import React, {
  MouseEventHandler,
  useCallback,
  useEffect,
  useLayoutEffect,
  useRef,
  useState,
} from 'react';
import {
  Box,
  Modal,
  Overlay,
  OverlayBackdrop,
  OverlayCenter,
  Text,
  Tooltip,
  TooltipProvider,
  as,
  toRem,
} from 'folds';
import classNames from 'classnames';
import { Room } from 'matrix-js-sdk';
import { type Relations } from 'matrix-js-sdk/lib/models/relations';
import FocusTrap from 'focus-trap-react';
import { useMatrixClient } from '../../../hooks/useMatrixClient';
import { eventWithShortcode, factoryEventSentBy } from '../../../utils/matrix';
import { Reaction, ReactionTooltipMsg } from '../../../components/message';
import { useRelations } from '../../../hooks/useRelations';
import * as css from './styles.css';
import { ReactionViewer } from '../reaction-viewer';
import { stopPropagation } from '../../../utils/keyboard';
import { useMediaAuthentication } from '../../../hooks/useMediaAuthentication';
import { expandedReactionMessages, fitReactionRow } from '../../../utils/reactionOverflow';

export type ReactionsProps = {
  room: Room;
  mEventId: string;
  canSendReaction?: boolean;
  relations: Relations;
  onReactionToggle: (targetEventId: string, key: string, shortcode?: string) => void;
};
export const Reactions = as<'div', ReactionsProps>(
  ({ className, room, relations, mEventId, canSendReaction, onReactionToggle, ...props }, ref) => {
    const mx = useMatrixClient();
    const useAuthentication = useMediaAuthentication();
    const [viewer, setViewer] = useState<boolean | string>(false);
    const myUserId = mx.getUserId();
    const reactions = useRelations(
      relations,
      useCallback((rel) => [...(rel.getSortedAnnotationsByKey() ?? [])], []),
    );

    // [Gitea #138] Collapse to one row + "+N" when the chips would wrap.
    // Overflowing chips stay in the DOM (invisible, clipped by max-height) so
    // the container keeps its natural width and every chip stays measurable.
    const [expanded, setExpandedState] = useState(() => expandedReactionMessages.has(mEventId));
    const setExpanded = (next: boolean) => {
      if (next) expandedReactionMessages.add(mEventId);
      else expandedReactionMessages.delete(mEventId);
      setExpandedState(next);
    };
    const [limit, setLimit] = useState<number | undefined>();
    const [rowHeight, setRowHeight] = useState<number | undefined>();
    const containerRef = useRef<HTMLDivElement | null>(null);
    const moreRef = useRef<HTMLButtonElement | null>(null);
    const chipRefs = useRef(new Map<string, HTMLElement>());
    const keys = reactions.map(([key]) => key).join('\u0000');

    const measure = useCallback(() => {
      const container = containerRef.current;
      if (!container) return;
      const rowWidth = container.getBoundingClientRect().width;
      const gap = parseFloat(getComputedStyle(container).columnGap) || 8;
      const chips = keys ? keys.split('\u0000').map((k) => chipRefs.current.get(k)) : [];
      const widths = chips.map((el) => el?.getBoundingClientRect().width ?? 0);
      const moreWidth = moreRef.current?.getBoundingClientRect().width ?? 48;
      setLimit(fitReactionRow(widths, moreWidth, gap, rowWidth));
      setRowHeight(Math.max(0, ...chips.map((el) => el?.getBoundingClientRect().height ?? 0)));
    }, [keys]);

    useLayoutEffect(() => {
      measure();
    }, [measure]);
    useEffect(() => {
      const container = containerRef.current;
      if (!container || typeof ResizeObserver === 'undefined') return undefined;
      const ro = new ResizeObserver(() => measure());
      ro.observe(container);
      return () => ro.disconnect();
    }, [measure]);

    const collapsed = !expanded && limit !== undefined;
    const hiddenCount = collapsed ? reactions.length - (limit ?? 0) : 0;
    const hiddenStyle: React.CSSProperties = { visibility: 'hidden', pointerEvents: 'none' };

    const handleViewReaction: MouseEventHandler<HTMLButtonElement> = (evt) => {
      evt.stopPropagation();
      evt.preventDefault();
      const key = evt.currentTarget.getAttribute('data-reaction-key');
      if (!key) setViewer(true);
      else setViewer(key);
    };

