#nullable enable

using System;
using System.Collections.Concurrent;
using System.Collections.Immutable;
using System.Linq;
using Microsoft.CodeAnalysis;
using Microsoft.CodeAnalysis.Diagnostics;

namespace ShrinkSDK.CodeGen.Analyzers;

[DiagnosticAnalyzer(LanguageNames.CSharp)]
public sealed class ShrinkCodeGenAnalyzer : DiagnosticAnalyzer
{
    private static readonly DiagnosticDescriptor InvalidEventHandler = new(
        "SHRINK001", "Invalid event subscriber signature",
        "Method '{0}' must use void(TEvent), UniTask(TEvent), or UniTask(TEvent, CancellationToken)",
        "ShrinkSDK.CodeGen", DiagnosticSeverity.Error, true);
    private static readonly DiagnosticDescriptor DuplicateNetworkContract = new(
        "SHRINK002", "Duplicate network opcode and route",
        "Network opcode/route '{0}' is already declared by '{1}'",
        "ShrinkSDK.CodeGen", DiagnosticSeverity.Error, true);
    private static readonly DiagnosticDescriptor InvalidInstaller = new(
        "SHRINK003", "Invalid application installer",
        "Type '{0}' has ShrinkAppModuleInstaller but does not implement IShrinkAppModuleInstaller",
        "ShrinkSDK.CodeGen", DiagnosticSeverity.Error, true);

    public override ImmutableArray<DiagnosticDescriptor> SupportedDiagnostics =>
        ImmutableArray.Create(InvalidEventHandler, DuplicateNetworkContract, InvalidInstaller);

    public override void Initialize(AnalysisContext context)
    {
        context.ConfigureGeneratedCodeAnalysis(GeneratedCodeAnalysisFlags.None);
        context.EnableConcurrentExecution();
        context.RegisterCompilationStartAction(start =>
        {
            var networkContracts = new ConcurrentDictionary<string, INamedTypeSymbol>(StringComparer.Ordinal);
            start.RegisterSymbolAction(symbolContext => AnalyzeMethod(symbolContext), SymbolKind.Method);
            start.RegisterSymbolAction(symbolContext => AnalyzeType(symbolContext, networkContracts), SymbolKind.NamedType);
        });
    }

    private static void AnalyzeMethod(SymbolAnalysisContext context)
    {
        var method = (IMethodSymbol)context.Symbol;
        if (!HasAttribute(method, "ShrinkEventBus.ShrinkSubscribeAttribute")) return;
        var parametersValid = method.Parameters.Length == 1 ||
            method.Parameters.Length == 2 && method.Parameters[1].Type.ToDisplayString() == "System.Threading.CancellationToken";
        var returnName = method.ReturnType.ToDisplayString();
        var returnValid = method.Parameters.Length == 1 && (method.ReturnsVoid || returnName == "Cysharp.Threading.Tasks.UniTask") ||
                          method.Parameters.Length == 2 && returnName == "Cysharp.Threading.Tasks.UniTask";
        if (!parametersValid || !returnValid)
            context.ReportDiagnostic(Diagnostic.Create(InvalidEventHandler, method.Locations.FirstOrDefault(), method.Name));
    }

    private static void AnalyzeType(SymbolAnalysisContext context, ConcurrentDictionary<string, INamedTypeSymbol> networkContracts)
    {
        var type = (INamedTypeSymbol)context.Symbol;
        if (HasAttribute(type, "ShrinkApp.ShrinkAppModuleInstallerAttribute") &&
            !type.AllInterfaces.Any(item => item.ToDisplayString() == "ShrinkApp.IShrinkAppModuleInstaller"))
            context.ReportDiagnostic(Diagnostic.Create(InvalidInstaller, type.Locations.FirstOrDefault(), type.Name));

        var network = type.GetAttributes().FirstOrDefault(attribute =>
            attribute.AttributeClass?.ToDisplayString() == "ShrinkNetwork.ShrinkNetworkMessageAttribute");
        if (network == null || network.ConstructorArguments.Length == 0) return;
        var opcode = network.ConstructorArguments[0].Value?.ToString() ?? string.Empty;
        var route = network.ConstructorArguments.Length > 1 ? network.ConstructorArguments[1].Value as string ?? string.Empty : string.Empty;
        var key = opcode + ":" + route;
        if (!networkContracts.TryAdd(key, type) && networkContracts.TryGetValue(key, out var previous))
            context.ReportDiagnostic(Diagnostic.Create(DuplicateNetworkContract, type.Locations.FirstOrDefault(), key, previous.Name));
    }

    private static bool HasAttribute(ISymbol symbol, string fullName) =>
        symbol.GetAttributes().Any(attribute => attribute.AttributeClass?.ToDisplayString() == fullName);
}