// 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 System.Collections.Generic;
using System.Linq;
using Mono.Cecil;
using Mono.Cecil.Cil;

namespace TLens.Analyzers
{
    sealed class TypeInstatiationAnalyzer : Analyzer
    {
        readonly Dictionary<TypeDefinition, List<MethodDefinition>> types = new Dictionary<TypeDefinition, List<MethodDefinition>>();

        protected override void ProcessMethod(MethodDefinition method)
        {
            var instrs = method.Body.Instructions;

            foreach (var instr in instrs)
            {
                switch (instr.OpCode.Code)
                {
                    case Code.Call:
                    case Code.Newobj:
                        if (instr.Operand is not MethodReference mr)
                            throw new NotImplementedException();

                        var md = mr.Resolve();

                        if (md == null)
                            continue;

                        if (!md.IsConstructor)
                            continue;

                        if (md.IsStatic)
                            throw new NotImplementedException();

                        var type = md.DeclaringType;

                        // Not interested in ctors chaining
                        if (type == method.DeclaringType)
                            continue;

                        // Not interested in base class initialization
                        if (md.DeclaringType == method.DeclaringType.BaseType)
                            continue;

                        if (!types.TryGetValue(type, out var existing))
                        {
                            existing = new List<MethodDefinition>();
                            types.Add(type, existing);
                        }

                        existing.Add(method);
                        break;
                }
            }
        }

        public override void PrintResults(int maxCount)
        {
            var entries = types.OrderBy(l => l.Value.Count).ThenByDescending(l => l.Key.GetEstimatedSize()).Take(maxCount);
            if (!entries.Any())
                return;

            PrintHeader("Limited type instantiations");

            foreach (var entry in entries)
            {
                Console.WriteLine($"Type '{entry.Key.FullName}' [size: {entry.Key.GetEstimatedSize()}] is instantiated only at");
                foreach (var values in entry.Value)
                {
                    Console.WriteLine($"\t{values.ToDisplay()}");
                }

                Console.WriteLine();
            }
        }
    }
}