtract(
                             ComplexUnitsConverter.EPSILON.multiply(BigDecimal.valueOf(3.0))),
                         new Measure[] {new Measure(1, MeasureUnit.FOOT),
                                        new Measure(BigDecimal.valueOf(12.0).subtract(
                                                        ComplexUnitsConverter.EPSILON.multiply(
                                                            BigDecimal.valueOf(36.0))),
                                                    MeasureUnit.INCH)},
                         0),

            // Testing precision with meter and light-year.
            //
            // DBL_EPSILON light-years, ~2.22E-16 light-years, is ~2.1 meters
            // (maximum precision when exponent is 0).
            //
            // 1e-16 light years is 0.946073 meters.

            // A 2.1 meter nudge under 2.0 light years, rounding up to 2.0 ly, 0 m.
            // TODO(icu-units#108): this matches double precision calculations
            // from C++, but BigDecimal is in use: do we want Java to be more
            // precise than C++?
            new TestCase("light-year", "light-year-and-meter",
                         BigDecimal.valueOf(2.0).subtract(ComplexUnitsConverter.EPSILON),
                         new Measure[] {new Measure(2, MeasureUnit.LIGHT_YEAR),
                                        new Measure(0, MeasureUnit.METER)},
                         0),

            // // TODO(icu-units#108): figure out precision thresholds for BigDecimal?
            // // This test passes in C++ due to double-precision rounding.
            // // A 2.1 meter nudge under 1.0 light years, rounding up to 1.0 ly, 0 m.
            // new TestCase("light-year", "light-year-and-meter",
            //              BigDecimal.valueOf(1.0).subtract(ComplexUnitsConverter.EPSILON),
            //              new Measure[] {new Measure(1, MeasureUnit.LIGHT_YEAR),
            //                             new Measure(0, MeasureUnit.METER)},
            //              0),

            // 1e-15 light years is 9.46073 meters (calculated using "bc" and
            // the CLDR conversion factor). With double-precision maths in C++,
            // we get 10.5. In this case, we're off by a bit more than 1 meter.
            // With Java BigDecimal, we get accurate results.
            new TestCase("light-year", "light-year-and-meter", BigDecimal.valueOf(1.0 + 1e-15),
                         new Measure[] {new Measure(1, MeasureUnit.LIGHT_YEAR),
                                        new Measure(9.46073, MeasureUnit.METER)},
                         0 /* meters, precision */),

            // TODO(icu-units#108): reconsider whether epsilon rounding is desirable:
            //
            // 2e-16 light years is 1.892146 meters. For C++ double, we consider
            // this in the noise, and thus expect a 0. (This test fails when
            // 2e-16 is increased to 4e-16.) For Java, using BigDecimal, we
            // actually get a good result.
            new TestCase("light-year", "light-year-and-meter", BigDecimal.valueOf(1.0 + 2e-16),
                         new Measure[] {new Measure(1, MeasureUnit.LIGHT_YEAR),
                                        new Measure(1.892146, MeasureUnit.METER)},
                         0),
        };

        ConversionRates rates = new ConversionRates();
        MeasureUnit input, output;
        List<Measure> measures;
        for (TestCase testCase : testCases) {
            input = MeasureUnit.forIdentifier(testCase.input);
            output = MeasureUnit.forIdentifier(testCase.output);
            final MeasureUnitImpl inputImpl = MeasureUnitImpl.forIdentifier(input.getIdentifier());
            final MeasureUnitImpl outputImpl = MeasureUnitImpl.forIdentifier(output.getIdentifier());
            ComplexUnitsConverter converter = new ComplexUnitsConverter(inputImpl, outputImpl, rates);
            measures = converter.convert(testCase.value, null);

            assertEquals("measures length", testCase.expected.length, measures.size());
            int i = 0;
            for (Measure measure : measures) {
                double accuracy = 0.0;
                if (i == testCase.expected.length - 1) {
                    accuracy = testCase.accuracy;
                }
                assertTrue("input " + testCase.value + ", output measure " + i + ": expected " +
                               testCase.expected[i] + ", expected unit " +
                               testCase.expected[i].getUnit() + " got unit " + measure.getUnit(),
                           testCase.expected[i].getUnit().equals(measure.getUnit()));
                assertEquals("input " + testCase.value + ", output measure " + i + ": expected " +
                                 testCase.expected[i] + ", expected number " +
                                 testCase.expected[i].getNumber() + " got number " + measure.getNumber(),
                             testCase.expected[i].getNumber().doubleValue(),
                             measure.getNumber().doubleValue(), accuracy);
                i++;
            }
        }

        // TODO(icu-units#63): test negative numbers!
    }


    @Test
    public void testComplexUnitConverterSorting() {

        MeasureUnitImpl source = MeasureUnitImpl.forIdentifier("meter");
        MeasureUnitImpl target = MeasureUnitImpl.forIdentifier("inch-and-foot");
        ConversionRates conversionRates = new ConversionRates();

