defmodule Ucwidth do
  @moduledoc """
  A module to determine the width of a Unicode charactor (or codepoint) on monotyped screens.

  A quick comparing between full-width and half-width:

  ```elixir
  "丐" # 1 full-width character
  "gg" # 2 half-width characters
  ```

  This module is ported from [Dr Markus Kuhn](https://www.cl.cam.ac.uk/~mgk25/)'s [ucwidth library](https://www.cl.cam.ac.uk/~mgk25/ucs/wcwidth.c) in C.
  """

  @max_codepoint 0x10FFFF

  # Combining characters take no room for displaying.
  # This list is copied from the original C code, which
  # is generated by:
  # 
  # ```sh
  # uniset +cat=Me +cat=Mn +cat=Cf -00AD +1160-11FF +200B c
  # ```
  @combining {
    {0x0300, 0x036F},
    {0x0483, 0x0486},
    {0x0488, 0x0489},
    {0x0591, 0x05BD},
    {0x05BF, 0x05BF},
    {0x05C1, 0x05C2},
    {0x05C4, 0x05C5},
    {0x05C7, 0x05C7},
    {0x0600, 0x0603},
    {0x0610, 0x0615},
    {0x064B, 0x065E},
    {0x0670, 0x0670},
    {0x06D6, 0x06E4},
    {0x06E7, 0x06E8},
    {0x06EA, 0x06ED},
    {0x070F, 0x070F},
    {0x0711, 0x0711},
    {0x0730, 0x074A},
    {0x07A6, 0x07B0},
    {0x07EB, 0x07F3},
    {0x0901, 0x0902},
    {0x093C, 0x093C},
    {0x0941, 0x0948},
    {0x094D, 0x094D},
    {0x0951, 0x0954},
    {0x0962, 0x0963},
    {0x0981, 0x0981},
    {0x09BC, 0x09BC},
    {0x09C1, 0x09C4},
    {0x09CD, 0x09CD},
    {0x09E2, 0x09E3},
    {0x0A01, 0x0A02},
    {0x0A3C, 0x0A3C},
    {0x0A41, 0x0A42},
    {0x0A47, 0x0A48},
    {0x0A4B, 0x0A4D},
    {0x0A70, 0x0A71},
    {0x0A81, 0x0A82},
    {0x0ABC, 0x0ABC},
    {0x0AC1, 0x0AC5},
    {0x0AC7, 0x0AC8},
    {0x0ACD, 0x0ACD},
    {0x0AE2, 0x0AE3},
    {0x0B01, 0x0B01},
    {0x0B3C, 0x0B3C},
    {0x0B3F, 0x0B3F},
    {0x0B41, 0x0B43},
    {0x0B4D, 0x0B4D},
    {0x0B56, 0x0B56},
    {0x0B82, 0x0B82},
    {0x0BC0, 0x0BC0},
    {0x0BCD, 0x0BCD},
    {0x0C3E, 0x0C40},
    {0x0C46, 0x0C48},
    {0x0C4A, 0x0C4D},
    {0x0C55, 0x0C56},
    {0x0CBC, 0x0CBC},
    {0x0CBF, 0x0CBF},
    {0x0CC6, 0x0CC6},
    {0x0CCC, 0x0CCD},
    {0x0CE2, 0x0CE3},
    {0x0D41, 0x0D43},
    {0x0D4D, 0x0D4D},
    {0x0DCA, 0x0DCA},
    {0x0DD2, 0x0DD4},
    {0x0DD6, 0x0DD6},
    {0x0E31, 0x0E31},
    {0x0E34, 0x0E3A},
    {0x0E47, 0x0E4E},
    {0x0EB1, 0x0EB1},
    {0x0EB4, 0x0EB9},
    {0x0EBB, 0x0EBC},
    {0x0EC8, 0x0ECD},
    {0x0F18, 0x0F19},
    {0x0F35, 0x0F35},
    {0x0F37, 0x0F37},
    {0x0F39, 0x0F39},
    {0x0F71, 0x0F7E},
    {0x0F80, 0x0F84},
    {0x0F86, 0x0F87},
    {0x0F90, 0x0F97},
    {0x0F99, 0x0FBC},
    {0x0FC6, 0x0FC6},
    {0x102D, 0x1030},
    {0x1032, 0x1032},
    {0x1036, 0x1037},
    {0x1039, 0x1039},
    {0x1058, 0x1059},
    {0x1160, 0x11FF},
    {0x135F, 0x135F},
    {0x1712, 0x1714},
    {0x1732, 0x1734},
    {0x1752, 0x1753},
    {0x1772, 0x1773},
    {0x17B4, 0x17B5},
    {0x17B7, 0x17BD},
    {0x17C6, 0x17C6},
    {0x17C9, 0x17D3},
    {0x17DD, 0x17DD},
    {0x180B, 0x180D},
    {0x18A9, 0x18A9},
    {0x1920, 0x1922},
    {0x1927, 0x1928},
    {0x1932, 0x1932},
    {0x1939, 0x193B},
    {0x1A17, 0x1A18},
    {0x1B00, 0x1B03},
    {0x1B34, 0x1B34},
    {0x1B36, 0x1B3A},
    {0x1B3C, 0x1B3C},
    {0x1B42, 0x1B42},
    {0x1B6B, 0x1B73},
    {0x1DC0, 0x1DCA},
    {0x1DFE, 0x1DFF},
    {0x200B, 0x200F},
    {0x202A, 0x202E},
    {0x2060, 0x2063},
    {0x206A, 0x206F},
    {0x20D0, 0x20EF},
    {0x302A, 0x302F},
    {0x3099, 0x309A},
    {0xA806, 0xA806},
    {0xA80B, 0xA80B},
    {0xA825, 0xA826},
    {0xFB1E, 0xFB1E},
    {0xFE00, 0xFE0F},
    {0xFE20, 0xFE23},
    {0xFEFF, 0xFEFF},
    {0xFFF9, 0xFFFB},
    {0x10A01, 0x10A03},
    {0x10A05, 0x10A06},
    {0x10A0C, 0x10A0F},
    {0x10A38, 0x10A3A},
    {0x10A3F, 0x10A3F},
    {0x1D167, 0x1D169},
    {0x1D173, 0x1D182},
    {0x1D185, 0x1D18B},
    {0x1D1AA, 0x1D1AD},
    {0x1D242, 0x1D244},
    {0xE0001, 0xE0001},
    {0xE0020, 0xE007F},
    {0xE0100, 0xE01EF}
  }

