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owenrees
7717278561
* create endgame play section * add cache tests * normalise FENs - trim and fuill move to 1 on addition * remove svg on root and allow navbar to exist across all pages * update nav items
47 lines
1.4 KiB
Elixir
47 lines
1.4 KiB
Elixir
defmodule Chesstrainer.FEN do
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@spec color_from_fen(String.t()) :: :white | :black | nil
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def color_from_fen(fen) do
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fen
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|> String.split(" ")
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|> Enum.at(1)
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|> color_initial_to_color_atom()
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end
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@doc """
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Normalizes a FEN string for storage.
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Trims surrounding whitespace and rewrites a fullmove number of `"0"` to
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`"1"`. The fullmove rewrite is a chess.js-compatibility fix — chess.js
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rejects fullmove `0` as invalid even though many board editors default
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to it. Other FEN fields are left untouched; structural errors are
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surfaced by the Endgame changeset, not silently masked here.
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## Examples
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iex> Chesstrainer.FEN.normalize(" 8/8/3k4/8/8/3K1R2/8/8 w - - 0 0\\n ")
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"8/8/3k4/8/8/3K1R2/8/8 w - - 0 1"
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iex> Chesstrainer.FEN.normalize("8/8/3k4/8/8/3K1R2/8/8 w - - 0 5")
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"8/8/3k4/8/8/3K1R2/8/8 w - - 0 5"
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iex> Chesstrainer.FEN.normalize("not a fen")
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"not a fen"
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"""
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@spec normalize(String.t()) :: String.t()
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def normalize(fen) when is_binary(fen) do
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trimmed = String.trim(fen)
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case String.split(trimmed, " ") do
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[board, active, castling, en_passant, halfmove, "0"] ->
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Enum.join([board, active, castling, en_passant, halfmove, "1"], " ")
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_ ->
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trimmed
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end
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end
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defp color_initial_to_color_atom("b"), do: :black
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defp color_initial_to_color_atom("w"), do: :white
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defp color_initial_to_color_atom(_), do: nil
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end
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