const { promisify } = require("util");
const path = require("path");
const fs = require("fs");
const moment = require("moment");
const csv = require("csv");
const _ = require("lodash");

const parseCsv = promisify(csv.parse);
const readFile = promisify(fs.readFile);

async function importFromCsv() {
  const text = await readFile(path.join(__dirname, "calculate_input.csv"), {
    encoding: "utf8"
  });

  const rows = await parseCsv(text, {
    from: 1,
    columns: [
      "code",
      "date",
      "type",
      "quantity",
      "unitPrice",
      "tradeValue",
      "brokerageGst",
      "gst",
      "contractNote",
      "totalValue"
    ],
    skip_empty_lines: true,
    skip_lines_with_error: true
  });

  return rows.map(row => {
    const { code, date, type, totalValue, quantity } = row;
    return {
      code,
      date: moment(date, "DD/MM/YYYY"),
      type: type.toLowerCase(),
      totalValue: Math.abs(parseFloat(totalValue)),
      quantity: Math.abs(parseInt(quantity, 10))
    };
  });
}

async function run() {
  const rows = await importFromCsv();
  const minDate = moment("2018-07-01");
  const maxDate = moment("2019-06-30");

  const soldThisYear = rows.filter(row => {
    const { type, date } = row;
    const isSell = type === "sell";
    const isYear = date.isSameOrAfter(minDate) && date.isSameOrBefore(maxDate);
    return isSell && isYear;
  });

  let allBuys = rows.filter(row => row.type === "buy");

  const transactionPairs = soldThisYear.map(sell => {
    const buy = allBuys.find(buy => {
      const sameCode = buy.code === sell.code;
      const sameQty = buy.quantity === sell.quantity;
      if (sameCode && sameQty) {
        allBuys = _.without(allBuys, buy);
        return buy;
      }
    });

    return { sell, buy };
  });

  const validPairs = transactionPairs.filter(({ buy, sell }) => {
    const valid = buy && sell;
    if (!valid) {
      console.error("Missing transaction: ");
      console.log("   Buy: ", buy);
      console.log("   Sell: ", sell);
      console.log("----------");
    }
    return valid;
  });

  const totalBuy = validPairs.reduce(
    (total, { buy }) => total + buy.totalValue,
    0
  );

  const totalSell = validPairs.reduce(
    (total, { sell }) => total + sell.totalValue,
    0
  );

  console.log("Total buy value: ", totalBuy);
  console.log("Total buy value: ", totalSell);
  console.log("Total profit: ", totalSell - totalBuy);
}

run();