Create DB management / versioning package

pkg/db/connect.go

@@ -0,0 +1,127 @@
+package db
+
+import (
+	_ "embed"
+	"errors"
+	"fmt"
+	"os"
+
+	"github.com/jmoiron/sqlx"
+	_ "github.com/mattn/go-sqlite3"
+)
+
+var (
+	// Tracks whether the DB connector has been initialized
+	is_initialized bool
+
+	// The SQL schema of the database under management
+	sql_schema *string
+
+	// Database starts at version 0.  First migration brings us to version 1
+	migrations     *[]string
+	version_number uint
+)
+
+var (
+	ErrTargetExists = errors.New("target already exists")
+)
+
+// Colors for terminal output
+const (
+	ColorReset  = "\033[0m"
+	ColorBlack  = "\033[30m"
+	ColorRed    = "\033[31m"
+	ColorGreen  = "\033[32m"
+	ColorYellow = "\033[33m"
+	ColorBlue   = "\033[34m"
+	ColorPurple = "\033[35m"
+	ColorCyan   = "\033[36m"
+	ColorGray   = "\033[37m"
+	ColorWhite  = "\033[97m"
+)
+
+func Init(schema *string, migrationsList *[]string) {
+	sql_schema = schema
+	migrations = migrationsList
+	version_number = uint(len(*migrations))
+	is_initialized = true
+}
+
+func Create(path string) (*sqlx.DB, error) {
+	// First check if the path already exists
+	_, err := os.Stat(path)
+	if err == nil {
+		return nil, ErrTargetExists
+	} else if !errors.Is(err, os.ErrNotExist) {
+		return nil, fmt.Errorf("path error: %w", err)
+	}
+
+	// Create DB file
+	fmt.Printf("Creating.............   %s\n", path)
+	db := sqlx.MustOpen("sqlite3", path+"?_foreign_keys=on&_journal_mode=WAL")
+	db.MustExec(*sql_schema)
+
+	return db, nil
+}
+
+func Connect(path string) (*sqlx.DB, error) {
+	db := sqlx.MustOpen("sqlite3", fmt.Sprintf("%s?_foreign_keys=on&_journal_mode=WAL", path))
+	err := CheckAndUpdateVersion(db)
+	return db, err
+}
+
+func CheckAndUpdateVersion(db *sqlx.DB) error {
+	var version uint
+	err := db.Get(&version, "select version from db_version")
+	if err != nil {
+		return fmt.Errorf("couldn't check database version: %w", err)
+	}
+
+	if version > version_number {
+		return VersionMismatchError{version_number, version}
+	}
+
+	if version_number > version {
+		fmt.Print(ColorYellow)
+		fmt.Printf("================================================\n")
+		fmt.Printf("Database version is out of date.  Upgrading database from version %d to version %d!\n", version,
+			version_number)
+		fmt.Print(ColorReset)
+		UpgradeFromXToY(db, version, version_number)
+	}
+
+	return nil
+}
+
+// Run all the migrations from version X to version Y, and update the `database_version` table's `version_number`
+func UpgradeFromXToY(db *sqlx.DB, x uint, y uint) {
+	for i := x; i < y; i++ {
+		fmt.Print(ColorCyan)
+		fmt.Println((*migrations)[i])
+		fmt.Print(ColorReset)
+
+		db.MustExec((*migrations)[i])
+		db.MustExec("update db_version set version = ?", i+1)
+
+		fmt.Print(ColorYellow)
+		fmt.Printf("Now at database schema version %d.\n", i+1)
+		fmt.Print(ColorReset)
+	}
+	fmt.Print(ColorGreen)
+	fmt.Printf("================================================\n")
+	fmt.Printf("Database version has been upgraded to version %d.\n", y)
+	fmt.Print(ColorReset)
+}
+
+type VersionMismatchError struct {
+	EngineVersion   uint
+	DatabaseVersion uint
+}
+
+func (e VersionMismatchError) Error() string {
+	return fmt.Sprintf(
+		`This profile was created with database schema version %d, which is newer than this application's database schema version, %d.
+Please upgrade this application to a newer version to use this profile.  Or downgrade the profile's schema version, somehow.`,
+		e.DatabaseVersion, e.EngineVersion,
+	)
+}