defmodule ExUc.Special do
  @moduledoc """
  # Special conversions.

  For conversions where simple formulas are not enough the config file will
  reference using an atom a method of this module.

  """

  alias ExUc.Units

  @precision Units.precision

  @doc """
  Converts from kilograms to pounds and ounces

  Returns String.t

  ## Parameters

    - value: Numeric value for kilograms.

  ## Examples
  ```

  iex>ExUc.Special.kg_to_lb_oz(20.15)
  "44 lb 6.76 oz"

  ```
  """
  def kg_to_lb_oz(kgs) do
    {:ok, kg_to_lb} = Units.get_conversion(:kg, :lb)
    {:ok, lb_to_oz} = Units.get_conversion(:lb, :oz)

    as_lbs = kgs * kg_to_lb
    lbs = trunc(as_lbs)
    partial_lbs = as_lbs - lbs
    ozs = Float.round(partial_lbs * lb_to_oz, @precision)

    case ozs do
      0 -> "#{lbs} lb 0 oz"
      _ -> "#{lbs} lb #{ozs} oz"
    end
  end

  @doc """
  Converts from meters to feet and inches.

  Returns String.t

  ## Parameters

    - meters: Numeric meters value

  ## Examples
  ```

  iex> ExUc.Special.m_to_ft_in(10.35)
  "33 ft 11.5 in"

  ```
  """
  def m_to_ft_in(meters) do
    {:ok, m_to_ft} = Units.get_conversion(:m, :ft)
    {:ok, ft_to_in} = Units.get_conversion(:ft, :in)

    as_feet = meters * m_to_ft
    feet = trunc(as_feet)
    partial_feet = as_feet - feet
    inches = Float.round(partial_feet * ft_to_in, @precision)

    case inches do
      0 -> "#{feet} ft 0 in"
      _ -> "#{feet} ft #{inches} in"
    end
  end

  @doc """
  Checks if a string is a special pounds and ounces value

  Returns Boolean

  ## Parameters

    - str: String with values and units.

  ## Examples
  ```

  iex>ExUc.Special.is_pounds_and_ounces?("23 lb 4 oz")
  true

  iex>ExUc.Special.is_pounds_and_ounces?("12.566 lb")
  false

  ```
  """
  def is_pounds_and_ounces?(str) do
    String.match?(str, ~r/(\d+(\.\d+)?)\s*lb.(\d+(\.\d+)?)\s*oz/)
  end

  @doc """
  Checks if a string is a special feet and inches value.

  Returns Boolean

  ## Parameters

    - str: String with values and units.

  ## Examples
  ```

  iex>ExUc.Special.is_feet_and_inches?("6 ft 2.2 in")
  true

  iex>ExUc.Special.is_feet_and_inches?("6 ft")
  false

  ```
  """
  def is_feet_and_inches?(str) do
    String.match?(str, ~r/(\d+(\.\d+)?)\s*ft.(\d+(\.\d+)?)\s*in/)
  end

  @doc """
  Converts from pounds and ounces, to pounds.

  Returns {VALUE_IN_POUNDS, "lb"}

  ## Parameters

    - str: String with pounds and ounces value

  ## Examples
  ```

  iex>ExUc.Special.lb_oz_to_lb("4 lb 5 oz")
  {4.3125, "lb"}

  ```
  """
  def lb_oz_to_lb(str) do
    [pounds_str, _lb, ounces_str, _oz] = String.split(str, " ")
    {pounds, _} = Float.parse(pounds_str)
    {ounces, _} = Float.parse(ounces_str)
    {:ok, oz_to_lb} = Units.get_conversion(:oz, :lb)
    all_pounds = pounds + (ounces * oz_to_lb)
    {all_pounds, "lb"}
  end

  @doc """
  Converts from feet and inches, to feet.

  Returns {VALUE_IN_FEET, "ft"}

  ## Parameters

    - str: String with feet and inches value

  ## Examples
  ```

  iex>ExUc.Special.ft_in_to_ft("7 ft 6 in")
  {7.5, "ft"}

  ```
  """
  def ft_in_to_ft(str) do
    [feet_str, _lb, inches_str, _oz] = String.split(str, " ")
    {feet, _} = Float.parse(feet_str)
    {inches, _} = Float.parse(inches_str)
    {:ok, in_to_ft} = Units.get_conversion(:in, :ft)
    all_feet = feet + (inches * in_to_ft)
    {all_feet, "ft"}
  end
end