using Extrudex.Domain.Entities;
using Extrudex.Domain.Enums;
using Extrudex.Domain.Interfaces;
using Extrudex.Infrastructure.Data;
using Microsoft.EntityFrameworkCore;
using Microsoft.Extensions.Logging;
using Microsoft.Extensions.Options;

namespace Extrudex.Infrastructure.Services;

/// <summary>
/// Configuration options for the Moonraker usage polling service.
/// </summary>
public class MoonrakerPollerOptions
{
    /// <summary>
    /// How often to poll each Moonraker printer for filament usage data.
    /// Default: 30 seconds.
    /// </summary>
    public TimeSpan PollInterval { get; set; } = TimeSpan.FromSeconds(30);

    /// <summary>
    /// Timeout for individual Moonraker HTTP requests.
    /// Default: 10 seconds.
    /// </summary>
    public TimeSpan RequestTimeout { get; set; } = TimeSpan.FromSeconds(10);

    /// <summary>
    /// Whether the polling service is enabled. Default: true.
    /// Set to false to disable polling (e.g., in development or testing).
    /// </summary>
    public bool Enabled { get; set; } = true;
}

/// <summary>
/// Background service that periodically polls Moonraker-connected printers
/// for filament usage data. When a print job is detected as complete,
/// the usage data is persisted to the FilamentUsage table via
/// <see cref="IFilamentUsageService"/>.
///
/// <para>Polling logic:</para>
/// <list type="number">
///   <item>Query the database for all active printers with ConnectionType == Moonraker.</item>
///   <item>For each printer, call <see cref="IMoonrakerClient.GetFilamentUsageAsync"/>.</item>
///   <item>If usage data is available and the print state is "complete",
///         create or update a FilamentUsage record.</item>
///   <item>If the printer is unreachable or returns malformed data, log a warning
///         and continue to the next printer (no crash).</item>
/// </list>
///
/// <para>Error handling:</para>
/// <list type="bullet">
///   <item>API unreachable: logged as warning, poller continues for other printers.</item>
///   <item>Malformed response: logged as warning, poller continues.</item>
///   <item>Database errors: logged as error, poller continues.</item>
/// </list>
/// </summary>
public class MoonrakerUsagePoller : BackgroundService
{
    private readonly IServiceScopeFactory _scopeFactory;
    private readonly ILogger<MoonrakerUsagePoller> _logger;
    private readonly MoonrakerPollerOptions _options;

    /// <summary>
    /// Tracks which Moonraker print jobs have already been recorded,
    /// keyed by "printerId:gcodeFileName" to avoid duplicate recording.
    /// </summary>
    private readonly HashSet<string> _recordedJobs = new();

    public MoonrakerUsagePoller(
        IServiceScopeFactory scopeFactory,
        ILogger<MoonrakerUsagePoller> logger,
        IOptions<MoonrakerPollerOptions> options)
    {
        _scopeFactory = scopeFactory;
        _logger = logger;
        _options = options.Value;
    }

    protected override async Task ExecuteAsync(CancellationToken stoppingToken)
    {
        if (!_options.Enabled)
        {
            _logger.LogInformation("Moonraker usage poller is disabled via configuration.");
            return;
        }

        _logger.LogInformation(
            "Moonraker usage poller starting. Poll interval: {Interval}",
            _options.PollInterval);

        while (!stoppingToken.IsCancellationRequested)
        {
            try
            {
                await PollAllPrintersAsync(stoppingToken);
            }
            catch (Exception ex)
            {
                _logger.LogError(ex,
                    "Unexpected error in Moonraker usage poller cycle. Continuing.");
            }

            await Task.Delay(_options.PollInterval, stoppingToken);
        }

        _logger.LogInformation("Moonraker usage poller stopping.");
    }

    /// <summary>
    /// Polls all active Moonraker printers for filament usage data
    /// and persists any completed print usage records.
    /// </summary>
    private async Task PollAllPrintersAsync(CancellationToken cancellationToken)
    {
        using var scope = _scopeFactory.CreateScope();
        var dbContext = scope.ServiceProvider.GetRequiredService<ExtrudexDbContext>();
        var moonrakerClient = scope.ServiceProvider.GetRequiredService<IMoonrakerClient>();
        var usageService = scope.ServiceProvider.GetRequiredService<IFilamentUsageService>();