    return (
      <Box
        className={classNames(css.ReactionsContainer, className)}
        gap="200"
        wrap="Wrap"
        {...props}
        style={{
          ...props.style,
          ...(collapsed && rowHeight
            ? // 2px breathing room so row-1 focus outlines are not clipped.
              { maxHeight: rowHeight + 4, overflow: 'hidden', padding: 2, margin: -2 }
            : {}),
        }}
        ref={(el) => {
          containerRef.current = el;
          if (typeof ref === 'function') ref(el);
          else if (ref) (ref as React.MutableRefObject<HTMLDivElement | null>).current = el;
        }}
      >
        {reactions.map(([key, events], index) => {
          const rEvents = Array.from(events);
          if (rEvents.length === 0 || typeof key !== 'string') return null;
          const myREvent = myUserId ? rEvents.find(factoryEventSentBy(myUserId)) : undefined;
          const isPressed = !!myREvent?.getRelation();
          const hidden = collapsed && index >= (limit ?? 0);
          const chip = (targetRef?: React.RefCallback<HTMLElement>) => (
            <Reaction
              ref={(el: HTMLElement | null) => {
                targetRef?.(el);
                if (el) chipRefs.current.set(key, el);
                else chipRefs.current.delete(key);
              }}
              data-reaction-key={key}
              aria-pressed={isPressed}
              key={key}
              mx={mx}
              reaction={key}
              shortcode={rEvents.find(eventWithShortcode)?.getContent().shortcode}
              count={events.size}
              onClick={canSendReaction ? () => onReactionToggle(mEventId, key) : undefined}
              onContextMenu={handleViewReaction}
              aria-disabled={!canSendReaction}
              aria-hidden={hidden || undefined}
              tabIndex={hidden ? -1 : undefined}
              style={hidden ? hiddenStyle : undefined}
              useAuthentication={useAuthentication}
            />
          );
          // The "+N" chip sits right after the last visible chip so it lands on row 1.
          const moreChip = index === (limit ?? 0) - 1 && (
            <button
              key="more"
              ref={moreRef}
              type="button"
              className={css.ReactionsMore}
              onClick={() => setExpanded(true)}
              aria-expanded={false}
              aria-label={`Show ${hiddenCount} more reactions`}
              aria-hidden={!collapsed || undefined}
              tabIndex={collapsed ? undefined : -1}
              style={collapsed ? undefined : { ...hiddenStyle, position: 'absolute' }}
            >
              <Text as="span" size="T300" dir="ltr">
                {`+${collapsed ? hiddenCount : reactions.length - 1}`}
              </Text>
            </button>
          );
          if (hidden) return <React.Fragment key={key}>{chip()}</React.Fragment>;

          return (
            <React.Fragment key={key}>
              <TooltipProvider
                position="Top"
                tooltip={
                  <Tooltip style={{ maxWidth: toRem(200) }}>
                    <Text className={css.ReactionsTooltipText} size="T300">
                      <ReactionTooltipMsg room={room} reaction={key} events={rEvents} />
                    </Text>
                  </Tooltip>
                }
              >
                {(targetRef) => chip(targetRef)}
              </TooltipProvider>
              {moreChip}
            </React.Fragment>
          );
        })}
        {expanded && limit !== undefined && (
          <button
            type="button"
            className={css.ReactionsMore}
            onClick={() => setExpanded(false)}
            aria-expanded
            aria-label="Show fewer reactions"
          >
            <Text as="span" size="T300">
              less
            </Text>
          </button>
        )}
        {reactions.length > 0 && (
          <Overlay
            onContextMenu={(evt: React.MouseEvent) => {
              evt.stopPropagation();
            }}
            open={!!viewer}
            backdrop={<OverlayBackdrop />}
          >
            <OverlayCenter>
              <FocusTrap
                focusTrapOptions={{
                  // #185 P5: move focus into the viewer so it is announced (it opened
                  // silently with focus left on the reaction behind it).
                  initialFocus: '[data-reaction-viewer]',
                  onDeactivate: () => setViewer(false),
                  clickOutsideDeactivates: true,
                  escapeDeactivates: stopPropagation,
                }}
              >
                <Modal
                  variant="Surface"
                  size="300"
                  role="dialog"
                  aria-modal="true"
                  aria-label="Reactions"
                  data-reaction-viewer=""
                  tabIndex={-1}
                  style={{ outline: 'none' }}
                >
                  <ReactionViewer
                    room={room}
                    initialKey={typeof viewer === 'string' ? viewer : undefined}
                    relations={relations}
                    requestClose={() => setViewer(false)}
                  />
                </Modal>
              </FocusTrap>
            </OverlayCenter>
          </Overlay>
        )}
      </Box>
    );
  },
);