SAN & UCI

UCIParser is pure, engine-agnostic translation between SAN and UCI against a Position. (Stockfish-specific output parsing lives in UCIOutputParser — see Engine protocol.)

The API

public enum UCIParser {
    static func uciToMove(_ uci: String, in position: Position) -> Move?
    static func uciToMove(_ uci: String, in legalMoves: [Move]) -> Move?
    static func uciToSAN(_ uci: String, in position: Position) -> String?
    static func sanToUCI(_ san: String, in position: Position) -> String?
    static func convertPVToSAN(_ uciMoves: [String], from position: Position,
                               initialLegalMoves: [Move]? = nil) -> [String]
}

Conversion methods

let position = Position.initial()

let move = UCIParser.uciToMove("e2e4", in: position)   // Move?
let san  = UCIParser.uciToSAN("e2e4", in: position)    // "e4"
let uci  = UCIParser.sanToUCI("Nf3", in: position)     // "g1f3"

uciToMove validates the UCI string against the legal moves in the position, so an illegal or malformed string yields nil. If you already have the legal-move list, the overload that takes [Move] skips regeneration:

let legal = MoveGenerator.legalMoves(for: position)
let move  = UCIParser.uciToMove("e2e4", in: legal)

Converting a principal variation

convertPVToSAN replays a UCI PV move-by-move and renders each in SAN. It stops at the first move it can't parse, so a truncated or illegal line yields the longest valid prefix:

let pv = ["e2e4", "e7e5", "g1f3", "b8c6", "f1b5"]
let sanLine = UCIParser.convertPVToSAN(pv, from: .initial())
// ["e4", "e5", "Nf3", "Nc6", "Bb5"]

This is suitable for rendering an engine's info … pv … line as human-readable notation.

Rendering SAN directly from a Move

If you already hold a Move, render it with the move generator instead — it produces full SAN including disambiguation and check/mate suffixes:

let san = MoveGenerator.algebraicNotation(for: move, in: position)

UCIParser.uciToSAN performs the UCI→Move→SAN conversion in a single call.