  @compile {:inline, full_width?: 1}

  @doc """
  Get width of the code point.

  ## Parameter

  This function accepts following type of paramters:

  - an integer within valid unicode code range (`0..0x11ffff`)
  - a single character string, e.g `"c"`, `"\\u{3f0a1}"`

  and returns the width of the character/codepoint.

  ## Width definition

  * `0` means this character is **invisible** and takes no space on screen.
  * `1` means it takes **one cell** to display. For instance, English letters are one cell wide.
  * `2` means it takes **two cells** to display. This is quite common in East Asian charsets.

  ## Examples


      iex> Ucwidth.width(0)
      0

      iex> Ucwidth.width("5")
      1

      iex> Ucwidth.width("\u303f")
      1

      iex> Ucwidth.width("\u2329")
      2

      iex> Ucwidth.width("\u2e80")
      2

      iex> Ucwidth.width(255)
      1

  If string length is greater than 1, `{:error, :bad_arg}` will be returned:

      iex> Ucwidth.width("abc")
      {:error, :bad_arg}

  """
  @spec width(non_neg_integer | String.t()) :: 0 | 1 | 2 | {:error, :bad_arg}

  def width(one_letter_string_or_integer)

  def width(<<code::utf8>>), do: width(code)
  def width(0), do: 0

  def width(code) when is_integer(code) and code in 0..@max_codepoint do
    cond do
      combining_char?(code) ->
        0

      full_width?(code) ->
        2

      :otherwise ->
        1
    end
  end

  def width(_), do: {:error, :bad_arg}

  @doc false
  def combining_char?(code) do
    bin_search(@combining, code, 0, tuple_size(@combining) - 1)
  end

  defp bin_search(_ranges, _target, min, max) when min > max, do: false

  defp bin_search(ranges, target, min, max) do
    half = div(min + max, 2)

    case elem(ranges, half) do
      {a, b} when target >= a and target <= b ->
        true

      {a, _} when target < a ->
        bin_search(ranges, target, min, half - 1)

      {_, b} when target > b ->
        bin_search(ranges, target, half + 1, max)
    end
  end

  defp full_width?(0x2329), do: true
  defp full_width?(0x232A), do: true
  defp full_width?(0x303F), do: false
  defp full_width?(code) when code in 0x1100..0x115F, do: true
  defp full_width?(code) when code in 0x2E80..0xA4CF, do: true
  defp full_width?(code) when code in 0xAC00..0xD7A3, do: true
  defp full_width?(code) when code in 0xF900..0xFAFF, do: true
  defp full_width?(code) when code in 0xFE10..0xFE19, do: true
  defp full_width?(code) when code in 0xFE30..0xFE6F, do: true
  defp full_width?(code) when code in 0xFF00..0xFF60, do: true
  defp full_width?(code) when code in 0xFFE0..0xFFE6, do: true
  defp full_width?(code) when code in 0x20000..0x2FFFD, do: true
  defp full_width?(code) when code in 0x30000..0x3FFFD, do: true
  defp full_width?(_otherwise), do: false
end