// Forked version of useReducerWithEmitEffect.js, but with 
// 1) the ability to send from within an effect
// 2) cancel an effect (with an option to cancel on unmount)
// NOTE: no tests and not 100% sure of the implementation.

const {
  useCallback,
  useEffect,
  useLayoutEffect,
  useReducer,
  useRef,
} = require('react');

let globalCancelId = 0;
let effectCapture = null;
let cancelCapture = null;

export function useReducerWithEmitEffect(reducer, initialArg, init) {
  let isMounted = useRef(false);
  let updateCounter = useRef(0);
  let cancelables = useRef(null);

  if (cancelables.current == null) {
    cancelables.current = Object.create(null);
  }

  // Track if isMounted
  useLayoutEffect(() => {
    isMounted.current = true;
    return () => {
      isMounted.current = false;
    };
  }, []);

  let wrappedReducer = useCallback(
    function(oldWrappedState, action) {
      effectCapture = [];
      cancelCapture = [];
      try {
        let newState = reducer(oldWrappedState.state, action.action);
        let lastAppliedContiguousUpdate =
          oldWrappedState.lastAppliedContiguousUpdate;
        let effects = oldWrappedState.effects || [];
        let cancels = oldWrappedState.cancels || [];
        if (lastAppliedContiguousUpdate + 1 === action.updateCount) {
          lastAppliedContiguousUpdate++;
          effects.push(...effectCapture);
          cancels.push(...cancelCapture);
        }
        return {
          state: newState,
          lastAppliedContiguousUpdate,
          effects,
          cancels,
        };
      } finally {
        effectCapture = null;
        cancelCapture = null;
      }
    },
    [reducer]
  );
  let [wrappedState, rawDispatch] = useReducer(
    wrappedReducer,
    undefined,
    function() {
      let initialState;
      if (init !== undefined) {
        initialState = init(initialArg);
      } else {
        initialState = initialArg;
      }
      return {
        state: initialState,
        lastAppliedContiguousUpdate: 0,
        effects: null,
        cancels: null,
      };
    }
  );
  let dispatch = useCallback(function(action) {
    if (isMounted.current) {
      updateCounter.current++;
      rawDispatch({ updateCount: updateCounter.current, action });
    }
  }, []);
  useEffect(function() {
    let ignoredEffects = Object.create(null);

    if (wrappedState.cancels) {
      wrappedState.cancels.forEach(function(id) {
        const cancelObj = cancelables.current[id];

        if (cancelObj && cancelObj.cancelFn) {
          cancelObj.cancelFn();
        } else {
          ignoredEffects[id] = true;
        }

        delete cancelables.current[id];
      });
    }

    if (wrappedState.effects) {
      wrappedState.effects.forEach(function(eff) {
        // Don't run if already canceled
        if (!ignoredEffects[eff.id]) {
          const cancelFn = eff.effectFn(dispatch);
          if (cancelFn && typeof cancelFn === 'function') {
            cancelables.current[eff.id] = { cancelFn, options: eff.options };
          }
        }
      });
    }

    wrappedState.cancels = null;
    wrappedState.effects = null;

    return () => {
      if (!isMounted.current) {
        Object.keys(cancelables.current).forEach(id => {
          const { cancelFn, options } = cancelables.current[id];

          if (options.cancelOnUnmount && cancelFn) {
            cancelFn();
          }

          delete cancelables.current[id];
        });
      }
    };
  });
  return [wrappedState.state, dispatch];
}

var defaultEmitOptions = {
  cancelOnUnmount: false,
};

export function emitEffect(effectFn, options) {
  if (!effectCapture) {
    throw new Error(
      'emitEffect can only be called from a useReducerWithEmitEffect reducer'
    );
  }

  const id = globalCancelId++;

  effectCapture.push({
    id: id,
    effectFn: effectFn,
    options: Object.assign({}, defaultEmitOptions, options),
  });

  return id;
}

export function cancelEffect(id) {
  if (!effectCapture) {
    throw new Error(
      'cancelEffect can only be called from a useReducerWithEmitEffect reducer'
    );
  }

  cancelCapture.push(id);
}