package sqlbuilder

import (
	"database/sql"

	"git.hexq.cn/tiglog/mydb"
)

// Tx represents a transaction on a SQL database. A transaction is like a
// regular Session except it has two extra methods: Commit and Rollback.
//
// A transaction needs to be committed (with Commit) to make changes permanent,
// changes can be discarded before committing by rolling back (with Rollback).
// After either committing or rolling back a transaction it can not longer be
// used and it's automatically closed.
type Tx interface {
	// All mydb.Session methods are available on transaction sessions. They will
	// run on the same transaction.
	mydb.Session

	Commit() error

	Rollback() error
}

// Adapter represents a SQL adapter.
type Adapter interface {
	// New wraps an active *sql.DB session and returns a SQLBuilder database.  The
	// adapter needs to be imported to the blank namespace in order for it to be
	// used here.
	//
	// This method is internally used by upper-db to create a builder backed by the
	// given database.  You may want to use your adapter's New function instead of
	// this one.
	New(*sql.DB) (mydb.Session, error)

	// NewTx wraps an active *sql.Tx transation and returns a SQLBuilder
	// transaction.  The adapter needs to be imported to the blank namespace in
	// order for it to be used.
	//
	// This method is internally used by upper-db to create a builder backed by the
	// given transaction.  You may want to use your adapter's NewTx function
	// instead of this one.
	NewTx(*sql.Tx) (Tx, error)

	// Open opens a SQL database.
	OpenDSN(mydb.ConnectionURL) (mydb.Session, error)
}

type dbAdapter struct {
	Adapter
}

func (d *dbAdapter) Open(conn mydb.ConnectionURL) (mydb.Session, error) {
	sess, err := d.Adapter.OpenDSN(conn)
	if err != nil {
		return nil, err
	}
	return sess.(mydb.Session), nil
}

func NewCompatAdapter(adapter Adapter) mydb.Adapter {
	return &dbAdapter{adapter}
}