package main

import (
	"bytes"
	"encoding/json"
	"encoding/xml"
	"fmt"
	"io"
	"math"
	"net/http"
	"os"
	"path/filepath"
	"strconv"
	"strings"
	"time"
)

// KML structure for parsing
type KML struct {
	XMLName  xml.Name    `xml:"kml"`
	Document KMLDocument `xml:"Document"`
}

type KMLDocument struct {
	Placemarks []KMLPlacemark `xml:"Placemark"`
}

type KMLPlacemark struct {
	LineString KMLLineString `xml:"LineString"`
}

type KMLLineString struct {
	Coordinates string `xml:"coordinates"`
}

// KML Metadata
type KMLMetadata struct {
	Filename    string    `json:"filename"`
	UserID      string    `json:"user_id"`
	DisplayName string    `json:"display_name"` // User's display name
	Distance    float64   `json:"distance"`     // in kilometers
	IsPublic    bool      `json:"is_public"`
	UploadedAt  time.Time `json:"uploaded_at"`
	Votes       int       `json:"votes"` // Net votes (calculated from voting system)
}

// SetVote sets a user's vote for a KML file in the database
func SetVote(kmlID int, userID string, vote int) error {
	if vote == 0 {
		_, err := db.Exec("DELETE FROM kml_votes WHERE kml_id = ? AND user_id = ?", kmlID, userID)
		return err
	}
	_, err := db.Exec(`
		INSERT INTO kml_votes (kml_id, user_id, vote_value)
		VALUES (?, ?, ?)
		ON DUPLICATE KEY UPDATE vote_value = ?
	`, kmlID, userID, vote, vote)
	return err
}

// CalculateNetVotes calculates net votes for a KML file from the database
func CalculateNetVotes(kmlID int) int {
	var total int
	err := db.QueryRow("SELECT COALESCE(SUM(vote_value), 0) FROM kml_votes WHERE kml_id = ?", kmlID).Scan(&total)
	if err != nil {
		return 0
	}
	return total
}

// Haversine formula to calculate distance between two lat/lng points
func haversineDistance(lat1, lon1, lat2, lon2 float64) float64 {
	const earthRadiusKm = 6371.0

	dLat := (lat2 - lat1) * math.Pi / 180.0
	dLon := (lon2 - lon1) * math.Pi / 180.0

	a := math.Sin(dLat/2)*math.Sin(dLat/2) +
		math.Cos(lat1*math.Pi/180.0)*math.Cos(lat2*math.Pi/180.0)*
			math.Sin(dLon/2)*math.Sin(dLon/2)

	c := 2 * math.Atan2(math.Sqrt(a), math.Sqrt(1-a))

	return earthRadiusKm * c
}

// ParseKMLDistance parses a KML file and calculates the total distance
func ParseKMLDistance(kmlData []byte) (float64, error) {
	decoder := xml.NewDecoder(bytes.NewReader(kmlData))
	totalDistance := 0.0

	for {
		token, err := decoder.Token()
		if err == io.EOF {
			break
		}
		if err != nil {
			return 0, err
		}

		switch se := token.(type) {
		case xml.StartElement:
			// We only care about coordinates within a LineString context.
			// However, since Points have only one coordinate and result in 0 anyway,
			// searching for any <coordinates> tag is both easier and robust enough.
			if se.Name.Local == "coordinates" {
				var coords string
				if err := decoder.DecodeElement(&coords, &se); err != nil {
					continue
				}

