using LiveRecorder.Application.Abstractions.Recording;
using LiveRecorder.Application.Abstractions.Settings;
using LiveRecorder.Application.Abstractions.Storage;
using LiveRecorder.Application.Common;
using LiveRecorder.Application.Models.Recovery;
using LiveRecorder.Application.Models.RecordTasks;
using LiveRecorder.Application.Services;
using LiveRecorder.Domain.Entities;
using LiveRecorder.Domain.Enums;
using LiveRecorder.Infrastructure.Persistence;
using Microsoft.EntityFrameworkCore;

namespace LiveRecorder.Infrastructure.Services;

public sealed class RecoveryService
{
    private readonly LiveRecorderDbContext _dbContext;
    private readonly ISystemSettingsService _systemSettingsService;
    private readonly IStorageGuardService _storageGuardService;
    private readonly IFfmpegService _ffmpegService;
    private readonly RecordService _recordService;

    public RecoveryService(
        LiveRecorderDbContext dbContext,
        ISystemSettingsService systemSettingsService,
        IStorageGuardService storageGuardService,
        IFfmpegService ffmpegService,
        RecordService recordService)
    {
        _dbContext = dbContext;
        _systemSettingsService = systemSettingsService;
        _storageGuardService = storageGuardService;
        _ffmpegService = ffmpegService;
        _recordService = recordService;
    }

    public async Task<RecoveryOverviewDto> GetOverviewAsync(CancellationToken cancellationToken = default)
    {
        var settings = await _systemSettingsService.GetAsync(cancellationToken);
        var storage = _storageGuardService.CheckCanStartOrResume(settings);
        var liveRooms = await ListRecoverableLiveRoomsAsync(cancellationToken);
        var finalizations = await ListRecoverableFinalizationsAsync(cancellationToken);

        return new RecoveryOverviewDto
        {
            Storage = new StorageGuardStatusDto
            {
                IsEnabled = storage.IsEnabled,
                HasEnoughSpace = storage.HasEnoughSpace,
                CheckedPath = storage.CheckedPath,
                AvailableBytes = storage.AvailableBytes,
                RequiredBytes = storage.RequiredBytes,
                Message = storage.Message,
                Tier = storage.Tier.ToString(),
                UsagePercent = storage.UsagePercent
            },
            LiveRooms = liveRooms,
            Finalizations = finalizations
        };
    }

    public async Task<RecoveryActionResultDto> RetryLiveRoomAsync(Guid liveRoomId, CancellationToken cancellationToken = default)
    {
        var room = await _dbContext.LiveRooms.FirstOrDefaultAsync(item => item.Id == liveRoomId, cancellationToken);
        if (room is null)
        {
            return FailureResult("Live room was not found.");
        }

        if (!room.IsEnabled)
        {
            return FailureResult("Live room is disabled and cannot be retried.");
        }

        if (room.AvailabilityStatus != LiveRoomAvailabilityStatus.Live)
        {
            return FailureResult("Live room is not currently online.");
        }

        var hasActiveSession = await _dbContext.RecordSessions.AnyAsync(
            item => item.LiveRoomId == room.Id &&
                    (item.Status == RecordSessionStatus.Starting ||
                     item.Status == RecordSessionStatus.Running ||
                     item.Status == RecordSessionStatus.Stopping),
            cancellationToken);

        if (hasActiveSession)
        {
            room.SetLastAutoStartDecision(
                AutoStartDecisionCodes.SkippedActiveSession,
                "Auto-start skipped because an active recording session already exists.",
                null,
                DateTimeOffset.UtcNow);
            await _dbContext.SaveChangesAsync(cancellationToken);
            return FailureResult("An active recording session already exists for this live room.");
        }

        try
        {
            var task = await _recordService.StartAsync(
                new StartRecordTaskRequest
                {
                    LiveRoomId = liveRoomId
                },
                trackAutoStartDecision: true,
                cancellationToken);

            var started = task.Status is RecordTaskStatus.Starting or RecordTaskStatus.Running;
            return new RecoveryActionResultDto
            {
                RequestedCount = 1,
                SuccessCount = started ? 1 : 0,
                FailedCount = started ? 0 : 1,
                Messages =
                [
                    started
                        ? $"Recording retry started for room {room.RoomId}."
                        : $"Recording retry did not start for room {room.RoomId}. Status={task.Status}; Error={task.ErrorMessage ?? "n/a"}"
                ]
            };
        }
        catch (Exception ex)
        {
            return FailureResult($"Recording retry failed for room {room.RoomId}: {ex.Message}");
        }
    }

    public async Task<RecoveryActionResultDto> RetryAllLiveRoomsAsync(CancellationToken cancellationToken = default)
    {
        var liveRooms = await ListRecoverableLiveRoomsAsync(cancellationToken);
        if (liveRooms.Count == 0)
        {
            return new RecoveryActionResultDto
            {
                RequestedCount = 0,
                SuccessCount = 0,
                FailedCount = 0,
                Messages = ["No live rooms currently require retry."]
            };
        }

