import fs from "fs";
import MarkdownIt from "markdown-it";
import { RuleBlock } from "markdown-it/lib/parser_block";

export default (md: MarkdownIt): void => {
  const parser: RuleBlock = (state, startLine, endLine, silent) => {
    const CH = "<".charCodeAt(0);
    const pos = state.bMarks[startLine] + state.tShift[startLine];
    const max = state.eMarks[startLine];
    if (state.sCount[startLine] - state.blkIndent >= 4) {
      return false;
    }
    for (let i = 0; i < 3; ++i) {
      const ch = state.src.charCodeAt(pos + i);
      if (ch !== CH || pos + i >= max) return false;
    }
    if (silent) {
      return true;
    }
    const start = pos + 3;
    const end = state.skipSpacesBack(max, pos);
    const rawPath = state.src
      .slice(start, end)
      .trim()
      .replace(/^@/, process.cwd());
    const content = fs.existsSync(rawPath)
      ? fs.readFileSync(rawPath).toString()
      : "Not found: " + rawPath;
    const meta = rawPath.replace(rawPath, "");
    state.line = startLine + 1;
    const token = state.push("fence", "code", 0);
    token.info = rawPath.split(".").pop() + meta;
    token.content = content;
    token.markup = "```";
    token.map = [startLine, startLine + 1];
    return true;
  };
  md.block.ruler.before("fence", "snippet", parser);
};