/*
 * Copyright 1999-2101 Alibaba Group.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

//
//  Created by zhouzhuo on 07/01/2017.
//


/// An instance property
struct Property {
    let key: String
    let value: Any

    /// An instance property description
    struct Description {
        public let key: String
        public let type: Any.Type
        public let offset: Int
        public func write(_ value: Any, to storage: UnsafeMutableRawPointer) {
            return extensions(of: type).write(value, to: storage.advanced(by: offset))
        }
    }
}

/// Retrieve properties for `instance`
func getProperties(forInstance instance: Any) -> [Property]? {
    if let props = getProperties(forType: type(of: instance)) {
        var copy = extensions(of: instance)
        let storage = copy.storage()
        return props.map {
            nextProperty(description: $0, storage: storage)
        }
    }
    return nil
}

private func nextProperty(description: Property.Description, storage: UnsafeRawPointer) -> Property {
    return Property(
        key: description.key,
        value: extensions(of: description.type).value(from: storage.advanced(by: description.offset))
    )
}

/// Retrieve property descriptions for `type`
func getProperties(forType type: Any.Type) -> [Property.Description]? {
    if let nominalType = Metadata.Struct(anyType: type) {
        return fetchProperties(nominalType: nominalType)
    } else if let nominalType = Metadata.Class(anyType: type) {
        return nominalType.properties()
    } else if let nominalType = Metadata.ObjcClassWrapper(anyType: type),
        let targetType = nominalType.targetType {
        return getProperties(forType: targetType)
    } else {
        return nil
    }
}

func fetchProperties<T : NominalType>(nominalType: T) -> [Property.Description]? {
    return propertiesForNominalType(nominalType)
}

private func propertiesForNominalType<T : NominalType>(_ type: T) -> [Property.Description]? {
    guard let nominalTypeDescriptor = type.nominalTypeDescriptor else {
        return nil
    }
    guard nominalTypeDescriptor.numberOfFields != 0 else {
        return []
    }
    guard let fieldTypes = type.fieldTypes, let fieldOffsets = type.fieldOffsets else {
        return nil
    }
    let fieldNames = nominalTypeDescriptor.fieldNames
    return (0..<nominalTypeDescriptor.numberOfFields).map { i in
        return Property.Description(key: fieldNames[i], type: fieldTypes[i], offset: fieldOffsets[i])
    }
}