// Package database - Data loader for external sources
//
// This module handles loading aviation data from external sources at runtime,
// maintaining license compliance by not embedding any AGPL or restricted data
// in the SkyView binary.
package database

import (
	"crypto/tls"
	"database/sql"
	"encoding/csv"
	"fmt"
	"io"
	"net/http"
	"os"
	"strconv"
	"strings"
	"time"
)

// DataLoader handles loading external data sources into the database
type DataLoader struct {
	conn   *sql.DB
	client *http.Client
}

// DataSource represents an external aviation data source
type DataSource struct {
	Name                string `json:"name"`
	License             string `json:"license"`
	URL                 string `json:"url"`
	RequiresConsent     bool   `json:"requires_consent"`
	UserAcceptedLicense bool   `json:"user_accepted_license"`
	Format              string `json:"format"` // "openflights", "ourairports", "csv"
	Version             string `json:"version"`
}

// LoadResult contains the results of a data loading operation
type LoadResult struct {
	Source       string    `json:"source"`
	RecordsTotal int       `json:"records_total"`
	RecordsNew   int       `json:"records_new"`
	RecordsError int       `json:"records_error"`
	Duration     time.Duration `json:"duration"`
	Errors       []string  `json:"errors,omitempty"`
}

// NewDataLoader creates a new data loader with HTTP client
func NewDataLoader(conn *sql.DB) *DataLoader {
	// Check for insecure TLS environment variable
	insecureTLS := os.Getenv("SKYVIEW_INSECURE_TLS") == "1"
	
	transport := &http.Transport{
		MaxIdleConns:       10,
		IdleConnTimeout:    90 * time.Second,
		DisableCompression: false,
	}
	
	// Allow insecure certificates if requested
	if insecureTLS {
		transport.TLSClientConfig = &tls.Config{
			InsecureSkipVerify: true,
		}
	}
	
	return &DataLoader{
		conn: conn,
		client: &http.Client{
			Timeout:   30 * time.Second,
			Transport: transport,
		},
	}
}

// GetAvailableDataSources returns all supported data sources with license info
func GetAvailableDataSources() []DataSource {
	return []DataSource{
		{
			Name:            "OpenFlights Airlines",
			License:         "AGPL-3.0",
			URL:             "https://raw.githubusercontent.com/jpatokal/openflights/master/data/airlines.dat",
			RequiresConsent: false, // Runtime data consumption doesn't require explicit consent
			Format:          "openflights",
			Version:         "latest",
		},
		{
			Name:            "OpenFlights Airports",
			License:         "AGPL-3.0", 
			URL:             "https://raw.githubusercontent.com/jpatokal/openflights/master/data/airports.dat",
			RequiresConsent: false, // Runtime data consumption doesn't require explicit consent
			Format:          "openflights",
			Version:         "latest",
		},
		{
			Name:            "OurAirports",
			License:         "Public Domain",
			URL:             "https://raw.githubusercontent.com/davidmegginson/ourairports-data/main/airports.csv",
			RequiresConsent: false,
			Format:          "ourairports",
			Version:         "latest",
		},
	}
}

// LoadDataSource downloads and imports data from an external source
func (dl *DataLoader) LoadDataSource(source DataSource) (*LoadResult, error) {
	result := &LoadResult{
		Source: source.Name,
	}
	startTime := time.Now()
	defer func() {
		result.Duration = time.Since(startTime)
	}()
	
	// Check license acceptance if required
	if source.RequiresConsent && !source.UserAcceptedLicense {
		return nil, fmt.Errorf("user has not accepted license for source: %s (%s)", source.Name, source.License)
	}
	
	// Download data
	resp, err := dl.client.Get(source.URL)
	if err != nil {
		return nil, fmt.Errorf("failed to download data from %s: %v", source.URL, err)
	}
	defer resp.Body.Close()
	
	if resp.StatusCode != http.StatusOK {
		return nil, fmt.Errorf("HTTP error downloading data: %s", resp.Status)
	}
	
	// Parse and load data based on format
	switch source.Format {
	case "openflights":
		if strings.Contains(source.Name, "Airlines") {
			return dl.loadOpenFlightsAirlines(resp.Body, source, result)
		} else if strings.Contains(source.Name, "Airports") {
			return dl.loadOpenFlightsAirports(resp.Body, source, result)
		}
		return nil, fmt.Errorf("unknown OpenFlights data type: %s", source.Name)
		
	case "ourairports":
		return dl.loadOurAirports(resp.Body, source, result)
		
	default:
		return nil, fmt.Errorf("unsupported data format: %s", source.Format)
	}
}