        ComplexUnitsConverter complexConverter = new ComplexUnitsConverter(source, target, conversionRates);
        List<Measure> measures = complexConverter.convert(BigDecimal.valueOf(10.0), null);

        assertEquals(measures.size(), 2);
        assertEquals("inch-and-foot unit 0", "inch", measures.get(0).getUnit().getIdentifier());
        assertEquals("inch-and-foot unit 1", "foot", measures.get(1).getUnit().getIdentifier());

        assertEquals("inch-and-foot value 0", 9.7008, measures.get(0).getNumber().doubleValue(), 0.0001);
        assertEquals("inch-and-foot value 1", 32, measures.get(1).getNumber().doubleValue(), 0.0001);
    }


    @Test
    public void testExtractConvertibility() {
        class TestData {
            MeasureUnitImpl source;
            MeasureUnitImpl target;
            UnitConverter.Convertibility expected;

            TestData(String source, String target, UnitConverter.Convertibility convertibility) {
                this.source = MeasureUnitImpl.UnitsParser.parseForIdentifier(source);
                this.target = MeasureUnitImpl.UnitsParser.parseForIdentifier(target);
                this.expected = convertibility;
            }
        }

        TestData[] tests = {
                new TestData("meter", "foot", UnitConverter.Convertibility.CONVERTIBLE),
                new TestData("kilometer", "foot", UnitConverter.Convertibility.CONVERTIBLE),
                new TestData("hectare", "square-foot", UnitConverter.Convertibility.CONVERTIBLE),
                new TestData("kilometer-per-second", "second-per-meter", UnitConverter.Convertibility.RECIPROCAL),
                new TestData("square-meter", "square-foot", UnitConverter.Convertibility.CONVERTIBLE),
                new TestData("kilometer-per-second", "foot-per-second", UnitConverter.Convertibility.CONVERTIBLE),
                new TestData("square-hectare", "pow4-foot", UnitConverter.Convertibility.CONVERTIBLE),
                new TestData("square-kilometer-per-second", "second-per-square-meter", UnitConverter.Convertibility.RECIPROCAL),
                new TestData("cubic-kilometer-per-second-meter", "second-per-square-meter", UnitConverter.Convertibility.RECIPROCAL),
                new TestData("square-meter-per-square-hour", "hectare-per-square-second", UnitConverter.Convertibility.CONVERTIBLE),
                new TestData("hertz", "revolution-per-second", UnitConverter.Convertibility.CONVERTIBLE),
                new TestData("millimeter", "meter", UnitConverter.Convertibility.CONVERTIBLE),
                new TestData("yard", "meter", UnitConverter.Convertibility.CONVERTIBLE),
                new TestData("ounce-troy", "kilogram", UnitConverter.Convertibility.CONVERTIBLE),
                new TestData("percent", "portion", UnitConverter.Convertibility.CONVERTIBLE),
                new TestData("ofhg", "kilogram-per-square-meter-square-second", UnitConverter.Convertibility.CONVERTIBLE),
                new TestData("second-per-meter", "meter-per-second", UnitConverter.Convertibility.RECIPROCAL),
        };
        ConversionRates conversionRates = new ConversionRates();

        for (TestData test :
                tests) {
            assertEquals(test.expected, UnitConverter.extractConvertibility(test.source, test.target, conversionRates));
        }
    }

    // TODO(icu-units#92): add UnitsTest::testConverter(), to replace or extend this test.
    @Test
    public void testConverterForTemperature() {
        class TestData {
            MeasureUnitImpl source;
            MeasureUnitImpl target;
            BigDecimal input;
            BigDecimal expected;

            TestData(String source, String target, double input, double expected) {
                this.source = MeasureUnitImpl.UnitsParser.parseForIdentifier(source);
                this.target = MeasureUnitImpl.UnitsParser.parseForIdentifier(target);
                this.input = BigDecimal.valueOf(input);
                this.expected = BigDecimal.valueOf(expected);
            }

        }

        TestData[] tests = {
                new TestData("celsius", "fahrenheit", 1000, 1832),
                new TestData("fahrenheit", "fahrenheit", 1000, 1000),
        };

        ConversionRates conversionRates = new ConversionRates();

        for (TestData test :
                tests) {
            UnitConverter converter = new UnitConverter(test.source, test.target, conversionRates);
            assertEquals(test.expected.doubleValue(), converter.convert(test.input).doubleValue(), (0.001));
        }

    }

    @Test
    public void testConverterWithCLDRTests() throws IOException {
        class TestCase {
            String category;
            String sourceString;
            String targetString;
            MeasureUnitImpl source;
            MeasureUnitImpl target;
            BigDecimal input;
            BigDecimal expected;

            TestCase(String line) {
                String[] fields = line
                        .replaceAll(" ", "") // Remove all the spaces.
                        .replaceAll(",", "") // Remove all the commas.
                        .replaceAll("\t", "")
                        .split(";");

                this.category = fields[0].replaceAll(" ", "");
                this.sourceString = fields[1];
                this.targetString = fields[2];
                this.source = MeasureUnitImpl.UnitsParser.parseForIdentifier(fields[1]);
                this.target = MeasureUnitImpl.UnitsParser.parseForIdentifier(fields[2]);
                this.input = BigDecimal.valueOf(1000);
                this.expected = new BigDecimal(fields[4]);
            }
        }

