/*
 This source file is part of the Swift.org open source project

 Copyright (c) 2021-2023 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
 See https://swift.org/CONTRIBUTORS.txt for Swift project authors
*/

import Foundation

extension SymbolGraph.Symbol {
    /// The arguments of a callable symbol.
    public struct FunctionSignature: Mixin, Codable {
        enum CodingKeys: String, CodingKey {
            case parameters
            case returns
        }

        public static let mixinKey = "functionSignature"

        /**
         The parameters of the function.
         */
        public var parameters: [FunctionParameter]

        /**
         The fragments spelling out the return type of the function signature if applicable.
         */
        public var returns: [DeclarationFragments.Fragment]

        public init(parameters: [SymbolGraph.Symbol.FunctionSignature.FunctionParameter], returns: [SymbolGraph.Symbol.DeclarationFragments.Fragment]) {
            self.parameters = parameters
            self.returns = returns
        }
        
        public init(from decoder: Decoder) throws {
            let container = try decoder.container(keyedBy: CodingKeys.self)
            parameters = try container.decodeIfPresent([FunctionParameter].self, forKey: .parameters) ?? []
            returns = try container.decodeIfPresent([DeclarationFragments.Fragment].self, forKey: .returns) ?? []
        }

        public func encode(to encoder: Encoder) throws {
            var container = encoder.container(keyedBy: CodingKeys.self)
            try container.encode(parameters, forKey: .parameters)
            try container.encode(returns, forKey: .returns)
        }
    }
    
    /// Convenience method to fetch the function signature mixin value.
    public var functionSignature : FunctionSignature? {
        (mixins[FunctionSignature.mixinKey] as? FunctionSignature)
    }
}
