// Package database provides SQLite storage for BGP routing data including ASNs, prefixes, announcements and peerings.
package database

import (
	"database/sql"
	_ "embed"
	"fmt"
	"log/slog"
	"os"
	"path/filepath"
	"runtime"
	"time"

	"git.eeqj.de/sneak/routewatch/pkg/asinfo"
	"github.com/google/uuid"
	_ "github.com/mattn/go-sqlite3" // CGO SQLite driver
)

//go:embed schema.sql
var dbSchema string

const dirPermissions = 0750 // rwxr-x---

// Database manages the SQLite database connection and operations.
type Database struct {
	db     *sql.DB
	logger *slog.Logger
	path   string
}

// Config holds database configuration
type Config struct {
	Path string
}

// getDefaultDatabasePath returns the appropriate database path for the OS
func getDefaultDatabasePath() string {
	const dbFilename = "db.sqlite"

	switch runtime.GOOS {
	case "darwin":
		// macOS: ~/Library/Application Support/berlin.sneak.app.routewatch/db.sqlite
		home, err := os.UserHomeDir()
		if err != nil {
			return dbFilename
		}
		appSupport := filepath.Join(home, "Library", "Application Support", "berlin.sneak.app.routewatch")
		if err := os.MkdirAll(appSupport, dirPermissions); err != nil {
			return dbFilename
		}

		return filepath.Join(appSupport, dbFilename)
	default:
		// Linux and others: /var/lib/routewatch/db.sqlite
		dbDir := "/var/lib/routewatch"
		if err := os.MkdirAll(dbDir, dirPermissions); err != nil {
			// Fall back to user's home directory if can't create system directory
			home, err := os.UserHomeDir()
			if err != nil {
				return dbFilename
			}
			userDir := filepath.Join(home, ".local", "share", "routewatch")
			if err := os.MkdirAll(userDir, dirPermissions); err != nil {
				return dbFilename
			}

			return filepath.Join(userDir, dbFilename)
		}

		return filepath.Join(dbDir, dbFilename)
	}
}

// NewConfig provides default database configuration
func NewConfig() Config {
	return Config{
		Path: getDefaultDatabasePath(),
	}
}

// New creates a new database connection and initializes the schema.
func New(logger *slog.Logger) (*Database, error) {
	config := NewConfig()

	return NewWithConfig(config, logger)
}

// NewWithConfig creates a new database connection with custom configuration
func NewWithConfig(config Config, logger *slog.Logger) (*Database, error) {
	// Log database path
	logger.Info("Opening database", "path", config.Path)

	// Ensure directory exists
	dir := filepath.Dir(config.Path)
	if err := os.MkdirAll(dir, dirPermissions); err != nil {
		return nil, fmt.Errorf("failed to create database directory: %w", err)
	}

	// Add connection parameters for go-sqlite3
	// Enable WAL mode and other performance optimizations
	dsn := fmt.Sprintf("file:%s?_busy_timeout=5000&_journal_mode=WAL&_synchronous=NORMAL&cache=shared", config.Path)
	db, err := sql.Open("sqlite3", dsn)
	if err != nil {
		return nil, fmt.Errorf("failed to open database: %w", err)
	}

	if err := db.Ping(); err != nil {
		return nil, fmt.Errorf("failed to ping database: %w", err)
	}

	// Set connection pool parameters
	db.SetMaxOpenConns(1) // Force serialization since SQLite doesn't handle true concurrency well
	db.SetMaxIdleConns(1)
	db.SetConnMaxLifetime(0)

	database := &Database{db: db, logger: logger, path: config.Path}

	if err := database.Initialize(); err != nil {
		return nil, fmt.Errorf("failed to initialize database: %w", err)
	}

	return database, nil
}

// Initialize creates the database schema if it doesn't exist.
func (d *Database) Initialize() error {
	// Set SQLite pragmas for better performance
	pragmas := []string{
		"PRAGMA journal_mode=WAL",        // Already set in connection string
		"PRAGMA synchronous=NORMAL",      // Faster than FULL, still safe
		"PRAGMA cache_size=-524288",      // 512MB cache (negative = KB)
		"PRAGMA temp_store=MEMORY",       // Use memory for temp tables
		"PRAGMA mmap_size=268435456",     // 256MB memory-mapped I/O
		"PRAGMA wal_autocheckpoint=1000", // Checkpoint every 1000 pages
		"PRAGMA wal_checkpoint(PASSIVE)", // Checkpoint now
		"PRAGMA optimize",                // Run optimizer
	}

	for _, pragma := range pragmas {
		if err := d.exec(pragma); err != nil {
			d.logger.Warn("Failed to set pragma", "pragma", pragma, "error", err)
		}
	}

	err := d.exec(dbSchema)

	return err
}

// Close closes the database connection.
func (d *Database) Close() error {
	return d.db.Close()
}

