using System.Collections.Generic;
using System.Collections.Immutable;
using System.Linq;
using Microsoft.CodeAnalysis;

namespace Cfa;

internal static class ImmutableDictionaryExtensions
{
    public static IEnumerable<KeyValuePair<ISymbol, IImmutableList<Call>>> Invert(
        this ImmutableDictionary<ISymbol, IImmutableList<Call>>.Builder builder
    ) =>
        builder
            .SelectMany(kvp => kvp.Value.Select(call => (from: kvp.Key, to: call.Target, kind: call.LinkKind)))
            .GroupBy(x => x.to, SymbolEqualityComparer.Default)
            .Select(g =>
                KeyValuePair.Create(g.Key, (IImmutableList<Call>)[.. g.Select(x => new Call(x.from, x.kind))])
            );
}