turash/bugulma/backend/internal/service/transportation_service.go

package service

import (
	"errors"
	"fmt"
	"math"
	"sort"

	"bugulma/backend/internal/domain"
	"bugulma/backend/internal/geospatial"
)

// TransportationService handles transportation cost calculations and route optimization
type TransportationService struct {
	geoCalc geospatial.Calculator
}

// NewTransportationService creates a new transportation service
func NewTransportationService(geoCalc geospatial.Calculator) *TransportationService {
	return &TransportationService{
		geoCalc: geoCalc,
	}
}

// Default transport profiles (simplified for Bugulma region)
var transportProfiles = map[domain.TransportMode]domain.TransportProfile{
	domain.TransportModeTruck: {
		CostPerKm:           0.12, // €0.12 per km for truck transport
		SpeedKmH:           60.0,  // 60 km/h average speed
		MaxCapacity:        25.0,  // 25 tons
		EnvironmentalFactor: 1.0,  // Baseline
	},
	domain.TransportModeRail: {
		CostPerKm:           0.08, // €0.08 per km (more efficient)
		SpeedKmH:           40.0,  // 40 km/h average speed
		MaxCapacity:       100.0,  // 100 tons
		EnvironmentalFactor: 0.7,  // Better for environment
	},
	domain.TransportModePipe: {
		CostPerKm:           0.05, // €0.05 per km (fixed infrastructure)
		SpeedKmH:          100.0,  // 100 km/h (fluid transport)
		MaxCapacity:      1000.0,  // 1000 tons (continuous flow)
		EnvironmentalFactor: 0.5,  // Excellent for environment
	},
}

// CalculateTransportCost calculates transportation cost between two points
func (t *TransportationService) CalculateTransportCost(
	fromLat, fromLng, toLat, toLng float64,
	mode domain.TransportMode,
	volume float64,
) (*TransportCost, error) {

	// Calculate distances
	straightResult, err := t.geoCalc.CalculateDistance(
		geospatial.Point{Latitude: fromLat, Longitude: fromLng},
		geospatial.Point{Latitude: toLat, Longitude: toLng},
	)
	if err != nil {
		return nil, err
	}

	// Estimate road distance (1.3x straight-line as approximation)
	roadDistance := straightResult.DistanceKm * 1.3

	profile, exists := transportProfiles[mode]
	if !exists {
		return nil, ErrInvalidTransportMode
	}

	// Check capacity
	if volume > profile.MaxCapacity {
		return nil, ErrVolumeExceedsCapacity
	}

	// Calculate costs
	transportCost := roadDistance * profile.CostPerKm
	timeToDeliver := (roadDistance / profile.SpeedKmH)

	cost := &TransportCost{
		TransportMode:       mode,
		StraightDistanceKm:  straightResult.DistanceKm,
		RoadDistanceKm:      roadDistance,
		CostEur:            transportCost,
		TimeHours:          timeToDeliver,
		EnvironmentalFactor: profile.EnvironmentalFactor,
		CapacityUtilization: (volume / profile.MaxCapacity) * 100,
	}

	return cost, nil
}

// FindOptimalTransportRoutes finds the most cost-effective transportation routes
func (t *TransportationService) FindOptimalTransportRoutes(
	fromLat, fromLng, toLat, toLng float64,
	volume float64,
) ([]*domain.TransportOption, error) {

	var options []*domain.TransportOption

	for mode, profile := range transportProfiles {
		// Check if the transport mode is feasible for this volume
		if volume > profile.MaxCapacity {
			continue
		}

		// Calculate distances
		result, err := t.geoCalc.CalculateDistance(
			geospatial.Point{Latitude: fromLat, Longitude: fromLng},
			geospatial.Point{Latitude: toLat, Longitude: toLng},
		)
		if err != nil {
			continue
		}

		// Estimate road distance
		roadDistance := result.DistanceKm * 1.3

		// Calculate costs
		transportCost := roadDistance * profile.CostPerKm
		timeToDeliver := (roadDistance / profile.SpeedKmH)

		// Environmental score (higher is better)
		environmentalScore := 10.0 / profile.EnvironmentalFactor

		option := &domain.TransportOption{
			TransportMode:       mode,
			DistanceKm:         roadDistance,
			CostEur:           transportCost,
			TimeHours:         timeToDeliver,
			EnvironmentalScore: environmentalScore,
			CapacityUtilization: (volume / profile.MaxCapacity) * 100,
		}

		// Calculate overall efficiency score
		option.OverallScore = t.calculateTransportEfficiency(option)

		options = append(options, option)
	}

	// Sort by overall score (highest first)
	sort.Slice(options, func(i, j int) bool {
		return options[i].OverallScore > options[j].OverallScore
	})

	return options, nil
}

// GetTransportProfile returns the profile for a transport mode
func (t *TransportationService) GetTransportProfile(mode domain.TransportMode) (domain.TransportProfile, error) {
	profile, exists := transportProfiles[mode]
	if !exists {
		return domain.TransportProfile{}, fmt.Errorf("invalid transport mode: %s", mode)
	}
	return profile, nil
}

// calculateTransportEfficiency computes an overall efficiency score for transport options
func (t *TransportationService) calculateTransportEfficiency(option *domain.TransportOption) float64 {
	// Multi-criteria scoring: cost, time, environment, capacity utilization
	costEfficiency := math.Max(0, 1.0-(option.CostEur/1000.0))          // Better under €1000
	timeEfficiency := math.Max(0, 1.0-(option.TimeHours/24.0))         // Better under 24 hours
	envEfficiency := option.EnvironmentalScore / 10.0                   // 0-1 scale
	capacityEfficiency := math.Min(option.CapacityUtilization/100.0, 1.0) // Optimal around 80-100%

	// Weighted average
	return (costEfficiency * 0.4) + (timeEfficiency * 0.3) + (envEfficiency * 0.2) + (capacityEfficiency * 0.1)
}

// TransportCost represents detailed transportation cost analysis
type TransportCost struct {
	TransportMode       domain.TransportMode `json:"transport_mode"`
	StraightDistanceKm  float64             `json:"straight_distance_km"`
	RoadDistanceKm      float64             `json:"road_distance_km"`
	CostEur            float64             `json:"cost_eur"`
	TimeHours          float64             `json:"time_hours"`
	EnvironmentalFactor float64            `json:"environmental_factor"`
	CapacityUtilization float64            `json:"capacity_utilization_percent"`
}

// Errors
var (
	ErrInvalidTransportMode  = errors.New("invalid transport mode specified")
	ErrVolumeExceedsCapacity = errors.New("transport volume exceeds capacity")
)