using JdeScoping.Core.Models;
using JdeScoping.Core.Models.Enums;
using JdeScoping.Core.Models.Infrastructure;
using JdeScoping.DataSync.Options;
using JdeScoping.DataSync.Contracts;
using JdeScoping.DataSync.Models;
using Microsoft.Extensions.Logging;
using Microsoft.Extensions.Options;

namespace JdeScoping.DataSync.Services;

/// <summary>
/// Checks schedules and determines which sync tasks need to be executed.
/// </summary>
public class ScheduleChecker : IScheduleChecker
{
    private readonly IDataUpdateRepository _repository;
    private readonly IOptions<DataSyncOptions> _options;
    private readonly ILogger<ScheduleChecker> _logger;

    /// <summary>
    /// Initializes a new instance of the <see cref="ScheduleChecker"/> class.
    /// </summary>
    public ScheduleChecker(
        IDataUpdateRepository repository,
        IOptions<DataSyncOptions> options,
        ILogger<ScheduleChecker> logger)
    {
        _repository = repository ?? throw new ArgumentNullException(nameof(repository));
        _options = options ?? throw new ArgumentNullException(nameof(options));
        _logger = logger ?? throw new ArgumentNullException(nameof(logger));
    }

    /// <inheritdoc/>
    public async Task<List<DataUpdateTask>> GetPendingTasksAsync(CancellationToken cancellationToken = default)
    {
        var lastUpdates = await _repository.GetLastDataUpdatesAsync(cancellationToken);
        var tasks = new List<DataUpdateTask>();
        var now = DateTime.UtcNow;

        foreach (var config in _options.Value.DataSources.Where(c => c.IsEnabled))
        {
            var task = CheckConfigSchedule(config, lastUpdates, now);
            if (task != null)
            {
                tasks.Add(task);
            }
        }

        if (tasks.Count > 0)
        {
            _logger.LogInformation(
                "Found {Count} pending sync tasks: {Tasks}",
                tasks.Count,
                string.Join(", ", tasks.Select(t => $"{t.TableName}({t.UpdateType})")));
        }
        else
        {
            _logger.LogDebug("No pending sync tasks found");
        }

        return tasks;
    }

    /// <summary>
    /// Checks a single data source config and returns a task if sync is needed.
    /// Priority order: Mass > Daily > Hourly
    /// </summary>
    private DataUpdateTask? CheckConfigSchedule(
        DataSourceConfig config,
        Dictionary<string, DataUpdate> lastUpdates,
        DateTime now)
    {
        // Get last updates for each type
        var massKey = GetUpdateKey(config.TableName, UpdateTypes.Mass);
        var dailyKey = GetUpdateKey(config.TableName, UpdateTypes.Daily);
        var hourlyKey = GetUpdateKey(config.TableName, UpdateTypes.Hourly);

        lastUpdates.TryGetValue(massKey, out var lastMass);
        lastUpdates.TryGetValue(dailyKey, out var lastDaily);
        lastUpdates.TryGetValue(hourlyKey, out var lastHourly);

        // Check Mass first (highest priority)
        if (config.MassConfig.Enabled && NeedsMassSync(config, lastMass, now))
        {
            _logger.LogDebug(
                "Mass sync needed for {Table}: last={LastSync}, interval={Interval}m",
                config.TableName,
                lastMass?.EndDt.ToString("o") ?? "never",
                config.MassConfig.IntervalMinutes);

            return CreateTask(config, UpdateTypes.Mass, null);
        }

        // Check Daily
        if (config.DailyConfig.Enabled && NeedsDailySync(config, lastDaily, lastMass, now))
        {
            var minimumDt = CalculateMinimumDt(lastDaily, config.DailyConfig.IntervalMinutes);

