// Part 2 and 3 about a really dumb investment strategy

//======================================================

object CW6b { // for purposes of generating a jar

//two test portfolios

val blchip_portfolio = List("GOOG", "AAPL", "MSFT", "IBM", "FB", "AMZN", "BIDU")

val rstate_portfolio = List("PLD", "PSA", "AMT", "AIV", "AVB", "BXP", "CCI", 

                            "DLR", "EQIX", "EQR", "ESS", "EXR", "FRT", "HCP") 

import io.Source

import scala.util._

// (1) The function below takes a stock symbol and a year as arguments.

//     It should read the corresponding CSV-file and reads the January 

//     data from the given year. The data should be collected in a list of

//     strings for each line in the CSV-file.

def get_january_data(symbol: String, year: Int) : List[String] = 

  Source.fromFile(symbol ++ ".csv")("ISO-8859-1").getLines.toList.filter(_.startsWith(year.toString))

//test cases

//blchip_portfolio.map(get_january_data(_, 2018))

//rstate_portfolio.map(get_january_data(_, 2018))

//get_january_data("GOOG", 1980)

//get_january_data("GOOG", 2010)

//get_january_data("FB", 2014)

//get_january_data("PLD", 1980)

//get_january_data("EQIX", 2010)

//get_january_data("ESS", 2014)

// (2) From the output of the get_january_data function, the next function 

//     should extract the first line (if it exists) and the corresponding

//     first trading price in that year with type Option[Double]. If no line 

//     is generated by get_january_data then the result is None; Some if 

//     there is a price.

def get_first_price(symbol: String, year: Int) : Option[Double] = {

  val data = Try(Some(get_january_data(symbol, year).head)) getOrElse None 

  data.map(_.split(",").toList(1).toDouble)

}

//test cases

//get_first_price("GOOG", 1980)

//get_first_price("GOOG", 2010)

//get_first_price("FB", 2014)

/*

for (i <- 1978 to 2018) {

  println(blchip_portfolio.map(get_first_price(_, i)))

}

for (i <- 1978 to 2018) {

  println(rstate_portfolio.map(get_first_price(_, i)))

}

*/ 

// (3) Complete the function below that obtains all first prices

//     for the stock symbols from a portfolio (list of strings) and 

//     for the given range of years. The inner lists are for the

//     stock symbols and the outer list for the years.

def get_prices(portfolio: List[String], years: Range): List[List[Option[Double]]] = 

  for (year <- years.toList) yield

    for (symbol <- portfolio) yield get_first_price(symbol, year)

//test cases

//val p_fb = get_prices(List("FB"), 2012 to 2014)

//val p = get_prices(List("GOOG", "AAPL"), 2010 to 2012)

//val tt = get_prices(List("BIDU"), 2004 to 2008)

//==============================================

// Do not change anything below, unless you want 

// to submit the file for the advanced part 3!

//==============================================

// (4) The function below calculates the change factor (delta) between

//     a price in year n and a price in year n + 1. 

def get_delta(price_old: Option[Double], price_new: Option[Double]) : Option[Double] = {

  (price_old, price_new) match {

    case (Some(x), Some(y)) => Some((y - x) / x)

    case _ => None

  }

}

// (5) The next function calculates all change factors for all prices (from a 

//     portfolio). The input to this function are the nested lists created by 

//     get_prices above.

def get_deltas(data: List[List[Option[Double]]]):  List[List[Option[Double]]] =

  for (i <- (0 until (data.length - 1)).toList) yield 

    for (j <- (0 until (data(0).length)).toList) yield get_delta(data(i)(j), data(i + 1)(j))

// test case using the prices calculated above

//val d = get_deltas(p)

//val ttd = get_deltas(tt)

// (6) Write a function that given change factors, a starting balance and an index,

//     calculates the yearly yield, i.e. new balance, according to our dumb investment 

//     strategy. Index points to a year in the data list.

def yearly_yield(data: List[List[Option[Double]]], balance: Long, index: Int): Long = {

  val somes = data(index).flatten

  val somes_length = somes.length

  if (somes_length == 0) balance

  else {

    val portion: Double = balance.toDouble / somes_length.toDouble

    balance + (for (x <- somes) yield (x * portion)).sum.toLong

  }

}

// (7) Write a function compound_yield that calculates the overall balance for a 

//     range of years where in each year the yearly profit is compounded to the new 

//     balances and then re-invested into our portfolio. For this use the function and 

//     results generated under (6). The function investment calls compound_yield

//     with the appropriate deltas and the first index.

def compound_yield(data: List[List[Option[Double]]], balance: Long, index: Int): Long = {

  if (index >= data.length) balance else {

    val new_balance = yearly_yield(data, balance, index)

    compound_yield(data, new_balance, index + 1)

  }

}

def investment(portfolio: List[String], years: Range, start_balance: Long): Long = {

  compound_yield(get_deltas(get_prices(portfolio, years)), start_balance, 0)

}

//test cases for the two portfolios given above

//println("Real data: " + investment(rstate_portfolio, 1978 to 2018, 100))

//println("Blue data: " + investment(blchip_portfolio, 1978 to 2018, 100))

}