database_render/internal/database/connection.go

package database

import (
	"database/sql"
	"fmt"
	"log/slog"
	"strings"
	"time"

	"github.com/rogeecn/database_render/internal/config"
	"gorm.io/driver/mysql"
	"gorm.io/driver/postgres"
	"gorm.io/driver/sqlite"
	"gorm.io/gorm"
	"gorm.io/gorm/logger"
)

// ConnectionManager manages database connections
type ConnectionManager struct {
	db     *gorm.DB
	sqlDB  *sql.DB
	config *config.DatabaseConfig
	logger *slog.Logger
}

// NewConnectionManager creates a new database connection manager
func NewConnectionManager(config *config.Config) (*ConnectionManager, error) {
	logger := slog.With("component", "database")

	cm := &ConnectionManager{
		config: &config.Database,
		logger: logger,
	}

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

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

	logger.Info("database connection established",
		"type", config.Database.Type,
		"host", config.Database.Host,
		"database", config.Database.DBName,
	)

	return cm, nil
}

// connect establishes the database connection
func (cm *ConnectionManager) connect() error {
	var dialector gorm.Dialector

	switch cm.config.Type {
	case "sqlite":
		dialector = sqlite.Open(cm.config.Path)
	case "mysql":
		dsn := fmt.Sprintf("%s:%s@tcp(%s:%d)/%s?charset=utf8mb4&parseTime=True&loc=Local",
			cm.config.User, cm.config.Password, cm.config.Host, cm.config.Port, cm.config.DBName)
		dialector = mysql.Open(dsn)
	case "postgres":
		if cm.config.DSN != "" {
			dialector = postgres.Open(cm.config.DSN)
		} else {
			dsn := fmt.Sprintf("host=%s port=%d user=%s password=%s dbname=%s sslmode=disable",
				cm.config.Host, cm.config.Port, cm.config.User, cm.config.Password, cm.config.DBName)
			dialector = postgres.Open(dsn)
		}
	default:
		return fmt.Errorf("unsupported database type: %s", cm.config.Type)
	}

	gormConfig := &gorm.Config{
		Logger: logger.Default.LogMode(logger.Info),
		NowFunc: func() time.Time {
			return time.Now().Local()
		},
	}

	db, err := gorm.Open(dialector, gormConfig)
	if err != nil {
		return fmt.Errorf("failed to open database: %w", err)
	}

	cm.db = db

	// Get underlying sql.DB for connection pooling
	sqlDB, err := db.DB()
	if err != nil {
		return fmt.Errorf("failed to get sql.DB: %w", err)
	}
	cm.sqlDB = sqlDB

	return nil
}

// configure sets up connection pool settings
func (cm *ConnectionManager) configure() error {
	if cm.sqlDB == nil {
		return fmt.Errorf("sql.DB is nil")
	}

	// Connection pool settings
	cm.sqlDB.SetMaxIdleConns(10)
	cm.sqlDB.SetMaxOpenConns(100)
	cm.sqlDB.SetConnMaxLifetime(time.Hour)

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

	return nil
}

// GetDB returns the GORM database instance
func (cm *ConnectionManager) GetDB() *gorm.DB {
	return cm.db
}

// GetSQLDB returns the underlying SQL database instance
func (cm *ConnectionManager) GetSQLDB() *sql.DB {
	return cm.sqlDB
}

// Close closes the database connection
func (cm *ConnectionManager) Close() error {
	if cm.sqlDB != nil {
		return cm.sqlDB.Close()
	}
	return nil
}

// Health checks the database health
func (cm *ConnectionManager) Health() error {
	if cm.sqlDB == nil {
		return fmt.Errorf("database not initialized")
	}
	return cm.sqlDB.Ping()
}

