// Modified version based on 'highlight-words-core'
import { isString } from 'lodash';
import BaseFoundation, { DefaultAdapter } from '../base/foundation';

interface HighlightAdapter extends Partial<DefaultAdapter> {}

interface ChunkQuery {
    autoEscape?: boolean;
    caseSensitive?: boolean;
    searchWords: SearchWords;
    sourceString: string
}
export interface Chunk {
    start: number;
    end: number;
    highlight: boolean;
    className: string;
    style: Record<string, string>
}

export interface ComplexSearchWord {
    text: string;
    className?: string;
    style?: Record<string, string>
}

export type SearchWord = string | ComplexSearchWord | undefined;
export type SearchWords = SearchWord[];

const escapeRegExpFn = (string: string) => string.replace(/[\-\[\]\/\{\}\(\)\*\+\?\.\\\^\$\|]/g, '\\$&');

export default class HighlightFoundation extends BaseFoundation<HighlightAdapter> {

    constructor(adapter?: HighlightAdapter) {
        super({
            ...adapter,
        });
    }

    /**
     * Creates an array of chunk objects representing both higlightable and non highlightable pieces of text that match each search word.
     *
        findAll ['z'], 'aaazaaazaaa'
            result #=> [
                { start: 0, end: 3, highlight: false }
                { start: 3, end: 4, highlight: true }
                { start: 4, end: 7, highlight: false }
                { start: 7, end: 8, highlight: true }
                { start: 8, end: 11, highlight: false }
            ]

        findAll ['do', 'dollar'], 'aaa do dollar aaa'
            #=> chunks: [
                    { start: 4, end: 6 },
                    { start: 7, end: 9 },
                    { start: 7, end: 13 },
                ]
            #=> chunksToHight: [
                    { start: 4, end: 6 },
                    { start: 7, end: 13 },
                ]
            #=> result: [
                    { start: 0, end: 4, highlight: false },
                    { start: 4, end: 6, highlight: true },
                    { start: 6, end: 7, highlight: false },
                    { start: 7, end: 13, highlight: true },
                    { start: 13, end: 17, highlight: false },
                ]

    * @return Array of "chunks" (where a Chunk is { start:number, end:number, highlight:boolean })
    */
    findAll = ({
        autoEscape = true,
        caseSensitive = false,
        searchWords,
        sourceString
    }: ChunkQuery) => {
        if (isString(searchWords)) {
            searchWords = [searchWords];
        }

        const chunks = this.findChunks({
            autoEscape,
            caseSensitive,
            searchWords,
            sourceString
        });
        const chunksToHighlight = this.combineChunks({ chunks });
        const result = this.fillInChunks({
            chunksToHighlight,
            totalLength: sourceString ? sourceString.length : 0
        });
        return result;
    };

    /**
        * Examine text for any matches.
        * If we find matches, add them to the returned array as a "chunk" object ({start:number, end:number}).
        * @return { start:number, end:number }[]
    */
    findChunks = ({
        autoEscape,
        caseSensitive,
        searchWords,
        sourceString
    }: ChunkQuery): Chunk[] => (
        searchWords
            .map(searchWord => typeof searchWord === 'string' ? { text: searchWord } : searchWord)
            .filter(searchWord => searchWord.text) // Remove empty words
            .reduce((chunks, searchWord) => {
                let searchText = searchWord.text;
                if (autoEscape) {
                    searchText = escapeRegExpFn(searchText);
                }
                const regex = new RegExp(searchText, caseSensitive ? 'g' : 'gi');

                let match;
                while ((match = regex.exec(sourceString))) {
                    const start = match.index;
                    const end = regex.lastIndex;
                    if (end > start) {
                        chunks.push({ 
                            highlight: true, 
                            start, 
                            end, 
                            className: searchWord.className,
                            style: searchWord.style
                        });
                    }
                    if (match.index === regex.lastIndex) {
                        regex.lastIndex++;
                    }
                }
                return chunks;
            }, [])
    );

    /**
   * Takes an array of {start:number, end:number} objects and combines chunks that overlap into single chunks.
   * @return {start:number, end:number}[]
   */
    combineChunks = ({ chunks }: { chunks: Chunk[] }): Chunk[] => {
        return chunks
            .sort((first, second) => first.start - second.start)
            .reduce((processedChunks, nextChunk) => {
            // First chunk just goes straight in the array...
                if (processedChunks.length === 0) {
                    return [nextChunk];
                } else {
                // ... subsequent chunks get checked to see if they overlap...
                    const prevChunk = processedChunks.pop();
                    if (nextChunk.start <= prevChunk.end) {
                    // It may be the case that prevChunk completely surrounds nextChunk, so take the
                    // largest of the end indeces.
                        const endIndex = Math.max(prevChunk.end, nextChunk.end);
                        processedChunks.push({
                            highlight: true,
                            start: prevChunk.start,
                            end: endIndex,
                            className: prevChunk.className || nextChunk.className,
                            style: { ...prevChunk.style, ...nextChunk.style }
                        });
                    } else {
                        processedChunks.push(prevChunk, nextChunk);
                    }
                    return processedChunks;
                }
            }, []);
    };

    /**
   * Given a set of chunks to highlight, create an additional set of chunks
   * to represent the bits of text between the highlighted text.
   * @param chunksToHighlight {start:number, end:number}[]
   * @param totalLength number
   * @return {start:number, end:number, highlight:boolean}[]
   */
    fillInChunks = ({ chunksToHighlight, totalLength }: { chunksToHighlight: Chunk[]; totalLength: number }): Chunk[] => {
        const allChunks: Chunk[] = [];
        const append = (start: number, end: number, highlight: boolean, className?: string, style?: Record<string, string>) => {
            if (end - start > 0) {
                allChunks.push({
                    start,
                    end,
                    highlight,
                    className,
                    style
                });
            }
        };

        if (chunksToHighlight.length === 0) {
            append(0, totalLength, false);
        } else {
            let lastIndex = 0;
            chunksToHighlight.forEach(chunk => {
                append(lastIndex, chunk.start, false);
                append(chunk.start, chunk.end, true, chunk.className, chunk.style);
                lastIndex = chunk.end;
            });
            append(lastIndex, totalLength, false);
        }
        return allChunks;
    };

}