            _logger.LogDebug(
                "Daily sync needed for {Table}: last={LastSync}, interval={Interval}m, minDT={MinDT}",
                config.TableName,
                lastDaily?.EndDt.ToString("o") ?? "never",
                config.DailyConfig.IntervalMinutes,
                minimumDt?.ToString("o") ?? "null");

            return CreateTask(config, UpdateTypes.Daily, minimumDt);
        }

        // Check Hourly (uses Daily's last timestamp for MinimumDT calculation, per legacy behavior)
        if (config.HourlyConfig.Enabled && NeedsHourlySync(config, lastHourly, lastDaily, lastMass, now))
        {
            // Use daily update timestamp for lookback, not hourly
            var minimumDt = CalculateMinimumDt(lastDaily, config.DailyConfig.IntervalMinutes);

            _logger.LogDebug(
                "Hourly sync needed for {Table}: last={LastSync}, interval={Interval}m, minDT={MinDT}",
                config.TableName,
                lastHourly?.EndDt.ToString("o") ?? "never",
                config.HourlyConfig.IntervalMinutes,
                minimumDt?.ToString("o") ?? "null");

            return CreateTask(config, UpdateTypes.Hourly, minimumDt);
        }

        return null;
    }

    /// <summary>
    /// Determines if a mass sync is needed.
    /// </summary>
    private bool NeedsMassSync(DataSourceConfig config, DataUpdate? lastMass, DateTime now)
    {
        // Never synced before - need mass sync
        if (lastMass == null)
        {
            return true;
        }

        // Check if successful last mass sync was within interval
        if (!lastMass.WasSuccessful)
        {
            // Last sync failed - try again
            return true;
        }

        var nextSyncDue = lastMass.EndDt.AddMinutes(config.MassConfig.IntervalMinutes);
        return now > nextSyncDue;
    }

    /// <summary>
    /// Determines if a daily sync is needed.
    /// </summary>
    private bool NeedsDailySync(DataSourceConfig config, DataUpdate? lastDaily, DataUpdate? lastMass, DateTime now)
    {
        // If no mass sync ever happened, we need mass first
        if (lastMass == null)
        {
            return false;
        }

        // Never done daily sync
        if (lastDaily == null)
        {
            return true;
        }

        // Check if successful last daily sync was within interval
        if (!lastDaily.WasSuccessful)
        {
            return true;
        }

        var nextSyncDue = lastDaily.EndDt.AddMinutes(config.DailyConfig.IntervalMinutes);
        return now > nextSyncDue;
    }

    /// <summary>
    /// Determines if an hourly sync is needed.
    /// </summary>
    private bool NeedsHourlySync(
        DataSourceConfig config,
        DataUpdate? lastHourly,
        DataUpdate? lastDaily,
        DataUpdate? lastMass,
        DateTime now)
    {
        // If no mass sync ever happened, we need mass first
        if (lastMass == null)
        {
            return false;
        }

        // Never done hourly sync
        if (lastHourly == null)
        {
            return true;
        }

        // Check if successful last hourly sync was within interval
        if (!lastHourly.WasSuccessful)
        {
            return true;
        }

        var nextSyncDue = lastHourly.EndDt.AddMinutes(config.HourlyConfig.IntervalMinutes);
        return now > nextSyncDue;
    }

    /// <summary>
    /// Calculates the MinimumDT for incremental updates using lookback multiplier.
    /// </summary>
    private DateTime? CalculateMinimumDt(DataUpdate? lastUpdate, int intervalMinutes)
    {
        if (lastUpdate == null)
        {
            return null;
        }

        var lookbackMinutes = _options.Value.LookbackMultiplier * intervalMinutes;
        return lastUpdate.EndDt.AddMinutes(-lookbackMinutes);
    }

    /// <summary>
    /// Creates a data update task.
    /// </summary>
    private static DataUpdateTask CreateTask(DataSourceConfig config, UpdateTypes updateType, DateTime? minimumDt)
    {
        return new DataUpdateTask
        {
            TableName = config.TableName,
            SourceSystem = config.SourceSystem,
            SourceData = config.SourceData,
            UpdateType = updateType,
            MinimumDt = minimumDt,
            Config = config
        };
    }

    /// <summary>
    /// Gets the dictionary key for looking up last updates.
    /// </summary>
    private static string GetUpdateKey(string tableName, UpdateTypes updateType)
    {
        return $"{tableName}_{(int)updateType}";
    }
}