/*
 * Copyright 2021 Palantir Technologies, Inc. All rights reserved.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

import { createContext, useCallback, useMemo, useReducer } from "react";

import { shallowCompareKeys } from "../../common/utils";
import { HotkeysDialog, type HotkeysDialogProps } from "../../components/hotkeys/hotkeysDialog";
import type { HotkeyConfig } from "../../hooks";

interface HotkeysContextState {
    /**
     * Whether the context instance is being used within a tree which has a <HotkeysProvider>.
     * It's technically ok if this is false, but not recommended, since that means any hotkeys
     * bound with that context instance will not show up in the hotkeys help dialog.
     */
    hasProvider: boolean;

    /** List of hotkeys accessible in the current scope, registered by currently mounted components, can be global or local. */
    hotkeys: HotkeyConfig[];

    /** Whether the global hotkeys dialog is open. */
    isDialogOpen: boolean;
}

type HotkeysAction =
    | { type: "ADD_HOTKEYS" | "REMOVE_HOTKEYS"; payload: HotkeyConfig[] }
    | { type: "CLOSE_DIALOG" | "OPEN_DIALOG" };

export type HotkeysContextInstance = readonly [HotkeysContextState, React.Dispatch<HotkeysAction>];

const initialHotkeysState: HotkeysContextState = { hasProvider: false, hotkeys: [], isDialogOpen: false };
const noOpDispatch: React.Dispatch<HotkeysAction> = () => null;

/**
 * A React context used to register and deregister hotkeys as components are mounted and unmounted in an application.
 * Users should take care to make sure that only _one_ of these is instantiated and used within an application, especially
 * if using global hotkeys.
 *
 * You will likely not be using this HotkeysContext directly, except in cases where you need to get a direct handle on an
 * existing context instance for advanced use cases involving nested HotkeysProviders.
 *
 * For more information, see the [HotkeysProvider documentation](https://blueprintjs.com/docs/#core/context/hotkeys-provider).
 */
export const HotkeysContext = createContext<HotkeysContextInstance>([initialHotkeysState, noOpDispatch]);

const hotkeysReducer = (state: HotkeysContextState, action: HotkeysAction) => {
    switch (action.type) {
        case "ADD_HOTKEYS":
            // only pick up unique hotkeys which haven't been registered already
            const newUniqueHotkeys = [];
            for (const a of action.payload) {
                let isUnique = true;
                for (const b of state.hotkeys) {
                    isUnique &&= !shallowCompareKeys(a, b, { exclude: ["onKeyDown", "onKeyUp"] });
                }
                if (isUnique) {
                    newUniqueHotkeys.push(a);
                }
            }
            return {
                ...state,
                hotkeys: [...state.hotkeys, ...newUniqueHotkeys],
            };
        case "REMOVE_HOTKEYS":
            return {
                ...state,
                hotkeys: state.hotkeys.filter(key => action.payload.indexOf(key) === -1),
            };
        case "OPEN_DIALOG":
            return { ...state, isDialogOpen: true };
        case "CLOSE_DIALOG":
            return { ...state, isDialogOpen: false };
        default:
            return state;
    }
};

export interface HotkeysProviderProps {
    /** Optional props to customize the rendered hotkeys dialog. */
    dialogProps?: Partial<Omit<HotkeysDialogProps, "hotkeys">>;

    /** If provided, this dialog render function will be used in place of the default implementation. */
    renderDialog?: (state: HotkeysContextState, contextActions: { handleDialogClose: () => void }) => React.JSX.Element;

    /** If provided, we will use this context instance instead of generating our own. */
    value?: HotkeysContextInstance;
}

/**
 * Hotkeys context provider, necessary for the `useHotkeys` hook.
 *
 * @see https://blueprintjs.com/docs/#core/context/hotkeys-provider
 */
export const HotkeysProvider = ({
    children,
    dialogProps,
    renderDialog,
    value,
}: React.PropsWithChildren<HotkeysProviderProps>) => {
    const hasExistingContext = value != null;
    const fallbackReducer = useReducer(hotkeysReducer, { ...initialHotkeysState, hasProvider: true });
    const [state, dispatch] = value ?? fallbackReducer;
    // The `useState` array isn't stable between renders -- so memo it outselves
    const contextValue = useMemo(() => [state, dispatch] as const, [state, dispatch]);
    const handleDialogClose = useCallback(() => dispatch({ type: "CLOSE_DIALOG" }), [dispatch]);

    const dialog = renderDialog?.(state, { handleDialogClose }) ?? (
        <HotkeysDialog
            {...dialogProps}
            isOpen={state.isDialogOpen}
            hotkeys={state.hotkeys}
            onClose={handleDialogClose}
        />
    );

    // if we are working with an existing context, we don't need to generate our own dialog
    return (
        <HotkeysContext.Provider value={contextValue}>
            {children}
            {hasExistingContext ? undefined : dialog}
        </HotkeysContext.Provider>
    );
};