JSONCodableMacro.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 SwiftDiagnostics

public struct JSONCodableMacro { }

extension JSONCodableMacro: MemberMacro {
    public static func expansion(
        of node: AttributeSyntax,
        providingMembersOf declaration: some DeclGroupSyntax,
        conformingTo protocols: [TypeSyntax],
        in context: some MacroExpansionContext
    ) throws -> [DeclSyntax] {
        guard declaration.is(StructDeclSyntax.self) else {
            context.diagnose(.init(
                node: node,
                message: JSONEncodableDiagnostic.notAStruct
            ))
            return []
        }

        let properties = extractStoredProperties(from: declaration.memberBlock, in: context)
        guard !properties.isEmpty else {
            return []
        }

        return [makeCodingFieldsDecl(from: properties, kind: .coding)]
    }
}

extension JSONCodableMacro: 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] {
        let encodableExtensions = try JSONEncodableMacro.expansion(
            of: node,
            attachedTo: declaration,
            providingExtensionsOf: type,
            conformingTo: protocols,
            in: context
        )
        let decodableExtensions = try JSONDecodableMacro.expansion(
            of: node,
            attachedTo: declaration,
            providingExtensionsOf: type,
            conformingTo: protocols,
            in: context
        )
        return encodableExtensions + decodableExtensions
    }
}