import fs from "fs";
import path from "path";
import cfg from "./config.mjs";

export default new class {
  #templates = {};
  #syntax = [
    [ "each", (t, _, args = t.slice(4).trim().split(" ")) => `util.forEach(${args[0]},(${(args[1] === "as" && args[2]) ? args[2] : "value"},key)=>{` ],
    [ "/each", () => "});" ],
    [ "if", t => `if(${t.slice(2).trim()}){` ],
    [ "elseif", t => `}else if(${t.slice(6).trim()}){` ],
    [ "else", () => "}else{" ],
    [ "/if", () => "}" ],
    [ "include", (t, data) => `html+='${this.render(cfg.websrv.cache ? t.slice(7).trim() : `views/${t.slice(7).trim()}`, data)}';` ],
    [ "=", t => `html+=${t.slice(1).trim()};` ]
  ];
  readdir(dir, root = dir, rel = dir.replace(`${root}/`, "")) {
    for(const d of fs.readdirSync(`${path.resolve()}/${dir}`))
      d.endsWith(".html")
        ? this.#templates[`${rel}/${d.split(".")[0]}`] = this.readtpl(dir, d)
        : this.readdir(`${dir}/${d}`, root);
  }
  readtpl(dir, d) {
    return fs.readFileSync(`${dir}/${d}`, "utf-8").replace(/\'/g, "\\'");
  }
  forEach(o, f) {
    if(Array.isArray(o))
      o.forEach(f);
    else if(typeof o === "object")
      Object.keys(o).forEach(k => f.call(null, o[k], k));
    else
      throw new Error(`${o} is not a iterable object`);
  }
  render(tpl, data = {}, f) {
    return new Function("util", "data", "let html = \"\";with(data){" + (cfg.websrv.cache ? this.#templates[tpl] : this.readtpl(path.resolve(), `${tpl}.html`))
      .trim()
      .replace(/[\n\r]/g, "")
      .split(/{{\s*([^}]+)\s*}}/)
      .filter(Boolean)
      .map(t => !(f = this.#syntax.filter(s => t.startsWith(s[0]))[0]) ? `html+='${t}';` : f[1](t, data))
      .join("") + "}return html.trim().replace(/>[\\n\\r\\s]*?</g, '><')"
    ).bind(null, { forEach: this.forEach })(data);
  }
};