import { deepEqual } from "fast-equals";
import * as React from "react";
import {
  Action,
  ActionId,
  ActionTree,
  KBarProviderProps,
  KBarState,
  KBarOptions,
  VisualState,
} from "./types";

type useStoreProps = KBarProviderProps;

export default function useStore(props: useStoreProps) {
  if (!props.actions) {
    throw new Error(
      "You must define a list of `actions` when calling KBarProvider"
    );
  }

  // TODO: at this point useReducer might be a better approach to managing state.
  const [state, setState] = React.useState<KBarState>({
    searchQuery: "",
    currentRootActionId: null,
    visualState: VisualState.hidden,
    actions: props.actions.reduce((acc, curr) => {
      acc[curr.id] = curr;
      return acc;
    }, {}),
  });

  React.useEffect(() => {
    setState((state) => ({
      ...state,
      actions: props.actions.reduce((acc, curr) => {
        acc[curr.id] = curr;
        return acc;
      }, {}),
    }));
  }, [props]);

  const currState = React.useRef(state);
  currState.current = state;

  const getState = React.useCallback(() => currState.current, []);
  const publisher = React.useMemo(() => new Publisher(getState), [getState]);

  React.useEffect(() => {
    currState.current = state;
    publisher.notify();
  }, [state, publisher]);

  const optionsRef = React.useRef({
    animations: {
      enterMs: 200,
      exitMs: 100,
    },
    ...props.options,
  } as KBarOptions);

  const registerActions = React.useCallback((actions: Action[]) => {
    const actionsByKey: ActionTree = actions.reduce((acc, curr) => {
      acc[curr.id] = curr;
      return acc;
    }, {});

    setState((state) => {
      actions.forEach((action) => {
        if (action.parent) {
          const parent =
            // parent could have already existed or parent is defined alongside children.
            state.actions[action.parent] || actionsByKey[action.parent];

          if (!parent) {
            throw new Error(`Action of id ${action.parent} does not exist.`);
          }

          if (!parent.children) parent.children = [];
          if (parent.children.includes(action.id)) return;
          parent.children.push(action.id);
        }
      });

      return {
        ...state,
        actions: {
          ...actionsByKey,
          ...state.actions,
        },
      };
    });

    return function unregister() {
      setState((state) => {
        const allActions = state.actions;
        const removeActionIds = actions.map((action) => action.id);
        removeActionIds.forEach((actionId) => {
          const action = state.actions[actionId];
          if (action?.parent) {
            const parent = state.actions[action.parent];
            if (!parent?.children) {
              return;
            }
            parent.children = parent.children.filter(
              (child) => child !== actionId
            );
          }
          delete allActions[actionId];
        });
        return {
          ...state,
          actions: allActions,
        };
      });
    };
  }, []);

  return React.useMemo(() => {
    return {
      getState,
      query: {
        setCurrentRootAction: (actionId: ActionId | null | undefined) => {
          setState((state) => ({
            ...state,
            currentRootActionId: actionId,
          }));
        },
        setVisualState: (
          cb: ((vs: VisualState) => VisualState) | VisualState
        ) => {
          setState((state) => ({
            ...state,
            visualState: typeof cb === "function" ? cb(state.visualState) : cb,
          }));
        },
        setSearch: (searchQuery: string) =>
          setState((state) => ({
            ...state,
            searchQuery,
          })),
        registerActions,
        toggle: () =>
          setState((state) => ({
            ...state,
            visualState: [
              VisualState.animatingOut,
              VisualState.hidden,
            ].includes(state.visualState)
              ? VisualState.animatingIn
              : VisualState.animatingOut,
          })),
      },
      options: optionsRef.current,
      subscribe: function subscribe<C>(
        collector: (state: KBarState) => C,
        cb: (collected: C) => void
      ) {
        return publisher.subscribe(collector, cb);
      },
    };
  }, [getState, publisher, registerActions]);
}

class Publisher {
  getState;
  subscribers: Subscriber[] = [];

  constructor(getState: () => KBarState) {
    this.getState = getState;
  }

  subscribe<C>(
    collector: (state: KBarState) => C,
    onChange: (collected: C) => void
  ) {
    const subscriber = new Subscriber(
      () => collector(this.getState()),
      onChange
    );
    this.subscribers.push(subscriber);
    return this.unsubscribe.bind(this, subscriber);
  }

  unsubscribe(subscriber: Subscriber) {
    if (this.subscribers.length) {
      const index = this.subscribers.indexOf(subscriber);
      if (index > -1) {
        return this.subscribers.splice(index, 1);
      }
    }
  }

  notify() {
    this.subscribers.forEach((subscriber) => subscriber.collect());
  }
}

class Subscriber {
  collected: any;
  collector;
  onChange;

  constructor(collector: () => any, onChange: (collected: any) => any) {
    this.collector = collector;
    this.onChange = onChange;
  }

  collect() {
    try {
      // grab latest state
      const recollect = this.collector();
      if (!deepEqual(recollect, this.collected)) {
        this.collected = recollect;
        if (this.onChange) {
          this.onChange(this.collected);
        }
      }
    } catch (error) {
      console.warn(error);
    }
  }
}