// loadOpenFlightsAirlines loads airline data in OpenFlights format
func (dl *DataLoader) loadOpenFlightsAirlines(reader io.Reader, source DataSource, result *LoadResult) (*LoadResult, error) {
	tx, err := dl.conn.Begin()
	if err != nil {
		return nil, fmt.Errorf("failed to begin transaction: %v", err)
	}
	defer tx.Rollback()
	
	// Record data source
	if err := dl.recordDataSource(tx, source); err != nil {
		return nil, err
	}
	
	// Clear existing data from this source
	_, err = tx.Exec(`DELETE FROM airlines WHERE data_source = ?`, source.Name)
	if err != nil {
		return nil, fmt.Errorf("failed to clear existing airline data: %v", err)
	}
	
	csvReader := csv.NewReader(reader)
	csvReader.FieldsPerRecord = -1 // Variable number of fields
	
	insertStmt, err := tx.Prepare(`
		INSERT OR REPLACE INTO airlines (id, name, alias, iata_code, icao_code, callsign, country, active, data_source)
		VALUES (?, ?, ?, ?, ?, ?, ?, ?, ?)
	`)
	if err != nil {
		return nil, fmt.Errorf("failed to prepare insert statement: %v", err)
	}
	defer insertStmt.Close()
	
	for {
		record, err := csvReader.Read()
		if err == io.EOF {
			break
		}
		if err != nil {
			result.RecordsError++
			result.Errors = append(result.Errors, fmt.Sprintf("CSV parse error: %v", err))
			continue
		}
		
		if len(record) < 7 {
			result.RecordsError++
			result.Errors = append(result.Errors, "insufficient fields in record")
			continue
		}
		
		result.RecordsTotal++
		
		// Parse OpenFlights airline format:
		// ID, Name, Alias, IATA, ICAO, Callsign, Country, Active
		id, _ := strconv.Atoi(record[0])
		name := strings.Trim(record[1], `"`)
		alias := strings.Trim(record[2], `"`)
		iata := strings.Trim(record[3], `"`)
		icao := strings.Trim(record[4], `"`)
		callsign := strings.Trim(record[5], `"`)
		country := strings.Trim(record[6], `"`)
		active := len(record) > 7 && strings.Trim(record[7], `"`) == "Y"
		
		// Convert \N to empty strings
		if alias == "\\N" { alias = "" }
		if iata == "\\N" { iata = "" }
		if icao == "\\N" { icao = "" }
		if callsign == "\\N" { callsign = "" }
		
		_, err = insertStmt.Exec(id, name, alias, iata, icao, callsign, country, active, source.Name)
		if err != nil {
			result.RecordsError++
			result.Errors = append(result.Errors, fmt.Sprintf("insert error for airline %s: %v", name, err))
			continue
		}
		
		result.RecordsNew++
	}
	
	// Update record count
	_, err = tx.Exec(`UPDATE data_sources SET record_count = ? WHERE name = ?`, result.RecordsNew, source.Name)
	if err != nil {
		return nil, fmt.Errorf("failed to update record count: %v", err)
	}
	
	return result, tx.Commit()
}

// loadOpenFlightsAirports loads airport data in OpenFlights format
func (dl *DataLoader) loadOpenFlightsAirports(reader io.Reader, source DataSource, result *LoadResult) (*LoadResult, error) {
	tx, err := dl.conn.Begin()
	if err != nil {
		return nil, fmt.Errorf("failed to begin transaction: %v", err)
	}
	defer tx.Rollback()
	
	// Record data source
	if err := dl.recordDataSource(tx, source); err != nil {
		return nil, err
	}
	
	// Clear existing data from this source
	_, err = tx.Exec(`DELETE FROM airports WHERE data_source = ?`, source.Name)
	if err != nil {
		return nil, fmt.Errorf("failed to clear existing airport data: %v", err)
	}
	
	csvReader := csv.NewReader(reader)
	csvReader.FieldsPerRecord = -1
	
	insertStmt, err := tx.Prepare(`
		INSERT OR REPLACE INTO airports (id, name, city, country, iata_code, icao_code, latitude, longitude, 
							  elevation_ft, timezone_offset, dst_type, timezone, data_source)
		VALUES (?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?)
	`)
	if err != nil {
		return nil, fmt.Errorf("failed to prepare insert statement: %v", err)
	}
	defer insertStmt.Close()
	
