skyview/internal/database/api_client.go

package database

import (
	"context"
	"encoding/json"
	"fmt"
	"io"
	"net/http"
	"sync"
	"time"
)

type ExternalAPIClient struct {
	httpClient *http.Client
	mutex      sync.RWMutex
	
	// Configuration
	timeout    time.Duration
	maxRetries int
	userAgent  string
	
	// Rate limiting
	lastRequest time.Time
	minInterval time.Duration
}

type APIClientConfig struct {
	Timeout     time.Duration
	MaxRetries  int
	UserAgent   string
	MinInterval time.Duration // Minimum interval between requests
}

type OpenSkyFlightInfo struct {
	ICAO           string    `json:"icao"`
	Callsign       string    `json:"callsign"`
	Origin         string    `json:"origin"`
	Destination    string    `json:"destination"`
	FirstSeen      time.Time `json:"first_seen"`
	LastSeen       time.Time `json:"last_seen"`
	AircraftType   string    `json:"aircraft_type"`
	Registration   string    `json:"registration"`
	FlightNumber   string    `json:"flight_number"`
	Airline        string    `json:"airline"`
}

type APIError struct {
	Operation   string
	StatusCode  int
	Message     string
	Retryable   bool
	RetryAfter  time.Duration
}

func (e *APIError) Error() string {
	return fmt.Sprintf("API error in %s: %s (status: %d, retryable: %v)", 
		e.Operation, e.Message, e.StatusCode, e.Retryable)
}

func NewExternalAPIClient(config APIClientConfig) *ExternalAPIClient {
	if config.Timeout == 0 {
		config.Timeout = 10 * time.Second
	}
	if config.MaxRetries == 0 {
		config.MaxRetries = 3
	}
	if config.UserAgent == "" {
		config.UserAgent = "SkyView-ADSB/1.0 (https://github.com/user/skyview)"
	}
	if config.MinInterval == 0 {
		config.MinInterval = 1 * time.Second // Default rate limit
	}
	
	return &ExternalAPIClient{
		httpClient: &http.Client{
			Timeout: config.Timeout,
		},
		timeout:     config.Timeout,
		maxRetries:  config.MaxRetries,
		userAgent:   config.UserAgent,
		minInterval: config.MinInterval,
	}
}

func (c *ExternalAPIClient) enforceRateLimit() {
	c.mutex.Lock()
	defer c.mutex.Unlock()
	
	elapsed := time.Since(c.lastRequest)
	if elapsed < c.minInterval {
		time.Sleep(c.minInterval - elapsed)
	}
	c.lastRequest = time.Now()
}

func (c *ExternalAPIClient) makeRequest(ctx context.Context, url string) (*http.Response, error) {
	c.enforceRateLimit()
	
	req, err := http.NewRequestWithContext(ctx, "GET", url, nil)
	if err != nil {
		return nil, err
	}
	
	req.Header.Set("User-Agent", c.userAgent)
	req.Header.Set("Accept", "application/json")
	
	var resp *http.Response
	var lastErr error
	
	for attempt := 0; attempt <= c.maxRetries; attempt++ {
		if attempt > 0 {
			// Exponential backoff
			backoff := time.Duration(1<<uint(attempt-1)) * time.Second
			select {
			case <-ctx.Done():
				return nil, ctx.Err()
			case <-time.After(backoff):
			}
		}
		
		resp, lastErr = c.httpClient.Do(req)
		if lastErr != nil {
			continue
		}
		
		// Check for retryable status codes
		if resp.StatusCode >= 500 || resp.StatusCode == 429 {
			resp.Body.Close()
			
			// Handle rate limiting
			if resp.StatusCode == 429 {
				retryAfter := parseRetryAfter(resp.Header.Get("Retry-After"))
				if retryAfter > 0 {
					select {
					case <-ctx.Done():
						return nil, ctx.Err()
					case <-time.After(retryAfter):
					}
				}
			}
			continue
		}
		
		// Success or non-retryable error
		break
	}
	
	if lastErr != nil {
		return nil, lastErr
	}
	
	return resp, nil
}

func (c *ExternalAPIClient) GetFlightInfoFromOpenSky(ctx context.Context, icao string) (*OpenSkyFlightInfo, error) {
	if icao == "" {
		return nil, fmt.Errorf("empty ICAO code")
	}
	
	// OpenSky Network API endpoint for flight information
	apiURL := fmt.Sprintf("https://opensky-network.org/api/flights/aircraft?icao24=%s&begin=%d&end=%d",
		icao,
		time.Now().Add(-24*time.Hour).Unix(),
		time.Now().Unix(),
	)
	
	resp, err := c.makeRequest(ctx, apiURL)
	if err != nil {
		return nil, &APIError{
			Operation: "opensky_flight_info",
			Message:   err.Error(),
			Retryable: true,
		}
	}
	defer resp.Body.Close()
	
	if resp.StatusCode != http.StatusOK {
		body, _ := io.ReadAll(resp.Body)
		return nil, &APIError{
			Operation:  "opensky_flight_info",
			StatusCode: resp.StatusCode,
			Message:    string(body),
			Retryable:  resp.StatusCode >= 500 || resp.StatusCode == 429,
		}
	}
	
	var flights [][]interface{}
	decoder := json.NewDecoder(resp.Body)
	if err := decoder.Decode(&flights); err != nil {
		return nil, &APIError{
			Operation: "opensky_parse_response",
			Message:   err.Error(),
			Retryable: false,
		}
	}
	
	if len(flights) == 0 {
		return nil, nil // No flight information available
	}
	
	// Parse the most recent flight
	flight := flights[0]
	if len(flight) < 10 {
		return nil, &APIError{
			Operation: "opensky_invalid_response",
			Message:   "invalid flight data format",
			Retryable: false,
		}
	}
	
