// Copyright (c) .NET Foundation and contributors. All rights reserved.
// Licensed under the MIT license. See LICENSE file in the project root for full license information.

using System;
using ILLink.Shared;
using ILLink.Shared.DataFlow;

namespace ILLink.RoslynAnalyzer.DataFlow
{
    // A lattice value that holds both a local state, and a context
    public struct LocalStateAndContext<TValue, TContext> : IEquatable<LocalStateAndContext<TValue, TContext>>
        where TValue : IEquatable<TValue>
        where TContext : IEquatable<TContext>
    {
        public LocalState<TValue> LocalState;
        public TContext Context;

        public LocalStateAndContext(LocalState<TValue> localState, TContext context)
        {
            LocalState = localState;
            Context = context;
        }

        public bool Equals(LocalStateAndContext<TValue, TContext> other) =>
            LocalState.Equals(other.LocalState) && Context.Equals(other.Context);

        public override bool Equals(object? obj) => obj is LocalStateAndContext<TValue, TContext> other && Equals(other);
        public override int GetHashCode() => HashUtils.Combine(LocalState, Context);
    }

    public readonly struct LocalStateAndContextLattice<TValue, TContext, TValueLattice, TContextLattice> : ILattice<LocalStateAndContext<TValue, TContext>>
        where TValue : struct, IEquatable<TValue>
        where TContext : struct, IEquatable<TContext>
        where TValueLattice : ILattice<TValue>
        where TContextLattice : ILattice<TContext>
    {
        public readonly LocalStateLattice<TValue, TValueLattice> LocalStateLattice;
        public readonly TContextLattice ContextLattice;

        public LocalStateAndContextLattice(LocalStateLattice<TValue, TValueLattice> localStateLattice, TContextLattice contextLattice)
        {
            LocalStateLattice = localStateLattice;
            ContextLattice = contextLattice;
            Top = new(LocalStateLattice.Top, ContextLattice.Top);
        }

        public LocalStateAndContext<TValue, TContext> Top { get; }

        public LocalStateAndContext<TValue, TContext> Meet(LocalStateAndContext<TValue, TContext> left, LocalStateAndContext<TValue, TContext> right)
        {
            return new LocalStateAndContext<TValue, TContext>
            {
                LocalState = LocalStateLattice.Meet(left.LocalState, right.LocalState),
                Context = ContextLattice.Meet(left.Context, right.Context)
            };
        }
    }
}