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

namespace InvercargillSql.Migrations {
    
    /**
     * Represents the referential action to take when a referenced row is deleted or updated.
     * These actions correspond to SQL standard foreign key actions.
     */
    public enum ReferentialAction {
        NO_ACTION,    // default - restricts the action but check is deferred
        CASCADE,      // cascade the change to dependent rows
        SET_NULL,     // set referencing column to NULL
        SET_DEFAULT,  // set referencing column to its default value
        RESTRICT;     // restricts the action, check is immediate
        
        /**
         * Converts the referential action to its SQL string representation.
         * @return The SQL keyword(s) for this action
         */
        public string to_sql() {
            switch (this) {
                case CASCADE: return "CASCADE";
                case SET_NULL: return "SET NULL";
                case SET_DEFAULT: return "SET DEFAULT";
                case RESTRICT: return "RESTRICT";
                default: return "NO ACTION";
            }
        }
    }
    
    public interface SchemaOperation : Object {
        public abstract string to_sql(SqlDialect dialect);
    }
    
    public class CreateTableOperation : Object, SchemaOperation {
        public string table_name { get; set; }
        public Vector<ColumnDefinition> columns { get; set; }
        public Vector<TableConstraint> constraints { get; set; }
        
        public CreateTableOperation() {
            columns = new Vector<ColumnDefinition>();
            constraints = new Vector<TableConstraint>();
        }
        
        public string to_sql(SqlDialect dialect) {
            return dialect.create_table_sql(this);
        }
    }
    
    public class DropTableOperation : Object, SchemaOperation {
        public string table_name { get; set; }
        
        public string to_sql(SqlDialect dialect) {
            return dialect.drop_table_sql(this);
        }
    }
    
    public class AddColumnOperation : Object, SchemaOperation {
        public string table_name { get; set; }
        public ColumnDefinition column { get; set; }
        
        /**
         * Optional foreign key constraint for the column being added.
         * When set, the dialect should include REFERENCES clause in the ADD COLUMN SQL.
         */
        public TableConstraint? foreign_key_constraint { get; set; }
        
        public string to_sql(SqlDialect dialect) {
            return dialect.add_column_sql(this);
        }
    }
    
    public class DropColumnOperation : Object, SchemaOperation {
        public string table_name { get; set; }
        public string column_name { get; set; }
        
        public string to_sql(SqlDialect dialect) {
            return dialect.drop_column_sql(this);
        }
    }
    
    public class RenameColumnOperation : Object, SchemaOperation {
        public string table_name { get; set; }
        public string old_name { get; set; }
        public string new_name { get; set; }
        
        public string to_sql(SqlDialect dialect) {
            return dialect.rename_column_sql(this);
        }
    }
    
    public class CreateIndexOperation : Object, SchemaOperation {
        public string index_name { get; set; }
        public string table_name { get; set; }
        public Vector<string> columns { get; set; }
        public bool is_unique { get; set; }
        
        public CreateIndexOperation() {
            columns = new Vector<string>();
        }
        
        public string to_sql(SqlDialect dialect) {
            return dialect.create_index_sql(this);
        }
    }
    
    public class DropIndexOperation : Object, SchemaOperation {
        public string index_name { get; set; }
        public string table_name { get; set; }
        
        public string to_sql(SqlDialect dialect) {
            return dialect.drop_index_sql(this);
        }
    }
    
    public class RawSqlOperation : Object, SchemaOperation {
        public string sql { get; set; }
        
        public string to_sql(SqlDialect dialect) {
            return sql;
        }
    }
    
    public class TableConstraint : Object {
        public string name { get; set; }
        public string constraint_type { get; set; }  // PRIMARY KEY, UNIQUE, FOREIGN KEY, etc.
        public Vector<string> columns { get; set; }
        public string? reference_table { get; set; }
        public Vector<string> reference_columns { get; set; }
        
        /**
         * The action to take when a referenced row is deleted.
         * Default is NO_ACTION per SQL standard.
         */
        public ReferentialAction on_delete_action { get; set; default = ReferentialAction.NO_ACTION; }
        
        /**
         * The action to take when a referenced row is updated.
         * Default is NO_ACTION per SQL standard.
         */
        public ReferentialAction on_update_action { get; set; default = ReferentialAction.NO_ACTION; }
        
        public TableConstraint() {
            columns = new Vector<string>();
            reference_columns = new Vector<string>();
        }
    }
    
    /**
     * Schema operation for dropping a foreign key constraint.
     * Can identify the constraint by name or by column (for auto-generated names).
     */
    public class DropForeignKeyOperation : Object, SchemaOperation {
        /**
         * The name of the table containing the foreign key constraint.
         */
        public string table_name { get; construct set; }
        
        /**
         * The name of the constraint to drop (optional).
         * Use this when the constraint name is known.
         */
        public string? constraint_name { get; construct set; }
        
        /**
         * The column name to find and drop the FK for (optional).
         * Use this for auto-generated constraint names.
         */
        public string? column_name { get; construct set; }
        
        /**
         * Creates a new drop foreign key operation.
         * @param table_name The table containing the FK constraint
         */
        public DropForeignKeyOperation(string table_name) {
            Object(table_name: table_name);
        }
        
        /**
         * Generates the SQL to drop the foreign key constraint.
         * Note: SQLite requires table recreation, handled by the dialect.
         */
        public string to_sql(SqlDialect dialect) {
            return dialect.drop_foreign_key_sql(this);
        }
    }
}