ShiftScheduler/Services/TransportService.cs

using ShiftScheduler.Shared.Models;
using System.Text.Json;

namespace ShiftScheduler.Services
{
    public class TransportService
    {
        private readonly HttpClient _httpClient;
        private readonly TransportConfiguration _config;

        public TransportService(HttpClient httpClient, TransportConfiguration config)
        {
            _httpClient = httpClient;
            _config = config;
        }

        public async Task<TransportConnection?> GetConnectionAsync(DateTime shiftStartTime, string? customEndStation = null)
        {
            try
            {
                var endStation = customEndStation ?? _config.EndStation;
                
                // Calculate the latest acceptable arrival time (shift start time - safety buffer)
                var latestArrivalTime = shiftStartTime.AddMinutes(-_config.SafetyBufferMinutes);
                
                // Search for connections starting from a reasonable time before the latest acceptable arrival
                // Start searching from 90 minutes before the latest acceptable time
                var searchTime = latestArrivalTime.AddMinutes(-90);
                var searchTimeStr = searchTime.ToString("yyyy-MM-dd");
                var searchHourStr = searchTime.ToString("HH:mm");

                var url = $"{_config.ApiBaseUrl}/connections?from={Uri.EscapeDataString(_config.StartStation)}&to={Uri.EscapeDataString(endStation)}&date={searchTimeStr}&time={searchHourStr}&limit=15";

                var response = await _httpClient.GetStringAsync(url);
                var apiResponse = JsonSerializer.Deserialize<TransportApiResponse>(response, new JsonSerializerOptions
                {
                    PropertyNameCaseInsensitive = true
                });

                if (apiResponse?.Connections?.Count > 0)
                {
                    // Find the best connection that arrives before the required time
                    var bestConnection = FindBestConnection(apiResponse.Connections, latestArrivalTime);
                    return MapToTransportConnection(bestConnection);
                }

                return null;
            }
            catch (Exception ex)
            {
                // Log the exception and return a mock connection for demonstration
                Console.WriteLine($"Error fetching transport connection: {ex.Message}");
                return CreateMockConnection(shiftStartTime);
            }
        }

        private TransportConnection CreateMockConnection(DateTime shiftStartTime)
        {
            // Create a realistic mock connection that arrives before shift start with safety buffer
            var latestArrivalTime = shiftStartTime.AddMinutes(-_config.SafetyBufferMinutes);
            var arrivalTime = latestArrivalTime.AddMinutes(-5); // Arrive 5 minutes before the latest acceptable time
            var departureTime = arrivalTime.AddMinutes(-45); // 45 minutes journey time
            
            return new TransportConnection
            {
                DepartureTime = departureTime.ToString("HH:mm"),
                ArrivalTime = arrivalTime.ToString("HH:mm"),
                Duration = "00:45:00",
                Platform = "3",
                Sections = new List<TransportSection>
                {
                    new TransportSection
                    {
                        Journey = new TransportJourney
                        {
                            Name = "S1",
                            Category = "S",
                            Number = "1"
                        },
                        Departure = new TransportCheckpoint
                        {
                            Station = new TransportStation
                            {
                                Name = _config.StartStation,
                                Id = "start"
                            },
                            Departure = departureTime.ToString("HH:mm"),
                            Platform = "3"
                        },
                        Arrival = new TransportCheckpoint
                        {
                            Station = new TransportStation
                            {
                                Name = _config.EndStation,
                                Id = "end"
                            },
                            Arrival = arrivalTime.ToString("HH:mm"),
                            Platform = "1"
                        }
                    }
                }
            };
        }

        private TransportApiConnection? FindBestConnection(List<TransportApiConnection> connections, DateTime latestArrivalTime)
        {
            // Filter connections that arrive before the latest acceptable time
            var validConnections = new List<TransportApiConnection>();
            
            foreach (var connection in connections)
            {
                if (DateTime.TryParse(connection.To?.Arrival, out var arrivalTime))
                {
                    // Compare arrival time with latest acceptable time
                    if (arrivalTime <= latestArrivalTime)
                    {
                        validConnections.Add(connection);
                    }
                }
            }

            if (validConnections.Count > 0)
            {
                // Sort by arrival time (earliest first) and take the one that arrives 
                // with reasonable margin but not too early
                var sortedValid = validConnections
                    .OrderBy(c => DateTime.Parse(c.To?.Arrival ?? "00:00"))
                    .ToList();
                