        // Get all active Moonraker printers
        var printers = await dbContext.Printers
            .Where(p => p.IsActive && p.ConnectionType == ConnectionType.Moonraker)
            .ToListAsync(cancellationToken);

        if (printers.Count == 0)
        {
            _logger.LogDebug("No active Moonraker printers found.");
            return;
        }

        _logger.LogDebug("Polling {Count} Moonraker printer(s).", printers.Count);

        foreach (var printer in printers)
        {
            await PollPrinterAsync(
                printer, moonrakerClient, usageService, dbContext, cancellationToken);
        }
    }

    /// <summary>
    /// Polls a single Moonraker printer for filament usage data.
    /// If a completed print job is detected with usage data, it is persisted.
    /// </summary>
    private async Task PollPrinterAsync(
        Printer printer,
        IMoonrakerClient moonrakerClient,
        IFilamentUsageService usageService,
        ExtrudexDbContext dbContext,
        CancellationToken cancellationToken)
    {
        _logger.LogDebug(
            "Polling Moonraker printer {PrinterName} ({Host}:{Port})",
            printer.Name, printer.HostnameOrIp, printer.Port);

        try
        {
            // Update last-seen timestamp regardless of usage data
            var usageData = await moonrakerClient.GetFilamentUsageAsync(
                printer.HostnameOrIp,
                printer.Port,
                printer.ApiKey,
                cancellationToken);

            if (usageData is null)
            {
                _logger.LogDebug(
                    "No filament usage data from printer {PrinterName}.",
                    printer.Name);
                return;
            }

            // Update printer last-seen timestamp
            printer.LastSeenAt = DateTime.UtcNow;
            await dbContext.SaveChangesAsync(cancellationToken);

            _logger.LogDebug(
                "Printer {PrinterName}: state={State}, mm={Mm}, file={File}",
                printer.Name, usageData.PrintState, usageData.MmExtruded,
                usageData.GcodeFileName);

            // Only record usage for completed prints
            if (usageData.MmExtruded <= 0)
            {
                _logger.LogDebug(
                    "Printer {PrinterName} has no filament usage to record.",
                    printer.Name);
                return;
            }

            if (!IsCompleteState(usageData.PrintState))
            {
                _logger.LogDebug(
                    "Printer {PrinterName} print state '{State}' is not complete; skipping.",
                    printer.Name, usageData.PrintState);
                return;
            }

            // Deduplicate: avoid recording the same completed job twice
            var deduplicationKey = $"{printer.Id}:{usageData.GcodeFileName}";
            if (_recordedJobs.Contains(deduplicationKey))
            {
                _logger.LogDebug(
                    "Printer {PrinterName} job '{File}' already recorded; skipping.",
                    printer.Name, usageData.GcodeFileName);
                return;
            }

            // Find or create a PrintJob for this usage
            var printJob = await FindOrCreatePrintJobAsync(
                dbContext, printer, usageData, cancellationToken);

            if (printJob is null)
            {
                _logger.LogWarning(
                    "Could not find or create print job for printer {PrinterName}. " +
                    "No active spool found.",
                    printer.Name);
                return;
            }

            // Calculate grams from mm extruded using spool properties
            var spool = await dbContext.Spools.FindAsync(
                new object[] { printJob.SpoolId }, cancellationToken);

            var gramsUsed = CalculateGramsUsed(usageData.MmExtruded, spool);

            await usageService.RecordUsageAsync(
                printJobId: printJob.Id,
                spoolId: printJob.SpoolId,
                printerId: printer.Id,
                gramsUsed: gramsUsed,
                mmExtruded: usageData.MmExtruded,
                notes: $"Moonraker auto-recorded: {usageData.GcodeFileName}",
                cancellationToken: cancellationToken);

