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 field.</summary>
    internal class FieldFinder : BaseInstructionHandler
    {
        /*********
        ** Fields
        *********/
        /// <summary>The full type name for which to find references.</summary>
        private readonly string FullTypeName;

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

        /// <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="fieldNames">The field names for which to find references.</param>
        /// <param name="result">The result to return for matching instructions.</param>
        public FieldFinder(string fullTypeName, string[] fieldNames, InstructionHandleResult result)
            : base(defaultPhrase: $"{string.Join(", ", fieldNames.Select(p => $"{fullTypeName}.{p}"))} field{(fieldNames.Length != 1 ? "s" : "")}") // default phrase should never be used
        {
            this.FullTypeName = fullTypeName;
            this.FieldNames = new HashSet<string>(fieldNames);
            this.Result = result;
        }

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

        /// <inheritdoc />
        public override bool Handle(ModuleDefinition module, ILProcessor cil, Instruction instruction)
        {
            if (this.FieldNames.Any())
            {
                FieldReference? fieldRef = RewriteHelper.AsFieldReference(instruction);
                if (fieldRef != null && fieldRef.DeclaringType.FullName == this.FullTypeName && this.FieldNames.Contains(fieldRef.Name))
                {
                    this.FieldNames.Remove(fieldRef.Name);

                    this.MarkFlag(this.Result);
                    this.Phrases.Add($"{this.FullTypeName}.{fieldRef.Name} field");
                }
            }

            return false;
        }
    }
}