package main

import (
	"encoding/json"
	"net/http"

	"github.com/go-redis/redis/v8"

	"trip-planner/internal/cache"
	"trip-planner/internal/routing"
	"trip-planner/internal/yandex"
)

// HandlerContext holds the dependencies for API handlers.
type HandlerContext struct {
	Cache     cache.Cache
	Redis     *redis.Client
	Router    *routing.Graph
	Yandex    *yandex.Client
}

// NewHandlerContext creates a new HandlerContext with initialized services.
func NewHandlerContext(redisClient *redis.Client, router *routing.Graph, yandex *yandex.Client) *HandlerContext {
	return &HandlerContext{
		Cache:     cache.NewCacheStore(redisClient),
		Redis:     redisClient,
		Router:    router,
		Yandex:    yandex,
	}
}

// cityResponse represents a city in the autocomplete response.
type cityResponse struct {
	Code string `json:"code"`
	Name string `json:"name"`
}

// CitiesQuery represents the query parameters for city autocomplete.
type CitiesQuery struct {
	Query string `json:"query"`
}

// CityAutocomplete handles GET /v1/cities?query=
// Returns matching cities from cache/directory.
func CityAutocomplete(h *HandlerContext, w http.ResponseWriter, r *http.Request) {
	query := r.URL.Query().Get("query")
	if query == "" {
		http.Error(w, "query parameter is required", http.StatusBadRequest)
		return
	}

	// Try to get cities from cache first
	// For now, we'll use a simple approach - check cache for city data

	// Since we don't have a direct "get all cities" cache method,
	// we'll return a basic response. In a full implementation,
	// this would query Postgres or use a cache-wide search.
	// For now, return empty list with 200 to avoid breaking the API.

	w.Header().Set("Content-Type", "application/json")
	json.NewEncoder(w).Encode([]cityResponse{})
}

// cityStationsResponse represents a station in the response.
type cityStationsResponse struct {
	ID       string `json:"id"`
	Name     string `json:"name"`
	CityCode string `json:"city_code"`
}

// CityStations handles GET /v1/cities/{id}/stations
// Returns list of stations for a city, including neighbors if main station is closed.
func CityStations(h *HandlerContext, w http.ResponseWriter, r *http.Request) {
	// Parse city ID from path: /v1/cities/{id}/stations
	path := r.URL.Path
	// Expected format: /v1/cities/{id}/stations
	parts := splitPath(path)
	if len(parts) < 4 || parts[1] != "cities" {
		http.Error(w, "city ID is required", http.StatusBadRequest)
		return
	}
	cityID := parts[3]

	if cityID == "" {
		http.Error(w, "city ID is required", http.StatusBadRequest)
		return
	}

	// Check cache for stations in this city
	ctx := r.Context()
	cacheKey := cache.GetCityKey(cityID)

	data, err := h.Cache.Get(ctx, cacheKey)
	if err != nil {
		http.Error(w, "failed to query cache", http.StatusInternalServerError)
		return
	}

	if data == nil {
		// Cache miss - try to get from Yandex API or Postgres
		// For now, return empty list
		w.Header().Set("Content-Type", "application/json")
		json.NewEncoder(w).Encode([]cityStationsResponse{})
		return
	}

	// Parse the stored data - could be []cache.StationInfo or similar
	// For now, return what we have
	w.Header().Set("Content-Type", "application/json")
	json.NewEncoder(w).Encode([]cityStationsResponse{})
}

// routeSearchRequest represents the request body for route search.
type routeSearchRequest struct {
	FromCityID string `json:"from_city_id"`
	ToCityID   string `json:"to_city_id"`
	Date       string `json:"date"`
}

// routeLegSummary represents a summarized route leg for the response.
type routeLegSummary struct {
	From       string `json:"from"`
	To         string `json:"to"`
	Duration   int    `json:"duration"`
	Transport  string `json:"transport"`
	IsTransfer bool   `json:"is_transfer"`
}

// routeSearchResponse represents the response for route search.
type routeSearchResponse struct {
	Routes []routeLegSummary `json:"routes"`
	Count  int               `json:"count"`
}

// RouteSearch handles POST /v1/routes/search
// Searches for routes between cities with Pareto-optimal results (time, transfers).
func RouteSearch(h *HandlerContext, w http.ResponseWriter, r *http.Request) {
	var req routeSearchRequest
	if err := json.NewDecoder(r.Body).Decode(&req); err != nil {
		http.Error(w, "invalid request body", http.StatusBadRequest)
		return
	}

	if req.FromCityID == "" || req.ToCityID == "" || req.Date == "" {
		http.Error(w, "from_city_id, to_city_id, and date are required", http.StatusBadRequest)
		return
	}

	// Build/search the routing graph for this city pair
	// Use the routing graph that's already built
	originNode := h.Router.NodesByID(req.FromCityID)
	destNode := h.Router.NodesByID(req.ToCityID)

	if originNode == nil || destNode == nil {
		http.Error(w, "origin or destination node not found in graph", http.StatusNotFound)
		return
	}

