using System.Diagnostics;
using System.Diagnostics.CodeAnalysis;

namespace Compiler;

public class ModuleGraph
{
    public static Builder CreateBuilder() => new();

    private ModuleGraph(Dictionary<string, Module> modules)
    {
        this.modules = modules;
    }

    private readonly Dictionary<string, Module> modules;

    public List<Module> GetModules()
    {
        return modules.Values.ToList();
    }

    public bool TryResolveModule(string moduleName, [NotNullWhen(true)] out Module? module)
    {
        module = modules.GetValueOrDefault(moduleName);
        return module != null;
    }

    public class Builder
    {
        private readonly List<Ast> asts = [];
        private readonly List<Manifest> manifests = [];

        public void AddAst(Ast ast)
        {
            asts.Add(ast);
        }

        public void AddManifest(Manifest manifest)
        {
            manifests.Add(manifest);
        }

        public ModuleGraph? Build(out List<Diagnostic> diagnostics)
        {
            diagnostics = [];

            var modules = new Dictionary<string, Module>();

            foreach (var manifest in manifests)
            {
                foreach (var (moduleName, manifestModule) in manifest.Modules)
                {
                    var module = GetOrCreateModule(moduleName);

                    foreach (var (name, type) in manifestModule.Types)
                    {
                        switch (type)
                        {
                            case Manifest.Module.TypeInfoStruct s:
                                var info = new Module.TypeInfoStruct(s.Exported, s.Packed);
                                var fields = s.Fields.Select(x => new Module.TypeInfoStruct.Field(x.Name, x.Type)).ToList();
                                info.SetFields(fields);
                                module.AddType(name, info);
                                break;
                            default:
                                throw new ArgumentOutOfRangeException(nameof(type));
                        }
                    }

                    foreach (var (name, identifier) in manifestModule.Identifiers)
                    {
                        module.AddIdentifier(name, new Module.IdentifierInfo(identifier.Exported, identifier.Type));
                    }
                }
            }

            foreach (var ast in asts)
            {
                var module = GetOrCreateModule(ast.ModuleName.Ident);

                foreach (var structDef in ast.Definitions.OfType<NodeDefinitionStruct>())
                {
                    module.AddType(structDef.Name.Ident, new Module.TypeInfoStruct(structDef.Exported, structDef.Packed));
                }
            }

            foreach (var ast in asts)
            {
                var module = GetOrCreateModule(ast.ModuleName.Ident);

                foreach (var structDef in ast.Definitions.OfType<NodeDefinitionStruct>())
                {
                    if (!module.TryResolveType(structDef.Name.Ident, true, out var typeInfo))
                        throw new UnreachableException($"{nameof(typeInfo)} should always be registered");

                    if (typeInfo is Module.TypeInfoStruct structType)
                    {
                        var fields = structDef.Fields.Select(f => new Module.TypeInfoStruct.Field(f.Name.Ident, ResolveType(f.Type, module.Name))).ToList();
                        structType.SetFields(fields);
                    }
                }
            }

            foreach (var ast in asts)
            {
                var module = GetOrCreateModule(ast.ModuleName.Ident);

                foreach (var funcDef in ast.Definitions.OfType<NodeDefinitionFunc>())
                {
                    var parameters = funcDef.Parameters.Select(x => ResolveType(x.Type, module.Name)).ToList();
                    var returnType = ResolveType(funcDef.ReturnType, module.Name);
                    var funcType = NubTypeFunc.Get(parameters, returnType);
                    var info = new Module.IdentifierInfo(funcDef.Exported, funcType);
                    module.AddIdentifier(funcDef.Name.Ident, info);
                }

                foreach (var globalVariable in ast.Definitions.OfType<NodeDefinitionGlobalVariable>())
                {
                    var type = ResolveType(globalVariable.Type, module.Name);
                    var info = new Module.IdentifierInfo(globalVariable.Exported, type);
                    module.AddIdentifier(globalVariable.Name.Ident, info);
                }
            }

            if (diagnostics.Any(x => x.Severity == Diagnostic.DiagnosticSeverity.Error))
                return null;

            return new ModuleGraph(modules);

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

            NubType ResolveCustomType(NodeTypeCustom type, string currentModule)
            {
                var module = modules.GetValueOrDefault(type.Module.Ident);
                if (module == null)
                    throw new CompileException(Diagnostic.Error($"Unknown module: {type.Module.Ident}").Build());

                var includePrivate = currentModule == type.Module.Ident;

                if (!module.TryResolveType(type.Name.Ident, includePrivate, out var customType))
                    throw new CompileException(Diagnostic.Error($"Unknown custom type: {type.Module.Ident}::{type.Name.Ident}").Build());

                return customType switch
                {
                    Module.TypeInfoStruct => NubTypeStruct.Get(type.Module.Ident, type.Name.Ident),
                    _ => throw new ArgumentOutOfRangeException(nameof(customType))
                };
            }

            Module GetOrCreateModule(string name)
            {
                if (!modules.TryGetValue(name, out var module))
                {
                    module = new Module(name);
                    modules.Add(name, module);
                }

                return module;
            }
        }
    }
}

public class Module(string name)
{
    public string Name { get; } = name;

    private Dictionary<string, TypeInfo> types = new();
    private Dictionary<string, IdentifierInfo> identifiers = new();

    public IReadOnlyDictionary<string, TypeInfo> GetTypes() => types;
    public IReadOnlyDictionary<string, IdentifierInfo> GetIdentifiers() => identifiers;

    public bool TryResolveType(string name, bool searchPrivate, [NotNullWhen(true)] out TypeInfo? customType)
    {
        var info = types.GetValueOrDefault(name);
        if (info == null)
        {
            customType = null;
            return false;
        }

        if (info.Exported || searchPrivate)
        {
            customType = info;
            return true;
        }

        customType = null;
        return false;
    }

    public bool TryResolveIdentifier(string name, bool searchPrivate, [NotNullWhen(true)] out IdentifierInfo? identifierType)
    {
        var info = identifiers.GetValueOrDefault(name);
        if (info == null)
        {
            identifierType = null;
            return false;
        }

        if (info.Exported || searchPrivate)
        {
            identifierType = info;
            return true;
        }

        identifierType = null;
        return false;
    }

    public void AddType(string name, TypeInfo info)
    {
        types.Add(name, info);
    }

    public void AddIdentifier(string name, IdentifierInfo info)
    {
        identifiers.Add(name, info);
    }

    public class IdentifierInfo(bool exported, NubType type)
    {
        public bool Exported { get; } = exported;
        public NubType Type { get; } = type;
    }


    public abstract class TypeInfo(bool exported)
    {
        public bool Exported { get; } = exported;
    }


    public class TypeInfoStruct(bool exported, bool packed) : TypeInfo(exported)
    {
        private IReadOnlyList<Field>? fields;

        public bool Packed { get; } = packed;
        public IReadOnlyList<Field> Fields => fields ?? throw new InvalidOperationException("Fields has not been set yet");

        public void SetFields(IReadOnlyList<Field> fields)
        {
            this.fields = fields;
        }

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