namespace Compiler;

public sealed class TypeResolver(string fileName)
{
    private readonly Dictionary<(string Module, string Name), NubTypeStruct> structTypes = [];

    public NubTypeStruct? GetNamedStruct(string module, string name) => structTypes.GetValueOrDefault((module, name));

    public static TypeResolver Create(string fileName, Ast ast, out List<Diagnostic> diagnostics)
    {
        diagnostics = [];
        var resolver = new TypeResolver(fileName);

        var moduleDefinitions = ast.Definitions.OfType<NodeDefinitionModule>().ToList();

        if (moduleDefinitions.Count == 0)
            diagnostics.Add(Diagnostic.Error($"'{fileName}' is not part of a module").At(fileName, 1, 1, 1).Build());

        foreach (var moduleDefinition in moduleDefinitions.Skip(1))
            diagnostics.Add(Diagnostic.Warning("Duplicate module definition").At(fileName, moduleDefinition).Build());

        if (moduleDefinitions.Count >= 1)
        {
            var currentModule = moduleDefinitions[0].Name.Ident;

            foreach (var structDef in ast.Definitions.OfType<NodeDefinitionStruct>())
            {
                if (resolver.structTypes.ContainsKey((currentModule, structDef.Name.Ident)))
                {
                    diagnostics.Add(Diagnostic.Error($"Duplicate struct: {structDef.Name.Ident}").At(fileName, structDef.Name).Build());
                    continue;
                }

                resolver.structTypes.Add((currentModule, structDef.Name.Ident), new NubTypeStruct());
            }

            foreach (var structDef in ast.Definitions.OfType<NodeDefinitionStruct>())
            {
                var structType = resolver.structTypes[(currentModule, structDef.Name.Ident)];

                try
                {
                    structType.ResolveFields(structDef.Fields.Select(f => new NubTypeStruct.Field(f.Name.Ident, resolver.Resolve(f.Type))).ToList());
                }
                catch (CompileException e)
                {
                    diagnostics.Add(e.Diagnostic);
                }
            }
        }

        return resolver;
    }

    public NubType Resolve(NodeType node)
    {
        return node switch
        {
            NodeTypeBool type => new NubTypeBool(),
            NodeTypeCustom type => ResolveStruct(type),
            NodeTypeFunc type => new NubTypeFunc(type.Parameters.Select(Resolve).ToList(), Resolve(type.ReturnType)),
            NodeTypePointer type => new NubTypePointer(Resolve(type.To)),
            NodeTypeSInt type => new NubTypeSInt(type.Width),
            NodeTypeUInt type => new NubTypeUInt(type.Width),
            NodeTypeString type => new NubTypeString(),
            NodeTypeVoid type => new NubTypeVoid(),
            _ => throw new ArgumentOutOfRangeException(nameof(node))
        };
    }

    private NubTypeStruct ResolveStruct(NodeTypeCustom type)
    {
        var structType = structTypes.GetValueOrDefault((type.Module.Ident, type.Name.Ident));
        if (structType == null)
            throw new CompileException(Diagnostic.Error($"Unknown custom type: {type.Module.Ident}::{type.Name.Ident}").At(fileName, type).Build());

        return structType;
    }
}

public abstract class NubType : IEquatable<NubType>
{
    public abstract override string ToString();

    public abstract bool Equals(NubType? other);

    public override bool Equals(object? obj)
    {
        if (obj is NubType otherNubType)
        {
            return Equals(otherNubType);
        }

        return false;
    }

    public abstract override int GetHashCode();

    public static bool operator ==(NubType? left, NubType? right) => Equals(left, right);
    public static bool operator !=(NubType? left, NubType? right) => !Equals(left, right);
}

public sealed class NubTypeVoid : NubType
{
    public override string ToString() => "void";

    public override bool Equals(NubType? other) => other is NubTypeVoid;
    public override int GetHashCode() => HashCode.Combine(typeof(NubTypeVoid));
}

public sealed class NubTypeUInt(int width) : NubType
{
    public readonly int Width = width;

    public override string ToString() => $"u{Width}";

    public override bool Equals(NubType? other) => other is NubTypeUInt otherUInt && Width == otherUInt.Width;
    public override int GetHashCode() => HashCode.Combine(typeof(NubTypeUInt), Width);
}

public sealed class NubTypeSInt(int width) : NubType
{
    public readonly int Width = width;

    public override string ToString() => $"i{Width}";

    public override bool Equals(NubType? other) => other is NubTypeSInt otherUInt && Width == otherUInt.Width;
    public override int GetHashCode() => HashCode.Combine(typeof(NubTypeSInt), Width);
}

public sealed class NubTypeBool : NubType
{
    public override string ToString() => "bool";

    public override bool Equals(NubType? other) => other is NubTypeBool;
    public override int GetHashCode() => HashCode.Combine(typeof(NubTypeBool));
}

public sealed class NubTypeString : NubType
{
    public override string ToString() => "string";

    public override bool Equals(NubType? other) => other is NubTypeString;
    public override int GetHashCode() => HashCode.Combine(typeof(NubTypeString));
}

public sealed class NubTypeStruct : NubType
{
    private List<Field>? _resolvedFields;
    public List<Field> Fields => _resolvedFields ?? throw new InvalidOperationException();

    public void ResolveFields(List<Field> fields)
    {
        if (_resolvedFields != null)
            throw new InvalidOperationException($"{ToString()} already resolved");

        _resolvedFields = fields;
    }

    public override string ToString()
    {
        if (_resolvedFields == null)
            return "struct <unresolved>";

        return $"struct {{ {string.Join(' ', Fields.Select(f => $"{f.Name}: {f.Type}"))} }}";
    }

    public override bool Equals(NubType? other)
    {
        if (other is not NubTypeStruct structType)
            return false;

        if (Fields.Count != structType.Fields.Count)
            return false;

        for (var i = 0; i < Fields.Count; i++)
        {
            if (Fields[i].Name != structType.Fields[i].Name)
                return false;

            if (Fields[i].Type != structType.Fields[i].Type)
                return false;
        }

        return true;
    }

    public override int GetHashCode()
    {
        var hash = new HashCode();
        hash.Add(typeof(NubTypeStruct));
        foreach (var field in Fields)
        {
            hash.Add(field.Name);
            hash.Add(field.Type);
        }

        return hash.ToHashCode();
    }

    public sealed class Field(string name, NubType type)
    {
        public readonly string Name = name;
        public readonly NubType Type = type;
    }
}

public sealed class NubTypePointer(NubType to) : NubType
{
    public readonly NubType To = to;
    public override string ToString() => $"^{To}";

    public override bool Equals(NubType? other) => other is NubTypePointer pointer && To == pointer.To;
    public override int GetHashCode() => HashCode.Combine(typeof(NubTypePointer));
}

public sealed class NubTypeFunc(List<NubType> parameters, NubType returnType) : NubType
{
    public readonly List<NubType> Parameters = parameters;
    public readonly NubType ReturnType = returnType;
    public override string ToString() => $"func({string.Join(' ', Parameters)}): {ReturnType}";

    public override bool Equals(NubType? other) => other is NubTypeFunc func && ReturnType.Equals(func.ReturnType) && Parameters.SequenceEqual(func.Parameters);

    public override int GetHashCode()
    {
        var hash = new HashCode();
        hash.Add(typeof(NubTypeFunc));
        hash.Add(ReturnType);
        foreach (var param in Parameters)
            hash.Add(param);

        return hash.ToHashCode();
    }
}