import {
  CodeLensProvider,
  TextDocument,
  CodeLens,
  Range,
  Command
} from "vscode";

export interface Reference {
  document: TextDocument;
  citekey: string;
  pagenr: number | null;
  range: Range;
}

export class ZoteroCodeLensProvider implements CodeLensProvider {
  // Each provider requires a provideCodeLenses function which will give the various documents
  // the code lenses
  async provideCodeLenses(document: TextDocument): Promise<CodeLens[]> {

    const references = this.findReferences(document);

    return references
      // sort by line, citekey, pagenr
      .sort((a, b) => {
        if (a.range.start.line !== b.range.start.line) {
          return a.range.start.line - b.range.start.line;
        }
        if (a.citekey !== b.citekey) {
          return a.citekey.localeCompare(b.citekey);
        }
        // nulls sort before anything else
        if (a.pagenr === null) {
          return -1;
        }
        if (b.pagenr === null) {
          return 1;
        }
        return a.pagenr - b.pagenr;
      })
      // remove duplicate items (which are in sequence)
      .filter((reference, index) => {
        if (index === 0) { return true; }
        if (
          references[index - 1].range.start.line !== reference.range.start.line ||
          references[index - 1].citekey !== reference.citekey ||
          references[index - 1].pagenr !== reference.pagenr
        ) {
          return true;
        }
        return false;
      })
      .map((reference, index) => {
        let title = "";
        if (
          index === 0 ||
          references[index - 1].range.start.line !== reference.range.start.line ||
          references[index - 1].citekey !== reference.citekey
        ) {
          title = `@${reference.citekey}`;
          if (reference.pagenr) {
            title += ` p.${reference.pagenr}`;
          }
        } else {
          // there has to be a pagenr because of filtering
          title = `p.${reference.pagenr}`; 
        }

        // ignore char pos so that the order of the array
        // is actually used (by default CodeLenses are sorted by position)
        const range = new Range(
          reference.range.start.line, 0,
          reference.range.end.line, 0
        );

        return [
          new CodeLens(range, {
            title: title,
            // command: 'zoterolens.showInZotero',
            command: 'zoterolens.openZoteroPDF',
            arguments: [reference]
          }),
          // new CodeLens(reference.range, {
          //   title: '(pdf)',
          //   command: 'zoterolens.openZoteroPDF',
          //   arguments: [reference]
          // })
        ]
      })
      .flat();


    // let codeLens = new CodeLens(topOfDocument, c);

    // return [codeLens];
  }

  // TODO match citations in brackets [@citation] inline @citatinon,
  // but also page number in [see @citation p.23] and
  // inlince @citation [p.23] (so brackets after inline)
  // TODO possibly use https://github.com/martinring/markdown-it-citations/blob/ba82a511de047a2438b4ac060c4c71b5a5c82da9/src/index.ts#L43
  findReferences(document: TextDocument): Reference[] {
    const matches: Reference[] = [];
    for (let lineNr = 0; lineNr < document.lineCount; lineNr++) {
      const line = document.lineAt(lineNr);
      let match: RegExpExecArray | null;
      let regex = /(?<=@)([\w\.]+)[, ]*\[?(?:[p]{0,2}\.)?(\d+)?(?:-+\d+)?\]?/g;
      regex.lastIndex = 0;
      const text = line.text;//.substring(0, 1000);
      while ((match = regex.exec(text))) {
        const result = {
          document: document,
          citekey: match[1],
          pagenr: match[2] ? parseInt(match[2]) : null,
          range: new Range(lineNr, match.index, lineNr, match.index + match[0].length)
        } as Reference;
        // if (result) {
        matches.push(result);
        // }
      }
    }
    return matches;
  }
}