				// Sum up distance from this LineString
				items := strings.Fields(coords)
				var prevLat, prevLon float64
				first := true

				for _, item := range items {
					parts := strings.Split(strings.TrimSpace(item), ",")
					if len(parts) < 2 {
						continue
					}

					var lon, lat float64
					_, err1 := fmt.Sscanf(parts[0], "%f", &lon)
					_, err2 := fmt.Sscanf(parts[1], "%f", &lat)
					if err1 != nil || err2 != nil {
						continue
					}

					if !first {
						totalDistance += haversineDistance(prevLat, prevLon, lat, lon)
					}

					prevLat = lat
					prevLon = lon
					first = false
				}
			}
		}
	}

	return totalDistance, nil
}

// HandleKMLUpload handles KML file uploads
func HandleKMLUpload(w http.ResponseWriter, r *http.Request) {
	if r.Method != http.MethodPost {
		http.Error(w, "Method not allowed", http.StatusMethodNotAllowed)
		return
	}

	userID, ok := getUserID(r.Context())
	if !ok {
		http.Error(w, "Unauthorized", http.StatusUnauthorized)
		return
	}

	// Parse multipart form
	if err := r.ParseMultipartForm(10 << 20); err != nil { // 10 MB limit
		http.Error(w, "Failed to parse form", http.StatusBadRequest)
		return
	}

	file, handler, err := r.FormFile("kml")
	if err != nil {
		http.Error(w, "No file uploaded", http.StatusBadRequest)
		return
	}
	defer file.Close()

	// Read file data
	data, err := io.ReadAll(file)
	if err != nil {
		http.Error(w, "Failed to read file", http.StatusInternalServerError)
		return
	}

	// Calculate distance
	distance, err := ParseKMLDistance(data)
	if err != nil {
		http.Error(w, fmt.Sprintf("Failed to parse KML: %v", err), http.StatusBadRequest)
		return
	}

	// Save KML file
	kmlDir := fmt.Sprintf("data/users/%s/kml", userID)
	if err := os.MkdirAll(kmlDir, 0755); err != nil {
		http.Error(w, "Failed to create directory", http.StatusInternalServerError)
		return
	}

	kmlPath := filepath.Join(kmlDir, handler.Filename)
	if err := os.WriteFile(kmlPath, data, 0644); err != nil {
		http.Error(w, "Failed to save file", http.StatusInternalServerError)
		return
	}

	// Save metadata to database
	_, err = db.Exec(`
		INSERT INTO kml_metadata (filename, user_id, distance, is_public, uploaded_at)
		VALUES (?, ?, ?, ?, NOW())
		ON DUPLICATE KEY UPDATE distance = ?, uploaded_at = NOW()
	`, handler.Filename, userID, distance, false, distance)
	if err != nil {
		http.Error(w, fmt.Sprintf("Failed to save metadata: %v", err), http.StatusInternalServerError)
		return
	}

	w.Header().Set("Content-Type", "application/json")
	json.NewEncoder(w).Encode(map[string]interface{}{
		"success":  true,
		"filename": handler.Filename,
		"distance": distance,
	})
}

// HandleKMLList lists KML files with pagination and sorting
func HandleKMLList(w http.ResponseWriter, r *http.Request) {
	userID, ok := getUserID(r.Context())
	if !ok {
		http.Error(w, "Unauthorized", http.StatusUnauthorized)
		return
	}

	// Parse pagination parameters
	limit, _ := strconv.Atoi(r.URL.Query().Get("limit"))
	if limit <= 0 {
		limit = 10
	}
	page, _ := strconv.Atoi(r.URL.Query().Get("page"))
	if page <= 0 {
		page = 1
	}
	offset := (page - 1) * limit

	sortBy := r.URL.Query().Get("sort_by")
	order := r.URL.Query().Get("order")
	if order != "ASC" {
		order = "DESC"
	}

	// 1. Get my files
	myFiles, err := queryKMLMetadata(`
		SELECT m.filename, m.user_id, u.display_name, m.distance, m.is_public, m.uploaded_at,
		       (SELECT COALESCE(SUM(v.vote_value), 0) FROM kml_votes v WHERE v.kml_id = m.id) as votes
		FROM kml_metadata m
		JOIN users u ON m.user_id = u.fitbit_user_id
		WHERE m.user_id = ?
		ORDER BY m.uploaded_at DESC
	`, userID)
	if err != nil {
		http.Error(w, err.Error(), http.StatusInternalServerError)
		return
	}

