// Package database provides persistent storage for aircraft data and callsign enhancement
// using SQLite with versioned schema migrations and comprehensive error handling.
//
// The database system supports:
//   - Aircraft position history with configurable retention
//   - Embedded OpenFlights airline and airport data
//   - External API result caching with TTL
//   - Schema migrations with rollback support
//   - Privacy mode for complete offline operation
package database

import (
	"database/sql"
	"fmt"
	"time"

	_ "github.com/mattn/go-sqlite3" // SQLite driver
)

// Database represents the main database connection and operations
type Database struct {
	conn      *sql.DB
	config    *Config
	migrator  *Migrator
	callsign  *CallsignManager
	history   *HistoryManager
}

// Config holds database configuration options
type Config struct {
	// Database file path (auto-resolved if empty)
	Path string `json:"path"`
	
	// Data retention settings
	MaxHistoryDays int  `json:"max_history_days"` // 0 = unlimited
	BackupOnUpgrade bool `json:"backup_on_upgrade"`
	
	// Connection settings
	MaxOpenConns    int           `json:"max_open_conns"`    // Default: 10
	MaxIdleConns    int           `json:"max_idle_conns"`    // Default: 5
	ConnMaxLifetime time.Duration `json:"conn_max_lifetime"` // Default: 1 hour
	
	// Maintenance settings
	VacuumInterval time.Duration `json:"vacuum_interval"` // Default: 24 hours
	CleanupInterval time.Duration `json:"cleanup_interval"` // Default: 1 hour
	
	// Compression settings
	EnableCompression bool   `json:"enable_compression"` // Enable automatic compression
	CompressionLevel  int    `json:"compression_level"`  // Compression level (1-9, default: 6)  
	PageSize         int    `json:"page_size"`          // SQLite page size (default: 4096)
}

// AircraftHistoryRecord represents a stored aircraft position update
type AircraftHistoryRecord struct {
	ID             int64     `json:"id"`
	ICAO           string    `json:"icao"`
	Timestamp      time.Time `json:"timestamp"`
	Latitude       *float64  `json:"latitude,omitempty"`
	Longitude      *float64  `json:"longitude,omitempty"`
	Altitude       *int      `json:"altitude,omitempty"`
	Speed          *int      `json:"speed,omitempty"`
	Track          *int      `json:"track,omitempty"`
	VerticalRate   *int      `json:"vertical_rate,omitempty"`
	Squawk         *string   `json:"squawk,omitempty"`
	Callsign       *string   `json:"callsign,omitempty"`
	SourceID       string    `json:"source_id"`
	SignalStrength *float64  `json:"signal_strength,omitempty"`
}

// CallsignInfo represents enriched callsign information
type CallsignInfo struct {
	OriginalCallsign string    `json:"original_callsign"`
	AirlineCode      string    `json:"airline_code"`
	FlightNumber     string    `json:"flight_number"`
	AirlineName      string    `json:"airline_name"`
	AirlineCountry   string    `json:"airline_country"`
	DisplayName      string    `json:"display_name"`
	IsValid          bool      `json:"is_valid"`
	LastUpdated      time.Time `json:"last_updated"`
}

// AirlineRecord represents embedded airline data from OpenFlights
type AirlineRecord struct {
	ID       int    `json:"id"`
	Name     string `json:"name"`
	Alias    string `json:"alias"`
	IATACode string `json:"iata_code"`
	ICAOCode string `json:"icao_code"`
	Callsign string `json:"callsign"`
	Country  string `json:"country"`
	Active   bool   `json:"active"`
}

// AirportRecord represents embedded airport data from OpenFlights
type AirportRecord struct {
	ID            int     `json:"id"`
	Name          string  `json:"name"`
	City          string  `json:"city"`
	Country       string  `json:"country"`
	IATA          string  `json:"iata"`
	ICAO          string  `json:"icao"`
	Latitude      float64 `json:"latitude"`
	Longitude     float64 `json:"longitude"`
	Altitude      int     `json:"altitude"`
	TimezoneOffset float64 `json:"timezone_offset"`
	DST           string  `json:"dst"`
	Timezone      string  `json:"timezone"`
}

