//

// JavaScriptKit

// Copyright (c) 2017 - present Alexis Aubry. Licensed under the MIT license.

//

import Foundation

/**

* A JavaScript expression that returns the value of a variable in the current JavaScript

* `this`. The variable is referenced by a key path relative to the current `this`.

*

* For instance, to get the title of the current document:

*

* ~~~swift

* let title = JSVariable<String>("document.title")

* // equivalent to the JS script: `this.document.title;`

* ~~~

*

* Instances of this class are specialized with the `T` generic parameter. It must be set to the

* type of the JavaScript variable to query. Check the documentation of the JavaScript variable

* to know what to set the parameter to.

*

* `T` must be a `Decodable` type. This includes:

*

* - Primitive values (Strings, Numbers, Booleans, ...)

* - Decodable enumerations

* - Objects decodable from JSON

* - Arrays of primitive values

* - Arrays of enumeration cases

* - Arrays of objects

* - Native dictionaries

*/

public final class JSVariable<T>: JSExpression where T: Decodable {

public typealias ReturnType = T

/// The path to the variable, relative to the current `this` object tree.

public let keyPath: String

/**

* Creates a new JavaScript variable description.

*

* - parameter keyPath: The dot-separated path to the variable, relative to the current `this`

* object tree.

*

* For instance, to get the title of the current document:

*

* ~~~swift

* let title = JSVariable<String>("document.title")

* // equivalent to the JS script: `this.document.title;`

* ~~~

*/

public init(_ keyPath: String) {

self.keyPath = keyPath

}

/// Creates the JavaScript text of the expression.

public func makeExpressionString() -> String {

return "this.\(keyPath);"

}

}