commit 9d264994d7a8b74f58362205709f9b683b129b7e · jonmsterling.com/swift-pterodactyl

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Sources/PterodactylSyntax/Grammar.swift

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       // SPDX-FileCopyrightText: 2025 The Project Pterodactyl Developers

     

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       //

     

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       // SPDX-License-Identifier: MPL-2.0

     

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       import Foundation

     

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       public protocol Grammar {

     

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       //	static var kind: L.TreeKind { get }

     

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       	static func before(_ parser: inout Parser) -> Bool

     

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       	static func inside(_ parser: inout Parser) -> SyntaxTreeKind

     

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       }

     

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       public extension Grammar {

     

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       	static func tryParse(_ parser: inout Parser) -> Bool {

     

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       		guard !parser.isEndOfFile && before(&parser) else { return false }

     

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       		parse(&parser)

     

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       		return true

     

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       	}

     

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       	static func parse(_ parser: inout Parser) {

     

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       		let mark = parser.open()

     

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       		let kind = inside(&parser)

     

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       		parser.close(mark: mark, kind: kind)

     

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       	}

     

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       }

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Sources/PterodactylSyntax/Parser.swift

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       // SPDX-FileCopyrightText: 2025 The Project Pterodactyl Developers

     

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       //

     

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       // SPDX-License-Identifier: MPL-2.0

     

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       public struct Parser {

     

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       	enum Event: Equatable {

     

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       		case open(kind: SyntaxTreeKind)

     

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       		case close

     

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       		case advance

     

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       	}

     

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       	public struct MarkOpened {

     

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       		internal let index: Int

     

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       	}

     

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       	let source: String

     

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       	let tokens: [Token]

     

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       	public init(source: String, tokens: [Token]) {

     

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       		self.source = source

     

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       		self.tokens = tokens

     

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       	}

     

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       	public private(set) var diagnostics: [Diagnostic] = []

     

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       	private var fuel: Int = 0

     

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       	private var position: Int = 0

     

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       	private var events: [Event] = []

     

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       	private var absoluteUtf16Offset: Int = 0

     

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       	public var absoluteRangeAtCursor: Range<Int> {

     

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       		return absoluteUtf16Offset..<absoluteUtf16Offset

     

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       	}

     

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       	public var absoluteRangeOfCurrentToken: Range<Int> {

     

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       		return absoluteUtf16Offset..<absoluteUtf16Offset + currentToken.utf16Length

     

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       	}

     

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       	public var isEndOfFile: Bool {

     

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       		position == tokens.count

     

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       	}

     

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       	public var currentToken: Token {

     

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       		if tokens.indices.contains(position) {

     

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       			return tokens[position]

     

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       		} else {

     

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       			return Token(

     

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       				kind: .eof,

     

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       				text: "",

     

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       			)

     

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       		}

     

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       	}

     

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       	public func isAt(kind: TokenKind) -> Bool {

     

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       		currentToken.kind == kind

     

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       	}

     

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       	public func isAt(kindSatisfying predicate: (TokenKind) -> Bool) -> Bool {

     

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       		return predicate(currentToken.kind)

     

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       	}

     

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       	public mutating func open() -> MarkOpened {

     

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       		let mark = MarkOpened(index: events.count)

     

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       		events.append(.open(kind: .error))

     

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       		return mark

     

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       	}

     

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       	public mutating func close(mark: MarkOpened, kind: SyntaxTreeKind) {

     

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       		events[mark.index] = .open(kind: kind)

     

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       		events.append(.close)

     

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       	}

     

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       	public mutating func advance() {

     

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       		precondition(!isEndOfFile)

     

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       		events.append(.advance)

     

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       		absoluteUtf16Offset += currentToken.utf16Length

     

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       		position += 1

     

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       		fuel = 256

     

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       	}

     

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       	public mutating func advance(error: String?) {

     

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       		let mark = open()

     

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       		if let error {

     

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       			let diagnostic = Diagnostic(

     

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       				message: error,

     

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       				absoluteRange: absoluteRangeOfCurrentToken

     

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       			)

     

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       			diagnostics.append(diagnostic)

     

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       		}

     

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       		advance()

     

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       		close(mark: mark, kind: .error)

     

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       	}

     

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       	public mutating func lookahead(_ k: Int) -> TokenKind? {

     

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       		precondition(fuel > 0, "Parser is stuck!")

     

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       		fuel -= 1

     

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       		let index = position + k

     

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       		guard tokens.indices.contains(index) else { return nil }

     

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       		return tokens[index].kind

     

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       	}

     

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       	public mutating func eat(kindSatisfying predicate: (TokenKind) -> Bool) -> Bool {

     

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       		guard !isEndOfFile && isAt(kindSatisfying: predicate) else { return false }

     

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       		advance()

     

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       		return true

     

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       	}

     

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       	public mutating func eat(kind: TokenKind) -> Bool {

     

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       		eat { $0 == kind }

     

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       	}

     

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       	public mutating func expect(kind: TokenKind, error: String? = nil) {

     

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       		if eat(kind: kind) { return }

     

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       		let diagnostic = Diagnostic(

     

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       			message: error ?? "Expected \(kind) but got \(currentToken.kind): `\(currentToken.text)`",

     

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       			absoluteRange: absoluteRangeAtCursor

     

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       		)

     

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       		diagnostics.append(diagnostic)

     

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       	}

     

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       	public var tree: SyntaxTree {

     

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       		var events = events

     

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       		var stack: [SyntaxTree] = []

     

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       		var cursor: Int = 0

     

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       		precondition(events.popLast() == .close)

     

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       		for event in events {

     

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       			switch event {

     

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       			case .open(let kind):

     

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       				stack.append(SyntaxTree(kind: kind, children: []))

     

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       			case .close:

     

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       				let tree = stack.popLast()!

     

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       				stack.modifyLast { last in

     

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       					last.children.append(.tree(tree))

     

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       				}

     

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       			case .advance:

     

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       				let token = tokens[cursor]

     

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       				cursor += 1

     

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       				stack.modifyLast { last in

     

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       					last.children.append(.token(token))

     

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       				}

     

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       			}

     

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       		}

     

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       		assert(stack.count == 1)

     

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       		return stack.popLast()!

     

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       	}

     

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       }

     

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       extension Array {

     

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       	fileprivate mutating func modifyLast(_ modifier: (inout Element) -> Void) {

     

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       		if var last = popLast() {

     

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       			modifier(&last)

     

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       			append(last)

     

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       		}

     

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       	}

     

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       }