        String codePage = "UTF-8";
        ArrayList<TestCase> tests = new ArrayList<>();
        try (BufferedReader f = TestUtil.getDataReader("cldr/units/unitsTest.txt", codePage)) {
            while (true) {
                String line = f.readLine();
                if (line == null) break;
                if (line.isEmpty() || line.startsWith("#")) continue;
                tests.add(new TestCase(line));
            }
        }

        ConversionRates conversionRates = new ConversionRates();

        for (TestCase testCase :
                tests) {
            UnitConverter converter = new UnitConverter(testCase.source, testCase.target, conversionRates);
            BigDecimal got = converter.convert(testCase.input);
            if (compareTwoBigDecimal(testCase.expected, got, BigDecimal.valueOf(0.000001))) {
                continue;
            } else {
                fail(new StringBuilder()
                        .append(testCase.category)
                        .append(": Converting 1000 ")
                        .append(testCase.sourceString)
                        .append(" to ")
                        .append(testCase.targetString)
                        .append(", got ")
                        .append(got)
                        .append(", expected ")
                        .append(testCase.expected.toString())
                        .toString());
            }
            BigDecimal inverted = converter.convertInverse(testCase.input);
            if (compareTwoBigDecimal(BigDecimal.valueOf(1000), inverted, BigDecimal.valueOf(0.000001))) {
                continue;
            } else {
                fail(new StringBuilder()
                .append("Converting back to ")
                .append(testCase.sourceString)
                .append(" from ")
                .append(testCase.targetString)
                .append(": got ")
                .append(inverted)
                .append(", expected 1000")
                .toString());
            }
        }
    }

    @Test
    public void testUnitPreferencesWithCLDRTests() throws IOException {
        class TestCase {

            final ArrayList<Pair<String, MeasureUnitImpl>> outputUnitInOrder = new ArrayList<>();
            final ArrayList<BigDecimal> expectedInOrder = new ArrayList<>();
            /**
             * Test Case Data
             */
            @SuppressWarnings("unused")
            String category;
            String usage;
            String region;
            Pair<String, MeasureUnitImpl> inputUnit;
            BigDecimal input;

            TestCase(String line) {
                String[] fields = line
                        .replaceAll(" ", "") // Remove all the spaces.
                        .replaceAll(",", "") // Remove all the commas.
                        .replaceAll("\t", "")
                        .split(";");

                String category = fields[0];
                String usage = fields[1];
                String region = fields[2];
                String inputValue = fields[4];
                String inputUnit = fields[5];
                ArrayList<Pair<String, String>> outputs = new ArrayList<>();

                for (int i = 6; i < fields.length - 2; i += 2) {
                    if (i == fields.length - 3) { // last field
                        outputs.add(Pair.of(fields[i + 2], fields[i + 1]));
                    } else {
                        outputs.add(Pair.of(fields[i + 1], fields[i]));
                    }
                }

                this.insertData(category, usage, region, inputUnit, inputValue, outputs);
            }

            private void insertData(String category,
                                    String usage,
                                    String region,
                                    String inputUnitString,
                                    String inputValue,
                                    ArrayList<Pair<String, String>> outputs /* Unit Identifier, expected value */) {
                this.category = category;
                this.usage = usage;
                this.region = region;
                this.inputUnit = Pair.of(inputUnitString, MeasureUnitImpl.UnitsParser.parseForIdentifier(inputUnitString));
                this.input = new BigDecimal(inputValue);
                for (Pair<String, String> output :
                        outputs) {
                    outputUnitInOrder.add(Pair.of(output.first, MeasureUnitImpl.UnitsParser.parseForIdentifier(output.first)));
                    expectedInOrder.add(new BigDecimal(output.second));
                }
            }
        }

        // Read Test data from the unitPreferencesTest
        String codePage = "UTF-8";
        ArrayList<TestCase> tests = new ArrayList<>();

        try (BufferedReader f = TestUtil.getDataReader("cldr/units/unitPreferencesTest.txt", codePage)) {
            while (true) {
                String line = f.readLine();
                if (line == null) break;
                if (line.isEmpty() || line.startsWith("#")) continue;
                tests.add(new TestCase(line));
            }
        }

        for (TestCase testCase :
                tests) {
            UnitsRouter router = new UnitsRouter(testCase.inputUnit.second, testCase.region, testCase.usage);
            List<Measure> measures = router.route(testCase.input, null).measures;

            assertEquals("Measures size must be the same as expected units",
                    measures.size(), testCase.expectedInOrder.size());
            assertEquals("Measures size must be the same as output units",
                    measures.size(), testCase.outputUnitInOrder.size());


            for (int i = 0; i < measures.size(); i++) {
                if (!UnitsTest
                        .compareTwoBigDecimal(testCase.expectedInOrder.get(i),
                                BigDecimal.valueOf(measures.get(i).getNumber().doubleValue()),
                                BigDecimal.valueOf(0.00001))) {
                    fail(testCase.toString() + measures.toString());
                }
            }
        }
    }
}