From 686c310466b1f1033c4fdaeaccc1005a89b31bd2 Mon Sep 17 00:00:00 2001
From: Michael Chus <mike@mchus.pro>
Date: Thu, 5 Feb 2026 23:30:33 +0300
Subject: [PATCH] Auto-apply migrations on startup

---
 cmd/reanimator-api/main.go           |   5 ++
 internal/repository/migrate/apply.go | 112 +++++++++++++++++++++++++++
 2 files changed, 117 insertions(+)
 create mode 100644 internal/repository/migrate/apply.go

diff --git a/cmd/reanimator-api/main.go b/cmd/reanimator-api/main.go
index 541151b..b753645 100644
--- a/cmd/reanimator-api/main.go
+++ b/cmd/reanimator-api/main.go
@@ -13,6 +13,7 @@ import (
 	"reanimator/internal/api"
 	"reanimator/internal/config"
 	"reanimator/internal/repository"
+	"reanimator/internal/repository/migrate"
 )
 
 func main() {
@@ -28,6 +29,10 @@ func main() {
 	defer func() {
 		_ = db.Close()
 	}()
+	if err := migrate.EnsureSchema(db, cfg.MigrationsDir); err != nil {
+		log.Fatalf("apply migrations: %v", err)
+	}
+	log.Printf("database schema ready")
 
 	srv := api.NewServer(cfg.HTTPAddr, cfg.ReadTimeout, cfg.WriteTimeout, db)
 
diff --git a/internal/repository/migrate/apply.go b/internal/repository/migrate/apply.go
new file mode 100644
index 0000000..f902da0
--- /dev/null
+++ b/internal/repository/migrate/apply.go
@@ -0,0 +1,112 @@
+package migrate
+
+import (
+	"database/sql"
+	"fmt"
+	"strings"
+	"time"
+)
+
+// EnsureSchema applies all "up" migrations when the database has no tables.
+func EnsureSchema(db *sql.DB, dir string) error {
+	if err := ensureSchemaMigrations(db); err != nil {
+		return err
+	}
+
+	empty, err := isDatabaseEmpty(db)
+	if err != nil {
+		return err
+	}
+
+	runner := Runner{Dir: dir}
+	migrations, err := runner.Load(Up)
+	if err != nil {
+		return err
+	}
+	if empty {
+		for _, migration := range migrations {
+			if err := execStatements(db, migration.SQL); err != nil {
+				return fmt.Errorf("apply %s: %w", migration.Name, err)
+			}
+			if err := recordMigration(db, migration.Name); err != nil {
+				return err
+			}
+		}
+		return nil
+	}
+
+	applied, err := loadAppliedMigrations(db)
+	if err != nil {
+		return err
+	}
+	for _, migration := range migrations {
+		if applied[migration.Name] {
+			continue
+		}
+		if err := execStatements(db, migration.SQL); err != nil {
+			return fmt.Errorf("apply %s: %w", migration.Name, err)
+		}
+		if err := recordMigration(db, migration.Name); err != nil {
+			return err
+		}
+	}
+
+	return nil
+}
+
+func isDatabaseEmpty(db *sql.DB) (bool, error) {
+	var count int
+	if err := db.QueryRow(`SELECT COUNT(*) FROM information_schema.tables WHERE table_schema = DATABASE()`).Scan(&count); err != nil {
+		return false, err
+	}
+	return count == 0, nil
+}
+
+func execStatements(db *sql.DB, sqlText string) error {
+	statements := strings.Split(sqlText, ";")
+	for _, stmt := range statements {
+		stmt = strings.TrimSpace(stmt)
+		if stmt == "" {
+			continue
+		}
+		if _, err := db.Exec(stmt); err != nil {
+			return err
+		}
+	}
+	return nil
+}
+
+func ensureSchemaMigrations(db *sql.DB) error {
+	_, err := db.Exec(`CREATE TABLE IF NOT EXISTS schema_migrations (
+		id BIGINT PRIMARY KEY AUTO_INCREMENT,
+		name VARCHAR(255) NOT NULL UNIQUE,
+		applied_at TIMESTAMP NOT NULL
+	)`)
+	return err
+}
+
+func loadAppliedMigrations(db *sql.DB) (map[string]bool, error) {
+	rows, err := db.Query(`SELECT name FROM schema_migrations`)
+	if err != nil {
+		return nil, err
+	}
+	defer rows.Close()
+
+	applied := map[string]bool{}
+	for rows.Next() {
+		var name string
+		if err := rows.Scan(&name); err != nil {
+			return nil, err
+		}
+		applied[name] = true
+	}
+	if err := rows.Err(); err != nil {
+		return nil, err
+	}
+	return applied, nil
+}
+
+func recordMigration(db *sql.DB, name string) error {
+	_, err := db.Exec(`INSERT INTO schema_migrations (name, applied_at) VALUES (?, ?)`, name, time.Now().UTC())
+	return err
+}