	info := &OpenSkyFlightInfo{
		ICAO: icao,
	}
	
	// Parse fields based on OpenSky API documentation
	if callsign, ok := flight[1].(string); ok {
		info.Callsign = callsign
	}
	if firstSeen, ok := flight[2].(float64); ok {
		info.FirstSeen = time.Unix(int64(firstSeen), 0)
	}
	if lastSeen, ok := flight[3].(float64); ok {
		info.LastSeen = time.Unix(int64(lastSeen), 0)
	}
	if origin, ok := flight[4].(string); ok {
		info.Origin = origin
	}
	if destination, ok := flight[5].(string); ok {
		info.Destination = destination
	}
	
	return info, nil
}

func (c *ExternalAPIClient) GetAircraftInfoFromOpenSky(ctx context.Context, icao string) (map[string]interface{}, error) {
	if icao == "" {
		return nil, fmt.Errorf("empty ICAO code")
	}
	
	// OpenSky Network metadata API
	apiURL := fmt.Sprintf("https://opensky-network.org/api/metadata/aircraft/icao/%s", icao)
	
	resp, err := c.makeRequest(ctx, apiURL)
	if err != nil {
		return nil, &APIError{
			Operation: "opensky_aircraft_info",
			Message:   err.Error(),
			Retryable: true,
		}
	}
	defer resp.Body.Close()
	
	if resp.StatusCode == http.StatusNotFound {
		return nil, nil // Aircraft not found
	}
	
	if resp.StatusCode != http.StatusOK {
		body, _ := io.ReadAll(resp.Body)
		return nil, &APIError{
			Operation:  "opensky_aircraft_info",
			StatusCode: resp.StatusCode,
			Message:    string(body),
			Retryable:  resp.StatusCode >= 500 || resp.StatusCode == 429,
		}
	}
	
	var aircraft map[string]interface{}
	decoder := json.NewDecoder(resp.Body)
	if err := decoder.Decode(&aircraft); err != nil {
		return nil, &APIError{
			Operation: "opensky_parse_aircraft",
			Message:   err.Error(),
			Retryable: false,
		}
	}
	
	return aircraft, nil
}

func (c *ExternalAPIClient) EnhanceCallsignWithExternalData(ctx context.Context, callsign, icao string) (map[string]interface{}, error) {
	enhancement := make(map[string]interface{})
	enhancement["callsign"] = callsign
	enhancement["icao"] = icao
	enhancement["enhanced"] = false
	
	// Try to get flight information from OpenSky
	if flightInfo, err := c.GetFlightInfoFromOpenSky(ctx, icao); err == nil && flightInfo != nil {
		enhancement["flight_info"] = map[string]interface{}{
			"origin":        flightInfo.Origin,
			"destination":   flightInfo.Destination,
			"first_seen":    flightInfo.FirstSeen,
			"last_seen":     flightInfo.LastSeen,
			"flight_number": flightInfo.FlightNumber,
			"airline":       flightInfo.Airline,
		}
		enhancement["enhanced"] = true
	}
	
	// Try to get aircraft metadata
	if aircraftInfo, err := c.GetAircraftInfoFromOpenSky(ctx, icao); err == nil && aircraftInfo != nil {
		enhancement["aircraft_info"] = aircraftInfo
		enhancement["enhanced"] = true
	}
	
	return enhancement, nil
}

func (c *ExternalAPIClient) BatchEnhanceCallsigns(ctx context.Context, callsigns map[string]string) (map[string]map[string]interface{}, error) {
	results := make(map[string]map[string]interface{})
	
	for callsign, icao := range callsigns {
		select {
		case <-ctx.Done():
			return results, ctx.Err()
		default:
		}
		
		enhanced, err := c.EnhanceCallsignWithExternalData(ctx, callsign, icao)
		if err != nil {
			// Log error but continue with other callsigns
			fmt.Printf("Warning: failed to enhance callsign %s (ICAO: %s): %v\n", callsign, icao, err)
			continue
		}
		
		results[callsign] = enhanced
	}
	
	return results, nil
}

func (c *ExternalAPIClient) TestConnection(ctx context.Context) error {
	// Test with a simple API call
	testURL := "https://opensky-network.org/api/states?time=0&lamin=0&lomin=0&lamax=1&lomax=1"
	
	resp, err := c.makeRequest(ctx, testURL)
	if err != nil {
		return fmt.Errorf("connection test failed: %w", err)
	}
	defer resp.Body.Close()
	
	if resp.StatusCode != http.StatusOK {
		return fmt.Errorf("connection test returned status %d", resp.StatusCode)
	}
	
	return nil
}

func parseRetryAfter(header string) time.Duration {
	if header == "" {
		return 0
	}
	
	// Try parsing as seconds
	if seconds, err := time.ParseDuration(header + "s"); err == nil {
		return seconds
	}
	
	// Try parsing as HTTP date
	if t, err := http.ParseTime(header); err == nil {
		return time.Until(t)
	}
	
	return 0
}

// HealthCheck provides information about the client's health
func (c *ExternalAPIClient) HealthCheck(ctx context.Context) map[string]interface{} {
	health := make(map[string]interface{})
	
	// Test connection
	if err := c.TestConnection(ctx); err != nil {
		health["status"] = "unhealthy"
		health["error"] = err.Error()
	} else {
		health["status"] = "healthy"
	}
	
	// Add configuration info
	health["timeout"] = c.timeout.String()
	health["max_retries"] = c.maxRetries
	health["min_interval"] = c.minInterval.String()
	health["user_agent"] = c.userAgent
	
	c.mutex.RLock()
	health["last_request"] = c.lastRequest
	c.mutex.RUnlock()
	
	return health
}