using System.Diagnostics.CodeAnalysis;
using System.Text;
using Microsoft.CodeAnalysis;
using Microsoft.CodeAnalysis.CSharp.Syntax;
using Speckle.ProxyGenerator.Enums;
using Speckle.ProxyGenerator.Extensions;
using Speckle.ProxyGenerator.Models;
using Speckle.ProxyGenerator.Types;
using Speckle.ProxyGenerator.Utils;

namespace Speckle.ProxyGenerator.FileGenerators;

internal class PartialInterfacesGenerator : BaseGenerator, IFilesGenerator
{
    private List<INamedTypeSymbol> _implementedInterfaces = new();

    public PartialInterfacesGenerator(Context context, bool supportsNullable)
        : base(context, supportsNullable) { }

    public IEnumerable<FileData> GenerateFiles()
    {
        foreach (var ci in Context.Candidates)
        {
            if (TryGenerateFile(ci.Key, ci.Value, out var file))
            {
                yield return file;
            }
        }
    }

    private bool TryGenerateFile(
        InterfaceDeclarationSyntax ci,
        ProxyData pd,
        [NotNullWhen(true)] out FileData? fileData
    )
    {
        fileData = default;

        if (
            !TryGetNamedTypeSymbolByFullName(
                [TypeKind.Interface],
                ci.Identifier.ToString(),
                pd.Usings,
                out var sourceInterfaceSymbol
            )
        )
        {
            return false;
        }

        if (
            !TryGetNamedTypeSymbolByFullName(
                [TypeKind.Class, TypeKind.Struct],
                pd.FullMetadataTypeName,
                pd.Usings,
                out var targetClassSymbol
            )
        )
        {
            return false;
        }

        var interfaceName = ResolveInterfaceNameWithOptionalTypeConstraints(
            targetClassSymbol.Symbol,
            pd.ShortInterfaceName
        );

        fileData = new FileData(
            $"{sourceInterfaceSymbol.Symbol.GetFullMetadataName()}.g.cs",
            CreatePartialInterfaceCode(
                pd.Namespace,
                targetClassSymbol,
                sourceInterfaceSymbol,
                interfaceName,
                pd
            )
        );

        return true;
    }

    private string CreatePartialInterfaceCode(
        string ns,
        ClassSymbol classSymbol,
        ClassSymbol interfaceSymbol,
        string interfaceName,
        ProxyData proxyData
    )
    {
        _implementedInterfaces.Clear();
        _implementedInterfaces.AddRange(
            classSymbol.Symbol.ResolveImplementedInterfaces(
                proxyData.Options.HasFlag(ImplementationOptions.ProxyBaseClasses),
                proxyData.Options.HasFlag(ImplementationOptions.ProxyInterfaces)
            )
        );
        if (proxyData.Options.HasFlag(ImplementationOptions.UseExtendedInterfaces))
        {
            var bases = interfaceSymbol
                .Symbol.ResolveBaseInterfaces(_implementedInterfaces)
                .ToList();
            if (
                bases.Count == 1
                && proxyData.Options.HasFlag(ImplementationOptions.ProxyForBaseInterface)
            )
            {
                proxyData.FullQualifiedMappedTypeName =
                    globalPrefix + bases.Single().GetFullMetadataName();
            }
            _implementedInterfaces.AddRange(bases);
            //don't readd self
            if (_implementedInterfaces.Contains(interfaceSymbol.Symbol))
            {
                _implementedInterfaces.Remove(interfaceSymbol.Symbol);
            }
        }

        _implementedInterfaces = _implementedInterfaces.Distinct().ToList();
        var isNew = GetExtendsProxyData(
                classSymbol,
                proxyData.Options.HasFlag(ImplementationOptions.UseExtendedInterfaces)
            )
            .Any();

        var implementedInterfacesNames = _implementedInterfaces
            .Select(i => i.ToFullyQualifiedDisplayString())
            .ToArray();
        var implements = implementedInterfacesNames.Any()
            ? $" : {string.Join(", ", implementedInterfacesNames)}"
            : string.Empty;
        var @new = isNew ? "new " : string.Empty;
        var (namespaceStart, namespaceEnd) = NamespaceBuilder.Build(ns);
        var events = GenerateEvents(classSymbol, proxyData);
        var properties = GenerateProperties(classSymbol, proxyData);
        var methods = GenerateMethods(classSymbol, proxyData).TrimEnd();

        return $@"//----------------------------------------------------------------------------------------
// <auto-generated>
//     This code was generated by https://github.com/specklesystems/ProxyGenerator.
//
//     Changes to this file may cause incorrect behavior and will be lost if
//     the code is regenerated.
// </auto-generated>
//----------------------------------------------------------------------------------------