// beginTx starts a new transaction with logging
func (d *Database) beginTx() (*loggingTx, error) {
	tx, err := d.db.Begin()
	if err != nil {
		return nil, err
	}

	return &loggingTx{Tx: tx, logger: d.logger}, nil
}

// GetOrCreateASN retrieves an existing ASN or creates a new one if it doesn't exist.
func (d *Database) GetOrCreateASN(number int, timestamp time.Time) (*ASN, error) {
	tx, err := d.beginTx()
	if err != nil {
		return nil, err
	}
	defer func() {
		if err := tx.Rollback(); err != nil && err != sql.ErrTxDone {
			d.logger.Error("Failed to rollback transaction", "error", err)
		}
	}()

	var asn ASN
	var idStr string
	var handle, description sql.NullString
	err = tx.QueryRow("SELECT id, number, handle, description, first_seen, last_seen FROM asns WHERE number = ?", number).
		Scan(&idStr, &asn.Number, &handle, &description, &asn.FirstSeen, &asn.LastSeen)

	if err == nil {
		// ASN exists, update last_seen
		asn.ID, _ = uuid.Parse(idStr)
		asn.Handle = handle.String
		asn.Description = description.String
		_, err = tx.Exec("UPDATE asns SET last_seen = ? WHERE id = ?", timestamp, asn.ID.String())
		if err != nil {
			return nil, err
		}
		asn.LastSeen = timestamp

		if err = tx.Commit(); err != nil {
			d.logger.Error("Failed to commit transaction for ASN update", "asn", number, "error", err)

			return nil, err
		}

		return &asn, nil
	}

	if err != sql.ErrNoRows {
		return nil, err
	}

	// ASN doesn't exist, create it with ASN info lookup
	asn = ASN{
		ID:        generateUUID(),
		Number:    number,
		FirstSeen: timestamp,
		LastSeen:  timestamp,
	}

	// Look up ASN info
	if info, ok := asinfo.Get(number); ok {
		asn.Handle = info.Handle
		asn.Description = info.Description
	}

	_, err = tx.Exec("INSERT INTO asns (id, number, handle, description, first_seen, last_seen) VALUES (?, ?, ?, ?, ?, ?)",
		asn.ID.String(), asn.Number, asn.Handle, asn.Description, asn.FirstSeen, asn.LastSeen)
	if err != nil {
		return nil, err
	}

	if err = tx.Commit(); err != nil {
		d.logger.Error("Failed to commit transaction for ASN creation", "asn", number, "error", err)

		return nil, err
	}

	return &asn, nil
}

// GetOrCreatePrefix retrieves an existing prefix or creates a new one if it doesn't exist.
func (d *Database) GetOrCreatePrefix(prefix string, timestamp time.Time) (*Prefix, error) {
	tx, err := d.beginTx()
	if err != nil {
		return nil, err
	}
	defer func() {
		if err := tx.Rollback(); err != nil && err != sql.ErrTxDone {
			d.logger.Error("Failed to rollback transaction", "error", err)
		}
	}()

	var p Prefix
	var idStr string
	err = tx.QueryRow("SELECT id, prefix, ip_version, first_seen, last_seen FROM prefixes WHERE prefix = ?", prefix).
		Scan(&idStr, &p.Prefix, &p.IPVersion, &p.FirstSeen, &p.LastSeen)

	if err == nil {
		// Prefix exists, update last_seen
		p.ID, _ = uuid.Parse(idStr)
		_, err = tx.Exec("UPDATE prefixes SET last_seen = ? WHERE id = ?", timestamp, p.ID.String())
		if err != nil {
			return nil, err
		}
		p.LastSeen = timestamp

		if err = tx.Commit(); err != nil {
			d.logger.Error("Failed to commit transaction for prefix update", "prefix", prefix, "error", err)

			return nil, err
		}

		return &p, nil
	}

	if err != sql.ErrNoRows {
		return nil, err
	}

	// Prefix doesn't exist, create it
	p = Prefix{
		ID:        generateUUID(),
		Prefix:    prefix,
		IPVersion: detectIPVersion(prefix),
		FirstSeen: timestamp,
		LastSeen:  timestamp,
	}
	_, err = tx.Exec("INSERT INTO prefixes (id, prefix, ip_version, first_seen, last_seen) VALUES (?, ?, ?, ?, ?)",
		p.ID.String(), p.Prefix, p.IPVersion, p.FirstSeen, p.LastSeen)
	if err != nil {
		return nil, err
	}

	if err = tx.Commit(); err != nil {
		d.logger.Error("Failed to commit transaction for prefix creation", "prefix", prefix, "error", err)

		return nil, err
	}

	return &p, nil
}

// RecordAnnouncement inserts a new BGP announcement or withdrawal into the database.
func (d *Database) RecordAnnouncement(announcement *Announcement) error {
	err := d.exec(`
		INSERT INTO announcements (id, prefix_id, asn_id, origin_asn_id, path, next_hop, timestamp, is_withdrawal)
		VALUES (?, ?, ?, ?, ?, ?, ?, ?)`,
		announcement.ID.String(), announcement.PrefixID.String(),
		announcement.ASNID.String(), announcement.OriginASNID.String(),
		announcement.Path, announcement.NextHop, announcement.Timestamp, announcement.IsWithdrawal)

