import React, { useEffect, useState } from 'react';
import {
  DataHoverClearEvent,
  DataHoverEvent,
  FALLBACK_COLOR,
  FieldDisplay,
  formattedValueToString,
  getFieldDisplayValues,
  PanelProps,
} from '@grafana/data';

import { PieChart } from './PieChart';

import { PieChartLegendOptions, PieChartLegendValues, PieChartOptions } from './types';
import { Subscription } from 'rxjs';
import {
  LegendDisplayMode,
  usePanelContext,
  useTheme2,
  VizLayout,
  VizLegend,
  VizLegendItem,
  SeriesVisibilityChangeBehavior,
} from '@grafana/ui';

const defaultLegendOptions: PieChartLegendOptions = {
  displayMode: LegendDisplayMode.List,
  placement: 'right',
  calcs: [],
  values: [PieChartLegendValues.Percent],
};

interface Props extends PanelProps<PieChartOptions> {}

/**
 * @beta
 */
export function PieChartPanel(props: Props) {
  const { data, timeZone, fieldConfig, replaceVariables, width, height, options } = props;

  const theme = useTheme2();
  const highlightedTitle = useSliceHighlightState();
  const fieldDisplayValues = getFieldDisplayValues({
    fieldConfig,
    reduceOptions: options.reduceOptions,
    data: data.series,
    theme: theme,
    replaceVariables,
    timeZone,
  });

  return (
    <VizLayout width={width} height={height} legend={getLegend(props, fieldDisplayValues)}>
      {(vizWidth: number, vizHeight: number) => {
        return (
          <PieChart
            width={vizWidth}
            height={vizHeight}
            highlightedTitle={highlightedTitle}
            fieldDisplayValues={fieldDisplayValues}
            tooltipOptions={options.tooltip}
            pieType={options.pieType}
            displayLabels={options.displayLabels}
          />
        );
      }}
    </VizLayout>
  );
}

function getLegend(props: Props, displayValues: FieldDisplay[]) {
  const legendOptions = props.options.legend ?? defaultLegendOptions;

  if (legendOptions.displayMode === LegendDisplayMode.Hidden) {
    return undefined;
  }
  const total = displayValues
    .filter((item) => {
      return !item.field.custom?.hideFrom?.viz;
    })
    .reduce((acc, item) => item.display.numeric + acc, 0);

  const legendItems = displayValues.map<VizLegendItem>((value, idx) => {
    const hidden = value.field.custom.hideFrom.viz;
    const display = value.display;
    return {
      label: display.title ?? '',
      color: display.color ?? FALLBACK_COLOR,
      yAxis: 1,
      disabled: hidden,
      getItemKey: () => (display.title ?? '') + idx,
      getDisplayValues: () => {
        const valuesToShow = legendOptions.values ?? [];
        let displayValues = [];

        if (valuesToShow.includes(PieChartLegendValues.Value)) {
          displayValues.push({ numeric: display.numeric, text: formattedValueToString(display), title: 'Value' });
        }

        if (valuesToShow.includes(PieChartLegendValues.Percent)) {
          const fractionOfTotal = hidden ? 0 : display.numeric / total;
          const percentOfTotal = fractionOfTotal * 100;

          displayValues.push({
            numeric: fractionOfTotal,
            percent: percentOfTotal,
            text: hidden ? '-' : percentOfTotal.toFixed(0) + '%',
            title: valuesToShow.length > 1 ? 'Percent' : undefined,
          });
        }

        return displayValues;
      },
    };
  });

  return (
    <VizLegend
      items={legendItems}
      seriesVisibilityChangeBehavior={SeriesVisibilityChangeBehavior.Hide}
      placement={legendOptions.placement}
      displayMode={legendOptions.displayMode}
    />
  );
}

function useSliceHighlightState() {
  const [highlightedTitle, setHighlightedTitle] = useState<string>();
  const { eventBus } = usePanelContext();

  useEffect(() => {
    const setHighlightedSlice = (event: DataHoverEvent) => {
      setHighlightedTitle(event.payload.dataId);
    };

    const resetHighlightedSlice = (event: DataHoverClearEvent) => {
      setHighlightedTitle(undefined);
    };

    const subs = new Subscription()
      .add(eventBus.getStream(DataHoverEvent).subscribe({ next: setHighlightedSlice }))
      .add(eventBus.getStream(DataHoverClearEvent).subscribe({ next: resetHighlightedSlice }));

    return () => {
      subs.unsubscribe();
    };
  }, [setHighlightedTitle, eventBus]);

  return highlightedTitle;
}