CommonEncodableMacro.swift

//===----------------------------------------------------------------------===//
//
// This source file is part of the Swift.org open source project
//
// Copyright (c) 2026 Apple Inc. and the Swift project authors
// Licensed under Apache License v2.0 with Runtime Library Exception
//
// See https://swift.org/LICENSE.txt for license information
// See https://swift.org/CONTRIBUTORS.txt for the list of Swift project authors
//
//===----------------------------------------------------------------------===//

import SwiftSyntax
import SwiftSyntaxMacros
import SwiftSyntaxBuilder
import SwiftDiagnostics

public struct CommonEncodableMacro { }

extension CommonEncodableMacro: ExtensionMacro {
    public static func expansion(
        of node: AttributeSyntax,
        attachedTo declaration: some DeclGroupSyntax,
        providingExtensionsOf type: some TypeSyntaxProtocol,
        conformingTo protocols: [TypeSyntax],
        in context: some MacroExpansionContext
    ) throws -> [ExtensionDeclSyntax] {
        guard validate(declaration: declaration, for: node, in: context) else {
            return []
        }
        
        guard let (typeName, properties) = extractTypeNameAndStoredProperties(
            attachedTo: declaration,
            for: node,
            providingExtensionsOf: type,
            in: context) else {
            return []
        }
        
        let codingFields = makeCodingFieldsExtension(for: typeName, from: properties, kind: CommonCodingFieldExpansionKind.encodingOnly)
        let impl = makeEncodableExtension(for: typeName, with: properties, kind: CommonEncodableExpansionKind())
        return [codingFields, impl].compactMap { $0 }
    }
}

struct CommonEncodableExpansionKind: EncodableExpansionKind {
    var protocolName: String { "CommonEncodable" }
    var encoderType: String { "inout some CommonEncoder & ~Copyable & ~Escapable" }
}