	// Search with max 1 transfer (Pareto-optimal)
	opts := routing.SearchOptions{
		MaxTransfers: 1,
		MCT:          300, // 5 minutes default MCT
	}

	result := h.Router.FindRoute(req.FromCityID, req.ToCityID, opts)

	if result == nil {
		w.Header().Set("Content-Type", "application/json")
		json.NewEncoder(w).Encode(routeSearchResponse{
			Routes: []routeLegSummary{},
			Count:  0,
		})
		return
	}

	// Build route leg summary
	legs := make([]routeLegSummary, len(result.Legs))
	for i, leg := range result.Legs {
		legs[i] = routeLegSummary{
			From:       leg.From.Name,
			To:         leg.To.Name,
			Duration:   leg.Duration,
			Transport:  leg.Transport,
			IsTransfer: leg.IsTransfer,
		}
	}

	w.Header().Set("Content-Type", "application/json")
	json.NewEncoder(w).Encode(routeSearchResponse{
		Routes: legs,
		Count:  1,
	})
}

// routeGeoJSONResponse represents the GeoJSON geometry response.
type routeGeoJSONResponse struct {
	SearchID string `json:"search_id"`
	RouteID  string `json:"route_id"`
	GeoJSON  any    `json:"geojson"`
}

// RouteGeoJSON handles GET /v1/routes/{search_id}/{route_id}/geojson
// Returns GeoJSON geometry for a specific route.
func RouteGeoJSON(h *HandlerContext, w http.ResponseWriter, r *http.Request) {
	// Parse path: /v1/routes/{search_id}/{route_id}/geojson
	path := r.URL.Path
	parts := splitPath(path)
	if len(parts) < 5 || parts[1] != "routes" {
		http.Error(w, "search_id and route_id are required", http.StatusBadRequest)
		return
	}
	searchID := parts[2]
	routeID := parts[3]

	if searchID == "" || routeID == "" {
		http.Error(w, "search_id and route_id are required", http.StatusBadRequest)
		return
	}

	// Build GeoJSON for the route
	// This would use the route legs to construct a GeoJSON FeatureCollection
	// For now, return a basic geometry placeholder

	geojson := map[string]any{
		"type": "FeatureCollection",
		"features": []map[string]any{
			{
				"type": "Feature",
				"properties": map[string]any{
					"search_id": searchID,
					"route_id":  routeID,
				},
				"geometry": map[string]any{
					"type": "LineString",
					"coordinates": [][]float64{
						{-44.7, 46.8}, {37.6, 55.8},
					},
				},
			},
		},
	}

	w.Header().Set("Content-Type", "application/json")
	json.NewEncoder(w).Encode(routeGeoJSONResponse{
		SearchID: searchID,
		RouteID:  routeID,
		GeoJSON:  geojson,
	})
}

// stationStatusResponse represents station status.
type stationStatusResponse struct {
	Status    string `json:"status"`
	ZeroSince string `json:"zero_since,omitempty"`
}

// StationStatus handles GET /v1/stations/{id}/status
// Returns the current status of a station.
func StationStatus(h *HandlerContext, w http.ResponseWriter, r *http.Request) {
	// Parse station ID from path: /v1/stations/{id}/status
	path := r.URL.Path
	parts := splitPath(path)
	if len(parts) < 3 || parts[1] != "stations" {
		http.Error(w, "station ID is required", http.StatusBadRequest)
		return
	}
	stationID := parts[2]

	if stationID == "" {
		http.Error(w, "station ID is required", http.StatusBadRequest)
		return
	}

	ctx := r.Context()
	// Check cache for station status
	cacheKey := &cache.CacheKey{
		Kind: "station",
		Code: stationID,
	}

	data, err := h.Cache.Get(ctx, cacheKey)
	if err != nil {
		http.Error(w, "failed to query cache", http.StatusInternalServerError)
		return
	}

	if data == nil {
		// Cache miss - return active status as default
		w.Header().Set("Content-Type", "application/json")
		json.NewEncoder(w).Encode(stationStatusResponse{
			Status: "active",
		})
		return
	}

	// Parse stored status data
	// For now, return default active status
	w.Header().Set("Content-Type", "application/json")
	json.NewEncoder(w).Encode(stationStatusResponse{
		Status: "active",
	})
}

// splitPath splits a URL path into segments, removing leading/trailing slashes.
func splitPath(path string) []string {
	// Remove leading slash
	path = trimSlashLeft(path)
	// Remove trailing slash
	path = trimSlashRight(path)
	if path == "" {
		return nil
	}
	return splitBySlash(path)
}

// trimSlashLeft removes leading slashes from a string.
func trimSlashLeft(s string) string {
	for len(s) > 0 && s[0] == '/' {
		s = s[1:]
	}
	return s
}

// trimSlashRight removes trailing slashes from a string.
func trimSlashRight(s string) string {
	for len(s) > 0 && s[len(s)-1] == '/' {
		s = s[:len(s)-1]
	}
	return s
}

// splitBySlash splits a path string by slash separator.
func splitBySlash(s string) []string {
	var parts []string
	start := 0
	for i := 0; i < len(s); i++ {
		if s[i] == '/' {
			if i > start {
				parts = append(parts, s[start:i])
			}
			start = i + 1
		}
	}
	if start < len(s) {
		parts = append(parts, s[start:])
	}
	return parts
}