using System.Text.Json;
using System.Text.Json.Nodes;
using StellaOps.AirGap.Policy;
using StellaOps.TaskRunner.Core.Execution;
using StellaOps.TaskRunner.Core.Planning;
using StellaOps.TaskRunner.Core.TaskPacks;

namespace StellaOps.TaskRunner.Infrastructure.Execution;

public sealed class FilesystemPackRunDispatcher : IPackRunJobDispatcher, IPackRunJobScheduler
{
    private readonly string queuePath;
    private readonly string archivePath;
    private readonly TaskPackManifestLoader manifestLoader = new();
    private readonly TaskPackPlanner planner;
    private readonly JsonSerializerOptions serializerOptions = new(JsonSerializerDefaults.Web); 

    public FilesystemPackRunDispatcher(string queuePath, string archivePath, IEgressPolicy? egressPolicy = null)
    {
        this.queuePath = queuePath ?? throw new ArgumentNullException(nameof(queuePath));
        this.archivePath = archivePath ?? throw new ArgumentNullException(nameof(archivePath));
        planner = new TaskPackPlanner(egressPolicy);
        Directory.CreateDirectory(queuePath);
        Directory.CreateDirectory(archivePath);
    }

    public string QueuePath => queuePath;

    public async Task<PackRunExecutionContext?> TryDequeueAsync(CancellationToken cancellationToken)
    {
        var files = Directory.GetFiles(queuePath, "*.json", SearchOption.TopDirectoryOnly)
            .OrderBy(path => path, StringComparer.Ordinal)
            .ToArray();

        foreach (var file in files)
        {
            cancellationToken.ThrowIfCancellationRequested();

            try
            {
                var jobJson = await File.ReadAllTextAsync(file, cancellationToken).ConfigureAwait(false);
                var job = JsonSerializer.Deserialize<JobEnvelope>(jobJson, serializerOptions);
                if (job is null)
                {
                    continue;
                }

                TaskPackPlan? plan = job.Plan;
                if (plan is null)
                {
                    if (string.IsNullOrWhiteSpace(job.ManifestPath))
                    {
                        continue;
                    }

                    var manifestPath = ResolvePath(queuePath, job.ManifestPath);
                    var inputsPath = job.InputsPath is null ? null : ResolvePath(queuePath, job.InputsPath);

                    var manifest = manifestLoader.Load(manifestPath);
                    var inputs = await LoadInputsAsync(inputsPath, cancellationToken).ConfigureAwait(false);
                    var planResult = planner.Plan(manifest, inputs);
                    if (!planResult.Success || planResult.Plan is null)
                    {
                        throw new InvalidOperationException($"Failed to plan pack for run {job.RunId}: {string.Join(';', planResult.Errors.Select(e => e.Message))}");
                    }

                    plan = planResult.Plan;
                }

                var archiveFile = Path.Combine(archivePath, Path.GetFileName(file));
                File.Move(file, archiveFile, overwrite: true);

                var requestedAt = job.RequestedAt ?? DateTimeOffset.UtcNow;
                var runId = string.IsNullOrWhiteSpace(job.RunId) ? Guid.NewGuid().ToString("n") : job.RunId;
                return new PackRunExecutionContext(runId, plan, requestedAt);
            }
            catch (Exception ex)
            {
                var failedPath = file + ".failed";
                File.Move(file, failedPath, overwrite: true);
                Console.Error.WriteLine($"Failed to dequeue job '{file}': {ex.Message}");
            }
        }

        return null;
    }

    public async Task ScheduleAsync(PackRunExecutionContext context, CancellationToken cancellationToken)
    {
        ArgumentNullException.ThrowIfNull(context);

        var envelope = new JobEnvelope(
            context.RunId,
            ManifestPath: null,
            InputsPath: null,
            context.RequestedAt,
            context.Plan);

        Directory.CreateDirectory(queuePath);
        var safeRunId = string.IsNullOrWhiteSpace(context.RunId) ? Guid.NewGuid().ToString("n") : SanitizeFileName(context.RunId);
        var fileName = $"{safeRunId}-{DateTimeOffset.UtcNow:yyyyMMddHHmmssfff}.json";
        var path = Path.Combine(queuePath, fileName);
        var json = JsonSerializer.Serialize(envelope, serializerOptions);
        await File.WriteAllTextAsync(path, json, cancellationToken).ConfigureAwait(false);
    }

    private static string ResolvePath(string root, string relative)
        => Path.IsPathRooted(relative) ? relative : Path.Combine(root, relative);

    private static async Task<IDictionary<string, JsonNode?>> LoadInputsAsync(string? path, CancellationToken cancellationToken)
    {
        if (string.IsNullOrWhiteSpace(path) || !File.Exists(path))
        {
            return new Dictionary<string, JsonNode?>(StringComparer.Ordinal);
        }

        var json = await File.ReadAllTextAsync(path, cancellationToken).ConfigureAwait(false);
        var node = JsonNode.Parse(json) as JsonObject;
        if (node is null)
        {
            return new Dictionary<string, JsonNode?>(StringComparer.Ordinal);
        }

        return node.ToDictionary(
            pair => pair.Key,
            pair => pair.Value,
            StringComparer.Ordinal);
    }

    private sealed record JobEnvelope(
        string? RunId,
        string? ManifestPath,
        string? InputsPath,
        DateTimeOffset? RequestedAt,
        TaskPackPlan? Plan);

    private static string SanitizeFileName(string value)
    {
        var safe = value.Trim();
        foreach (var invalid in Path.GetInvalidFileNameChars())
        {
            safe = safe.Replace(invalid, '_');
        }

        return safe;
    }
}