            // Mark job as recorded to prevent duplicates
            _recordedJobs.Add(deduplicationKey);

            _logger.LogInformation(
                "Recorded Moonraker usage for printer {PrinterName}: " +
                "{Mm}mm / {Grams}g, job '{File}'",
                printer.Name, usageData.MmExtruded, gramsUsed,
                usageData.GcodeFileName);
        }
        catch (HttpRequestException ex)
        {
            _logger.LogWarning(ex,
                "Moonraker API unreachable for printer {PrinterName} ({Host}:{Port}). " +
                "Will retry next cycle.",
                printer.Name, printer.HostnameOrIp, printer.Port);
        }
        catch (TaskCanceledException) when (cancellationToken.IsCancellationRequested)
        {
            // Shutdown requested — rethrow to exit the poll loop
            throw;
        }
        catch (TaskCanceledException ex)
        {
            _logger.LogWarning(ex,
                "Moonraker request timed out for printer {PrinterName} ({Host}:{Port}).",
                printer.Name, printer.HostnameOrIp, printer.Port);
        }
        catch (Exception ex)
        {
            _logger.LogError(ex,
                "Unexpected error polling Moonraker printer {PrinterName}. " +
                "Continuing to next printer.",
                printer.Name);
        }
    }

    /// <summary>
    /// Determines if a Moonraker print state indicates a completed job
    /// that should have its usage recorded.
    /// </summary>
    private static bool IsCompleteState(string state) =>
        state.Equals("complete", StringComparison.OrdinalIgnoreCase) ||
        state.Equals("completed", StringComparison.OrdinalIgnoreCase);

    /// <summary>
    /// Finds an existing PrintJob for the current g-code file on this printer,
    /// or creates a new one. Returns null if no spool is available.
    /// </summary>
    private async Task<PrintJob?> FindOrCreatePrintJobAsync(
        ExtrudexDbContext dbContext,
        Printer printer,
        MoonrakerFilamentUsage usageData,
        CancellationToken cancellationToken)
    {
        // Try to find an existing print job for this g-code file on this printer
        if (!string.IsNullOrEmpty(usageData.GcodeFileName))
        {
            var existingJob = await dbContext.PrintJobs
                .Where(j => j.PrinterId == printer.Id &&
                            j.GcodeFilePath == usageData.GcodeFileName &&
                            j.DataSource == DataSource.Moonraker &&
                            j.Status != JobStatus.Cancelled)
                .OrderByDescending(j => j.CreatedAt)
                .FirstOrDefaultAsync(cancellationToken);

            if (existingJob is not null)
            {
                // Update the existing job with completion data
                existingJob.MmExtruded = usageData.MmExtruded;
                existingJob.GramsDerived = CalculateGramsUsed(
                    usageData.MmExtruded,
                    await dbContext.Spools.FindAsync(
                        new object[] { existingJob.SpoolId }, cancellationToken));
                existingJob.Status = JobStatus.Completed;
                existingJob.CompletedAt = usageData.CompletedAt ?? DateTime.UtcNow;
                existingJob.StartedAt ??= usageData.StartedAt;

                await dbContext.SaveChangesAsync(cancellationToken);
                return existingJob;
            }
        }

