/** @module data */
/** @hidden */ 
let _ = require('lodash');

/**
 * Helper class to extract and process search tags from objects.
 * The search tags can be kept individually or embedded as hash tags inside text
 * like "This text has #hash_tag that can be used for search."
 */
export class TagsProcessor {
    private static NORMALIZE_REGEX = /(_|#)+/g;
    private static COMPRESS_REGEX = /( |_|#)+/g;
    private static SPLIT_REGEX = /(,|;)+/;
    private static HASHTAG_REGEX = /#\w+/g;

    /**
     * Normalizes a tag by replacing special symbols like '_' and '#' with spaces.
     * When tags are normalized then can be presented to user in similar shape and form.
     *
     * @param tag   the tag to normalize.
     * @return      a normalized tag.
     */
    public static normalizeTag(tag: string): string {
        return tag 
            ? _.trim(tag.replace(this.NORMALIZE_REGEX, ' ')) 
            : null;
    }

    /**
     * Compress a tag by removing special symbols like spaces, '_' and '#'
     * and converting the tag to lower case.
     * When tags are compressed they can be matched in search queries.
     *
     * @param tag   the tag to compress.
     * @return      a compressed tag.
     */
    public static compressTag(tag: string): string {
        return tag
            ? tag.replace(this.COMPRESS_REGEX, '').toLocaleLowerCase()
            : null;
    }

    /**
     * Compares two tags using their compressed form.
     *
     * @param tag1  the first tag.
     * @param tag2  the second tag.
     * @return      true if the tags are equal and false otherwise.
     */
    public static equalTags(tag1: string, tag2: string): boolean {
        if (tag1 == null && tag2 == null)
            return true;
        if (tag1 == null || tag2 == null)
            return false;
        return TagsProcessor.compressTag(tag1) == TagsProcessor.compressTag(tag2);
    }

    /**
     * Normalizes a list of tags.
     *
     * @param tags  the tags to normalize.
     * @return      a list with normalized tags.
     */
    public static normalizeTags(tags: string[]): string[] {
        return _.map(tags, (tag) => TagsProcessor.normalizeTag(tag));
    }

    /**
     * Normalizes a comma-separated list of tags.
     *
     * @param tagList  a comma-separated list of tags to normalize.
     * @return      a list with normalized tags.
     */
    public static normalizeTagList(tagList: string): string[] {
        let tags = tagList.split(this.SPLIT_REGEX);
        // Remove separators (JS only)
        for (let index = 0; index < tags.length - 1; index++)
           tags.splice(index + 1, 1);
        return this.normalizeTags(tags);
    }

    /**
     * Compresses a list of tags.
     *
     * @param tags  the tags to compress.
     * @return      a list with normalized tags.
     */
    public static compressTags(tags: string[]): string[] {
        return _.map(tags, (tag) => TagsProcessor.compressTag(tag));
    }

    /**
     * Compresses a comma-separated list of tags.
     *
     * @param tagList  a comma-separated list of tags to compress.
     * @return      a list with compressed tags.
     */
    public static compressTagList(tagList: string): string[] {
        let tags = tagList.split(this.SPLIT_REGEX);
        // Remove separators (JS only)
        for (let index = 0; index < tags.length - 1; index++)
           tags.splice(index + 1, 1);
        return this.compressTags(tags);
    }

    /**
     * Extracts hash tags from a text.
     *
     * @param text    a text that contains hash tags
     * @return        a list with extracted and compressed tags.
     */
    public static extractHashTags(text: string): string[] {
        let tags: string[];

        if (text != '') {
            let hashTags = text.match(TagsProcessor.HASHTAG_REGEX);
            tags = TagsProcessor.compressTags(hashTags);
        }

        return _.uniq(tags);
    }

    private static extractString(field: any): string {
        if (field == null) return '';
        if (_.isString(field)) return field;
        if (!_.isObject(field)) return '';
        
        let result = '';
        for (let prop in field) {
            result += ' ' + TagsProcessor.extractString(field[prop]);
        }
        return result;
    }

    /**
     * Extracts hash tags from selected fields in an object.
     *
     * @param obj           an object which contains hash tags.
     * @param searchFields  a list of fields in the objects where to extract tags
     * @return              a list of extracted and compressed tags.
     */
    public static extractHashTagsFromValue(obj: any, ...searchFields: string[]): string[] {
        // Todo: Use recursive
        let tags = TagsProcessor.compressTags(obj.tags);

        _.each(searchFields, (field) => {
            let text = TagsProcessor.extractString(obj[field]);

            if (text != '') {
                let hashTags = text.match(TagsProcessor.HASHTAG_REGEX);
                tags = tags.concat(TagsProcessor.compressTags(hashTags));
            }
        });

        return _.uniq(tags);
    }
}