Module:Pgn
--[[
the purpose of this module is to provide pgn analysis local functionality
main local function, called pgn2fen:
input: either algebraic notation or full pgn of a single game
output:
- 1 table of positions (using FEN notation), one per each move of the game
- 1 lua table with pgn metadata (if present)
purpose:
using this local , we can create utility local functions to be used by templates.
the utility local function will work something like so:
it receives (in addition to the pgn, of course) list of moves and captions, and some wikicode in "nowiki" tag.
per each move, it will replace the token FEN with the fen of the move, and the token COMMENT with the comment (if any) of the move.
it will then parse the wikicode, return all the parser results concataneted.
others may fund other ways to use it.
the logic:
the analysis part copies freely from the javascipt "pgn" program.
main object: "board": 0-based table(one dimensional array) of 64 squares (0-63),
each square is either empty or contains the letter of the charToFile, e.g., "pP" is pawn.
utility local functions
index to row/col
row/col to index
disambig(file, row): if file is number, return it, otherwise return rowtoindex().
create(fen): returns ready board
generateFen(board) - selbverständlich
pieceAt(coords): returns the piece at row/col
findPieces(piece): returns list of all squares containing specific piece ("black king", "white rook" etc).
roadIsClear(start/end row/column): start and end _must_ be on the same row, same column, or a diagonal. will error if not.
returns true if all the squares between start and end are clear.
canMove(source, dest, capture): boolean (capture is usually reduntant, except for en passant)
promote(coordinate, designation, color)
move(color, algebraic notation): finds out which piece should move, error if no piece or more than one piece found,
and execute the move.
rawPgnAnalysis(input)
gets a pgn or algebraic notation, returns a table withthe metadata, and a second table with the algebraic notation individual moves
main:
-- metadata, notations := rawPgnAnalysis(input)
-- result := empty table
-- startFen := metadata.fen || default; results += startFen
-- board := create(startFen)
-- loop through notations
----- pass board, color and notation, get modified board
----- results += generateFen()
-- return result
the "meat" is the "canMove. however, as it turns out, it is not that difficult.
the only complexity is with pawns, both because they are asymmetrical, and irregular. brute force (as elegantly as possible)
other pieces are a breeze. color does not matter. calc da := abs(delta raw), db := abs(delta column)
piece | rule
Knight: da * db - 2 = 0
Rook: da * db = 0
Bishop: da - db = 0
King db | db = 1 (bitwise or)
Queen da * db * (da - db) = 0
move:
find out which piece. find all of them on the board. ask each if it can execute the move, and count "yes".
there should be only one yes (some execptions to be handled). execute the move.
]]
local BLACK = "black"
local WHITE = "white"
local PAWN = "P"
local ROOK = "R"
local KNIGHT = "N"
local BISHOP = "B"
local QUEEN = "Q"
local KING = "K"
local KINGSIDE = 7
local QUEENSIDE = 12
local DEFAULT_BOARD = 'rnbqkbnr/pppppppp/8/8/8/8/PPPPPPPP/RNBQKBNR'
local bit32 = bit32 or require('bit32')
--[[ following lines require when running locally - uncomment.
mw = mw or {
ustring = string,
text = {
['split'] = local function(s, pattern)
local res = {}
while true do
local start, finish = s:find(pattern)
if finish and finish > 1 then
local frag = s:sub(1, start - 1)
table.insert(res, frag)
s = s:sub(finish + 1)
else
break
end
end
if #s then table.insert(res, s) end
return res
end,
['trim'] = local function(t)
t = type(t) == 'string' and t:gsub('^%s+', '')
t = t:gsub('%s+$', '')
return t
end
}
}
]]
-- in lua 5.3, unpack is not a first class citizen anymore, but - assign table.unpack
local unpack = unpack or table.unpack
local function apply(f, ...)
res = {}
targ = {...}
for ind = 1, #targ do
res[ind] = f(targ[ind])
end
return unpack(res)
end
local function empty(s)
return not s or mw.text.trim(s) == ''
end
local function falseIfEmpty(s)
return not empty(s) and s
end
local function charToFile(ch)
return falseIfEmpty(ch) and string.byte(ch) - string.byte('a')
end
local function charToRow(ch)
return falseIfEmpty(ch) and tonumber(ch) - 1
end
local function indexToCoords(index)
return index % 8, math.floor(index / 8)
end
local function coordsToIndex(file, row)
return row * 8 + file
end
local function charToPiece(letter)
local piece = mw.ustring.upper(letter)
return piece, piece == letter and WHITE or BLACK
end
local function pieceToChar(piece, color)
return color == WHITE and piece or mw.ustring.lower(piece)
end
local function ambigToIndex(file, row)
if row == nil then return file end
return coordsToIndex(file, row)
end
local function enPasantRow(color)
return color == WHITE and 5 or 2
end
local function sign(a)
return a < 0 and -1
or a > 0 and 1
or 0
end
local function pieceAt(board, fileOrInd, row) -- called with 2 params, fileOrInd is the index, otherwise it's the file.
