using System.Collections.Immutable;
using System.Diagnostics;
using System.Reflection;
using System.Security.Cryptography;
using System.Text;
using System.Text.Json;
using System.Text.Json.Serialization;
using Microsoft.Extensions.DependencyInjection;
using Microsoft.Extensions.Logging.Abstractions;
using StellaOps.Scanner.Analyzers.Lang;
using StellaOps.Scanner.Analyzers.Lang.Plugin;
using StellaOps.Scanner.Core.Security;

internal sealed record SmokeScenario(string Name, string[] UsageHintRelatives)
{
    public IReadOnlyList<string> ResolveUsageHints(string scenarioRoot)
        => UsageHintRelatives.Select(relative => Path.GetFullPath(Path.Combine(scenarioRoot, relative))).ToArray();
}

internal sealed class SmokeOptions
{
    public string RepoRoot { get; set; } = Directory.GetCurrentDirectory();
    public string PluginDirectoryName { get; set; } = "StellaOps.Scanner.Analyzers.Lang.Python";
    public string FixtureRelativePath { get; set; } = Path.Combine("src", "StellaOps.Scanner.Analyzers.Lang.Python.Tests", "Fixtures", "lang", "python");

    public static SmokeOptions Parse(string[] args)
    {
        var options = new SmokeOptions();

        for (var index = 0; index < args.Length; index++)
        {
            var current = args[index];
            switch (current)
            {
                case "--repo-root":
                case "-r":
                    options.RepoRoot = RequireValue(args, ref index, current);
                    break;
                case "--plugin-directory":
                case "-p":
                    options.PluginDirectoryName = RequireValue(args, ref index, current);
                    break;
                case "--fixture-path":
                case "-f":
                    options.FixtureRelativePath = RequireValue(args, ref index, current);
                    break;
                case "--help":
                case "-h":
                    PrintUsage();
                    Environment.Exit(0);
                    break;
                default:
                    throw new ArgumentException($"Unknown argument '{current}'. Use --help for usage.");
            }
        }

        options.RepoRoot = Path.GetFullPath(options.RepoRoot);
        return options;
    }

    private static string RequireValue(string[] args, ref int index, string switchName)
    {
        if (index + 1 >= args.Length)
        {
            throw new ArgumentException($"Missing value for '{switchName}'.");
        }

        index++;
        var value = args[index];
        if (string.IsNullOrWhiteSpace(value))
        {
            throw new ArgumentException($"Value for '{switchName}' cannot be empty.");
        }

        return value;
    }

    private static void PrintUsage()
    {
        Console.WriteLine("Language Analyzer Smoke Harness");
        Console.WriteLine("Usage: dotnet run --project tools/LanguageAnalyzerSmoke -- [options]");
        Console.WriteLine();
        Console.WriteLine("Options:");
        Console.WriteLine("  -r, --repo-root <path>        Repository root (defaults to current working directory)");
        Console.WriteLine("  -p, --plugin-directory <name> Analyzer plug-in directory under plugins/scanner/analyzers/lang (defaults to StellaOps.Scanner.Analyzers.Lang.Python)");
        Console.WriteLine("  -f, --fixture-path <path>     Relative path to fixtures root (defaults to src/Scanner/__Tests/StellaOps.Scanner.Analyzers.Lang.Python.Tests/Fixtures/lang/python)");
        Console.WriteLine("  -h, --help                    Show usage information");
    }
}

internal sealed record PluginManifest
{
    [JsonPropertyName("schemaVersion")]
    public string SchemaVersion { get; init; } = string.Empty;

    [JsonPropertyName("id")]
    public string Id { get; init; } = string.Empty;

    [JsonPropertyName("displayName")]
    public string DisplayName { get; init; } = string.Empty;

    [JsonPropertyName("version")]
    public string Version { get; init; } = string.Empty;

    [JsonPropertyName("requiresRestart")]
    public bool RequiresRestart { get; init; }

    [JsonPropertyName("entryPoint")]
    public PluginEntryPoint EntryPoint { get; init; } = new();

    [JsonPropertyName("capabilities")]
    public IReadOnlyList<string> Capabilities { get; init; } = Array.Empty<string>();

    [JsonPropertyName("metadata")]
    public IReadOnlyDictionary<string, string> Metadata { get; init; } = ImmutableDictionary<string, string>.Empty;
}

internal sealed record PluginEntryPoint
{
    [JsonPropertyName("type")]
    public string Type { get; init; } = string.Empty;

    [JsonPropertyName("assembly")]
    public string Assembly { get; init; } = string.Empty;

