// 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 LimitedMethodCalls : Analyzer
    {
        readonly Dictionary<MethodDefinition, List<MethodDefinition>> methods = new Dictionary<MethodDefinition, List<MethodDefinition>>();

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

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

                        var md = mr.Resolve();

                        if (md == null)
                            continue;

                        if (md == method)
                            continue;

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

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

        public override void PrintResults(int maxCount)
        {
            var entries = methods.Where(l => l.Value.Count <= 3).OrderBy(l => l.Value.Count).ThenByDescending(l => l.Key.GetEstimatedSize()).Take(maxCount);
            if (!entries.Any())
                return;

            PrintHeader("Methods called sparsely");

            foreach (var entry in entries)
            {
                Console.WriteLine($"Method {entry.Key.ToDisplay(showSize: true)} is used only at");
                foreach (var values in entry.Value)
                {
                    Console.WriteLine($"\t{values.ToDisplay()}");
                }

                Console.WriteLine();
            }
        }
    }
}