{SupportsNullable.IIf("#nullable enable")}
using System;

{namespaceStart}
    public partial interface {interfaceName}{implements}
    {{
        {@new}{classSymbol} _Instance {{ get; }}

{events +
properties +
methods}
    }}
{namespaceEnd}
{SupportsNullable.IIf("#nullable restore")}";
    }

    private Func<T, bool> InterfaceFilter<T>()
        where T : ISymbol
    {
        var hashSet = new HashSet<string>();
        foreach (var @interface in _implementedInterfaces)
        {
            var members = @interface.AllInterfaces.Aggregate(
                @interface.GetMembers(),
                (xs, x) => xs.AddRange(x.GetMembers())
            );
            foreach (var member in members)
            {
                hashSet.Add(member.Name);
            }
        }

        // Member is not already implemented in another interface.
        return t => !hashSet.Contains(t.Name);
    }

    private string GenerateProperties(ClassSymbol targetClassSymbol, ProxyData proxyData)
    {
        var str = new StringBuilder();

        foreach (
            var property in MemberHelper.GetPublicProperties(
                targetClassSymbol,
                proxyData,
                InterfaceFilter<IPropertySymbol>()
            )
        )
        {
            var (_, type) = GetPropertyType(property, out var isReplaced);

            var getterSetter = isReplaced
                ? ToPropertyDetails(property, type)
                : ToPropertyDetails(property);
            if (getterSetter is null)
            {
                continue;
            }

            var propertyName = getterSetter.Value.PropertyName;

            if (property.IsIndexer)
            {
                var methodParameters = GetMethodParameters(property.Parameters, true);
                propertyName = $"this[{string.Join(", ", methodParameters)}]";
            }

            foreach (var attribute in property.GetAttributesAsList())
            {
                str.AppendLine($"        {attribute}");
            }

            str.AppendLine(
                $"        {getterSetter.Value.PropertyType} {propertyName} {getterSetter.Value.GetSet}"
            );
            str.AppendLine();
        }
        return str.ToString();
    }

    private string GenerateMethods(ClassSymbol targetClassSymbol, ProxyData proxyData)
    {
        var str = new StringBuilder();
        foreach (
            var method in MemberHelper.GetPublicMethods(
                targetClassSymbol,
                proxyData,
                InterfaceFilter<IMethodSymbol>()
            )
        )
        {
            var methodParameters = GetMethodParameters(method.Parameters, true);
            var whereStatement = GetWhereStatementFromMethod(method);

            foreach (var attribute in method.GetAttributesAsList())
            {
                str.AppendLine($"        {attribute}");
            }

            var (_, type) = GetReplacedTypeAsString(method.ReturnType, null, out _);
            str.AppendLine(
                $"        {type} {method.GetMethodNameWithOptionalTypeParameters()}({string.Join(", ", methodParameters)}){whereStatement};"
            );
            str.AppendLine();
        }

        return str.ToString();
    }

    private string GenerateEvents(ClassSymbol targetClassSymbol, ProxyData proxyData)
    {
        var str = new StringBuilder();
        foreach (
            var @event in MemberHelper.GetPublicEvents(
                targetClassSymbol,
                proxyData,
                InterfaceFilter<IMethodSymbol>()
            )
        )
        {
            var ps = @event.First().Parameters.First();

            string? type;
            if (ps.GetTypeEnum() == TypeEnum.Complex)
            {
                (_, type) = GetParameterType(ps, out _);
            }
            else
            {
                type = ps.Type.ToString();
            }

            foreach (var attribute in ps.GetAttributesAsList())
            {
                str.AppendLine($"        {attribute}");
            }

            str.AppendLine($"        event {type} {@event.Key.GetSanitizedName()};");
            str.AppendLine();
        }

        return str.ToString();
    }

    public (string PropertyType, string? PropertyName, string GetSet)? ToPropertyDetails(
        IPropertySymbol property,
        string? overrideType = null
    )
    {
        var getIsPublic = property.GetMethod.IsPublic();
        var setIsPublic = property.SetMethod.IsPublic();

        if (!getIsPublic && !setIsPublic)
        {
            return null;
        }

        var get = getIsPublic ? "get; " : string.Empty;
        var set = setIsPublic ? "set; " : string.Empty;

        string? type;
        if (!string.IsNullOrEmpty(overrideType))
        {
            type = overrideType;
        }
        else
        {
            (_, type) = FixType(
                property.Type.ToFullyQualifiedDisplayString(),
                property.NullableAnnotation,
                null
            );
        }

        return (type!, property.GetSanitizedName(), $"{{ {get}{set}}}");
    }
}