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1// SPDX-FileCopyrightText: 2025 The Project Pterodactyl Developers
2//
3// SPDX-License-Identifier: MPL-2.0
4
5import Foundation
6
7/// This is an abstraction of grammatical productions.
8public protocol Grammar: Sendable {
9 /// The kinds of tree that the production produces.
10 static var kinds: [SyntaxTreeKind] { get }
11
12 /// Indicates whether the current parser state is consistent with the grammatical production starting here. When a given grammatical element is optional, this can be used to avoid backtracking. This is a *precondition* for parsing.
13 static func before(_ parser: inout Parser) -> Bool
14
15 /// Parse the grammatical production, assuming the precondition indicated by ``before(_:)``. This function should not be called outside this module (instead, use ``parse(_:)`` and ``tryParse(_:)``.
16 static func inside(_ parser: inout Parser) -> ParseResult
17}
18
19public struct ParseResult {
20 public var kind: SyntaxTreeKind
21 public var metadata: SyntaxTreeMetadata? = nil
22
23 public init(kind: SyntaxTreeKind, metadata: SyntaxTreeMetadata? = nil) {
24 self.kind = kind
25 self.metadata = metadata
26 }
27}
28
29
30extension Grammar {
31 public static func tryParse(_ parser: inout Parser) -> Bool {
32 guard !parser.isEndOfFile && before(&parser) else { return false }
33 parse(&parser)
34 return true
35 }
36
37 public static func parse(_ parser: inout Parser) {
38 let mark = parser.open()
39 let result = inside(&parser)
40 parser.close(mark: mark, kind: result.kind, metadata: result.metadata)
41 }
42}