using System;
using System.Collections.Immutable;
using System.Linq;
using System.Reflection.Metadata;
// ReSharper disable MemberCanBePrivate.Global

namespace Robust.Shared.ContentPack
{
    internal sealed partial class AssemblyTypeChecker
    {
        internal abstract record MType
        {
            public virtual bool WhitelistEquals(MType other)
            {
                return false;
            }

            public virtual bool IsCoreTypeDefined()
            {
                return false;
            }

            /// <summary>
            /// Outputs this type in a format re-parseable for the sandbox config whitelist.
            /// </summary>
            public virtual string? WhitelistToString()
            {
                return ToString();
            }
        }

        internal abstract class MMemberRef
        {
            public readonly MType ParentType;
            public readonly string Name;

            protected MMemberRef(MType parentType, string name)
            {
                ParentType = parentType;
                Name = name;
            }
        }

        internal sealed class MMemberRefMethod : MMemberRef
        {
            public readonly MType ReturnType;
            public readonly int GenericParameterCount;
            public readonly ImmutableArray<MType> ParameterTypes;

            public MMemberRefMethod(MType parentType, string name, MType returnType,
                int genericParameterCount, ImmutableArray<MType> parameterTypes) : base(parentType, name)
            {
                ReturnType = returnType;
                GenericParameterCount = genericParameterCount;
                ParameterTypes = parameterTypes;
            }

            public override string ToString()
            {
                return $"{ReturnType} {ParentType}.{Name}({string.Join(", ", ParameterTypes)})";
            }
        }

        internal sealed class MMemberRefField : MMemberRef
        {
            public readonly MType FieldType;

            public MMemberRefField(MType parentType, string name, MType fieldType) : base(parentType, name)
            {
                FieldType = fieldType;
            }

            public override string ToString()
            {
                return $"{FieldType} {ParentType}.{Name}";
            }
        }

        internal sealed record MTypeParsed(string FullName, MTypeParsed? NestedParent = null) : MType
        {
            public override string ToString()
            {
                return NestedParent != null ? $"{NestedParent}/{FullName}" : FullName;
            }

            public override bool WhitelistEquals(MType other)
            {
                switch (other)
                {
                    case MTypeParsed parsed:
                        if (NestedParent != null)
                        {
                            if (parsed.NestedParent == null || !NestedParent.WhitelistEquals(parsed.NestedParent))
                            {
                                return false;
                            }
                        }

                        return parsed.FullName == FullName;
                    case MTypeReferenced referenced:
                        if (NestedParent != null)
                        {
                            if (referenced.ResolutionScope is not MResScopeType parentRes ||
                                !NestedParent.WhitelistEquals(parentRes.Type))
                            {
                                return false;
                            }
                        }

                        var refFullName = referenced.Namespace == null
                            ? referenced.Name
                            : $"{referenced.Namespace}.{referenced.Name}";
                        return FullName == refFullName;
                    default:
                        return false;
                }
            }
        }

        internal sealed record MTypePrimitive(PrimitiveTypeCode TypeCode) : MType
        {
            public override string ToString()
            {
                return TypeCode switch
                {
                    PrimitiveTypeCode.Void => "void",
                    PrimitiveTypeCode.Boolean => "bool",
                    PrimitiveTypeCode.Char => "char",
                    PrimitiveTypeCode.SByte => "int8",
                    PrimitiveTypeCode.Byte => "unsigned int8",
                    PrimitiveTypeCode.Int16 => "int16",
                    PrimitiveTypeCode.UInt16 => "unsigned int16",
                    PrimitiveTypeCode.Int32 => "int32",
                    PrimitiveTypeCode.UInt32 => "unsigned int32",
                    PrimitiveTypeCode.Int64 => "int64",
                    PrimitiveTypeCode.UInt64 => "unsigned int64",
                    PrimitiveTypeCode.Single => "float32",
                    PrimitiveTypeCode.Double => "float64",
                    PrimitiveTypeCode.String => "string",
                    // ReSharper disable once StringLiteralTypo
                    PrimitiveTypeCode.TypedReference => "typedref",
                    PrimitiveTypeCode.IntPtr => "native int",
                    PrimitiveTypeCode.UIntPtr => "unsigned native int",
                    PrimitiveTypeCode.Object => "object",
                    _ => "???"
                };
            }