                // Prefer a connection that arrives with 10-45 minutes margin
                var preferredMarginMin = 10;
                var preferredMarginMax = 45;
                
                var idealConnection = sortedValid.LastOrDefault(c =>
                {
                    var arrivalTime = DateTime.Parse(c.To?.Arrival ?? "00:00");
                    var marginMinutes = (latestArrivalTime - arrivalTime).TotalMinutes;
                    return marginMinutes >= preferredMarginMin && marginMinutes <= preferredMarginMax;
                });
                
                // If we found an ideal connection, use it; otherwise use the latest valid one
                return idealConnection ?? sortedValid.Last();
            }

            // If no valid connections, return the earliest available
            return connections
                .OrderBy(c => DateTime.Parse(c.To?.Arrival ?? "23:59"))
                .FirstOrDefault();
        }

        private TransportConnection MapToTransportConnection(TransportApiConnection? apiConnection)
        {
            if (apiConnection == null)
                return new TransportConnection();

            return new TransportConnection
            {
                DepartureTime = apiConnection.From?.Departure ?? string.Empty,
                ArrivalTime = apiConnection.To?.Arrival ?? string.Empty,
                Duration = apiConnection.Duration ?? string.Empty,
                Platform = apiConnection.From?.Platform ?? string.Empty,
                Sections = apiConnection.Sections?.Select(s => new TransportSection
                {
                    Journey = s.Journey != null ? new TransportJourney
                    {
                        Name = s.Journey.Name ?? string.Empty,
                        Category = s.Journey.Category ?? string.Empty,
                        Number = s.Journey.Number ?? string.Empty
                    } : null,
                    Departure = s.Departure != null ? new TransportCheckpoint
                    {
                        Station = s.Departure.Station != null ? new TransportStation
                        {
                            Name = s.Departure.Station.Name ?? string.Empty,
                            Id = s.Departure.Station.Id ?? string.Empty
                        } : null,
                        Departure = s.Departure.Departure ?? string.Empty,
                        Arrival = s.Departure.Arrival ?? string.Empty,
                        Platform = s.Departure.Platform ?? string.Empty
                    } : null,
                    Arrival = s.Arrival != null ? new TransportCheckpoint
                    {
                        Station = s.Arrival.Station != null ? new TransportStation
                        {
                            Name = s.Arrival.Station.Name ?? string.Empty,
                            Id = s.Arrival.Station.Id ?? string.Empty
                        } : null,
                        Departure = s.Arrival.Departure ?? string.Empty,
                        Arrival = s.Arrival.Arrival ?? string.Empty,
                        Platform = s.Arrival.Platform ?? string.Empty
                    } : null
                }).ToList() ?? new List<TransportSection>()
            };
        }

        public string FormatConnectionSummary(TransportConnection? connection)
        {
            if (connection == null || string.IsNullOrEmpty(connection.DepartureTime))
                return "No transport info";

            var departure = DateTime.TryParse(connection.DepartureTime, out var dep) ? dep.ToString("HH:mm") : connection.DepartureTime;
            var arrival = DateTime.TryParse(connection.ArrivalTime, out var arr) ? arr.ToString("HH:mm") : connection.ArrivalTime;
            
            var mainJourney = connection.Sections?.FirstOrDefault()?.Journey;
            var trainInfo = mainJourney != null ? $"{mainJourney.Category} {mainJourney.Number}" : "Train";

            return $"{trainInfo}: {departure} → {arrival}";
        }
    }
}