// GetTableNames returns all table names in the database
func (cm *ConnectionManager) GetTableNames() ([]string, error) {
	var tableNames []string

	switch cm.config.Type {
	case "sqlite":
		rows, err := cm.db.Raw("SELECT name FROM sqlite_master WHERE type='table' AND name NOT LIKE 'sqlite_%'").Rows()
		if err != nil {
			return nil, err
		}
		defer rows.Close()

		for rows.Next() {
			var name string
			if err := rows.Scan(&name); err != nil {
				return nil, err
			}
			tableNames = append(tableNames, name)
		}

	case "mysql":
		rows, err := cm.db.Raw("SHOW TABLES").Rows()
		if err != nil {
			return nil, err
		}
		defer rows.Close()

		for rows.Next() {
			var name string
			if err := rows.Scan(&name); err != nil {
				return nil, err
			}
			tableNames = append(tableNames, name)
		}

	case "postgres":
		rows, err := cm.db.Raw("SELECT tablename FROM pg_tables WHERE schemaname = 'public'").Rows()
		if err != nil {
			return nil, err
		}
		defer rows.Close()

		for rows.Next() {
			var name string
			if err := rows.Scan(&name); err != nil {
				return nil, err
			}
			tableNames = append(tableNames, name)
		}
	}

	return tableNames, nil
}

// GetTableColumns returns column information for a table
func (cm *ConnectionManager) GetTableColumns(tableName string) ([]ColumnInfo, error) {
	var columns []ColumnInfo

	switch cm.config.Type {
	case "sqlite":
		rows, err := cm.db.Raw(fmt.Sprintf("PRAGMA table_info(%s)", tableName)).Rows()
		if err != nil {
			return nil, err
		}
		defer rows.Close()

		for rows.Next() {
			var col ColumnInfo
			var notused interface{}
			if err := rows.Scan(&col.Position, &col.Name, &col.Type, &col.NotNull, &notused, &col.DefaultValue); err != nil {
				return nil, err
			}
			col.DatabaseType = cm.config.Type
			columns = append(columns, col)
		}

	case "mysql":
		rows, err := cm.db.Raw(fmt.Sprintf("DESCRIBE %s", tableName)).Rows()
		if err != nil {
			return nil, err
		}
		defer rows.Close()

		for rows.Next() {
			var col ColumnInfo
			var key, extra, nullStr string
			if err := rows.Scan(&col.Name, &col.Type, &nullStr, &key, &col.DefaultValue, &extra); err != nil {
				return nil, err
			}
			col.NotNull = nullStr == "NO"
			col.DatabaseType = cm.config.Type
			columns = append(columns, col)
		}

	case "postgres":
		query := `
			SELECT
				column_name,
				data_type,
				is_nullable,
				column_default
			FROM information_schema.columns
			WHERE table_name = $1
			ORDER BY ordinal_position
		`
		rows, err := cm.db.Raw(query, tableName).Rows()
		if err != nil {
			return nil, err
		}
		defer rows.Close()

		for rows.Next() {
			var col ColumnInfo
			var nullable string
			if err := rows.Scan(&col.Name, &col.Type, &nullable, &col.DefaultValue); err != nil {
				return nil, err
			}
			col.NotNull = nullable == "NO"
			col.DatabaseType = cm.config.Type
			columns = append(columns, col)
		}
	}

	return columns, nil
}

// ColumnInfo represents database column information
type ColumnInfo struct {
	Name         string
	Type         string
	NotNull      bool
	DefaultValue interface{}
	Position     int
	DatabaseType string
}

// GetTableData retrieves paginated data from a table
func (cm *ConnectionManager) GetTableData(
	tableName string,
	page, pageSize int,
	search string,
	sortField string,
	sortOrder string,
) ([]map[string]interface{}, int64, error) {
	var total int64
	var data []map[string]interface{}

	// Build count query for pagination
	countQuery := fmt.Sprintf("SELECT COUNT(*) FROM %s", tableName)
	if search != "" {
		// For search, we need to get column names first
		columns, err := cm.GetTableColumns(tableName)
		if err != nil {
			return nil, 0, err
		}

		// Build WHERE clause for text columns
		var whereConditions []string
		for _, col := range columns {
			if cm.isSearchableColumn(col.Type) {
				whereConditions = append(whereConditions, fmt.Sprintf("%s LIKE '%%%s%%'", col.Name, search))
			}
		}

		if len(whereConditions) > 0 {
			countQuery += " WHERE " + strings.Join(whereConditions, " OR ")
		}
	}

	if err := cm.db.Raw(countQuery).Scan(&total).Error; err != nil {
		return nil, 0, err
	}

