native macOS codings agent orchestrator prowl.onev.cat
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4.7 kB · 134 lines
Swift
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nonisolated struct WorkflowExpressionParser { private var tokens: [String] = [] private var offset = 0 private var depth = 0 private static let precedence = [ "??": 1, "||": 2, "&&": 3, "==": 4, "!=": 4, "<": 5, "<=": 5, ">": 5, ">=": 5, "+": 6, "-": 6, "*": 7, "/": 7, "%": 7, ]
init(_ source: String) throws { guard source.utf8.count <= 16_384 else { throw WorkflowExpressionError.limit("Expression exceeds 16 KiB.") } var remaining = source[...] let token = #/ \s*("(?:[^"\\]|\\.)*"|'(?:[^'\\]|\\.)*'| [0-9]+(?:\.[0-9]+)?(?:[eE][+-]?[0-9]+)?|[a-zA-Z_][a-zA-Z0-9_]*| \?\?|\|\||&&|==|!=|<=|>=|[.\[\](),!+*\/%<>-]) /# while !remaining.trimmingCharacters(in: .whitespacesAndNewlines).isEmpty { guard let match = remaining.prefixMatch(of: token) else { throw WorkflowExpressionError.syntax("Invalid token near '\(remaining.prefix(30))'.") } guard tokens.count < 256 else { throw WorkflowExpressionError.limit("Expression exceeds 256 tokens.") } tokens.append(String(match.1)) remaining = remaining[match.range.upperBound...] } }
mutating func parse() throws -> WorkflowExpressionNode { let result = try expression() guard offset == tokens.count else { throw WorkflowExpressionError.syntax("Unexpected token '\(peek)'.") } return result }
private var peek: String { offset < tokens.count ? tokens[offset] : "" }
@discardableResult private mutating func consume(_ token: String) -> Bool { guard peek == token else { return false } offset += 1 return true }
private mutating func require(_ token: String) throws { guard consume(token) else { throw WorkflowExpressionError.syntax("Expected '\(token)'.") } }
private mutating func expression(_ minimum: Int = 1) throws -> WorkflowExpressionNode { depth += 1 defer { depth -= 1 } guard depth <= 64 else { throw WorkflowExpressionError.limit("Expression nesting exceeds 64.") } var left = try primary() while let precedence = Self.precedence[peek], precedence >= minimum { let operation = peek offset += 1 let right = try expression(precedence + 1) left = .binary(operation, left, right) } return left }
private mutating func primary() throws -> WorkflowExpressionNode { var value: WorkflowExpressionNode if consume("!") { return try .unary("!", expression(8)) } if consume("-") { return try .unary("-", expression(8)) } if consume("(") { value = try expression() try require(")") } else if consume("[") { value = try .array(arguments(ending: "]")) } else { value = try atom() } while true { if consume(".") { let name = peek guard name.wholeMatch(of: /[a-zA-Z_][a-zA-Z0-9_]*/) != nil else { throw WorkflowExpressionError.syntax("Expected a field name.") } offset += 1 value = .field(value, name) } else if consume("[") { value = try .index(value, expression()) try require("]") } else { break } } return value }
private mutating func atom() throws -> WorkflowExpressionNode { let token = peek guard !token.isEmpty else { throw WorkflowExpressionError.syntax("Expected an expression.") } offset += 1 switch token { case "true": return .literal(.boolean(true)) case "false": return .literal(.boolean(false)) case "null": return .literal(.null) default: break } if token.hasPrefix("\"") { return try .literal(.string(JSONDecoder().decode(String.self, from: Data(token.utf8)))) } if token.hasPrefix("'") { let body = String(token.dropFirst().dropLast()).replacing("\\'", with: "'") return .literal(.string(body)) } if let integer = Int(token) { let value = WorkflowJSONValue.integer(integer) try WorkflowJSON.validate(value) return .literal(value) } if let number = Double(token) { let value = WorkflowJSONValue.number(number) try WorkflowJSON.validate(value) return .literal(value) } guard token.wholeMatch(of: /[a-zA-Z_][a-zA-Z0-9_]*/) != nil else { throw WorkflowExpressionError.syntax("Unexpected token '\(token)'.") } if consume("(") { return try .call(token, arguments(ending: ")")) } return .name(token) }
private mutating func arguments(ending: String) throws -> [WorkflowExpressionNode] { if consume(ending) { return [] } var result = [try expression()] while consume(",") { result.append(try expression()) } try require(ending) return result }}