Invercargill-Sql/src/migrations/migration-builder.vala

using Invercargill.DataStructures;
using InvercargillSql.Dialects;
using InvercargillSql.Orm;

namespace InvercargillSql.Migrations {
    
    /**
     * Delegate for configuring table creation within a migration.
     * 
     * @param t the TableBuilder to configure
     */
    public delegate void TableConfig(TableBuilder t);
    
    /**
     * Delegate for configuring table alterations within a migration.
     * 
     * @param t the AlterTableBuilder to configure
     */
    public delegate void AlterConfig(AlterTableBuilder t);
    
    /**
     * Main builder class providing the fluent API for defining migration operations.
     * 
     * MigrationBuilder is the central class used in Migration.up() and Migration.down()
     * methods to define schema changes. It supports creating/dropping tables, altering
     * table structure, and executing raw SQL.
     * 
     * Index creation is now handled within TableBuilder and AlterTableBuilder using
     * the fluent index() method.
     * 
     * All methods return the builder instance for method chaining.
     * 
     * Example usage:
     * {{{
     * public override void up(MigrationBuilder b) {
     *     b.create_table("users", t => {
     *         t.column<int>("id", c => c.type_int().primary_key().auto_increment());
     *         t.column<string>("email", c => c.type_text().not_null().unique());
     *         t.column<string>("name", c => c.type_text().not_null());
     *         t.index("idx_users_email").on_column("email");
     *     });
     * }
     * 
     * public override void down(MigrationBuilder b) {
     *     b.drop_table("users");  // Indexes are dropped automatically with the table
     * }
     * }}}
     */
    public class MigrationBuilder : Object {
        private SqlDialect _dialect;
        private Vector<SchemaOperation> _operations;
        
        /**
         * Creates a new MigrationBuilder for the specified SQL dialect.
         * 
         * @param dialect the SQL dialect to use for generating SQL statements
         */
        public MigrationBuilder(SqlDialect dialect) {
            _dialect = dialect;
            _operations = new Vector<SchemaOperation>();
        }
        
        /**
         * Creates a new table with the specified name and configuration.
         * 
         * The configuration delegate receives a TableBuilder that can be used
         * to define columns, constraints, and indexes.
         * 
         * Indexes defined within the TableBuilder are emitted after the CREATE TABLE
         * statement in the generated SQL.
         * 
         * @param name the name of the table to create
         * @param config a delegate that configures the table structure
         * @return this builder for method chaining
         */
        public MigrationBuilder create_table(string name, owned TableConfig config) {
            var builder = new TableBuilder(this, name);
            config(builder);
            
            // Add the CREATE TABLE operation
            _operations.add(builder.build_operation());
            
            // Add any index operations defined within the table builder
            foreach (var index_op in builder.get_index_operations()) {
                _operations.add(index_op);
            }
            
            return this;
        }
        
        /**
         * Drops the specified table.
         * 
         * Note: In most databases, dropping a table automatically drops all
         * associated indexes.
         * 
         * @param name the name of the table to drop
         * @return this builder for method chaining
         */
        public MigrationBuilder drop_table(string name) {
            _operations.add(new DropTableOperation() { table_name = name });
            return this;
        }
        
        /**
         * Alters an existing table with the specified configuration.
         * 
         * The configuration delegate receives an AlterTableBuilder that can be used
         * to add, drop, or rename columns, and to create or drop indexes.
         * 
         * @param name the name of the table to alter
         * @param config a delegate that configures the alterations
         * @return this builder for method chaining
         */
        public MigrationBuilder alter_table(string name, owned AlterConfig config) {
            var builder = new AlterTableBuilder(this, name);
            config(builder);
            foreach (var op in builder.get_operations()) {
                _operations.add(op);
            }
            return this;
        }
        
        /**
         * Executes raw SQL directly.
         * 
         * Use with caution as this bypasses the dialect abstraction.
         * 
         * @param sql the raw SQL to execute
         * @return this builder for method chaining
         */
        public MigrationBuilder execute_sql(string sql) {
            _operations.add(new RawSqlOperation() { sql = sql });
            return this;
        }
        
        /**
         * Adds a column operation from a column builder.
         * 
         * This is used internally by MigrationColumnBuilder to add configured
         * columns directly to the operations list.
         * 
         * @param table_name the name of the table
         * @param col the column definition to add
         */
        internal void add_column_from_builder(string table_name, ColumnDefinition col) {
            _operations.add(new AddColumnOperation() {
                table_name = table_name,
                column = col
            });
        }
        
        /**
         * Gets all schema operations collected by this builder.
         * 
         * @return a Vector of SchemaOperation objects
         */
        public Vector<SchemaOperation> get_operations() {
            return _operations;
        }
        
        /**
         * Executes all collected operations against the specified connection.
         * 
         * Each operation is converted to SQL using the dialect and executed
         * in the order they were added.
         * 
         * @param conn the database connection to execute against
         * @throws SqlError if any operation fails
         */
        public void execute(Connection conn) throws SqlError {
            foreach (var op in _operations) {
                var sql = op.to_sql(_dialect);
                conn.execute(sql);
            }
        }
    }
}