	// 2. Get public files (with pagination and sorting)
	sortClause := "votes"
	switch sortBy {
	case "date":
		sortClause = "m.uploaded_at"
	case "distance":
		sortClause = "m.distance"
	}

	publicFiles, err := queryKMLMetadata(fmt.Sprintf(`
		SELECT m.filename, m.user_id, u.display_name, m.distance, m.is_public, m.uploaded_at,
		       (SELECT COALESCE(SUM(v.vote_value), 0) FROM kml_votes v WHERE v.kml_id = m.id) as votes
		FROM kml_metadata m
		JOIN users u ON m.user_id = u.fitbit_user_id
		WHERE m.is_public = 1
		ORDER BY %s %s
		LIMIT ? OFFSET ?
	`, sortClause, order), limit, offset)
	if err != nil {
		http.Error(w, err.Error(), http.StatusInternalServerError)
		return
	}

	w.Header().Set("Content-Type", "application/json")
	json.NewEncoder(w).Encode(map[string]interface{}{
		"my_files":     myFiles,
		"public_files": publicFiles,
		"page":         page,
		"limit":        limit,
	})
}

func queryKMLMetadata(query string, args ...interface{}) ([]KMLMetadata, error) {
	rows, err := db.Query(query, args...)
	if err != nil {
		return nil, err
	}
	defer rows.Close()

	var files []KMLMetadata
	for rows.Next() {
		var m KMLMetadata
		err := rows.Scan(&m.Filename, &m.UserID, &m.DisplayName, &m.Distance, &m.IsPublic, &m.UploadedAt, &m.Votes)
		if err != nil {
			return nil, err
		}
		files = append(files, m)
	}
	return files, nil
}

// HandleKMLPrivacyToggle toggles the privacy setting of a KML file
func HandleKMLPrivacyToggle(w http.ResponseWriter, r *http.Request) {
	if r.Method != http.MethodPost {
		http.Error(w, "Method not allowed", http.StatusMethodNotAllowed)
		return
	}

	userID, ok := getUserID(r.Context())
	if !ok {
		http.Error(w, "Unauthorized", http.StatusUnauthorized)
		return
	}

	var req struct {
		Filename string `json:"filename"`
	}
	if err := json.NewDecoder(r.Body).Decode(&req); err != nil {
		http.Error(w, "Invalid request", http.StatusBadRequest)
		return
	}

	// Toggle privacy in database
	if _, err := db.Exec("UPDATE kml_metadata SET is_public = NOT is_public WHERE filename = ? AND user_id = ?", req.Filename, userID); err != nil {
		http.Error(w, "Failed to update metadata", http.StatusInternalServerError)
		return
	}

	var isPublic bool
	if err := db.QueryRow("SELECT is_public FROM kml_metadata WHERE filename = ? AND user_id = ?", req.Filename, userID).Scan(&isPublic); err != nil {
		http.Error(w, "Failed to fetch updated metadata", http.StatusInternalServerError)
		return
	}

	w.Header().Set("Content-Type", "application/json")
	json.NewEncoder(w).Encode(map[string]interface{}{
		"success":   true,
		"is_public": isPublic,
	})
}

// HandleKMLVote handles voting on KML files (toggle upvote/downvote/none)
func HandleKMLVote(w http.ResponseWriter, r *http.Request) {
	if r.Method != http.MethodPost {
		http.Error(w, "Method not allowed", http.StatusMethodNotAllowed)
		return
	}

	userID, ok := getUserID(r.Context())
	if !ok {
		http.Error(w, "Unauthorized", http.StatusUnauthorized)
		return
	}

	var req struct {
		OwnerID  string `json:"owner_id"`
		Filename string `json:"filename"`
		Vote     int    `json:"vote"` // +1, -1, or 0 to remove vote
	}
	if err := json.NewDecoder(r.Body).Decode(&req); err != nil {
		http.Error(w, "Invalid request", http.StatusBadRequest)
		return
	}

