JSObject.swift

import _CJavaScriptKit

/// `JSObject` represents an object in JavaScript and supports dynamic member lookup.
/// Any member access like `object.foo` will dynamically request the JavaScript and Swift
/// runtime bridge library for a member with the specified name in this object.
///
/// And this object supports to call a member method of the object.
///
/// e.g.
/// ```swift
/// let document = JSObject.global.document.object!
/// let divElement = document.createElement!("div")
/// ```
///
/// The lifetime of this object is managed by the JavaScript and Swift runtime bridge library with
/// reference counting system.
@dynamicMemberLookup
public class JSObject: Equatable {
    internal var id: JavaScriptObjectRef
    init(id: JavaScriptObjectRef) {
        self.id = id
    }

    /// Returns the `name` member method binding this object as `this` context.
    ///
    /// e.g.
    /// ```swift
    /// let document = JSObject.global.document.object!
    /// let divElement = document.createElement!("div")
    /// ```
    ///
    /// - Parameter name: The name of this object's member to access.
    /// - Returns: The `name` member method binding this object as `this` context.
    @_disfavoredOverload
    public subscript(_ name: String) -> ((JSValueConvertible...) -> JSValue)? {
        guard let function = self[name].function else { return nil }
        return { (arguments: JSValueConvertible...) in
            function(this: self, arguments: arguments)
        }
    }

    /// A convenience method of `subscript(_ name: String) -> ((JSValueConvertible...) -> JSValue)?`
    /// to access the member through Dynamic Member Lookup.
    @_disfavoredOverload
    public subscript(dynamicMember name: String) -> ((JSValueConvertible...) -> JSValue)? {
        self[name]
    }

    /// A convenience method of `subscript(_ name: String) -> JSValue`
    /// to access the member through Dynamic Member Lookup.
    public subscript(dynamicMember name: String) -> JSValue {
        get { self[name] }
        set { self[name] = newValue }
    }

    /// Access the `name` member dynamically through JavaScript and Swift runtime bridge library.
    /// - Parameter name: The name of this object's member to access.
    /// - Returns: The value of the `name` member of this object.
    public subscript(_ name: String) -> JSValue {
        get { getJSValue(this: self, name: name) }
        set { setJSValue(this: self, name: name, value: newValue) }
    }

    /// Access the `index` member dynamically through JavaScript and Swift runtime bridge library.
    /// - Parameter index: The index of this object's member to access.
    /// - Returns: The value of the `index` member of this object.
    public subscript(_ index: Int) -> JSValue {
        get { getJSValue(this: self, index: Int32(index)) }
        set { setJSValue(this: self, index: Int32(index), value: newValue) }
    }

  /// Return `true` if this value is an instance of the passed `constructor` function.
    /// - Parameter constructor: The constructor function to check.
    /// - Returns: The result of `instanceof` in the JavaScript environment.
    public func isInstanceOf(_ constructor: JSFunction) -> Bool {
        _instanceof(id, constructor.id)
    }

    static let _JS_Predef_Value_Global: JavaScriptObjectRef = 0

    /// A `JSObject` of the global scope object.
    /// This allows access to the global properties and global names by accessing the `JSObject` returned.
    public static let global = JSObject(id: _JS_Predef_Value_Global)

    deinit { _release(id) }

    /// Returns a Boolean value indicating whether two values point to same objects.
    ///
    /// - Parameters:
    ///   - lhs: A object to compare.
    ///   - rhs: Another object to compare.
    public static func == (lhs: JSObject, rhs: JSObject) -> Bool {
        return lhs.id == rhs.id
    }

    public class func construct(from value: JSValue) -> Self? {
        return value.object as? Self
    }

    public func jsValue() -> JSValue {
        .object(self)
    }
}

extension JSObject: CustomStringConvertible {
    public var description: String { self.toString!().string! }
}