Mix.install([
			{:flow, "~> 1.2.4"},
			{:ex_cldr_collation, "~> 0.7.2"}
])

defmodule Brc do
	require Logger
	
  def run(path) do
    for {city, [min, max, mean]} <- parse_file(path) do
      "#{city}=#{min}/#{max}/#{Float.round(mean, 1)}"
    end
    |> Enum.sort(Cldr.Collation)
    |> Enum.join(",")
    |> then(fn out -> "{" <> out <> "}" end)
    |> IO.puts()
  end

  def parse_file(path) do
    Logger.info("parse file #{path}")

		File.stream!(path)
		|> Flow.from_enumerable()
		|> Flow.map(&parse_line/1)
		|> Flow.partition()
    |> Flow.reduce(fn -> %{} end, fn {city, temp}, acc ->
      Map.update(acc, city, [temp, temp, temp], fn [prev_min, prev_max, mean] ->
        [min(prev_min, temp), max(prev_max, temp), (mean + temp) / 2]
      end)
    end)
  end

  def parse_line(line) do
    [city, temp] = String.trim(line) |> String.split(";")
    {city, String.to_float(temp)}
  end
end

Brc.run("./priv/data.txt")