	return err
}

// RecordPeering records a peering relationship between two ASNs.
func (d *Database) RecordPeering(fromASNID, toASNID string, timestamp time.Time) error {
	tx, err := d.beginTx()
	if err != nil {
		return err
	}
	defer func() {
		if err := tx.Rollback(); err != nil && err != sql.ErrTxDone {
			d.logger.Error("Failed to rollback transaction", "error", err)
		}
	}()

	var exists bool
	err = tx.QueryRow("SELECT EXISTS(SELECT 1 FROM asn_peerings WHERE from_asn_id = ? AND to_asn_id = ?)",
		fromASNID, toASNID).Scan(&exists)
	if err != nil {
		return err
	}

	if exists {
		_, err = tx.Exec("UPDATE asn_peerings SET last_seen = ? WHERE from_asn_id = ? AND to_asn_id = ?",
			timestamp, fromASNID, toASNID)
	} else {
		_, err = tx.Exec(`
			INSERT INTO asn_peerings (id, from_asn_id, to_asn_id, first_seen, last_seen)
			VALUES (?, ?, ?, ?, ?)`,
			generateUUID().String(), fromASNID, toASNID, timestamp, timestamp)
	}
	if err != nil {
		return err
	}

	if err = tx.Commit(); err != nil {
		d.logger.Error("Failed to commit transaction for peering",
			"from_asn_id", fromASNID,
			"to_asn_id", toASNID,
			"error", err,
		)

		return err
	}

	return nil
}

// UpdatePeer updates or creates a BGP peer record
func (d *Database) UpdatePeer(peerIP string, peerASN int, messageType string, timestamp time.Time) error {
	tx, err := d.beginTx()
	if err != nil {
		return err
	}
	defer func() {
		if err := tx.Rollback(); err != nil && err != sql.ErrTxDone {
			d.logger.Error("Failed to rollback transaction", "error", err)
		}
	}()

	var exists bool
	err = tx.QueryRow("SELECT EXISTS(SELECT 1 FROM bgp_peers WHERE peer_ip = ?)", peerIP).Scan(&exists)
	if err != nil {
		return err
	}

	if exists {
		_, err = tx.Exec(
			"UPDATE bgp_peers SET peer_asn = ?, last_seen = ?, last_message_type = ? WHERE peer_ip = ?",
			peerASN, timestamp, messageType, peerIP,
		)
	} else {
		_, err = tx.Exec(
			"INSERT INTO bgp_peers (id, peer_ip, peer_asn, first_seen, last_seen, last_message_type) VALUES (?, ?, ?, ?, ?, ?)",
			generateUUID().String(), peerIP, peerASN, timestamp, timestamp, messageType,
		)
	}
	if err != nil {
		return err
	}

	if err = tx.Commit(); err != nil {
		d.logger.Error("Failed to commit transaction for peer update",
			"peer_ip", peerIP,
			"peer_asn", peerASN,
			"error", err,
		)

		return err
	}

	return nil
}

// GetStats returns database statistics
func (d *Database) GetStats() (Stats, error) {
	var stats Stats

	// Count ASNs
	d.logger.Info("Counting ASNs")
	err := d.queryRow("SELECT COUNT(*) FROM asns").Scan(&stats.ASNs)
	if err != nil {
		return stats, err
	}

	// Count prefixes
	d.logger.Info("Counting prefixes")
	err = d.queryRow("SELECT COUNT(*) FROM prefixes").Scan(&stats.Prefixes)
	if err != nil {
		return stats, err
	}

	// Count IPv4 and IPv6 prefixes
	d.logger.Info("Counting IPv4 prefixes")
	const ipVersionV4 = 4
	err = d.queryRow("SELECT COUNT(*) FROM prefixes WHERE ip_version = ?", ipVersionV4).Scan(&stats.IPv4Prefixes)
	if err != nil {
		return stats, err
	}

	d.logger.Info("Counting IPv6 prefixes")
	const ipVersionV6 = 6
	err = d.queryRow("SELECT COUNT(*) FROM prefixes WHERE ip_version = ?", ipVersionV6).Scan(&stats.IPv6Prefixes)
	if err != nil {
		return stats, err
	}

	// Count peerings
	d.logger.Info("Counting peerings")
	err = d.queryRow("SELECT COUNT(*) FROM asn_peerings").Scan(&stats.Peerings)
	if err != nil {
		return stats, err
	}

	// Get database file size
	d.logger.Info("Getting database file size")
	fileInfo, err := os.Stat(d.path)
	if err != nil {
		d.logger.Warn("Failed to get database file size", "error", err)
		stats.FileSizeBytes = 0
	} else {
		stats.FileSizeBytes = fileInfo.Size()
	}

	d.logger.Info("Stats collection complete")

	return stats, nil
}