	// Validate vote value
	if req.Vote != -1 && req.Vote != 0 && req.Vote != 1 {
		http.Error(w, "Invalid vote value (must be -1, 0, or 1)", http.StatusBadRequest)
		return
	}

	// Get KML ID
	var kmlID int
	err := db.QueryRow("SELECT id FROM kml_metadata WHERE user_id = ? AND filename = ?", req.OwnerID, req.Filename).Scan(&kmlID)
	if err != nil {
		http.Error(w, "KML not found", http.StatusNotFound)
		return
	}

	// Set the vote
	if err := SetVote(kmlID, userID, req.Vote); err != nil {
		http.Error(w, "Failed to save vote", http.StatusInternalServerError)
		return
	}

	// Calculate new net votes
	netVotes := CalculateNetVotes(kmlID)

	w.Header().Set("Content-Type", "application/json")
	json.NewEncoder(w).Encode(map[string]interface{}{
		"success":   true,
		"net_votes": netVotes,
	})
}

// HandleKMLDelete deletes a KML file with ownership verification
func HandleKMLDelete(w http.ResponseWriter, r *http.Request) {
	if r.Method != http.MethodDelete && r.Method != http.MethodPost {
		http.Error(w, "Method not allowed", http.StatusMethodNotAllowed)
		return
	}

	userID, ok := getUserID(r.Context())
	if !ok {
		http.Error(w, "Unauthorized", http.StatusUnauthorized)
		return
	}

	var req struct {
		Filename string `json:"filename"`
	}
	if err := json.NewDecoder(r.Body).Decode(&req); err != nil {
		http.Error(w, "Invalid request", http.StatusBadRequest)
		return
	}

	// Verify ownership and delete metadata from database
	if _, err := db.Exec("DELETE FROM kml_metadata WHERE filename = ? AND user_id = ?", req.Filename, userID); err != nil {
		http.Error(w, "Failed to delete metadata or file not found", http.StatusInternalServerError)
		return
	}

	// Delete KML file
	kmlPath := fmt.Sprintf("data/users/%s/kml/%s", userID, req.Filename)
	os.Remove(kmlPath)

	w.Header().Set("Content-Type", "application/json")
	json.NewEncoder(w).Encode(map[string]interface{}{
		"success": true,
	})
}

// HandleKMLDownload serves a KML file for downloading/viewing
func HandleKMLDownload(w http.ResponseWriter, r *http.Request) {
	userID, ok := getUserID(r.Context())
	if !ok {
		http.Error(w, "Unauthorized", http.StatusUnauthorized)
		return
	}

	ownerID := r.URL.Query().Get("owner_id")
	filename := r.URL.Query().Get("filename")

	if ownerID == "" || filename == "" {
		http.Error(w, "Missing owner_id or filename", http.StatusBadRequest)
		return
	}

	// Verify permission: ownerID == userID OR file is public
	if ownerID != userID {
		var isPublic bool
		err := db.QueryRow("SELECT is_public FROM kml_metadata WHERE user_id = ? AND filename = ?", ownerID, filename).Scan(&isPublic)
		if err != nil {
			http.Error(w, "File not found", http.StatusNotFound)
			return
		}

		if !isPublic {
			http.Error(w, "Forbidden", http.StatusForbidden)
			return
		}
	}

	kmlPath := fmt.Sprintf("data/users/%s/kml/%s", ownerID, filename)
	data, err := os.ReadFile(kmlPath)
	if err != nil {
		http.Error(w, "File not found", http.StatusNotFound)
		return
	}

	w.Header().Set("Content-Type", "application/vnd.google-earth.kml+xml")
	w.Header().Set("Content-Disposition", fmt.Sprintf("attachment; filename=%s", filename))
	w.Write(data)
}