            public override string WhitelistToString()
            {
                return TypeCode switch
                {
                    PrimitiveTypeCode.Void => "void",
                    PrimitiveTypeCode.Boolean => "bool",
                    PrimitiveTypeCode.Char => "char",
                    PrimitiveTypeCode.SByte => "sbyte",
                    PrimitiveTypeCode.Byte => "byte",
                    PrimitiveTypeCode.Int16 => "short",
                    PrimitiveTypeCode.UInt16 => "ushort",
                    PrimitiveTypeCode.Int32 => "int",
                    PrimitiveTypeCode.UInt32 => "uint",
                    PrimitiveTypeCode.Int64 => "long",
                    PrimitiveTypeCode.UInt64 => "ulong",
                    PrimitiveTypeCode.Single => "float",
                    PrimitiveTypeCode.Double => "double",
                    PrimitiveTypeCode.String => "string",
                    // ReSharper disable once StringLiteralTypo
                    PrimitiveTypeCode.TypedReference => "typedref",
                    // ReSharper disable once StringLiteralTypo
                    PrimitiveTypeCode.IntPtr => "nint",
                    // ReSharper disable once StringLiteralTypo
                    PrimitiveTypeCode.UIntPtr => "unint",
                    PrimitiveTypeCode.Object => "object",
                    _ => "???"
                };
            }

            public override bool WhitelistEquals(MType other)
            {
                return Equals(other);
            }
        }

        // Normal single dimensional array with zero lower bound.
        internal sealed record MTypeSZArray(MType ElementType) : MType
        {
            public override string ToString()
            {
                return $"{ElementType}[]";
            }

            public override string WhitelistToString()
            {
                return $"{ElementType.WhitelistToString()}[]";
            }

            public override bool WhitelistEquals(MType other)
            {
                return other is MTypeSZArray arr && ElementType.WhitelistEquals(arr.ElementType);
            }
        }

        // Multi-dimension arrays with funny lower and upper bounds.
        internal sealed record MTypeWackyArray(MType ElementType, ArrayShape Shape) : MType
        {
            public override string ToString()
            {
                return $"{ElementType}[TODO]";
            }

            public override string WhitelistToString()
            {
                return $"{ElementType.WhitelistToString()}[TODO]";
            }

            public override bool WhitelistEquals(MType other)
            {
                return other is MTypeWackyArray arr && ShapesEqual(Shape, arr.Shape) && ElementType.WhitelistEquals(arr);
            }

            private static bool ShapesEqual(in ArrayShape a, in ArrayShape b)
            {
                return a.Rank == b.Rank && a.LowerBounds.SequenceEqual(b.LowerBounds) && a.Sizes.SequenceEqual(b.Sizes);
            }

            public override bool IsCoreTypeDefined()
            {
                return ElementType.IsCoreTypeDefined();
            }
        }

        internal sealed record MTypeByRef(MType ElementType) : MType
        {
            public override string ToString()
            {
                return $"{ElementType}&";
            }

            public override string WhitelistToString()
            {
                return $"ref {ElementType.WhitelistToString()}";
            }

            public override bool WhitelistEquals(MType other)
            {
                return other is MTypeByRef byRef && ElementType.WhitelistEquals(byRef.ElementType);
            }
        }

        internal sealed record MTypePointer(MType ElementType) : MType
        {
            public override string ToString()
            {
                return $"{ElementType}*";
            }

            public override string WhitelistToString()
            {
                return $"{ElementType.WhitelistToString()}*";
            }

            public override bool WhitelistEquals(MType other)
            {
                return other is MTypePointer ptr && ElementType.WhitelistEquals(ptr.ElementType);
            }
        }

        internal sealed record MTypeGeneric(MType GenericType, ImmutableArray<MType> TypeArguments) : MType
        {
            public override string ToString()
            {
                return $"{GenericType}<{string.Join(", ", TypeArguments)}>";
            }

