package com.trafficaudit.holiday.service;

import org.junit.jupiter.api.Test;

import javax.imageio.ImageIO;
import java.awt.image.BufferedImage;
import java.io.ByteArrayInputStream;
import java.math.BigDecimal;

import static org.junit.jupiter.api.Assertions.assertArrayEquals;
import static org.junit.jupiter.api.Assertions.assertEquals;
import static org.junit.jupiter.api.Assertions.assertFalse;
import static org.junit.jupiter.api.Assertions.assertNotNull;
import static org.junit.jupiter.api.Assertions.assertTrue;

class HolidayTrendChartServiceTest {

    @Test
    void rendersLinePieAndStackedChartsAsPng() throws Exception {
        HolidayTrendChartService service = new HolidayTrendChartService();
        HolidayTrendChartService.ChartSeries first = new HolidayTrendChartService.ChartSeries();
        first.setName("2026年");
        first.setValues(java.util.Arrays.asList(
                java.math.BigDecimal.ONE, java.math.BigDecimal.TEN, null));
        HolidayTrendChartService.ChartSeries second = new HolidayTrendChartService.ChartSeries();
        second.setName("2025年");
        second.setValues(java.util.Arrays.asList(
                java.math.BigDecimal.valueOf(2), java.math.BigDecimal.valueOf(8),
                java.math.BigDecimal.valueOf(4)));

        byte[] line = service.lineChart("万人次", java.util.Arrays.asList(first, second), false);
        assertPng(line);
        assertNoLargeLightGrayBackground(line);

        HolidayTrendChartService.ChartCategory category = new HolidayTrendChartService.ChartCategory();
        category.setName("铁路");
        category.setValue(java.math.BigDecimal.TEN);
        byte[] pie = service.pieChart("人次", java.util.Collections.singletonList(category), 400, 300);
        assertPng(pie);

        byte[] stacked = service.stackedBarChart("占比", java.util.Arrays.asList("10月1日", "10月2日"),
                java.util.Arrays.asList(first, second), true, 500, 320);
        assertPng(stacked);
        assertNoLargeLightGrayBackground(stacked);
    }

    @Test
    void roundsLineDataToTheSamePrecisionAsLabels() {
        assertEquals(new BigDecimal("0.49"),
                HolidayTrendChartService.displayValue(new BigDecimal("0.4904"), false, 2));
        assertEquals(new BigDecimal("0.49"),
                HolidayTrendChartService.displayValue(new BigDecimal("0.4911"), false, 2));
        assertEquals(new BigDecimal("0.491"),
                HolidayTrendChartService.displayValue(new BigDecimal("0.4911"), false, 3));
        assertEquals(new BigDecimal("0.123"),
                HolidayTrendChartService.displayValue(new BigDecimal("0.1234"), true, 2));
    }

    @Test
    void rendersSameGeometryWhenValuesRoundToSameLabel() {
        HolidayTrendChartService service = new HolidayTrendChartService();
        HolidayTrendChartService.ChartSeries first = new HolidayTrendChartService.ChartSeries();
        first.setName("平均拥挤度");
        first.setValues(java.util.Arrays.asList(
                new BigDecimal("0.4904"), new BigDecimal("0.4923"), new BigDecimal("0.5100")));
        HolidayTrendChartService.ChartSeries second = new HolidayTrendChartService.ChartSeries();
        second.setName("平均拥挤度");
        second.setValues(java.util.Arrays.asList(
                new BigDecimal("0.4911"), new BigDecimal("0.4934"), new BigDecimal("0.5100")));

        byte[] firstChart = service.lineChart("拥挤度",
                java.util.Collections.singletonList(first), false, 2, 1100, 590);
        byte[] secondChart = service.lineChart("拥挤度",
                java.util.Collections.singletonList(second), false, 2, 1100, 590);

        assertPng(firstChart);
        assertPng(secondChart);
        assertArrayEquals(firstChart, secondChart);
    }

    @Test
    void scalesLineChartHeightForBetterVerticalSeparation() throws Exception {
        HolidayTrendChartService service = new HolidayTrendChartService();
        HolidayTrendChartService.ChartSeries series = new HolidayTrendChartService.ChartSeries();
        series.setName("测试");
        series.setValues(java.util.Arrays.asList(
                new BigDecimal("1.00"), new BigDecimal("2.00"), new BigDecimal("3.00")));

        byte[] png = service.lineChart("万人次",
                java.util.Collections.singletonList(series), false, 1100, 590);
        BufferedImage image = ImageIO.read(new ByteArrayInputStream(png));

        assertNotNull(image);
        assertEquals(HolidayTrendChartService.scaleLineChartHeight(590), image.getHeight());
    }

    @Test
    void rendersHigherPrecisionLineLabelsWhenRequested() {
        HolidayTrendChartService service = new HolidayTrendChartService();
        HolidayTrendChartService.ChartSeries congestion = new HolidayTrendChartService.ChartSeries();
        congestion.setName("平均拥挤度");
        congestion.setValues(java.util.Arrays.asList(
                new java.math.BigDecimal("0.467029"),
                new java.math.BigDecimal("0.490890"),
                new java.math.BigDecimal("0.492414")));

        byte[] twoDecimals = service.lineChart("拥挤度",
                java.util.Collections.singletonList(congestion), false, 2, 1100, 590);
        byte[] threeDecimals = service.lineChart("拥挤度",
                java.util.Collections.singletonList(congestion), false, 3, 1100, 590);

        assertPng(twoDecimals);
        assertPng(threeDecimals);
        assertFalse(java.util.Arrays.equals(twoDecimals, threeDecimals));
    }

