import type { CompletionContext, CompletionResult } from '@codemirror/autocomplete';
import type { Element, MarkdownConfig } from '@lezer/markdown';
import { styleTags, tags } from '@lezer/highlight';
import { Content } from '../content.util';

function fuzzyMatch(text: string, search: string): number {
    const textLower = text.toLowerCase().normalize('NFC');
    const searchLower = search.toLowerCase().normalize('NFC');
    
    let searchIndex = 0;
    let score = 0;
    
    for (let i = 0; i < textLower.length && searchIndex < searchLower.length; i++) {
        if (textLower[i] === searchLower[searchIndex]) {
            score += 1;
            if (i === searchIndex) score += 2; // Bonus for sequential match
            searchIndex++;
        }
    }
    
    return searchIndex === searchLower.length ? score : 0;
}

export const wikilink: MarkdownConfig = {
    defineNodes: [
      'Wikilink',
      'WikilinkMeta',
      'WikilinkHref',
      'WikilinkTitle',
    ],
    parseInline: [{
        name: 'Wikilink',
        before: 'Link',
        parse(cx, next, pos)
        {
            // 91 == '['
            if (next !== 91 || cx.slice(pos, pos + 1).charCodeAt(0) !== 91) return -1;
            
            const match = /!?\[\[([^\[\]\|\#]+)?(#+[^\[\]\|\#]+)?(\|[^\[\]\|\#]+)?\]\]/.exec(cx.slice(pos, cx.end));
            if(!match) return -1;

            const start = pos, children: Element[] = [], end = start + match[0].length;

            children.push(cx.elt('WikilinkMeta', start, start + 2));

            if(match[1] && !match[2] && !match[3]) //Link only
            {
                children.push(cx.elt('WikilinkTitle', start + 2, end - 2));
            }
            else if(!match[1] && match[2] && match[3]) //Hash and title
            {
                children.push(cx.elt('WikilinkHref', start + 2, start + 2 + match[2].length));
                children.push(cx.elt('WikilinkMeta', start + 2 + match[2].length, start + 2 + match[2].length + 1));
                children.push(cx.elt('WikilinkTitle', start + 2 + match[2].length + 1, start + 2 + match[2].length + match[3].length));
            }
            else if(!match[1] && !match[2] && match[3]) //Hash only
            {
                children.push(cx.elt('WikilinkTitle', start + 2, end - 2));
            }
            else if(match[1] && match[2] && !match[3]) //Link and hash
            {
                children.push(cx.elt('WikilinkHref', start + 2, start + 2 + match[1].length));
                children.push(cx.elt('WikilinkTitle', start + 2 + match[1].length, start + 2 + match[1].length + match[2].length));
            }
            else if(match[1] && !match[2] && match[3]) //Link and title
            {
                children.push(cx.elt('WikilinkHref', start + 2, start + 2 + match[1].length));
                children.push(cx.elt('WikilinkMeta', start + 2 + match[1].length, start + 2 + match[1].length + 1));
                children.push(cx.elt('WikilinkTitle', start + 2 + match[1].length + 1, start + 2 + match[1].length + match[3].length));
            }
            else if(match[1] && match[2] && match[3]) //Link, hash and title
            {
                children.push(cx.elt('WikilinkHref', start + 2, start + 2 + match[1].length + match[2].length));
                children.push(cx.elt('WikilinkMeta', start + 2 + match[1].length + match[2].length, start + 2 + match[1].length + match[2].length + 1));
                children.push(cx.elt('WikilinkTitle', start + 2 + match[1].length + match[2].length + 1, start + 2 + match[1].length + match[2].length + match[3].length));
            }

            children.push(cx.elt('WikilinkMeta', end - 2, end));

            return cx.addElement(cx.elt('Wikilink', start, end, children));
        },
    }],
    props: [
        styleTags({
            'Wikilink': tags.special(tags.content),
            'WikilinkMeta': tags.meta,
            'WikilinkHref': tags.link,
            'WikilinkTitle': tags.special(tags.link),
        })
    ]
};
export const autocompletion = (context: CompletionContext): CompletionResult | null => {
    const word = context.matchBefore(/\[\[[\w\s-]*/);
    if (!word || (word.from === word.to && !context.explicit))
        return null;

    const searchTerm = word.text.slice(2).toLowerCase();

    const options = Object.values(Content.files).filter(e => e.type !== 'folder').map(e => ({ ...e, score: fuzzyMatch(e.title, searchTerm) })).filter(e => e.score > 0).sort((a, b) => b.score - a.score).slice(0, 50);

    return {
        from: word.from + 2,
        options: options.map(e => ({
            label: e.title,
            detail: e.path,
            apply: (view, completion, from, to) => {
                view.dispatch({
                    changes: {
                        from: word.from,
                        to: word.to,
                        insert: `[[${e.path}]]`
                    },
                    selection: { anchor: word.from + e.path.length + 2 }
                });
            },
            type: 'text'
        })),
        validFor: /^[\[\w\s-]*$/,
    }
};