Improve package structure (#207)

* Improve package structure

* Set up travis

pkg/cli/database/sql.go

@@ -0,0 +1,136 @@
+/* Copyright (C) 2019 Monomax Software Pty Ltd
+ *
+ * This file is part of Dnote CLI.
+ *
+ * Dnote CLI is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * Dnote CLI is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with Dnote CLI.  If not, see <https://www.gnu.org/licenses/>.
+ */
+
+package database
+
+import (
+	"database/sql"
+
+	"github.com/pkg/errors"
+	// use sqlite
+	_ "github.com/mattn/go-sqlite3"
+)
+
+// SQLCommon is the minimal interface required by a db connection
+type SQLCommon interface {
+	Exec(query string, args ...interface{}) (sql.Result, error)
+	Prepare(query string) (*sql.Stmt, error)
+	Query(query string, args ...interface{}) (*sql.Rows, error)
+	QueryRow(query string, args ...interface{}) *sql.Row
+}
+
+// sqlDb is an interface implemented by *sql.DB
+type sqlDb interface {
+	Begin() (*sql.Tx, error)
+}
+
+// sqlTx is an interface implemented by *sql.Tx
+type sqlTx interface {
+	Commit() error
+	Rollback() error
+}
+
+// DB contains information about the current database connection
+type DB struct {
+	Conn     SQLCommon
+	Filepath string
+}
+
+// Begin begins a transaction
+func (d *DB) Begin() (*DB, error) {
+	if db, ok := d.Conn.(sqlDb); ok && db != nil {
+		tx, err := db.Begin()
+		if err != nil {
+			return nil, err
+		}
+
+		return &DB{Conn: tx}, nil
+	}
+
+	return nil, errors.New("can't start transaction")
+}
+
+// Commit commits a transaction
+func (d *DB) Commit() error {
+	if db, ok := d.Conn.(sqlTx); ok && db != nil {
+		if err := db.Commit(); err != nil {
+			return err
+		}
+	}
+
+	return errors.New("invalid transaction")
+}
+
+// Rollback rolls back a transaction
+func (d *DB) Rollback() error {
+	if db, ok := d.Conn.(sqlTx); ok && db != nil {
+		if err := db.Rollback(); err != nil {
+			return err
+		}
+	}
+
+	return errors.New("invalid transaction")
+}
+
+// Exec executes a sql
+func (d *DB) Exec(query string, values ...interface{}) (sql.Result, error) {
+	return d.Conn.Exec(query, values...)
+}
+
+// Prepare prepares a sql
+func (d *DB) Prepare(query string) (*sql.Stmt, error) {
+	return d.Conn.Prepare(query)
+}
+
+// Query queries rows
+func (d *DB) Query(query string, values ...interface{}) (*sql.Rows, error) {
+	return d.Conn.Query(query, values...)
+}
+
+// QueryRow queries a row
+func (d *DB) QueryRow(query string, values ...interface{}) *sql.Row {
+	return d.Conn.QueryRow(query, values...)
+}
+
+type closer interface {
+	Close() error
+}
+
+// Close closes a db connection
+func (d *DB) Close() error {
+	if db, ok := d.Conn.(closer); ok {
+		return db.Close()
+	}
+
+	return errors.New("can't close db")
+}
+
+// Open initializes a new connection to the sqlite database
+func Open(dbPath string) (*DB, error) {
+	dbConn, err := sql.Open("sqlite3", dbPath)
+	if err != nil {
+		return nil, errors.Wrap(err, "opening db connection")
+	}
+
+	db := &DB{
+		Conn:     dbConn,
+		Filepath: dbPath,
+	}
+
+	return db, nil
+}