            public override string WhitelistToString()
            {
                return $"{GenericType.WhitelistToString()}<{string.Join(", ", TypeArguments.Select(t => t.WhitelistToString()))}>";
            }

            public override bool WhitelistEquals(MType other)
            {
                if (!(other is MTypeGeneric generic))
                {
                    return false;
                }

                if (TypeArguments.Length != generic.TypeArguments.Length)
                {
                    return false;
                }

                for (var i = 0; i < TypeArguments.Length; i++)
                {
                    var argA = TypeArguments[i];
                    var argB = generic.TypeArguments[i];

                    if (!argA.WhitelistEquals(argB))
                    {
                        return false;
                    }
                }

                return GenericType.WhitelistEquals(generic.GenericType);
            }

            public bool Equals(MTypeGeneric? otherGeneric)
            {
                return otherGeneric != null && GenericType.Equals(otherGeneric.GenericType) &&
                       TypeArguments.SequenceEqual(otherGeneric.TypeArguments);
            }

            public override int GetHashCode()
            {
                var hc = new HashCode();
                hc.Add(GenericType);
                foreach (var typeArg in TypeArguments)
                {
                    hc.Add(typeArg);
                }

                return hc.ToHashCode();
            }

            public override bool IsCoreTypeDefined()
            {
                return GenericType.IsCoreTypeDefined();
            }
        }

        internal sealed record MTypeDefined(string Name, string? Namespace, MTypeDefined? Enclosing) : MType
        {
            public override string ToString()
            {
                var name = Namespace != null ? $"{Namespace}.{Name}" : Name;

                if (Enclosing != null)
                {
                    return $"{Enclosing}/{name}";
                }

                return name;
            }

            public override bool IsCoreTypeDefined()
            {
                return true;
            }
        }

        internal sealed record MTypeReferenced(MResScope ResolutionScope, string Name, string? Namespace) : MType
        {
            public override string ToString()
            {
                if (Namespace == null)
                {
                    return $"{ResolutionScope}{Name}";
                }

                return $"{ResolutionScope}{Namespace}.{Name}";
            }

            public override string WhitelistToString()
            {
                if (Namespace == null)
                {
                    return Name;
                }

                return $"{Namespace}.{Name}";
            }

            public override bool WhitelistEquals(MType other)
            {
                return other switch
                {
                    MTypeParsed p => p.WhitelistEquals(this),
                    // TODO: ResolutionScope doesn't actually implement equals
                    // This is fine since we're not comparing these anywhere
                    MTypeReferenced r => r.Namespace == Namespace && r.Name == Name &&
                                         r.ResolutionScope.Equals(ResolutionScope),
                    _ => false
                };
            }
        }

        internal abstract record MResScope
        {
        }

        internal sealed record MResScopeType(MType Type) : MResScope
        {
            public override string ToString()
            {
                return $"{Type}/";
            }
        }

        internal sealed record MResScopeAssembly(string Name) : MResScope
        {
            public override string ToString()
            {
                return $"[{Name}]";
            }
        }

        internal sealed record MTypeGenericTypePlaceHolder(int Index) : MType
        {
            public override string ToString()
            {
                return $"!{Index}";
            }

            public override bool WhitelistEquals(MType other)
            {
                return Equals(other);
            }
        }

        internal sealed record MTypeGenericMethodPlaceHolder(int Index) : MType
        {
            public override string ToString()
            {
                return $"!!{Index}";
            }

            public override bool WhitelistEquals(MType other)
            {
                return Equals(other);
            }
        }

        internal sealed record MTypeModified(MType UnmodifiedType, MType ModifierType, bool Required) : MType
        {
            public override string ToString()
            {
                var modName = Required ? "modreq" : "modopt";
                return $"{UnmodifiedType} {modName}({ModifierType})";
            }

            public override string? WhitelistToString()
            {
                return UnmodifiedType.WhitelistToString();
            }

            public override bool WhitelistEquals(MType other)
            {
                // TODO: This is asymmetric shit.
                return UnmodifiedType.WhitelistEquals(other);
            }
        }
    }
}