using System.Collections.Generic;
using System.Linq;
using Mono.Cecil;
using Mono.Cecil.Cil;
using StardewModdingAPI.Framework.ModLoading.Framework;

namespace StardewModdingAPI.Framework.ModLoading.Finders
{
    /// <summary>Finds incompatible CIL instructions that reference a given event.</summary>
    internal class EventFinder : BaseInstructionHandler
    {
        /*********
        ** Fields
        *********/
        /// <summary>The full type name for which to find references.</summary>
        private readonly string FullTypeName;

        /// <summary>The method names for which to find references.</summary>
        private readonly ISet<string> MethodNames;

        /// <summary>The result to return for matching instructions.</summary>
        private readonly InstructionHandleResult Result;


        /*********
        ** Public methods
        *********/
        /// <summary>Construct an instance.</summary>
        /// <param name="fullTypeName">The full type name for which to find references.</param>
        /// <param name="eventNames">The event names for which to find references.</param>
        /// <param name="result">The result to return for matching instructions.</param>
        public EventFinder(string fullTypeName, string[] eventNames, InstructionHandleResult result)
            : base(defaultPhrase: $"{string.Join(", ", eventNames.Select(p => $"{fullTypeName}.{p}"))} event{(eventNames.Length != 1 ? "s" : "")}") // default phrase should never be used
        {
            this.FullTypeName = fullTypeName;
            this.Result = result;

            this.MethodNames = new HashSet<string>();
            foreach (string name in eventNames)
            {
                this.MethodNames.Add($"add_{name}");
                this.MethodNames.Add($"remove_{name}");
            }
        }

        /// <summary>Construct an instance.</summary>
        /// <param name="fullTypeName">The full type name for which to find references.</param>
        /// <param name="eventName">The event name for which to find references.</param>
        /// <param name="result">The result to return for matching instructions.</param>
        public EventFinder(string fullTypeName, string eventName, InstructionHandleResult result)
            : this(fullTypeName, new[] { eventName }, result) { }

        /// <inheritdoc />
        public override bool Handle(ModuleDefinition module, ILProcessor cil, Instruction instruction)
        {
            if (this.MethodNames.Any())
            {
                MethodReference? methodRef = RewriteHelper.AsMethodReference(instruction);
                if (methodRef != null && methodRef.DeclaringType.FullName == this.FullTypeName && this.MethodNames.Contains(methodRef.Name))
                {
                    string eventName = methodRef.Name.Split(new[] { '_' }, 2)[1];
                    this.MethodNames.Remove($"add_{eventName}");
                    this.MethodNames.Remove($"remove_{eventName}");

                    this.MarkFlag(this.Result);
                    this.Phrases.Add($"{this.FullTypeName}.{eventName} event");
                }
            }

            return false;
        }
    }
}