import { readdir, readFile } from "fs/promises";
import { join } from "path";
import * as yaml from "js-yaml";
import { plainToClass } from "class-transformer";
import { validate } from "class-validator";

import { init, Page, Exercise, Grader } from "./db/page";
import { Page as PageConfig, Exercise as ExerciseConfig, Grader as GraderConfig } from "./page";

// TODO: configure this thru cmdline or something later
let materials_dir = "../material";
let db_file = "test.db";

let db;
let SLUG_RE = /([A-Za-z\-\_]+)/;

async function loadPageIntoDb(name: string): Promise<void> {
  let slug_match = name.match(SLUG_RE);
  let slug = slug_match[0];

  // if this slug has already been loaded into the database, don't do anything
  let hasPage = await Page.count({ where: { slug }}) > 0;
  if (hasPage) { return; }

  let path = join(materials_dir, name);
  let rawData = await readFile(path, { encoding: "utf8" });
  let parsedData = yaml.load(rawData);
  let page_cfg = plainToClass(PageConfig, parsedData);
  await validate(page_cfg);

  // save page
  let page = new Page({
    slug,
    title: page_cfg.title,
    type: page_cfg.type,
    content: page_cfg.content,
  });
  await page.save();

  // save exercises
  async function loadExerciseIntoDb(ex_cfg: ExerciseConfig): Promise<void> {
    let exercise = new Exercise({
      page_slug: slug,
      name: ex_cfg.name,
    });
    await exercise.save();

    async function loadGraderIntoDb([language, grader_cfg]: [string, GraderConfig]): Promise<void> {
      let grader = new Grader({
        page_slug: slug,
        exercise_name: ex_cfg.name,
        language,
        style: grader_cfg.style,
        props: grader_cfg.props,
      });
      await grader.save();
    }

    let graders = ex_cfg.graders;
    if (graders != null) {
      await Promise.all(Object.entries(graders).map(loadGraderIntoDb));
    }
  }

  let exercises = page_cfg.exercises;
  if (exercises != null) {
    await Promise.all(exercises.map(loadExerciseIntoDb));
  }
}

async function main() {
  db = await init(db_file);

  // TODO: streaming version of readdir when the folder gets big
  let names = await readdir(materials_dir);
  
  await Promise.all(names
    .filter(name => name.toLowerCase().endsWith(".yml"))
    .map(loadPageIntoDb)
  );
}

main();