/*
 * Copyright (C) 2025 Jakub Žitník
 *
 * This program is free software: you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 */

import fs from "fs/promises";
import { setup } from "./call.js";

const PREVIOUS = "db/v3/_previous.json";
const FINAL = "db/v3/v3.json";
const EXCLUDE_CLASSES = new Set(["ABSENCE"]);

async function checkFileExists(filePath) {
  try {
    await fs.access(filePath);
    return true;
  } catch (err) {
    return false;
  }
}

function arraysAreEqual(arr1, arr2) {
  if (arr1.length !== arr2.length) return false;
  for (let i = 0; i < arr1.length; i++) {
    if (arr1[i] !== arr2[i]) return false;
  }
  return true;
}

function getTime() {
  const currentDate = new Date();
  return currentDate.getHours().toString().padStart(2, "0") + ":" + currentDate.getMinutes().toString().padStart(2, "0");
}

function setupFinal() {
  return {
    schedule: [],
    status: {
      lastUpdated: getTime(),
    }
  }
}

export default async function parseV3(fileV2Path) {
  const call = await setup();

  let clearRun = false;
  let previousStr = "{}";

  if (await checkFileExists(PREVIOUS)) {
    previousStr = await fs.readFile(PREVIOUS, "utf8");
  } else {
    clearRun = true;
  }

  const now = JSON.parse(await fs.readFile(fileV2Path, "utf8"));
  const previous = JSON.parse(previousStr);
  const previousDays = previous.props?.map(p => p.date) || [];

  let final;
  if (await checkFileExists(FINAL)) {
    final = JSON.parse(await fs.readFile(FINAL, "utf8"));
  } else {
    final = setupFinal();
    clearRun = true;
  }

  let i = 0;
  for (const prop of now.props) {
    const date = new Date(prop.date);
    const dayIndex = (date.getDay() + 6) % 7;

    if (!final.schedule[i]) {
      final.schedule[i] = {};
    }

    const day = now.schedule[i];
    const batch = {};

    for (const cls of Object.keys(day)) {
      if (EXCLUDE_CLASSES.has(cls)) continue;

      const newClass = day[cls];

      if (clearRun || !previousDays.includes(prop.date)) {
        batch[cls] = newClass;
        continue;
      }

      const oldPropIndex = previous.props.findIndex(
        p => p.date === prop.date
      );
      const oldClass = previous.schedule[oldPropIndex]?.[cls] || [];

      if (!arraysAreEqual(oldClass, newClass)) {
        batch[cls] = newClass;
      }
    }

    if (Object.keys(batch).length > 0) {
      const results = await call(batch, dayIndex);

      for (const cls of Object.keys(results)) {
        final.schedule[i][cls] = results[cls];
      }
    }

    i++;
  }

  if (!clearRun) {
    final.status.lastUpdated = getTime();
  }

  final.props = now.props;

  await fs.writeFile(FINAL, JSON.stringify(final), "utf8");
  await fs.copyFile(fileV2Path, PREVIOUS);
}

parseV3("db/v2.json");