Began implementing a database backend

5 files changed, 292 insertions, 0 deletions

diff --git a/pkg/database/database.go b/pkg/database/database.go
new file mode 100644
index 0000000..c89a334
--- /dev/null
+++ b/pkg/database/database.go
@@ -0,0 +1,58 @@
+package database
+
+import (
+	"database/sql"
+	"time"
+
+	_ "github.com/mattn/go-sqlite3"
+)
+
+// DBEnv is the struct that holds this package together
+type DBEnv struct {
+	db *sql.DB
+}
+
+// InitDB initializes database access and the connection pool
+func InitDB(dbType string, dsn string) (*DBEnv, error) {
+	db, err := sql.Open(dbType, dsn)
+	if err != nil {
+		return nil, newInitError(dsn, err)
+	}
+	db.SetMaxOpenConns(25)
+	db.SetMaxIdleConns(25)
+	db.SetConnMaxLifetime(5 * time.Minute)
+
+	if err := db.Ping(); err != nil {
+		_ = db.Close() // TODO think about handling this error case?
+		return nil, newInitError(dsn, err)
+	}
+
+	return &DBEnv{db: db}, nil
+}
+
+// Migrate performs the migrations of the database to the latest schema_version
+func (env *DBEnv) Migrate() error {
+	var currentVersion int
+	if err := env.db.QueryRow(`SELECT version FROM schema_version`).Scan(&currentVersion); err != nil {
+		currentVersion = 0
+	}
+	for version := currentVersion; version < len(migrations); version++ {
+		newVersion := version + 1
+		tx, err := env.db.Begin()
+		if err != nil {
+			return newTransactionError("Could not begin transaction", err)
+		}
+		if err := migrations[version](tx); err != nil {
+			tx.Rollback()
+			return newMigrationError(newVersion, err)
+		}
+		if _, err := tx.Exec(`DELETE FROM schema_version; INSERT INTO schema_version (version) VALUES ($1)`, newVersion); err != nil {
+			tx.Rollback()
+			return newMigrationError(newVersion, err)
+		}
+		if err := tx.Commit(); err != nil {
+			return newTransactionError("Could not commit transaction", err)
+		}
+	}
+	return nil
+}
diff --git a/pkg/database/database_test.go b/pkg/database/database_test.go
new file mode 100644
index 0000000..aad7953
--- /dev/null
+++ b/pkg/database/database_test.go
@@ -0,0 +1,143 @@
+package database
+
+import (
+	"database/sql"
+	"os"
+	"reflect"
+	"testing"
+
+	"github.com/DATA-DOG/go-sqlmock"
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+)
+
+func TestInitDB(t *testing.T) {
+	// Test cases
+	testCases := []struct {
+		name          string
+		dbType        string
+		dsn           string
+		expectedError interface{}
+	}{
+		{"Invalid dbType", "non-existant", "test", &InitError{}},
+		{"Non existant path", "sqlite3", "/non-existant/non-existant", &InitError{}},
+		{"Working DB", "sqlite3", "file::memory:?_foreign_keys=on", nil},
+	}
+	for _, tc := range testCases {
+		t.Run(tc.name, func(t *testing.T) {
+			db, err := InitDB(tc.dbType, tc.dsn)
+			if tc.expectedError != nil {
+				require.Error(t, err)
+				assert.Equalf(t, reflect.TypeOf(err), reflect.TypeOf(tc.expectedError), "Invalid error type. Got %s but expected %s", reflect.TypeOf(err), reflect.TypeOf(tc.expectedError))
+				require.Nil(t, db)
+			} else {
+				require.NoError(t, err)
+				require.NotNil(t, db)
+			}
+		})
+	}
+}
+
+func TestMigrate(t *testing.T) {
+	badMigration := []func(tx *sql.Tx) error{
+		func(tx *sql.Tx) (err error) {
+			return newMigrationError(0, nil)
+		},
+	}
+	noSchemaVersionMigration := []func(tx *sql.Tx) error{
+		func(tx *sql.Tx) (err error) {
+			return nil
+		},
+	}
+	onlyFirstMigration := []func(tx *sql.Tx) error{migrations[0]}
+	notFromScratchMigration := []func(tx *sql.Tx) error{
+		func(tx *sql.Tx) (err error) {
+			return &MigrationError{version: 1, err: nil}
+		},
+		func(tx *sql.Tx) (err error) {
+			return nil
+		},
+	}
+	os.Remove("testfile_notFromScratch.db")
+	notFromScratchDB, err := InitDB("sqlite3", "file:testfile_notFromScratch.db?_foreign_keys=on")
+	if err != nil {
+		t.Fatalf("Failed to init testfile.db : %+v", err)
+	}
+	defer os.Remove("testfile_notFromScratch.db")
+	migrations = onlyFirstMigration
+	if err := notFromScratchDB.Migrate(); err != nil {
+		t.Fatalf("Failed to migrate testfile.db to first schema version : %+v", err)
+	}
+
+	// Test cases
+	testCases := []struct {
+		name          string
+		dsn           string
+		migrs         []func(tx *sql.Tx) error
+		expectedError interface{}
+	}{
+		{"bad migration", "file::memory:?_foreign_keys=on", badMigration, &MigrationError{}},
+		{"no schema_version migration", "file::memory:?_foreign_keys=on", noSchemaVersionMigration, &MigrationError{}},
+		{"not from scratch", "file:testfile_notFromScratch.db?_foreign_keys=on", notFromScratchMigration, nil},
+		{"from scratch", "file::memory:?_foreign_keys=on", allMigrations, nil},