	for {
		record, err := csvReader.Read()
		if err == io.EOF {
			break
		}
		if err != nil {
			result.RecordsError++
			result.Errors = append(result.Errors, fmt.Sprintf("CSV parse error: %v", err))
			continue
		}
		
		if len(record) < 12 {
			result.RecordsError++
			result.Errors = append(result.Errors, "insufficient fields in airport record")
			continue
		}
		
		result.RecordsTotal++
		
		// Parse OpenFlights airport format
		id, _ := strconv.Atoi(record[0])
		name := strings.Trim(record[1], `"`)
		city := strings.Trim(record[2], `"`)
		country := strings.Trim(record[3], `"`)
		iata := strings.Trim(record[4], `"`)
		icao := strings.Trim(record[5], `"`)
		lat, _ := strconv.ParseFloat(record[6], 64)
		lon, _ := strconv.ParseFloat(record[7], 64)
		alt, _ := strconv.Atoi(record[8])
		tzOffset, _ := strconv.ParseFloat(record[9], 64)
		dst := strings.Trim(record[10], `"`)
		timezone := strings.Trim(record[11], `"`)
		
		// Convert \N to empty strings
		if iata == "\\N" { iata = "" }
		if icao == "\\N" { icao = "" }
		if dst == "\\N" { dst = "" }
		if timezone == "\\N" { timezone = "" }
		
		_, err = insertStmt.Exec(id, name, city, country, iata, icao, lat, lon, alt, tzOffset, dst, timezone, source.Name)
		if err != nil {
			result.RecordsError++
			result.Errors = append(result.Errors, fmt.Sprintf("insert error for airport %s: %v", name, err))
			continue
		}
		
		result.RecordsNew++
	}
	
	// Update record count
	_, err = tx.Exec(`UPDATE data_sources SET record_count = ? WHERE name = ?`, result.RecordsNew, source.Name)
	if err != nil {
		return nil, fmt.Errorf("failed to update record count: %v", err)
	}
	
	return result, tx.Commit()
}

// loadOurAirports loads airport data in OurAirports CSV format
func (dl *DataLoader) loadOurAirports(reader io.Reader, source DataSource, result *LoadResult) (*LoadResult, error) {
	// Start database transaction
	tx, err := dl.conn.Begin()
	if err != nil {
		return nil, fmt.Errorf("failed to begin transaction: %v", err)
	}
	defer tx.Rollback()
	
	csvReader := csv.NewReader(reader)
	
	// Read header row
	headers, err := csvReader.Read()
	if err != nil {
		result.RecordsError = 1
		result.Errors = []string{fmt.Sprintf("Failed to read CSV header: %v", err)}
		return result, err
	}
	
	// Create header index map for easier field access
	headerIndex := make(map[string]int)
	for i, header := range headers {
		headerIndex[strings.TrimSpace(header)] = i
	}
	
	// Prepare statement for airports
	stmt, err := tx.Prepare(`
		INSERT OR REPLACE INTO airports (
			source_id, name, ident, type, icao_code, iata_code, 
			latitude, longitude, elevation_ft, country_code, 
			municipality, continent, scheduled_service, 
			home_link, wikipedia_link, keywords, data_source
		) VALUES (?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?)
	`)
	if err != nil {
		result.RecordsError = 1
		result.Errors = []string{fmt.Sprintf("Failed to prepare statement: %v", err)}
		return result, err
	}
	defer stmt.Close()
	
	// Process each row
	for {
		record, err := csvReader.Read()
		if err == io.EOF {
			break
		}
		if err != nil {
			result.RecordsError++
			result.Errors = append(result.Errors, fmt.Sprintf("CSV read error: %v", err))
			continue
		}
		
		// Skip rows with insufficient fields
		if len(record) < len(headerIndex) {
			result.RecordsError++
			continue
		}
		
		// Extract fields using header index
		sourceID := getFieldByHeader(record, headerIndex, "id")
		ident := getFieldByHeader(record, headerIndex, "ident")
		name := getFieldByHeader(record, headerIndex, "name")
		icaoCode := getFieldByHeader(record, headerIndex, "icao_code")
		iataCode := getFieldByHeader(record, headerIndex, "iata_code")
		airportType := getFieldByHeader(record, headerIndex, "type")
		countryCode := getFieldByHeader(record, headerIndex, "iso_country")
		municipality := getFieldByHeader(record, headerIndex, "municipality")
		continent := getFieldByHeader(record, headerIndex, "continent")
		homeLink := getFieldByHeader(record, headerIndex, "home_link")
		wikipediaLink := getFieldByHeader(record, headerIndex, "wikipedia_link")
		keywords := getFieldByHeader(record, headerIndex, "keywords")
		
