/*
Copyright 2022 The Matrix.org Foundation C.I.C.

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 React, { useState, ReactNode, ChangeEvent, KeyboardEvent, useRef, ReactElement } from "react";
import classNames from "classnames";

import Autocompleter from "../../autocomplete/AutocompleteProvider";
import { Key } from "../../Keyboard";
import { ICompletion } from "../../autocomplete/Autocompleter";
import AccessibleButton from "../../components/views/elements/AccessibleButton";
import { Icon as PillRemoveIcon } from "../../../res/img/icon-pill-remove.svg";
import { Icon as SearchIcon } from "../../../res/img/element-icons/roomlist/search.svg";
import useFocus from "../../hooks/useFocus";

interface AutocompleteInputProps {
    provider: Autocompleter;
    placeholder: string;
    selection: ICompletion[];
    onSelectionChange: (selection: ICompletion[]) => void;
    maxSuggestions?: number;
    renderSuggestion?: (s: ICompletion) => ReactElement;
    renderSelection?: (m: ICompletion) => ReactElement;
    additionalFilter?: (suggestion: ICompletion) => boolean;
}

export const AutocompleteInput: React.FC<AutocompleteInputProps> = ({
    provider,
    renderSuggestion,
    renderSelection,
    maxSuggestions = 5,
    placeholder,
    onSelectionChange,
    selection,
    additionalFilter,
}) => {
    const [query, setQuery] = useState<string>("");
    const [suggestions, setSuggestions] = useState<ICompletion[]>([]);
    const [isFocused, onFocusChangeHandlerFunctions] = useFocus();
    const editorContainerRef = useRef<HTMLDivElement>(null);
    const editorRef = useRef<HTMLInputElement>(null);

    const focusEditor = (): void => {
        editorRef?.current?.focus();
    };

    const onQueryChange = async (e: ChangeEvent<HTMLInputElement>): Promise<void> => {
        const value = e.target.value.trim();
        setQuery(value);

        let matches = await provider.getCompletions(
            query,
            { start: query.length, end: query.length },
            true,
            maxSuggestions,
        );

        if (additionalFilter) {
            matches = matches.filter(additionalFilter);
        }

        setSuggestions(matches);
    };

    const onClickInputArea = (): void => {
        focusEditor();
    };

    const onKeyDown = (e: KeyboardEvent): void => {
        const hasModifiers = e.ctrlKey || e.shiftKey || e.metaKey;

        // when the field is empty and the user hits backspace remove the right-most target
        if (!query && selection.length > 0 && e.key === Key.BACKSPACE && !hasModifiers) {
            removeSelection(selection[selection.length - 1]);
        }
    };

    const toggleSelection = (completion: ICompletion): void => {
        const newSelection = [...selection];
        const index = selection.findIndex((selection) => selection.completionId === completion.completionId);

        if (index >= 0) {
            newSelection.splice(index, 1);
        } else {
            newSelection.push(completion);
        }

        onSelectionChange(newSelection);
        focusEditor();
    };

    const removeSelection = (completion: ICompletion): void => {
        const newSelection = [...selection];
        const index = selection.findIndex((selection) => selection.completionId === completion.completionId);

        if (index >= 0) {
            newSelection.splice(index, 1);
            onSelectionChange(newSelection);
        }
    };

    const hasPlaceholder = (): boolean => selection.length === 0 && query.length === 0;

    return (
        <div className="mx_AutocompleteInput">
            <div
                ref={editorContainerRef}
                className={classNames({
                    "mx_AutocompleteInput_editor": true,
                    "mx_AutocompleteInput_editor--focused": isFocused,
                    "mx_AutocompleteInput_editor--has-suggestions": suggestions.length > 0,
                })}
                onClick={onClickInputArea}
                data-testid="autocomplete-editor"
            >
                <SearchIcon className="mx_AutocompleteInput_search_icon" width={16} height={16} />
                {selection.map((item) => (
                    <SelectionItem
                        key={item.completionId}
                        item={item}
                        onClick={removeSelection}
                        render={renderSelection}
                    />
                ))}
                <input
                    ref={editorRef}
                    type="text"
                    onKeyDown={onKeyDown}
                    onChange={onQueryChange}
                    value={query}
                    autoComplete="off"
                    placeholder={hasPlaceholder() ? placeholder : undefined}
                    data-testid="autocomplete-input"
                    {...onFocusChangeHandlerFunctions}
                />
            </div>
            {isFocused && suggestions.length ? (
                <div
                    className="mx_AutocompleteInput_matches"
                    style={{ top: editorContainerRef.current?.clientHeight }}
                    data-testid="autocomplete-matches"
                >
                    {suggestions.map((item) => (
                        <SuggestionItem
                            key={item.completionId}
                            item={item}
                            selection={selection}
                            onClick={toggleSelection}
                            render={renderSuggestion}
                        />
                    ))}
                </div>
            ) : null}
        </div>
    );
};

type SelectionItemProps = {
    item: ICompletion;
    onClick: (completion: ICompletion) => void;
    render?: (completion: ICompletion) => ReactElement;
};

const SelectionItem: React.FC<SelectionItemProps> = ({ item, onClick, render }) => {
    const withContainer = (children: ReactNode): ReactElement => (
        <span
            className="mx_AutocompleteInput_editor_selection"
            data-testid={`autocomplete-selection-item-${item.completionId}`}
        >
            <span className="mx_AutocompleteInput_editor_selection_pill">{children}</span>
            <AccessibleButton
                className="mx_AutocompleteInput_editor_selection_remove_button"
                onClick={() => onClick(item)}
                data-testid={`autocomplete-selection-remove-button-${item.completionId}`}
            >
                <PillRemoveIcon width={8} height={8} />
            </AccessibleButton>
        </span>
    );

    if (render) {
        return withContainer(render(item));
    }

    return withContainer(<span className="mx_AutocompleteInput_editor_selection_text">{item.completion}</span>);
};

type SuggestionItemProps = {
    item: ICompletion;
    selection: ICompletion[];
    onClick: (completion: ICompletion) => void;
    render?: (completion: ICompletion) => ReactElement;
};

const SuggestionItem: React.FC<SuggestionItemProps> = ({ item, selection, onClick, render }) => {
    const isSelected = selection.some((selection) => selection.completionId === item.completionId);
    const classes = classNames({
        "mx_AutocompleteInput_suggestion": true,
        "mx_AutocompleteInput_suggestion--selected": isSelected,
    });

    const withContainer = (children: ReactNode): ReactElement => (
        <div
            className={classes}
            // `onClick` cannot be used here as it would lead to focus loss and closing the suggestion list.
            onMouseDown={(event) => {
                event.preventDefault();
                onClick(item);
            }}
            data-testid={`autocomplete-suggestion-item-${item.completionId}`}
        >
            {children}
        </div>
    );

    if (render) {
        return withContainer(render(item));
    }

    return withContainer(
        <>
            <span className="mx_AutocompleteInput_suggestion_title">{item.completion}</span>
            <span className="mx_AutocompleteInput_suggestion_description">{item.completionId}</span>
        </>,
    );
};