import { useCallback, useEffect, useRef, useState } from 'react';

import { ipcChannels } from '../../../shared/ipc/contracts';
import type {
  SceneNpcTokensSessionEvent,
  SceneNpcTokensSessionState,
} from '../../../shared/types';
import {
  clampNpcTokenSessionScale,
  DEFAULT_NPC_TOKEN_SESSION_SCALE,
} from '../../../shared/types/appPlayers';
import { getDndApi } from '../dndApi';

function withScale(state: SceneNpcTokensSessionState): SceneNpcTokensSessionState {
  return {
    ...state,
    scale: clampNpcTokenSessionScale(state.scale),
  };
}

function applyEvent(
  prev: SceneNpcTokensSessionState,
  event: SceneNpcTokensSessionEvent,
): SceneNpcTokensSessionState {
  if (event.kind === 'clear') {
    return {
      revision: prev.revision + 1,
      byPlacementId: {},
      scale: DEFAULT_NPC_TOKEN_SESSION_SCALE,
    };
  }
  if (event.kind === 'setScale') {
    const scale = clampNpcTokenSessionScale(event.scale);
    if (prev.scale === scale) return prev;
    return { ...prev, revision: prev.revision + 1, scale };
  }
  return {
    revision: prev.revision + 1,
    byPlacementId: {
      ...prev.byPlacementId,
      [event.placementId]: { nx: event.nx, ny: event.ny },
    },
    scale: prev.scale ?? DEFAULT_NPC_TOKEN_SESSION_SCALE,
  };
}

export function useSceneNpcTokensSession(): [
  SceneNpcTokensSessionState,
  { dispatch: (event: SceneNpcTokensSessionEvent) => void },
] {
  const api = getDndApi();
  const [state, setState] = useState<SceneNpcTokensSessionState>({
    revision: 0,
    byPlacementId: {},
    scale: DEFAULT_NPC_TOKEN_SESSION_SCALE,
  });
  const localRevRef = useRef(0);

  useEffect(() => {
    void api.invoke(ipcChannels.sceneNpcTokensSession.getState, {}).then((res) => {
      const next = withScale(res.state);
      // Не затираем более свежий optimistic/broadcast стейт устаревшим getState.
      if (next.revision < localRevRef.current) return;
      localRevRef.current = next.revision;
      setState(next);
    });
    return api.on(ipcChannels.sceneNpcTokensSession.stateChanged, ({ state: incoming }) => {
      const next = withScale(incoming);
      if (next.revision < localRevRef.current) return;
      localRevRef.current = next.revision;
      setState(next);
    });
  }, [api]);

  const dispatch = useCallback(
    (event: SceneNpcTokensSessionEvent) => {
      setState((prev) => {
        const next = applyEvent(prev, event);
        localRevRef.current = Math.max(localRevRef.current, next.revision);
        return next;
      });
      void api.invoke(ipcChannels.sceneNpcTokensSession.dispatch, { event });
    },
    [api],
  );

  return [state, { dispatch }];
}