memberlookup.swift

//
//  main.swift
//  DynamicMemberLookupXML
//
//  Created by Chris Eidhof on 03.08.18.
//  Copyright © 2018 objc.io. All rights reserved.
//

import Foundation

enum Node {
    case tag(Tag)
    case text(String)
    
    var pretty: String {
        switch self {
        case let .tag(t): return t.pretty
        case let .text(t): return t
        }
    }
}

@dynamicMemberLookup
class Tag {
    var tag: String
    var children: [Node] = []
    var attributes: [String:String]
    init(_ name: String) {
        self.tag = name
        self.children = []
        self.attributes = [:]
    }
    subscript(dynamicMember member: String) -> (Any...) -> () {
        let new = Tag(member)
        children.append(.tag(new))
        return { (args: Any...) in
            for x in args {
                if let attr = x as? Attr {
                    new.attributes[attr.key] = attr.value
                } else if let s = x as? String {
                    new.children.append(.text(s))
                } else {
                    fatalError()
                }
            }
        }
    }
    
    var pretty: String {
        let atts = attributes.map { "\($0.0)=\"\($0.1)\"" }.joined(separator: " ")
        let c = children.map { $0.pretty }.joined(separator: "\n")
        return "<\(tag) \(atts)>\n\(c)\n</\(tag)>"
    }
}

infix operator .=
struct Attr { let key: String; let value: String }
func .=(lhs: String, rhs: String) -> Attr { return Attr(key: lhs, value: rhs)}

let p = Tag("person")
p.span("class" .= "wide", "Test")
p.h1("Hello")

print("done")
print(p.pretty)