import React, {useMemo} from 'react';
import {StyleSheet, Text, View} from 'react-native';
import Svg, {Circle, Line, Path, Rect} from 'react-native-svg';

import {colors, spacing} from '../../../theme';
import type {MetricTrendPoint} from '../insights/metricInsights';

interface MetricTrendChartProps {
  points: readonly MetricTrendPoint[];
  color: string;
  unit: string;
  digits: number;
  referenceRange: {minimum: number; maximum: number} | null;
}

const WIDTH = 320;
const HEIGHT = 104;
const PAD_X = 8;
const PAD_Y = 13;

const dateLabel = (value: string): string =>
  new Date(value).toLocaleDateString('fr-FR', {
    day: '2-digit',
    month: 'short',
  });

const createPath = (coordinates: readonly {x: number; y: number}[]): string => {
  if (coordinates.length === 0) return '';
  if (coordinates.length === 1) {
    const only = coordinates[0]!;
    return `M ${only.x} ${only.y}`;
  }
  return coordinates.reduce((path, point, index) => {
    if (index === 0) return `M ${point.x} ${point.y}`;
    const previous = coordinates[index - 1]!;
    const controlX = (previous.x + point.x) / 2;
    return `${path} C ${controlX} ${previous.y}, ${controlX} ${point.y}, ${point.x} ${point.y}`;
  }, '');
};

export function MetricTrendChart({
  points,
  color,
  unit,
  digits,
  referenceRange,
}: MetricTrendChartProps): React.JSX.Element {
  const model = useMemo(() => {
    if (points.length === 0) return null;
    const allValues = [
      ...points.map(point => point.value),
      ...(referenceRange === null
        ? []
        : [referenceRange.minimum, referenceRange.maximum]),
    ];
    const rawMinimum = Math.min(...allValues);
    const rawMaximum = Math.max(...allValues);
    const padding = Math.max((rawMaximum - rawMinimum) * 0.18, Math.abs(rawMaximum) * 0.02, 0.5);
    const minimum = rawMinimum - padding;
    const maximum = rawMaximum + padding;
    const scaleY = (value: number): number =>
      PAD_Y + ((maximum - value) / Math.max(maximum - minimum, 0.0001)) * (HEIGHT - PAD_Y * 2);
    const coordinates = points.map((point, index) => ({
      x:
        points.length === 1
          ? WIDTH / 2
          : PAD_X + (index / (points.length - 1)) * (WIDTH - PAD_X * 2),
      y: scaleY(point.value),
    }));
    return {
      coordinates,
      path: createPath(coordinates),
      rangeY:
        referenceRange === null
          ? null
          : {
              top: scaleY(referenceRange.maximum),
              bottom: scaleY(referenceRange.minimum),
            },
    };
  }, [points, referenceRange]);

  if (model === null || points.length < 2) {
    return (
      <View style={styles.empty} accessibilityLabel="Tendance indisponible">
        <Text style={styles.emptyTitle}>Tendance en construction</Text>
        <Text style={styles.emptyText}>
          Encore {Math.max(0, 2 - points.length)} mesure comparable pour tracer une évolution.
        </Text>
      </View>
    );
  }

  const first = points[0]!;
  const last = points[points.length - 1]!;
  const firstCoordinate = model.coordinates[0]!;
  const lastCoordinate = model.coordinates[model.coordinates.length - 1]!;
  const valueLabel = `${last.value.toFixed(digits)} ${unit}`;

  return (
    <View
      accessible
      accessibilityRole="image"
      accessibilityLabel={`Tendance de ${points.length} mesures, de ${first.value.toFixed(digits)} à ${valueLabel}`}>
      <Svg width="100%" height={HEIGHT} viewBox={`0 0 ${WIDTH} ${HEIGHT}`}>
        {model.rangeY === null ? null : (
          <Rect
            x={PAD_X}
            y={model.rangeY.top}
            width={WIDTH - PAD_X * 2}
            height={Math.max(2, model.rangeY.bottom - model.rangeY.top)}
            fill={colors.accent}
            opacity={0.08}
            rx={4}
          />
        )}
        <Line x1={PAD_X} y1={HEIGHT - PAD_Y} x2={WIDTH - PAD_X} y2={HEIGHT - PAD_Y} stroke={colors.border} strokeWidth={1} />
        <Line x1={firstCoordinate.x} y1={PAD_Y} x2={firstCoordinate.x} y2={HEIGHT - PAD_Y} stroke={colors.border} strokeWidth={1} />
        <Line x1={lastCoordinate.x} y1={PAD_Y} x2={lastCoordinate.x} y2={HEIGHT - PAD_Y} stroke={colors.border} strokeWidth={1} />
        <Path d={model.path} fill="none" stroke={color} strokeWidth={2.5} strokeLinecap="round" strokeLinejoin="round" />
        {model.coordinates.map((coordinate, index) => (
          <Circle
            key={points[index]!.id}
            cx={coordinate.x}
            cy={coordinate.y}
            r={index === 0 || index === model.coordinates.length - 1 ? 4 : 2.2}
            fill={color}
            opacity={index === 0 || index === model.coordinates.length - 1 ? 1 : 0.62}
          />
        ))}
      </Svg>
      <View style={styles.labels}>
        <Text style={styles.date}>{dateLabel(first.measuredAt)}</Text>
        <Text style={[styles.lastValue, {color}]}>{valueLabel}</Text>
        <Text style={styles.date}>{dateLabel(last.measuredAt)}</Text>
      </View>
      <Text style={styles.caption}>
        {points.length} mesures réelles{referenceRange === null ? '' : ' · zone pâle : repère personnel'}
      </Text>
    </View>
  );
}

const styles = StyleSheet.create({
  empty: {
    minHeight: 96,
    justifyContent: 'center',
    paddingVertical: spacing.md,
    borderTopWidth: StyleSheet.hairlineWidth,
    borderTopColor: colors.border,
  },
  emptyTitle: {color: colors.text, fontSize: 13, fontWeight: '700'},
  emptyText: {color: colors.muted, fontSize: 11, lineHeight: 16, marginTop: 3},
  labels: {
    marginTop: -2,
    flexDirection: 'row',
    justifyContent: 'space-between',
    alignItems: 'center',
  },
  date: {color: colors.muted, fontSize: 10},
  lastValue: {fontSize: 11, fontWeight: '800', fontVariant: ['tabular-nums']},
  caption: {color: colors.muted, fontSize: 9, marginTop: spacing.xs},
});