        // No existing job — find the first active spool for this printer
        // via AMS slots, or fall back to any active spool
        var spool = await FindActiveSpoolForPrinterAsync(dbContext, printer, cancellationToken);

        if (spool is null)
        {
            return null;
        }

        var gramsDerived = CalculateGramsUsed(usageData.MmExtruded, spool);

        var newJob = new PrintJob
        {
            PrinterId = printer.Id,
            SpoolId = spool.Id,
            PrintName = usageData.GcodeFileName ?? "Moonraker Print",
            GcodeFilePath = usageData.GcodeFileName,
            MmExtruded = usageData.MmExtruded,
            GramsDerived = gramsDerived,
            FilamentDiameterAtPrintMm = spool.FilamentDiameterMm,
            MaterialDensityAtPrint = GetMaterialDensity(spool),
            DataSource = DataSource.Moonraker,
            Status = JobStatus.Completed,
            StartedAt = usageData.StartedAt ?? DateTime.UtcNow,
            CompletedAt = usageData.CompletedAt ?? DateTime.UtcNow,
            Notes = "Auto-created by Moonraker usage poller"
        };

        dbContext.PrintJobs.Add(newJob);
        await dbContext.SaveChangesAsync(cancellationToken);

        return newJob;
    }

    /// <summary>
    /// Finds an active spool associated with the printer via AMS slots,
    /// or falls back to any active spool in the system.
    /// </summary>
    private static async Task<Spool?> FindActiveSpoolForPrinterAsync(
        ExtrudexDbContext dbContext,
        Printer printer,
        CancellationToken cancellationToken)
    {
        // Try to find a spool loaded in the printer's AMS
        var amsSpool = await dbContext.AmsSlots
            .Include(s => s.Spool)
            .ThenInclude(s => s!.MaterialBase)
            .Include(s => s.AmsUnit)
            .Where(s => s.AmsUnit.PrinterId == printer.Id && s.Spool != null && s.Spool.IsActive)
            .Select(s => s.Spool)
            .FirstOrDefaultAsync(cancellationToken);

        if (amsSpool is not null)
            return amsSpool;

        // Fallback: any active spool (for non-AMS printers)
        return await dbContext.Spools
            .Include(s => s.MaterialBase)
            .Where(s => s.IsActive)
            .OrderByDescending(s => s.WeightRemainingGrams)
            .FirstOrDefaultAsync(cancellationToken);
    }

    /// <summary>
    /// Calculates grams used from mm extruded using the spool's filament
    /// diameter and the material density.
    /// Formula: grams = mm × π × (diameter/2)² × density
    /// Where density is in g/cm³, diameter in mm, giving grams.
    /// </summary>
    private static decimal CalculateGramsUsed(decimal mmExtruded, Spool? spool)
    {
        if (spool is null)
            return 0m;

        var diameterMm = spool.FilamentDiameterMm;
        var densityGcm3 = GetMaterialDensity(spool);

        // Cross-section area (mm²) = π × (diameter/2)²
        var radiusMm = diameterMm / 2m;
        var crossSectionArea = Math.PI * (double)radiusMm * (double)radiusMm;

        // Volume (mm³) = mm_extruded × cross_section_area
        // Convert mm³ to cm³: 1 cm³ = 1000 mm³
        // Weight (g) = volume_cm³ × density (g/cm³)
        var volumeMm3 = (double)mmExtruded * crossSectionArea;
        var volumeCm3 = volumeMm3 / 1000.0;
        var grams = volumeCm3 * (double)densityGcm3;

        return Math.Round((decimal)grams, 2);
    }

    /// <summary>
    /// Returns the material density for the spool's material base.
    /// Falls back to 1.24 g/cm³ (typical PLA density) if not available.
    /// </summary>
    private static decimal GetMaterialDensity(Spool? spool)
    {
        // Standard material densities (g/cm³)
        // These would ideally come from the MaterialBase entity,
        // but we use sensible defaults for the initial integration.
        return spool?.MaterialBase?.Name?.ToUpperInvariant() switch
        {
            "PLA" => 1.24m,
            "PETG" => 1.27m,
            "ABS" => 1.04m,
            "ASA" => 1.07m,
            "TPU" => 1.21m,
            "NYLON" or "PA" => 1.13m,
            "PC" => 1.20m,
            _ => 1.24m // Default to PLA density
        };
    }
}