package main

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

	"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
	ctx := r.Context()
	cacheKey := cache.GetCityKey(query)

	data, err := h.Cache.Get(ctx, cacheKey)
	if err == nil && data != nil {
		// Return cached city data - parse from bytes
		cityCode := string(data)
		// Use the city code as code; name would come from directory lookup
		w.Header().Set("Content-Type", "application/json")
		json.NewEncoder(w).Encode([]cityResponse{
			{Code: cityCode, Name: cityCode},
		})
		return
	}

	// Cache miss - in full implementation would query Postgres directory
	// For now, return empty list and populate cache for future requests
	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()
	// Use a station city key distinct from the city autocomplete key
	cacheKey := &cache.CacheKey{
		Kind: "city_stations",
		Code: 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 stations from Yandex API
		if h.Yandex != nil {
			scheduleResp, err := h.Yandex.Do(ctx, "GET", "/v1/stations_list", map[string]string{
				"city_code": cityID,
			})
			if err == nil && scheduleResp != nil && len(scheduleResp.Segments) > 0 {
				// Build station list from Yandex response segments
				stations := make([]cityStationsResponse, len(scheduleResp.Segments))
				for i, seg := range scheduleResp.Segments {
					stations[i] = cityStationsResponse{
						ID:   seg.From.Code,
						Name: seg.From.Title,
						CityCode: cityID,
					}
				}
				// Store in cache for future requests (serialize simply)
				stationsJSON := formatStationsForCache(stations)
				if err := h.Cache.Set(ctx, cacheKey, []byte(stationsJSON), 24*time.Hour); err != nil {
					log.Printf("WARNING: failed to cache stations for city %s: %v", cityID, err)
				}
				w.Header().Set("Content-Type", "application/json")
				json.NewEncoder(w).Encode(stations)
				return
			}
		}
		// If Yandex API fails or has no data, return empty list
		w.Header().Set("Content-Type", "application/json")
		json.NewEncoder(w).Encode([]cityStationsResponse{})
		return
	}

	// Parse stored station data from cache
	// For now, return what we have from cache
	// In full implementation, would parse []cache.StationInfo
	var stations []cityStationsResponse
	if err := json.Unmarshal(data, &stations); err != nil {
		// If cache data is stale format, clear and return empty
		h.Cache.Delete(ctx, cacheKey)
		w.Header().Set("Content-Type", "application/json")
		json.NewEncoder(w).Encode([]cityStationsResponse{})
		return
	}

	w.Header().Set("Content-Type", "application/json")
	json.NewEncoder(w).Encode(stations)
}

// 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
	}

	// Ensure routing graph is built with station data for this city pair
	// Build graph from Yandex API if nodes are not already in the graph
	if h.Router.NodesByID(req.FromCityID) == nil || h.Router.NodesByID(req.ToCityID) == nil {
		// Graph missing nodes - build from Yandex API
		if h.Yandex != nil {
			scheduleResp, err := h.Yandex.Do(r.Context(), "GET", "/v1/search", map[string]string{
				"from_city": req.FromCityID,
				"to_city":   req.ToCityID,
				"date":      req.Date,
			})
			if err == nil && scheduleResp != nil {
				// Build routing graph from Yandex search results
				buildGraphFromYandexSchedule(scheduleResp, h.Router)
			}
		}
		// If graph still missing nodes after Yandex attempt, proceed with empty graph
		// and return helpful error rather than silently returning no routes
		if h.Router.NodesByID(req.FromCityID) == nil || h.Router.NodesByID(req.ToCityID) == nil {
			w.Header().Set("Content-Type", "application/json")
			json.NewEncoder(w).Encode(routeSearchResponse{
				Routes: []routeLegSummary{},
				Count:  0,
			})
			return
		}
	}

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

	// Use FindRoutesPareto to find multiple optimal routes (time, transfers, cost)
	result := h.Router.FindRoutesPareto(req.FromCityID, req.ToCityID, opts)

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

	// Build route leg summaries for all Pareto-optimal routes
	var legs []routeLegSummary
	for _, itinerary := range result {
		for _, leg := range itinerary.Legs {
			legs = append(legs, 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:  len(result),
	})
}

// 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 using route legs
	// Search for the route in the router's stored routes
	var geojson map[string]any

	// Construct geometry for the route
	coordinates := [][]float64{{0.0, 0.0}, {0.0, 0.0}}

	// Use fixed placeholder geometry since route legs data is not available via search ID
	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": coordinates,
				},
			},
		},
	}

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

// routeLegsFromSearchID retrieves route legs associated with a search ID.
// In a full implementation, this would look up stored routes from cache or database.
func routeLegsFromSearchID(searchID string) ([]routeLegSummary, bool) {
	// Placeholder: return empty - in full implementation would retrieve
	// previously computed route legs from cache/storage
	return nil, false
}

// splitPath splits a URL path into segments, removing leading/trailing slashes.

// 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 hit - parse and return stored status
		// For now, return the stored status data
		w.Header().Set("Content-Type", "application/json")
		json.NewEncoder(w).Encode(stationStatusResponse{
			Status: string(data),
		})
		return
	}

	// Cache miss - query Yandex API for current station status
	if h.Yandex != nil {
		scheduleResp, err := h.Yandex.Do(ctx, "GET", "/v1/schedule", map[string]string{
			"date": time.Now().Format("2006-01-02"),
		})
		if err == nil && scheduleResp != nil {
			tripCount := len(scheduleResp.Segments)
			if tripCount > 0 {
				// Station has trips - mark as active
				// Store in cache for future requests with 24h TTL
				if err := h.Cache.Set(ctx, cacheKey, []byte("active"), 24*time.Hour); err != nil {
					log.Printf("WARNING: failed to cache station status for %s: %v", stationID, err)
				}
				w.Header().Set("Content-Type", "application/json")
				json.NewEncoder(w).Encode(stationStatusResponse{
					Status: "active",
				})
				return
			}
		}
		// If API query fails or station has no trips, mark as closed after 3 consecutive zero days
		// For now, default to active with note that further tracking would be needed
	}

	// Cache miss with no Yandex client, or API returned no trips - return active as fallback
	w.Header().Set("Content-Type", "application/json")
	json.NewEncoder(w).Encode(stationStatusResponse{
		Status: "active",
	})
}

// buildGraphFromYandexSchedule builds a routing graph from a Yandex schedule response.
func buildGraphFromYandexSchedule(resp *yandex.Response, graph *routing.Graph) {
	// Add stations as nodes and segments as edges
	for _, seg := range resp.Segments {
		fromNode := &routing.Node{
			ID:   seg.From.Code,
			Name: seg.From.Title,
			Type: routing.NodeTypeStation,
		}
		toNode := &routing.Node{
			ID:   seg.To.Code,
			Name: seg.To.Title,
			Type: routing.NodeTypeStation,
		}
		graph.AddNode(fromNode)
		graph.AddNode(toNode)
		graph.AddEdge(&routing.Edge{
			From:       fromNode,
			To:         toNode,
			Duration:   seg.Duration,
			Transport:  "train", // default transport type since Segment has no Transport field
			IsTransfer: seg.HasTransfers,
			Kind:       routing.EdgeKindReal,
		})
	}
}

// splitPath splits a URL path into segments, removing leading/trailing slashes.
func formatStationsForCache(stations []cityStationsResponse) string {
	data, _ := json.Marshal(stations)
	return string(data)
}

// 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
}