        var messages = new List<string>();
        var successCount = 0;
        foreach (var item in liveRooms)
        {
            var result = await RetryLiveRoomAsync(item.LiveRoomId, cancellationToken);
            successCount += result.SuccessCount;
            messages.AddRange(result.Messages);
        }

        return new RecoveryActionResultDto
        {
            RequestedCount = liveRooms.Count,
            SuccessCount = successCount,
            FailedCount = liveRooms.Count - successCount,
            Messages = messages
        };
    }

    public async Task<RecoveryActionResultDto> ResumeFinalizationAsync(Guid recordTaskId, CancellationToken cancellationToken = default)
    {
        var started = await _ffmpegService.StartManualFinalizeTaskAsync(recordTaskId, cancellationToken);
        return new RecoveryActionResultDto
        {
            RequestedCount = 1,
            SuccessCount = started ? 1 : 0,
            FailedCount = started ? 0 : 1,
            Messages =
            [
                started
                    ? $"MP4 finalization resumed for task {recordTaskId}."
                    : $"MP4 finalization could not be resumed for task {recordTaskId}."
            ]
        };
    }

    public async Task<RecoveryActionResultDto> ResumeAllFinalizationsAsync(CancellationToken cancellationToken = default)
    {
        var finalizations = await ListRecoverableFinalizationsAsync(cancellationToken);
        if (finalizations.Count == 0)
        {
            return new RecoveryActionResultDto
            {
                RequestedCount = 0,
                SuccessCount = 0,
                FailedCount = 0,
                Messages = ["No MP4 finalization tasks currently require recovery."]
            };
        }

        var successCount = 0;
        var messages = new List<string>();
        foreach (var item in finalizations)
        {
            var started = await _ffmpegService.StartManualFinalizeTaskAsync(item.RecordTaskId, cancellationToken);
            if (started)
            {
                successCount++;
            }

            messages.Add(
                started
                    ? $"MP4 finalization resumed for task {item.RecordTaskId}."
                    : $"MP4 finalization could not be resumed for task {item.RecordTaskId}.");
        }

        return new RecoveryActionResultDto
        {
            RequestedCount = finalizations.Count,
            SuccessCount = successCount,
            FailedCount = finalizations.Count - successCount,
            Messages = messages
        };
    }

    private async Task<IReadOnlyList<RecoverableLiveRoomDto>> ListRecoverableLiveRoomsAsync(CancellationToken cancellationToken)
    {
        var activeLiveRoomIds = await _dbContext.RecordSessions
            .AsNoTracking()
            .Where(item => item.Status == RecordSessionStatus.Starting ||
                           item.Status == RecordSessionStatus.Running ||
                           item.Status == RecordSessionStatus.Stopping)
            .Select(item => item.LiveRoomId)
            .Distinct()
            .ToListAsync(cancellationToken);

        var rooms = await _dbContext.LiveRooms
            .AsNoTracking()
            .Where(item => item.IsEnabled &&
                           item.AvailabilityStatus == LiveRoomAvailabilityStatus.Live &&
                           item.LastAutoStartDecisionCode != AutoStartDecisionCodes.Started)
            .ToListAsync(cancellationToken);

        return rooms
            .Where(item => !activeLiveRoomIds.Contains(item.Id))
            .OrderByDescending(item => item.LastAutoStartDecisionAt ?? item.LastCheckedAt ?? item.UpdatedAt)
            .Select(item => new RecoverableLiveRoomDto
            {
                LiveRoomId = item.Id,
                PlatformName = item.Platform.ToString(),
                RoomId = item.RoomId,
                Title = item.Title,
                AnchorName = item.AnchorName,
                LastAutoStartDecisionCode = item.LastAutoStartDecisionCode,
                LastAutoStartDecisionSummary = item.LastAutoStartDecisionSummary,
                LastAutoStartDecisionDetail = item.LastAutoStartDecisionDetail,
                LastAutoStartDecisionAt = item.LastAutoStartDecisionAt,
                LastCheckedAt = item.LastCheckedAt
            })
            .ToList();
    }

    private async Task<IReadOnlyList<RecoverableFinalizationDto>> ListRecoverableFinalizationsAsync(CancellationToken cancellationToken)
    {
        var tasks = await _dbContext.RecordTasks
            .AsNoTracking()
            .Include(item => item.LiveRoom)
            .Include(item => item.RecordSession)
            .Include(item => item.Result)
            .Where(item => item.OutputFormat == RecordOutputFormat.Mp4 &&
                           item.RecordSession != null)
            .ToListAsync(cancellationToken);

