//===----------------------------------------------------------------------===//
//
// This source file is part of the Swift.org open source project
//
// Copyright (c) 2023 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
//
//===----------------------------------------------------------------------===//

import SwiftDiagnostics
import SwiftOperators
import SwiftSyntax
import SwiftSyntaxBuilder
import SwiftSyntaxMacros

extension AttributeSyntax {
  var availability: AttributeSyntax? {
    if attributeName.identifier == "available" {
      return self
    } else {
      return nil
    }
  }
}

extension IfConfigClauseSyntax.Elements {
  var availability: IfConfigClauseSyntax.Elements? {
    switch self {
    case .attributes(let attributes):
      if let availability = attributes.availability {
        return .attributes(availability)
      } else {
        return nil
      }
    default:
      return nil
    }
  }
}

extension IfConfigClauseSyntax {
  var availability: IfConfigClauseSyntax? {
    if let availability = elements?.availability {
      return with(\.elements, availability)
    } else {
      return nil
    }
  }

  var clonedAsIf: IfConfigClauseSyntax {
    detached.with(\.poundKeyword, .poundIfToken())
  }
}

extension IfConfigDeclSyntax {
  var availability: IfConfigDeclSyntax? {
    var elements = [IfConfigClauseListSyntax.Element]()
    for clause in clauses {
      if let availability = clause.availability {
        if elements.isEmpty {
          elements.append(availability.clonedAsIf)
        } else {
          elements.append(availability)
        }
      }
    }
    if elements.isEmpty {
      return nil
    } else {
      return with(\.clauses, IfConfigClauseListSyntax(elements))
    }

  }
}

extension AttributeListSyntax.Element {
  var availability: AttributeListSyntax.Element? {
    switch self {
    case .attribute(let attribute):
      if let availability = attribute.availability {
        return .attribute(availability)
      }
    case .ifConfigDecl(let ifConfig):
      if let availability = ifConfig.availability {
        return .ifConfigDecl(availability)
      }
    @unknown default:
      return nil
    }
    return nil
  }
}

extension AttributeListSyntax {
  var availability: AttributeListSyntax? {
    var elements = [AttributeListSyntax.Element]()
    for element in self {
      if let availability = element.availability {
        elements.append(availability)
      }
    }
    if elements.isEmpty {
      return nil
    }
    return AttributeListSyntax(elements)
  }
}