JSONAPI/Sources/JSONAPI/Document/APIDescription.swift

//
//  APIDescription.swift
//  JSONAPI
//
//  Created by Mathew Polzin on 12/1/18.
//

/// This is what the JSON API Spec calls the "JSON:API Object"
public protocol APIDescriptionType: Codable, Equatable {
	associatedtype Meta
}

/// This is what the JSON API Spec calls the "JSON:API Object"
public struct APIDescription<Meta: JSONAPI.Meta>: APIDescriptionType {
	public let version: String
	public let meta: Meta
}

public struct NoAPIDescription: APIDescriptionType, CustomStringConvertible {
	public typealias Meta = NoMetadata

	public init() {}

	public static var none: NoAPIDescription { return .init() }

	public var description: String { return "No JSON:API Object" }
}

extension APIDescription {
	private enum CodingKeys: String, CodingKey {
		case version
		case meta
	}

	public init(from decoder: Decoder) throws {
		let container = try decoder.container(keyedBy: CodingKeys.self)

		// The spec says that if a version is not specified, it should be assumed to be at least 1.0
		version = (try? container.decode(String.self, forKey: .version)) ?? "1.0"

		if let metaVal = NoMetadata() as? Meta {
			meta = metaVal
		} else {
			meta = try container.decode(Meta.self, forKey: .meta)
		}
	}

	public func encode(to encoder: Encoder) throws {
		var container = encoder.container(keyedBy: CodingKeys.self)

		try container.encode(version, forKey: .version)

		if Meta.self != NoMetadata.self {
			try container.encode(meta, forKey: .meta)
		}
	}
}