// DatabaseError represents database operation errors
type DatabaseError struct {
	Operation string
	Err       error
	Query     string
	Retryable bool
}

func (e *DatabaseError) Error() string {
	if e.Query != "" {
		return fmt.Sprintf("database %s error: %v (query: %s)", e.Operation, e.Err, e.Query)
	}
	return fmt.Sprintf("database %s error: %v", e.Operation, e.Err)
}

func (e *DatabaseError) Unwrap() error {
	return e.Err
}

// NewDatabase creates a new database connection with the given configuration
func NewDatabase(config *Config) (*Database, error) {
	if config == nil {
		config = DefaultConfig()
	}
	
	// Resolve database path
	dbPath, err := ResolveDatabasePath(config.Path)
	if err != nil {
		return nil, &DatabaseError{
			Operation: "path_resolution",
			Err:       err,
			Retryable: false,
		}
	}
	config.Path = dbPath
	
	// Open database connection
	conn, err := sql.Open("sqlite3", buildConnectionString(dbPath))
	if err != nil {
		return nil, &DatabaseError{
			Operation: "connect",
			Err:       err,
			Retryable: true,
		}
	}
	
	// Configure connection pool
	conn.SetMaxOpenConns(config.MaxOpenConns)
	conn.SetMaxIdleConns(config.MaxIdleConns)
	conn.SetConnMaxLifetime(config.ConnMaxLifetime)
	
	// Test connection
	if err := conn.Ping(); err != nil {
		conn.Close()
		return nil, &DatabaseError{
			Operation: "ping",
			Err:       err,
			Retryable: true,
		}
	}
	
	db := &Database{
		conn:   conn,
		config: config,
	}
	
	// Initialize components
	db.migrator = NewMigrator(conn)
	db.callsign = NewCallsignManager(conn)
	db.history = NewHistoryManager(conn, config.MaxHistoryDays)
	
	return db, nil
}

// Initialize runs database migrations and sets up embedded data
func (db *Database) Initialize() error {
	// Run schema migrations
	if err := db.migrator.MigrateToLatest(); err != nil {
		return &DatabaseError{
			Operation: "migration",
			Err:       err,
			Retryable: false,
		}
	}
	
	// Load embedded OpenFlights data if not already loaded
	if err := db.callsign.LoadEmbeddedData(); err != nil {
		return &DatabaseError{
			Operation: "load_embedded_data",
			Err:       err,
			Retryable: false,
		}
	}
	
	return nil
}

// GetConfig returns the database configuration
func (db *Database) GetConfig() *Config {
	return db.config
}

// GetConnection returns the underlying database connection
func (db *Database) GetConnection() *sql.DB {
	return db.conn
}

// GetHistoryManager returns the history manager
func (db *Database) GetHistoryManager() *HistoryManager {
	return db.history
}

// GetCallsignManager returns the callsign manager
func (db *Database) GetCallsignManager() *CallsignManager {
	return db.callsign
}

// Close closes the database connection and stops background tasks
func (db *Database) Close() error {
	if db.conn != nil {
		return db.conn.Close()
	}
	return nil
}

// Health returns the database health status
func (db *Database) Health() error {
	if db.conn == nil {
		return fmt.Errorf("database connection not initialized")
	}
	return db.conn.Ping()
}


// DefaultConfig returns the default database configuration
func DefaultConfig() *Config {
	return &Config{
		Path:            "", // Auto-resolved
		MaxHistoryDays:  7,
		BackupOnUpgrade: true,
		MaxOpenConns:    10,
		MaxIdleConns:    5,
		ConnMaxLifetime: time.Hour,
		VacuumInterval:  24 * time.Hour,
		CleanupInterval: time.Hour,
	}
}

// buildConnectionString creates SQLite connection string with optimizations
func buildConnectionString(path string) string {
	return fmt.Sprintf("%s?_journal_mode=WAL&_synchronous=NORMAL&_cache_size=-64000&_temp_store=MEMORY&_foreign_keys=ON", path)
}