+	}
+	for _, tc := range testCases {
+		t.Run(tc.name, func(t *testing.T) {
+			db, err := InitDB("sqlite3", tc.dsn)
+			require.NoError(t, err)
+			migrations = tc.migrs
+			err = db.Migrate()
+			if tc.expectedError != nil {
+				require.Error(t, err)
+				assert.Equalf(t, reflect.TypeOf(err), reflect.TypeOf(tc.expectedError), "Invalid error type. Got %s but expected %s", reflect.TypeOf(err), reflect.TypeOf(tc.expectedError))
+			} else {
+				require.NoError(t, err)
+			}
+		})
+	}
+}
+
+func TestMigrateWithSQLMock(t *testing.T) {
+	fakeMigration := []func(tx *sql.Tx) error{
+		func(tx *sql.Tx) (err error) {
+			return nil
+		},
+	}
+	// Transaction begin error
+	dbBeginError, _, err := sqlmock.New()
+	if err != nil {
+		t.Fatalf("an error '%s' was not expected when opening a stub database connection", err)
+	}
+	defer dbBeginError.Close()
+	// Transaction commit error
+	dbCommitError, mockCommitError, err := sqlmock.New()
+	if err != nil {
+		t.Fatalf("an error '%s' was not expected when opening a stub database connection", err)
+	}
+	defer dbCommitError.Close()
+	mockCommitError.ExpectBegin()
+	mockCommitError.ExpectExec(`DELETE FROM schema_version`).WillReturnResult(sqlmock.NewResult(1, 1))
+	// Test cases
+	testCases := []struct {
+		name          string
+		db            *DBEnv
+		migrs         []func(tx *sql.Tx) error
+		expectedError interface{}
+	}{
+		{"begin transaction error", &DBEnv{db: dbBeginError}, fakeMigration, &TransactionError{}},
+		{"commit transaction error", &DBEnv{db: dbCommitError}, fakeMigration, &TransactionError{}},
+	}
+	for _, tc := range testCases {
+		t.Run(tc.name, func(t *testing.T) {
+			migrations = tc.migrs
+			err = tc.db.Migrate()
+			migrations = allMigrations
+			if tc.expectedError != nil {
+				require.Error(t, err)
+				assert.Equalf(t, reflect.TypeOf(err), reflect.TypeOf(tc.expectedError), "Invalid error type. Got %s but expected %s", reflect.TypeOf(err), reflect.TypeOf(tc.expectedError))
+			} else {
+				require.NoError(t, err)
+			}
+		})
+	}
+}
diff --git a/pkg/database/error.go b/pkg/database/error.go
new file mode 100644
index 0000000..1681dd5
--- /dev/null
+++ b/pkg/database/error.go
@@ -0,0 +1,57 @@
+package database
+
+import "fmt"
+
+// database init error
+type InitError struct {
+	path string
+	err  error
+}
+
+func (e *InitError) Error() string {
+	return fmt.Sprintf("Failed to open database : %s", e.path)
+}
+func (e *InitError) Unwrap() error { return e.err }
+
+func newInitError(path string, err error) error {
+	return &InitError{
+		path: path,
+		err:  err,
+	}
+}
+
+// database migration error
+type MigrationError struct {
+	version int
+	err     error
+}
+
+func (e *MigrationError) Error() string {
+	return fmt.Sprintf("Failed to migrate database to version %d : %s", e.version, e.err)
+}
+func (e *MigrationError) Unwrap() error { return e.err }
+
+func newMigrationError(version int, err error) error {
+	return &MigrationError{
+		version: version,
+		err:     err,
+	}
+}
+
+// database transaction error
+type TransactionError struct {
+	msg string
+	err error
+}
+
+func (e *TransactionError) Error() string {
+	return fmt.Sprintf("Failed to perform transaction : %s", e.msg)
+}
+func (e *TransactionError) Unwrap() error { return e.err }
+
+func newTransactionError(msg string, err error) error {
+	return &TransactionError{
+		msg: msg,
+		err: err,
+	}
+}
diff --git a/pkg/database/error_test.go b/pkg/database/error_test.go
new file mode 100644
index 0000000..8031305
--- /dev/null
+++ b/pkg/database/error_test.go
@@ -0,0 +1,15 @@
+package database
+
+import "testing"
+
+func TestErrorsCoverage(t *testing.T) {
+	initErr := InitError{}
+	_ = initErr.Error()
+	_ = initErr.Unwrap()
+	migrationErr := MigrationError{}
+	_ = migrationErr.Error()
+	_ = migrationErr.Unwrap()
+	transactionErr := TransactionError{}
+	_ = transactionErr.Error()
+	_ = transactionErr.Unwrap()
+}
diff --git a/pkg/database/migrations.go b/pkg/database/migrations.go
new file mode 100644
index 0000000..cec3c41
--- /dev/null
+++ b/pkg/database/migrations.go
@@ -0,0 +1,19 @@
+package database
+
+import "database/sql"
+
+// allMigrations is the list of migrations to perform to get an up to date database
+// Order is important. Add new migrations at the end of the list.
+var allMigrations = []func(tx *sql.Tx) error{
+	func(tx *sql.Tx) (err error) {
+		sql := `
+			CREATE TABLE schema_version (
+				version INTEGER NOT NULL
+			);`
+		_, err = tx.Exec(sql)
+		return err
+	},
+}
+
+// This variable exists so that tests can override it
+var migrations = allMigrations