using System;
using System.Collections.Generic;
using System.Collections.ObjectModel;
using System.IO;
using System.Linq;
using System.Threading;
using System.Threading.Tasks;
using Microsoft.Extensions.DependencyInjection;
using Microsoft.Extensions.Logging;
using Microsoft.Extensions.Options;
using StellaOps.Scanner.Analyzers.OS;
using StellaOps.Scanner.Analyzers.OS.Abstractions;
using StellaOps.Scanner.Analyzers.OS.Plugin;
using StellaOps.Scanner.Core.Contracts;
using StellaOps.Scanner.Worker.Options;

namespace StellaOps.Scanner.Worker.Processing;

internal sealed class OsScanAnalyzerDispatcher : IScanAnalyzerDispatcher
{
    private readonly IServiceScopeFactory _scopeFactory;
    private readonly OsAnalyzerPluginCatalog _catalog;
    private readonly ScannerWorkerOptions _options;
    private readonly ILogger<OsScanAnalyzerDispatcher> _logger;
    private IReadOnlyList<string> _pluginDirectories = Array.Empty<string>();

    public OsScanAnalyzerDispatcher(
        IServiceScopeFactory scopeFactory,
        OsAnalyzerPluginCatalog catalog,
        IOptions<ScannerWorkerOptions> options,
        ILogger<OsScanAnalyzerDispatcher> logger)
    {
        _scopeFactory = scopeFactory ?? throw new ArgumentNullException(nameof(scopeFactory));
        _catalog = catalog ?? throw new ArgumentNullException(nameof(catalog));
        _options = options?.Value ?? throw new ArgumentNullException(nameof(options));
        _logger = logger ?? throw new ArgumentNullException(nameof(logger));

        LoadPlugins();
    }

    public async ValueTask ExecuteAsync(ScanJobContext context, CancellationToken cancellationToken)
    {
        ArgumentNullException.ThrowIfNull(context);

        using var scope = _scopeFactory.CreateScope();
        var services = scope.ServiceProvider;
        var analyzers = _catalog.CreateAnalyzers(services);
        if (analyzers.Count == 0)
        {
            _logger.LogWarning("No OS analyzers available; skipping analyzer stage for job {JobId}.", context.JobId);
            return;
        }

        var metadata = new Dictionary<string, string>(context.Lease.Metadata, StringComparer.Ordinal);
        var rootfsPath = ResolvePath(metadata, _options.Analyzers.RootFilesystemMetadataKey);
        if (rootfsPath is null)
        {
            _logger.LogWarning(
                "Metadata key '{MetadataKey}' missing for job {JobId}; unable to locate root filesystem. OS analyzers skipped.",
                _options.Analyzers.RootFilesystemMetadataKey,
                context.JobId);
            return;
        }

        var workspacePath = ResolvePath(metadata, _options.Analyzers.WorkspaceMetadataKey);
        var loggerFactory = services.GetRequiredService<ILoggerFactory>();

        var results = new List<OSPackageAnalyzerResult>(analyzers.Count);

        foreach (var analyzer in analyzers)
        {
            cancellationToken.ThrowIfCancellationRequested();
            var analyzerLogger = loggerFactory.CreateLogger(analyzer.GetType());
            var analyzerContext = new OSPackageAnalyzerContext(rootfsPath, workspacePath, context.TimeProvider, analyzerLogger, metadata);

            try
            {
                var result = await analyzer.AnalyzeAsync(analyzerContext, cancellationToken).ConfigureAwait(false);
                results.Add(result);
            }
            catch (Exception ex)
            {
                _logger.LogError(ex, "Analyzer {AnalyzerId} failed for job {JobId}.", analyzer.AnalyzerId, context.JobId);
            }
        }

        if (results.Count > 0)
        {
            var dictionary = results.ToDictionary(result => result.AnalyzerId, StringComparer.OrdinalIgnoreCase);
            context.Analysis.Set(ScanAnalysisKeys.OsPackageAnalyzers, dictionary);
        }
    }

    private void LoadPlugins()
    {
        var directories = new List<string>();
        foreach (var configured in _options.Analyzers.PluginDirectories)
        {
            if (string.IsNullOrWhiteSpace(configured))
            {
                continue;
            }

            var path = configured;
            if (!Path.IsPathRooted(path))
            {
                path = Path.GetFullPath(Path.Combine(AppContext.BaseDirectory, path));
            }

            directories.Add(path);
        }

        if (directories.Count == 0)
        {
            directories.Add(Path.Combine(AppContext.BaseDirectory, "plugins", "scanner", "analyzers", "os"));
        }

        _pluginDirectories = new ReadOnlyCollection<string>(directories);

        for (var i = 0; i < _pluginDirectories.Count; i++)
        {
            var directory = _pluginDirectories[i];
            var seal = i == _pluginDirectories.Count - 1;

            try
            {
                _catalog.LoadFromDirectory(directory, seal);
            }
            catch (Exception ex)
            {
                _logger.LogWarning(ex, "Failed to load analyzer plug-ins from {Directory}.", directory);
            }
        }
    }

    private static string? ResolvePath(IReadOnlyDictionary<string, string> metadata, string key)
    {
        if (string.IsNullOrWhiteSpace(key))
        {
            return null;
        }

        if (!metadata.TryGetValue(key, out var value) || string.IsNullOrWhiteSpace(value))
        {
            return null;
        }

        var trimmed = value.Trim();
        return Path.IsPathRooted(trimmed)
            ? trimmed
            : Path.GetFullPath(trimmed);
    }
}