local letter = board[ambigToIndex(fileOrInd, row)]
if not letter then return end
return charToPiece(letter)
end
local function findPieces(board, piece, color)
local result = {}
local lookFor = pieceToChar(piece, color)
for index = 0, 63 do
local letter = board[index]
if letter == lookFor then table.insert(result, index) end
end
return result
end
local function roadIsClear(board, ind1, ind2)
if ind1 == ind2 then error('call to roadIsClear with identical indices', ind1) end
local file1, row1 = indexToCoords(ind1)
local file2, row2 = indexToCoords(ind2)
if (file1 - file2) * (row1 - row2) * (math.abs(row1 - row2) - math.abs(file1 - file2)) ~= 0 then
error('sent two indices to roadIsClear which are not same row, col, or diagonal: ', ind1, ind2)
end
local hdelta = sign(file2 - file1)
local vdelta = sign(row2 - row1)
local row, file = row1 + vdelta, file1 + hdelta
while row ~= row2 or file ~= file2 do
if pieceAt(board, file, row) then return false end
row = row + vdelta
file = file + hdelta
end
return true
end
local function pawnCanMove(board, color, startFile, startRow, file, row, capture)
local hor, ver = file - startFile, row - startRow
local absVer = math.abs(ver)
if capture then
local ok = hor * hor == 1 and (
color == WHITE and ver == 1 or
color == BLACK and ver == - 1
)
local enpassant = ok and
row == enPasantRow(color) and
pieceAt(board, file, row) == nil
return ok, enpassant
else
if hor ~= 0 then return false end
end
if absVer == 2 then
if not roadIsClear(board, coordsToIndex(startFile, startRow), coordsToIndex(file, row)) then return false end
return color == WHITE and startRow == 1 and ver == 2 or
color == BLACK and startRow == 6 and ver == -2
end
return color == WHITE and ver == 1 or color == BLACK and ver == -1
end
local function canMove(board, start, dest, capture, verbose)
local startFile, startRow = indexToCoords(start)
local file, row = indexToCoords(dest)
local piece, color = pieceAt(board, startFile, startRow)
if piece == PAWN then return pawnCanMove(board, color, startFile, startRow, file, row, capture) end
local dx, dy = math.abs(startFile - file), math.abs(startRow - row)
return piece == KNIGHT and dx * dy == 2
or piece == KING and bit32.bor(dx, dy) == 1
or (
piece == ROOK and dx * dy == 0
or piece == BISHOP and dx == dy
or piece == QUEEN and dx * dy * (dx - dy) == 0
) and roadIsClear(board, start, dest, verbose)
end
local function exposed(board, color) -- only test for queen, rook, bishop.
local king = findPieces(board, KING, color)[1]
for ind = 1, 63 do
local letter = board[ind]
if letter then
local _, pcolor = charToPiece(letter)
if pcolor ~= color and canMove(board, ind, king, true) then
return true
end
end
end
end
local function clone(orig)
local res = {}
for k, v in pairs(orig) do res[k] = v end
return res
end
local function place(board, piece, color, file, row) -- in case of chess960, we have to search
board[ambigToIndex(file, row)] = pieceToChar(piece, color)
return board
end
local function clear(board, file, row)
board[ambigToIndex(file, row)] = nil
return board
end
local function doCastle(board, color, side)
local row = color == WHITE and 0 or 7
local startFile, step = 0, 1
local kingDestFile, rookDestFile = 2, 3
local king = findPieces(board, KING, color)[1]
local rook
if side == KINGSIDE then
startFile, step = 7, -1
kingDestFile, rookDestFile = 6, 5
end
for file = startFile, 7 - startFile, step do
local piece = pieceAt(board, file, row)
if piece == ROOK then
rook = coordsToIndex(file, row)
break
end
end
board = clear(board, king)
board = clear(board, rook)
board = place(board, KING, color, kingDestFile, row)
board = place(board, ROOK, color, rookDestFile, row)
return board
end
local function doEnPassant(board, pawn, file, row)
local _, color = pieceAt(board, pawn)
board = clear(board, pawn)
board = place(board, PAWN, color, file, row)
if row == 5 then board = clear(board, file, 4) end
if row == 2 then board = clear(board, file, 3) end
return board
end
local function generateFen(board)
local res = ''
local offset = 0
for row = 7, 0, -1 do
for file = 0, 7 do
piece = board[coordsToIndex(file, row)]
res = res .. (piece or '1')
end
if row > 0 then res = res .. '/' end
end
return mw.ustring.gsub(res, '1+', function( s ) return #s end )
end
local function findCandidate(board, piece, color, oldFile, oldRow, file, row, capture, notation)
local enpassant = {}
local candidates, newCands = findPieces(board, piece, color), {} -- all black pawns or white kings etc.