    [JsonPropertyName("typeName")]
    public string TypeName { get; init; } = string.Empty;
}

file static class Program
{
    private static readonly SmokeScenario[] PythonScenarios =
    {
        new("simple-venv", new[] { Path.Combine("bin", "simple-tool") }),
        new("pip-cache", new[] { Path.Combine("lib", "python3.11", "site-packages", "cache_pkg-1.2.3.data", "scripts", "cache-tool") }),
        new("layered-editable", new[] { Path.Combine("layer1", "usr", "bin", "layered-cli") })
    };

    public static async Task<int> Main(string[] args)
    {
        try
        {
            var options = SmokeOptions.Parse(args);
            await RunAsync(options).ConfigureAwait(false);
            Console.WriteLine("✅ Python analyzer smoke checks passed");
            return 0;
        }
        catch (Exception ex)
        {
            Console.Error.WriteLine($"❌ {ex.Message}");
            return 1;
        }
    }

    private static async Task RunAsync(SmokeOptions options)
    {
        ValidateOptions(options);

        var pluginRoot = Path.Combine(options.RepoRoot, "plugins", "scanner", "analyzers", "lang", options.PluginDirectoryName);
        var manifestPath = Path.Combine(pluginRoot, "manifest.json");
        if (!File.Exists(manifestPath))
        {
            throw new FileNotFoundException($"Plug-in manifest not found at '{manifestPath}'.", manifestPath);
        }

        using var manifestStream = File.OpenRead(manifestPath);
        var manifest = JsonSerializer.Deserialize<PluginManifest>(manifestStream, new JsonSerializerOptions
        {
            PropertyNameCaseInsensitive = true,
            ReadCommentHandling = JsonCommentHandling.Skip
        }) ?? throw new InvalidOperationException($"Unable to parse manifest '{manifestPath}'.");

        ValidateManifest(manifest, options.PluginDirectoryName);

        var pluginAssemblyPath = Path.Combine(pluginRoot, manifest.EntryPoint.Assembly);
        if (!File.Exists(pluginAssemblyPath))
        {
            throw new FileNotFoundException($"Plug-in assembly '{manifest.EntryPoint.Assembly}' not found under '{pluginRoot}'.", pluginAssemblyPath);
        }

        var sha256 = ComputeSha256(pluginAssemblyPath);
        Console.WriteLine($"→ Plug-in assembly SHA-256: {sha256}");

        using var serviceProvider = BuildServiceProvider();
        var catalog = new LanguageAnalyzerPluginCatalog(new RestartOnlyPluginGuard(), NullLogger<LanguageAnalyzerPluginCatalog>.Instance);
        catalog.LoadFromDirectory(pluginRoot, seal: true);

        if (catalog.Plugins.Count == 0)
        {
            throw new InvalidOperationException($"No analyzer plug-ins were loaded from '{pluginRoot}'.");
        }

        var analyzerSet = catalog.CreateAnalyzers(serviceProvider);
        if (analyzerSet.Count == 0)
        {
            throw new InvalidOperationException("Language analyzer plug-ins reported no analyzers.");
        }

        var analyzerIds = analyzerSet.Select(analyzer => analyzer.Id).ToArray();
        Console.WriteLine($"→ Loaded analyzers: {string.Join(", ", analyzerIds)}");

        if (!analyzerIds.Contains("python", StringComparer.OrdinalIgnoreCase))
        {
            throw new InvalidOperationException("Python analyzer was not created by the plug-in.");
        }

        var fixtureRoot = Path.GetFullPath(Path.Combine(options.RepoRoot, options.FixtureRelativePath));
        if (!Directory.Exists(fixtureRoot))
        {
            throw new DirectoryNotFoundException($"Fixture directory '{fixtureRoot}' does not exist.");
        }

        foreach (var scenario in PythonScenarios)
        {
            await RunScenarioAsync(scenario, fixtureRoot, catalog, serviceProvider).ConfigureAwait(false);
        }
    }

    private static ServiceProvider BuildServiceProvider()
    {
        var services = new ServiceCollection();
        services.AddLogging();
        return services.BuildServiceProvider();
    }

    private static async Task RunScenarioAsync(SmokeScenario scenario, string fixtureRoot, ILanguageAnalyzerPluginCatalog catalog, IServiceProvider services)
    {
        var scenarioRoot = Path.Combine(fixtureRoot, scenario.Name);
        if (!Directory.Exists(scenarioRoot))
        {
            throw new DirectoryNotFoundException($"Scenario '{scenario.Name}' directory missing at '{scenarioRoot}'.");
        }

        var goldenPath = Path.Combine(scenarioRoot, "expected.json");
        string? goldenNormalized = null;
        if (File.Exists(goldenPath))
        {
            goldenNormalized = NormalizeJson(await File.ReadAllTextAsync(goldenPath).ConfigureAwait(false));
        }

        var usageHints = new LanguageUsageHints(scenario.ResolveUsageHints(scenarioRoot));
        var context = new LanguageAnalyzerContext(scenarioRoot, TimeProvider.System, usageHints, services);

