feat: wip postgres support

internal/database/postgres.go

@@ -0,0 +1,83 @@
+package database
+
+import (
+	"database/sql"
+	"errors"
+	"fmt"
+
+	_ "github.com/lib/pq"
+	"github.com/rs/zerolog/log"
+)
+
+func (db *DB) openPostgres() error {
+	var err error
+
+	// open database connection
+	if db.handler, err = sql.Open("postgres", db.DSN); err != nil {
+		log.Fatal().Err(err).Msg("could not open postgres connection")
+		return err
+	}
+
+	err = db.handler.Ping()
+	if err != nil {
+		log.Fatal().Err(err).Msg("could not ping postgres database")
+		return err
+	}
+
+	// migrate db
+	if err = db.migratePostgres(); err != nil {
+		log.Fatal().Err(err).Msg("could not migrate postgres database")
+		return err
+	}
+
+	return nil
+}
+
+func (db *DB) migratePostgres() error {
+	tx, err := db.handler.Begin()
+	if err != nil {
+		return err
+	}
+	defer tx.Rollback()
+
+	initialSchema := `CREATE TABLE IF NOT EXISTS schema_migrations (
+	id INTEGER PRIMARY KEY,
+	version INTEGER NOT NULL
+);`
+
+	if _, err := tx.Exec(initialSchema); err != nil {
+		return fmt.Errorf("failed to create schema_migrations table: %s", err)
+	}
+
+	var version int
+	err = tx.QueryRow(`SELECT version FROM schema_migrations`).Scan(&version)
+	if err != nil && !errors.Is(err, sql.ErrNoRows) {
+		return err
+	}
+
+	if version == len(migrations) {
+		return nil
+	}
+	if version > len(migrations) {
+		return fmt.Errorf("old")
+	}
+
+	if version == 0 {
+		if _, err := tx.Exec(schema); err != nil {
+			return fmt.Errorf("failed to initialize schema: %v", err)
+		}
+	} else {
+		for i := version; i < len(migrations); i++ {
+			if _, err := tx.Exec(migrations[i]); err != nil {
+				return fmt.Errorf("failed to execute migration #%v: %v", i, err)
+			}
+		}
+	}
+
+	_, err = tx.Exec(`INSERT INTO schema_migrations (id, version) VALUES (1, $1) ON CONFLICT (id) DO UPDATE SET version = $1`, len(migrations))
+	if err != nil {
+		return fmt.Errorf("failed to bump schema version: %v", err)
+	}
+
+	return tx.Commit()
+}