		// Parse coordinates
		var latitude, longitude float64
		if latStr := getFieldByHeader(record, headerIndex, "latitude_deg"); latStr != "" {
			if lat, err := strconv.ParseFloat(latStr, 64); err == nil {
				latitude = lat
			}
		}
		if lngStr := getFieldByHeader(record, headerIndex, "longitude_deg"); lngStr != "" {
			if lng, err := strconv.ParseFloat(lngStr, 64); err == nil {
				longitude = lng
			}
		}
		
		// Parse elevation
		var elevation int
		if elevStr := getFieldByHeader(record, headerIndex, "elevation_ft"); elevStr != "" {
			if elev, err := strconv.Atoi(elevStr); err == nil {
				elevation = elev
			}
		}
		
		// Parse scheduled service
		scheduledService := getFieldByHeader(record, headerIndex, "scheduled_service") == "yes"
		
		// Insert airport record
		_, err = stmt.Exec(
			sourceID, name, ident, airportType, icaoCode, iataCode,
			latitude, longitude, elevation, countryCode, municipality, continent,
			scheduledService, homeLink, wikipediaLink, keywords, source.Name,
		)
		if err != nil {
			result.RecordsError++
			result.Errors = append(result.Errors, fmt.Sprintf("Insert error for %s: %v", ident, err))
		} else {
			result.RecordsNew++
		}
	}
	
	// Update data source tracking
	_, err = tx.Exec(`
		INSERT OR REPLACE INTO data_sources (name, license, url, imported_at, record_count, user_accepted_license)
		VALUES (?, ?, ?, CURRENT_TIMESTAMP, ?, ?)
	`, source.Name, source.License, source.URL, result.RecordsNew, source.UserAcceptedLicense)
	if err != nil {
		return result, fmt.Errorf("failed to update data source tracking: %v", err)
	}
	
	return result, tx.Commit()
}

// getFieldByHeader safely gets a field value by header name
func getFieldByHeader(record []string, headerIndex map[string]int, fieldName string) string {
	if idx, exists := headerIndex[fieldName]; exists && idx < len(record) {
		return strings.TrimSpace(record[idx])
	}
	return ""
}

// GetLoadedDataSources returns all data sources that have been imported
func (dl *DataLoader) GetLoadedDataSources() ([]DataSource, error) {
	query := `
		SELECT name, license, url, COALESCE(version, 'latest'), user_accepted_license
		FROM data_sources
		ORDER BY name
	`
	
	rows, err := dl.conn.Query(query)
	if err != nil {
		return nil, err
	}
	defer rows.Close()
	
	var sources []DataSource
	for rows.Next() {
		var source DataSource
		err := rows.Scan(
			&source.Name,
			&source.License,
			&source.URL,
			&source.Version,
			&source.UserAcceptedLicense,
		)
		if err != nil {
			return nil, err
		}
		sources = append(sources, source)
	}
	
	return sources, rows.Err()
}

// recordDataSource records information about the data source being imported
func (dl *DataLoader) recordDataSource(tx *sql.Tx, source DataSource) error {
	_, err := tx.Exec(`
		INSERT OR REPLACE INTO data_sources 
		(name, license, url, version, user_accepted_license) 
		VALUES (?, ?, ?, ?, ?)
	`, source.Name, source.License, source.URL, source.Version, source.UserAcceptedLicense)
	
	return err
}


// ClearDataSource removes all data from a specific source
func (dl *DataLoader) ClearDataSource(sourceName string) error {
	tx, err := dl.conn.Begin()
	if err != nil {
		return fmt.Errorf("failed to begin transaction: %v", err)
	}
	defer tx.Rollback()
	
	// Clear from all tables
	_, err = tx.Exec(`DELETE FROM airlines WHERE data_source = ?`, sourceName)
	if err != nil {
		return fmt.Errorf("failed to clear airlines: %v", err)
	}
	
	_, err = tx.Exec(`DELETE FROM airports WHERE data_source = ?`, sourceName)
	if err != nil {
		return fmt.Errorf("failed to clear airports: %v", err)
	}
	
	_, err = tx.Exec(`DELETE FROM data_sources WHERE name = ?`, sourceName)
	if err != nil {
		return fmt.Errorf("failed to clear data source record: %v", err)
	}
	
	return tx.Commit()
}