        var coldEngine = new LanguageAnalyzerEngine(catalog.CreateAnalyzers(services));
        var coldStopwatch = Stopwatch.StartNew();
        var coldResult = await coldEngine.AnalyzeAsync(context, CancellationToken.None).ConfigureAwait(false);
        coldStopwatch.Stop();

        if (coldResult.Components.Count == 0)
        {
            throw new InvalidOperationException($"Scenario '{scenario.Name}' produced no components during cold run.");
        }

        var coldJson = NormalizeJson(coldResult.ToJson(indent: true));
        if (goldenNormalized is string expected && !string.Equals(coldJson, expected, StringComparison.Ordinal))
        {
            Console.WriteLine($"⚠️ Scenario '{scenario.Name}' output deviates from repository golden snapshot.");
        }

        var warmEngine = new LanguageAnalyzerEngine(catalog.CreateAnalyzers(services));
        var warmStopwatch = Stopwatch.StartNew();
        var warmResult = await warmEngine.AnalyzeAsync(context, CancellationToken.None).ConfigureAwait(false);
        warmStopwatch.Stop();

        var warmJson = NormalizeJson(warmResult.ToJson(indent: true));
        if (!string.Equals(coldJson, warmJson, StringComparison.Ordinal))
        {
            throw new InvalidOperationException($"Scenario '{scenario.Name}' produced different outputs between cold and warm runs.");
        }

        EnsureDurationWithinBudget(scenario.Name, coldStopwatch.Elapsed, warmStopwatch.Elapsed);

        Console.WriteLine($"✓ Scenario '{scenario.Name}' — components {coldResult.Components.Count}, cold {coldStopwatch.Elapsed.TotalMilliseconds:F1} ms, warm {warmStopwatch.Elapsed.TotalMilliseconds:F1} ms");
    }

    private static void EnsureDurationWithinBudget(string scenarioName, TimeSpan coldDuration, TimeSpan warmDuration)
    {
        var coldBudget = TimeSpan.FromSeconds(30);
        var warmBudget = TimeSpan.FromSeconds(5);

        if (coldDuration > coldBudget)
        {
            throw new InvalidOperationException($"Scenario '{scenarioName}' cold run exceeded budget ({coldDuration.TotalSeconds:F2}s > {coldBudget.TotalSeconds:F2}s).");
        }

        if (warmDuration > warmBudget)
        {
            throw new InvalidOperationException($"Scenario '{scenarioName}' warm run exceeded budget ({warmDuration.TotalSeconds:F2}s > {warmBudget.TotalSeconds:F2}s).");
        }
    }

    private static string NormalizeJson(string json)
        => json.Replace("\r\n", "\n", StringComparison.Ordinal).TrimEnd();

    private static void ValidateOptions(SmokeOptions options)
    {
        if (!Directory.Exists(options.RepoRoot))
        {
            throw new DirectoryNotFoundException($"Repository root '{options.RepoRoot}' does not exist.");
        }
    }

    private static void ValidateManifest(PluginManifest manifest, string expectedDirectory)
    {
        if (!string.Equals(manifest.SchemaVersion, "1.0", StringComparison.Ordinal))
        {
            throw new InvalidOperationException($"Unexpected manifest schema version '{manifest.SchemaVersion}'.");
        }

        if (!manifest.RequiresRestart)
        {
            throw new InvalidOperationException("Language analyzer plug-in must be marked as restart-only.");
        }

        if (!string.Equals(manifest.EntryPoint.Type, "dotnet", StringComparison.OrdinalIgnoreCase))
        {
            throw new InvalidOperationException($"Unsupported entry point type '{manifest.EntryPoint.Type}'.");
        }

        if (!manifest.Capabilities.Contains("python", StringComparer.OrdinalIgnoreCase))
        {
            throw new InvalidOperationException("Manifest capabilities do not include 'python'.");
        }

        if (!string.Equals(manifest.EntryPoint.TypeName, "StellaOps.Scanner.Analyzers.Lang.Python.PythonAnalyzerPlugin", StringComparison.Ordinal))
        {
            throw new InvalidOperationException($"Unexpected entry point type name '{manifest.EntryPoint.TypeName}'.");
        }

        if (!string.Equals(manifest.Id, "stellaops.analyzer.lang.python", StringComparison.OrdinalIgnoreCase))
        {
            throw new InvalidOperationException($"Manifest id '{manifest.Id}' does not match expected plug-in id for directory '{expectedDirectory}'.");
        }
    }

    private static string ComputeSha256(string path)
    {
        using var hash = SHA256.Create();
        using var stream = File.OpenRead(path);
        var digest = hash.ComputeHash(stream);
        var builder = new StringBuilder(digest.Length * 2);
        foreach (var b in digest)
        {
            builder.Append(b.ToString("x2"));
        }
        return builder.ToString();
    }
}