    @Test
    void rendersLineChartWithConfiguredDayLabels() {
        HolidayTrendChartService service = new HolidayTrendChartService();
        HolidayTrendChartService.ChartSeries congestion = new HolidayTrendChartService.ChartSeries();
        congestion.setName("\u5e73\u5747\u62e5\u6324\u5ea6");
        congestion.setValues(java.util.Arrays.asList(
                new BigDecimal("0.50"), new BigDecimal("0.48"), new BigDecimal("0.47"),
                new BigDecimal("0.49"), new BigDecimal("0.49"), new BigDecimal("0.49"),
                new BigDecimal("0.47")));
        java.util.List<String> sevenDays = java.util.Arrays.asList(
                "10\u67081\u65e5", "10\u67082\u65e5", "10\u67083\u65e5", "10\u67084\u65e5",
                "10\u67085\u65e5", "10\u67086\u65e5", "10\u67087\u65e5");

        byte[] custom = service.lineChart("\u62e5\u6324\u5ea6",
                java.util.Collections.singletonList(congestion), false, 2, sevenDays, 1100, 590);
        byte[] defaults = service.lineChart("\u62e5\u6324\u5ea6",
                java.util.Collections.singletonList(congestion), false, 2, 1100, 590);

        assertPng(custom);
        assertPng(defaults);
        assertFalse(java.util.Arrays.equals(custom, defaults),
                "custom day labels should change the rendered axis");
    }

    @Test
    void pinsRequestedLineLabelToFixedAnchor() throws Exception {
        HolidayTrendChartService service = new HolidayTrendChartService();
        HolidayTrendChartService.ChartSeries series = new HolidayTrendChartService.ChartSeries();
        series.setName("2026\u5e74");
        series.setValues(java.util.Collections.singletonList(new BigDecimal("72.4")));
        java.util.List<HolidayTrendChartService.ChartSeries> single =
                java.util.Collections.singletonList(series);

        byte[] plain = service.lineChart("\u4e07\u4eba\u6b21", single, false, 2, 1100, 590);
        byte[] emptyOverrides = service.lineChart("\u4e07\u4eba\u6b21", single, false, 2,
                HolidayTrendChartService.DAY_LABELS, 1100, 590,
                java.util.Collections.emptyList());
        assertArrayEquals(plain, emptyOverrides,
                "an empty override list must keep the automatic placement");

        byte[] unmatched = service.lineChart("\u4e07\u4eba\u6b21", single, false, 2,
                HolidayTrendChartService.DAY_LABELS, 1100, 590,
                java.util.Collections.singletonList(new HolidayTrendChartService.LineLabelOverride(
                        0, 7, HolidayTrendChartService.LineLabelAnchor.ABOVE)));
        assertArrayEquals(plain, unmatched,
                "an override for a label that does not exist must not change rendering");

        byte[] above = service.lineChart("\u4e07\u4eba\u6b21", single, false, 2,
                HolidayTrendChartService.DAY_LABELS, 1100, 590,
                java.util.Collections.singletonList(new HolidayTrendChartService.LineLabelOverride(
                        0, 0, HolidayTrendChartService.LineLabelAnchor.ABOVE)));
        byte[] below = service.lineChart("\u4e07\u4eba\u6b21", single, false, 2,
                HolidayTrendChartService.DAY_LABELS, 1100, 590,
                java.util.Collections.singletonList(new HolidayTrendChartService.LineLabelOverride(
                        0, 0, HolidayTrendChartService.LineLabelAnchor.BELOW)));

        assertPng(above);
        assertPng(below);
        assertFalse(java.util.Arrays.equals(above, below),
                "ABOVE and BELOW anchors must render differently");
        assertTrue(meanSeriesColorY(above) < meanSeriesColorY(below),
                "the ABOVE anchor must place the label higher than the BELOW anchor");
    }

    private double meanSeriesColorY(byte[] data) throws Exception {
        BufferedImage image = ImageIO.read(new ByteArrayInputStream(data));
        assertNotNull(image);
        int target = 0xC0504D;
        long count = 0;
        long sum = 0;
        for (int y = 0; y < image.getHeight() - 60; y++) {
            for (int x = 0; x < image.getWidth(); x++) {
                if ((image.getRGB(x, y) & 0xFFFFFF) == target) {
                    count++;
                    sum += y;
                }
            }
        }
        assertTrue(count > 0, "expected series-coloured pixels for the item label");
        return (double) sum / count;
    }

    private void assertNoLargeLightGrayBackground(byte[] data) throws Exception {
        BufferedImage image = ImageIO.read(new ByteArrayInputStream(data));
        int matches = 0;
        for (int y = 0; y < image.getHeight(); y++) {
            for (int x = 0; x < image.getWidth(); x++) {
                int rgb = image.getRGB(x, y) & 0xFFFFFF;
                if (rgb == 0xF3F4F3) matches++;
            }
        }
        assertTrue(matches < image.getWidth() * image.getHeight() / 20,
                "chart still contains a large light-gray background area");
    }

    private void assertPng(byte[] data) {
        assertNotNull(data);
        assertTrue(data.length > 100);
        assertTrue(data[0] == (byte) 0x89 && data[1] == 0x50
                && data[2] == 0x4e && data[3] == 0x47);
    }
}