        return tasks
            .Where(IsRecoverableFinalization)
            .OrderByDescending(item => item.UpdatedAt)
            .Select(item => new RecoverableFinalizationDto
            {
                RecordTaskId = item.Id,
                RecordSessionId = item.RecordSessionId,
                LiveRoomId = item.LiveRoomId,
                LiveRoomTitle = item.LiveRoom?.Title ?? item.LiveRoom?.AnchorName ?? item.LiveRoom?.RoomId ?? item.LiveRoomId.ToString(),
                RoomId = item.LiveRoom?.RoomId ?? "-",
                PlatformName = item.LiveRoom?.Platform.ToString() ?? "Unknown",
                SegmentIndex = item.SegmentIndex,
                Status = item.Status,
                OutputFilePath = item.OutputFilePath,
                Reason = BuildFinalizationReason(item),
                CreatedAt = item.CreatedAt,
                EndedAt = item.EndedAt
            })
            .ToList();
    }

    private static bool IsRecoverableFinalization(RecordTask recordTask)
    {
        if (recordTask.RecordSession is null ||
            recordTask.OutputFormat != RecordOutputFormat.Mp4)
        {
            return false;
        }

        if (recordTask.Status == RecordTaskStatus.Processing)
        {
            return true;
        }

        if (recordTask.Status is RecordTaskStatus.Starting or RecordTaskStatus.Running or RecordTaskStatus.Stopping)
        {
            return false;
        }

        if (recordTask.RecordSession.Status is RecordSessionStatus.Starting or RecordSessionStatus.Running or RecordSessionStatus.Stopping)
        {
            return false;
        }

        if (string.IsNullOrWhiteSpace(recordTask.OutputFilePath))
        {
            return false;
        }

        var recorderOutputPath = ResolveManualFinalizeSourcePath(recordTask, recordTask.RecordSession);
        if (!File.Exists(recorderOutputPath))
        {
            return false;
        }

        if (recordTask.Status == RecordTaskStatus.Completed)
        {
            var finalOutputPath = NormalizeAbsolutePath(recordTask.OutputFilePath);
            return !HasUsableOutput(finalOutputPath, CalculateFileSize(finalOutputPath));
        }

        return true;
    }

    private static string BuildFinalizationReason(RecordTask recordTask)
    {
        if (recordTask.Status == RecordTaskStatus.Processing)
        {
            return string.IsNullOrWhiteSpace(recordTask.ErrorMessage)
                ? "MP4 finalization is queued or paused and can be resumed."
                : recordTask.ErrorMessage!;
        }

        if (recordTask.Status == RecordTaskStatus.Completed)
        {
            return "The final MP4 output is missing, but the intermediate recording file is still available.";
        }

        return "Manual MP4 finalization can be retried from the intermediate recording file.";
    }

    private static string ResolveManualFinalizeSourcePath(RecordTask recordTask, RecordSession recordSession)
    {
        var resultPath = recordTask.Result?.FilePath;
        if (!string.IsNullOrWhiteSpace(resultPath) &&
            resultPath.EndsWith(".ts", StringComparison.OrdinalIgnoreCase))
        {
            var normalizedResultPath = NormalizeAbsolutePath(resultPath);
            if (File.Exists(normalizedResultPath))
            {
                return normalizedResultPath;
            }
        }

        return NormalizeAbsolutePath(
            GetRecorderOutputPath(
                recordTask.OutputFilePath ?? resultPath ?? string.Empty,
                recordSession.OutputFormat,
                recordSession.SaveMode));
    }

    private static string GetRecorderOutputPath(
        string finalOutputPath,
        RecordOutputFormat outputFormat,
        RecordSaveMode saveMode)
    {
        if (outputFormat != RecordOutputFormat.Mp4)
        {
            return finalOutputPath;
        }

        if (saveMode == RecordSaveMode.SingleFile)
        {
            return Path.Combine(
                Path.GetDirectoryName(finalOutputPath)!,
                $"{Path.GetFileNameWithoutExtension(finalOutputPath)}.recording.ts");
        }

        return Path.ChangeExtension(finalOutputPath, ".ts");
    }

    private static long? CalculateFileSize(string? outputPath)
    {
        if (string.IsNullOrWhiteSpace(outputPath))
        {
            return null;
        }

        if (File.Exists(outputPath))
        {
            return new FileInfo(outputPath).Length;
        }

        if (Directory.Exists(outputPath))
        {
            return new DirectoryInfo(outputPath)
                .EnumerateFiles("*", SearchOption.TopDirectoryOnly)
                .Sum(static file => file.Length);
        }

        return null;
    }

    private static bool HasUsableOutput(string? outputPath, long? fileSize)
    {
        if (string.IsNullOrWhiteSpace(outputPath))
        {
            return false;
        }

        if (File.Exists(outputPath))
        {
            return fileSize.GetValueOrDefault() > 0;
        }

        if (Directory.Exists(outputPath))
        {
            return Directory.EnumerateFiles(outputPath, "*", SearchOption.TopDirectoryOnly).Any();
        }

        return false;
    }

    private static string NormalizeAbsolutePath(string path) =>
        Path.IsPathRooted(path)
            ? path
            : Path.GetFullPath(path, AppContext.BaseDirectory);

    private static RecoveryActionResultDto FailureResult(string message) => new()
    {
        RequestedCount = 1,
        SuccessCount = 0,
        FailedCount = 1,
        Messages = [message]
    };
}