if oldFile or oldRow then
local newCands = {}
for _, cand in ipairs(candidates) do
local file, row = indexToCoords(cand)
if file == oldFile then table.insert(newCands, cand) end
if row == oldRow then table.insert(newCands, cand) end
end
candidates, newCands = newCands, {}
end
local dest = coordsToIndex(file, row)
for _, candidate in ipairs(candidates) do
local can
can, enpassant[candidate] = canMove(board, candidate, dest, capture)
if can then table.insert(newCands, candidate) end
end
candidates, newCands = newCands, {}
if #candidates == 1 then return candidates[1], enpassant[candidates[1]] end
if #candidates == 0 then
error('could not find a piece that can execute ' .. notation)
end
-- we have more than one candidate. this means that all but one of them can't really move, b/c it will expose the king
-- test for it by creating a new board with this candidate removed, and see if the king became exposed
for _, candidate in ipairs(candidates) do
local cloneBoard = clone(board) -- first, clone the board
cloneBoard = clear(cloneBoard, candidate) -- now, remove the piece
if not exposed(cloneBoard, color) then table.insert(newCands, candidate) end
end
candidates, newCands = newCands, {}
if #candidates == 1 then return candidates[1] end
error(mw.ustring.format('too many (%d, expected 1) pieces can execute %s at board %s', #candidates, notation, generateFen(board)))
end
local function move(board, notation, color)
local endGame = {['1-0']=true, ['0-1']=true, ['1/2-1/2']=true, ['*']=true}
local cleanNotation = mw.ustring.gsub(notation, '[!?+# ]', '')
if cleanNotation == 'O-O' then
return doCastle(board, color, KINGSIDE)
end
if cleanNotation == 'O-O-O' then
return doCastle(board, color, QUEENSIDE)
end
if endGame[cleanNotation] then
return board, true
end
local pattern = '([RNBKQ]?)([a-h]?)([1-8]?)(x?)([a-h])([1-8])(=?[RNBKQ]?)'
local _, _, piece, oldFile, oldRow, isCapture, file, row, promotion = mw.ustring.find(cleanNotation, pattern)
oldFile, file = apply(charToFile, oldFile, file)
oldRow, row = apply(charToRow, oldRow, row)
piece = falseIfEmpty(piece) or PAWN
promotion = falseIfEmpty(promotion)
isCapture = falseIfEmpty(isCapture)
local candidate, enpassant = findCandidate(board, piece, color, oldFile, oldRow, file, row, isCapture, notation) -- findCandidates should panic if # != 1
if enpassant then
return doEnPassant(board, candidate, file, row)
end
board[coordsToIndex(file, row)] = promotion and pieceToChar(promotion:sub(-1), color) or board[candidate]
board = clear(board, candidate)
return board
end
local function create( fen )
-- converts FEN notation to 64 entry array of positions. copied from enwiki Module:Chessboard (in some distant past i prolly wrote it)
local res = {}
local row = 8
-- Loop over rows, which are delimited by /
for srow in string.gmatch( "/" .. fen, "/%w+" ) do
srow = srow:sub(2)
row = row - 1
local ind = row * 8
-- Loop over all letters and numbers in the row
for piece in srow:gmatch( "%w" ) do
if piece:match( "%d" ) then -- if a digit
ind = ind + piece
else -- not a digit
res[ind] = piece
ind = ind + 1
end
end
end
return res
end
local function processMeta(grossMeta)
res = {}
-- process grossMEta here
for item in mw.ustring.gmatch(grossMeta or '', '%[([^%]]*)%]') do
key, val = item:match('([^"]+)"([^"]*)"')
if key and val then
res[mw.text.trim(key)] = mw.text.trim(val) -- add mw.text.trim()
else
error('strange item detected: ' .. item .. #items) -- error later
end
end
return res
end
local function analyzePgn(pgn)
local grossMeta = pgn:match('%[(.*)%]') -- first open to to last bracket
pgn = string.gsub(pgn, '%[(.*)%]', '')
local steps = mw.text.split(pgn, '%s*%d+%.%s*')
local moves = {}
for _, step in ipairs(steps) do
if mw.ustring.len(mw.text.trim(step)) then
ssteps = mw.text.split(step, '%s+')
for _, sstep in ipairs(ssteps) do
if sstep and not mw.ustring.match(sstep, '^%s*$') then table.insert(moves, sstep) end
end
end
end
return processMeta(grossMeta), moves
end
local function pgn2fen(pgn)
local metadata, notationList = analyzePgn(pgn)
local fen = metadata.fen or DEFAULT_BOARD
local board = create(fen)
local res = {fen}
local colors = {BLACK, WHITE}
for step, notation in ipairs(notationList) do
local color = colors[step % 2 + 1]
board = move(board, notation, color)
local fen = generateFen(board)
table.insert(res, fen)
end
return res, metadata
end
return {
pgn2fen = pgn2fen,
main = function(pgn)
local res, metadata = pgn2fen(pgn)
return metadata, res
end,
}