	// Build data query
	dataQuery := fmt.Sprintf("SELECT * FROM %s", tableName)
	if search != "" {
		columns, err := cm.GetTableColumns(tableName)
		if err != nil {
			return nil, 0, err
		}

		var whereConditions []string
		for _, col := range columns {
			if cm.isSearchableColumn(col.Type) {
				whereConditions = append(whereConditions, fmt.Sprintf("%s LIKE '%%%s%%'", col.Name, search))
			}
		}

		if len(whereConditions) > 0 {
			dataQuery += " WHERE " + strings.Join(whereConditions, " OR ")
		}
	}

	// Add sorting
	if sortField != "" {
		order := "ASC"
		if sortOrder == "desc" {
			order = "DESC"
		}
		dataQuery += fmt.Sprintf(" ORDER BY %s %s", sortField, order)
	}

	// Add pagination
	offset := (page - 1) * pageSize
	dataQuery += fmt.Sprintf(" LIMIT %d OFFSET %d", pageSize, offset)

	// Execute query
	rows, err := cm.db.Raw(dataQuery).Rows()
	if err != nil {
		return nil, 0, err
	}
	defer rows.Close()

	// Get column names
	columnNames, err := rows.Columns()
	if err != nil {
		return nil, 0, err
	}

	// Scan data
	for rows.Next() {
		values := make([]interface{}, len(columnNames))
		valuePtrs := make([]interface{}, len(columnNames))

		for i := range values {
			valuePtrs[i] = &values[i]
		}

		if err := rows.Scan(valuePtrs...); err != nil {
			return nil, 0, err
		}

		row := make(map[string]interface{})
		for i, col := range columnNames {
			val := values[i]

			// Handle NULL values
			if val == nil {
				row[col] = nil
				continue
			}

			// Convert []byte to string for JSON compatibility
			if b, ok := val.([]byte); ok {
				row[col] = string(b)
			} else {
				row[col] = val
			}
		}

		data = append(data, row)
	}

	return data, total, nil
}

// isSearchableColumn determines if a column type is searchable
func (cm *ConnectionManager) isSearchableColumn(columnType string) bool {
	searchableTypes := []string{
		"VARCHAR", "TEXT", "CHAR", "STRING",
		"varchar", "text", "char", "string",
	}

	for _, t := range searchableTypes {
		if strings.Contains(strings.ToUpper(columnType), strings.ToUpper(t)) {
			return true
		}
	}
	return false
}

// GetTableDataByID retrieves a single record by ID
func (cm *ConnectionManager) GetTableDataByID(tableName string, id interface{}) (map[string]interface{}, error) {
	// Find primary key column
	columns, err := cm.GetTableColumns(tableName)
	if err != nil {
		return nil, err
	}

	var primaryKey string
	for _, col := range columns {
		// Assume 'id' is the primary key if it exists
		if col.Name == "id" || col.Name == "ID" {
			primaryKey = col.Name
			break
		}
	}

	if primaryKey == "" {
		// Fallback to first column
		primaryKey = columns[0].Name
	}

	query := fmt.Sprintf("SELECT * FROM %s WHERE %s = ?", tableName, primaryKey)

	rows, err := cm.db.Raw(query, id).Rows()
	if err != nil {
		return nil, err
	}
	defer rows.Close()

	columnNames, err := rows.Columns()
	if err != nil {
		return nil, err
	}

	if rows.Next() {
		values := make([]interface{}, len(columnNames))
		valuePtrs := make([]interface{}, len(columnNames))

		for i := range values {
			valuePtrs[i] = &values[i]
		}

		if err := rows.Scan(valuePtrs...); err != nil {
			return nil, err
		}

		row := make(map[string]interface{})
		for i, col := range columnNames {
			val := values[i]

			if val == nil {
				row[col] = nil
				continue
			}

			if b, ok := val.([]byte); ok {
				row[col] = string(b)
			} else {
				row[col] = val
			}
		}

		return row, nil
	}

	return nil, fmt.Errorf("record not found")
}