1 files changed, 175 insertions, 0 deletions
diff --git a/database.go b/database.go
new file mode 100644
index 0000000..20ec5a6
--- /dev/null
+++ b/database.go
@@ -0,0 +1,175 @@
+
+package main
+
+import (
+	"log"
+	"fmt"
+	"path/filepath"
+	"io"
+	"os"
+	"os/signal"
+	"os/user"
+	"os/exec"
+	"strconv"
+	"syscall"
+	"database/sql"
+
+	_ "github.com/go-sql-driver/mysql"
+)
+
+const databaseSchemaVersion int = 2  // this defines the needed version for the
+                                     // executable
+
+type Database struct {
+	config DatabaseConfig
+	target string
+	Backend *sql.DB
+}
+
+func InitDatabase(config DatabaseConfig) Database {
+
+	db := NewDatabase(config)
+	db.Connect()
+	db.Ping()
+	db.Migrate(config.Migrations)
+
+	// allow graceful shutdown
+	var listener = make(chan os.Signal)
+	signal.Notify(listener, syscall.SIGTERM)
+	signal.Notify(listener, syscall.SIGINT)
+	go func() {
+		signal := <-listener
+		log.Printf("\nGot signal '%+v'. Shutting down ...\n", signal)
+		db.Cleanup()
+		os.Exit(0)  // TODO this does not belong to a database - write utils file 'shutdown.go'
+	}()
+
+	return db
+}
+
+func NewDatabase(config DatabaseConfig) Database {
+
+	db := Database{}
+
+	db.config = config
+	var username string
+	user_ptr,err := user.Current()
+	if err != nil {
+		log.Fatal(err)
+	}
+	username = user_ptr.Username
+	db.target = fmt.Sprintf("%s@unix(%s)/%s", username, config.Socket, config.Database)
+
+	return db
+}
+
+func (db *Database) Connect() {
+	var err error
+	db.Backend,err = sql.Open("mysql", db.target)
+	if err != nil {
+		log.Fatal(err)
+	}
+	log.Printf("Connected to database '%s'\n", db.target)
+}
+
+func (db *Database) Ping() {
+	err := db.Backend.Ping()
+	if err != nil {
+		log.Fatal(err)
+	} else {
+		log.Println("Database is responding")
+	}
+}
+
+func (db *Database) Migrate(dir string) {
+
+	const t = databaseSchemaVersion  // targeted database schema version
+
+	for {
+		v := db.SchemaVersion()  // read schema version from DB table
+
+		// handle current database schema which is newer than targeted one
+		if v > t {
+			log.Fatalf(
+			    "Current database schema version is %d but newest is %d!", v, t)
+		}
+
+		// break if targeted version is already reached
+		if v == t {
+			break
+		}
+
+		// execute migration
+		log.Printf("Starting database schema migration to version %d.\n", v+1)
+		path := filepath.Join(dir, fmt.Sprintf("%04d_migration.sql", v+1))
+		RunSql(path)
+		log.Printf("Finished database schema migration to version %d.\n", v+1)
+	}
+}
+
+func RunSql(path string) {
+
+	script, err := os.Open(path)
+	if err != nil {
+		log.Fatalf("Could not open SQL script '%s'!\n", path)
+	}
+
+	cmd := exec.Command("mariadb")
+	stdin, err := cmd.StdinPipe()
+	if err != nil {
+		log.Fatalf("Could not open stdin of mariadb process!\n%v", err)
+	}
+
+	err = cmd.Start()
+	if err != nil {
+		log.Fatalf("Could not start mariadb process!\n%v", err)
+	}
+	io.Copy(stdin, script)
+	stdin.Close()
+
+	err = cmd.Wait()
+	if err != nil {
+		log.Fatalf("Failed to wait for SQL script to finish!\n%v", err)
+	}
+}
+
+func (db *Database) SchemaVersion() int {
+
+	// ask database for schema version
+	cmd := "SELECT value FROM meta WHERE (identifier='version');"
+	rows, err := db.Backend.Query(cmd)
+
+	// handle missing meta table
+	if err != nil {
+		log.Fatal(err)
+	}
+
+	// handle successful schema version query
+	defer rows.Close()
+	rows.Next()
+	var version string
+	err = rows.Scan(&version)
+
+	// handle missing version field in meta table
+	if err != nil {
+		log.Fatal(err)
+	}
+
+	// convert to integer and handle error
+	v, err := strconv.Atoi(version)
+	if err != nil {
+		log.Fatalf("Could not convert database schema version '%s' to int.\n",
+		           version)
+	}
+
+	return v
+}
+
+func (db *Database) Cleanup() {
+	err := db.Backend.Close()
+	if err != nil {
+		log.Println("Could not close database connection")
+	} else {
+		log.Println("Closed database connection")
+	}
+}