// Sources/SwiftProtobuf/ExtensionFieldValueSet.swift - Extension support

//

// Copyright (c) 2014 - 2016 Apple Inc. and the project authors

// Licensed under Apache License v2.0 with Runtime Library Exception

//

// See LICENSE.txt for license information:

// https://github.com/apple/swift-protobuf/blob/main/LICENSE.txt

//

// -----------------------------------------------------------------------------

///

/// A collection of extension field values on a particular object.

/// This is only used within messages to manage the values of extension fields;

/// it does not need to be very sophisticated.

///

// -----------------------------------------------------------------------------

public struct ExtensionFieldValueSet: Hashable, Sendable {

    fileprivate var values = [Int: any AnyExtensionField]()

    public static func == (

        lhs: ExtensionFieldValueSet,

        rhs: ExtensionFieldValueSet

    ) -> Bool {

        guard lhs.values.count == rhs.values.count else {

            return false

        }

        for (index, l) in lhs.values {

            if let r = rhs.values[index] {

                if type(of: l) != type(of: r) {

                    return false

                }

                if !l.isEqual(other: r) {

                    return false

                }

            } else {

                return false

            }

        }

        return true

    }

    public init() {}

    public func hash(into hasher: inout Hasher) {

        // AnyExtensionField is not Hashable, and the Self constraint that would

        // add breaks some of the uses of it; so the only choice is to manually

        // mix things in. However, one must remember to do things in an order

        // independent manner.

        var hash = 16_777_619

        for (fieldNumber, v) in values {

            var localHasher = hasher

            localHasher.combine(fieldNumber)

            v.hash(into: &localHasher)

            hash = hash &+ localHasher.finalize()

        }

        hasher.combine(hash)

    }

    public func traverse<V: Visitor>(visitor: inout V, start: Int, end: Int) throws {

        let validIndexes = values.keys.filter { $0 >= start && $0 < end }

        for i in validIndexes.sorted() {

            let value = values[i]!

            try value.traverse(visitor: &visitor)

        }

    }

    public subscript(index: Int) -> (any AnyExtensionField)? {

        get { values[index] }

        set { values[index] = newValue }

    }

    mutating func modify<ReturnType>(

        index: Int,

        _ modifier: (inout (any AnyExtensionField)?) throws -> ReturnType

    ) rethrows -> ReturnType {

        // This internal helper exists to invoke the _modify accessor on Dictionary for the given operation, which can avoid CoWs

        // during the modification operation.

        try modifier(&values[index])

    }

    public var isInitialized: Bool {

        for (_, v) in values {

            if !v.isInitialized {

                return false

            }

        }

        return true

    }

}