commit f80de360baba708a9aa57ccec280639455954334
Author: Magnus Åhall <magnus.ahall@gibon.se>
Date:   Tue Aug 1 17:10:35 2023 +0200

    Initial commit

diff --git a/database.go b/database.go
new file mode 100644
index 0000000..18b3856
--- /dev/null
+++ b/database.go
@@ -0,0 +1,31 @@
+package dbschema
+
+import (
+	// Standard
+	"database/sql"
+	"fmt"
+)
+
+func newDatabase(host string, port int, dbName, user, pass string) (dbase Database, err error) {// {{{
+	dbase.Host = host
+	dbase.Port = port
+	dbase.DbName = dbName
+	dbase.Username = user
+	dbase.Password = pass
+
+	dbase.db, err = sql.Open("postgres", dbase.sqlConnString())
+	return
+}// }}}
+
+func (dbase Database) sqlConnString() string {// {{{
+	return fmt.Sprintf(
+		"postgresql://%s:%s@%s:%d/%s?sslmode=disable",
+		dbase.Username,
+		dbase.Password,
+		dbase.Host,
+		dbase.Port,
+		dbase.DbName,
+	)
+}// }}}
+
+// vim: foldmethod=marker
diff --git a/go.mod b/go.mod
new file mode 100644
index 0000000..eb920fa
--- /dev/null
+++ b/go.mod
@@ -0,0 +1,5 @@
+module git.gibonuddevalla.se/go/dbschema
+
+go 1.20
+
+require github.com/lib/pq v1.10.9
diff --git a/go.sum b/go.sum
new file mode 100644
index 0000000..aeddeae
--- /dev/null
+++ b/go.sum
@@ -0,0 +1,2 @@
+github.com/lib/pq v1.10.9 h1:YXG7RB+JIjhP29X+OtkiDnYaXQwpS4JEWq7dtCCRUEw=
+github.com/lib/pq v1.10.9/go.mod h1:AlVN5x4E4T544tWzH6hKfbfQvm3HdbOxrmggDNAPY9o=
diff --git a/schema.go b/schema.go
new file mode 100644
index 0000000..56050c2
--- /dev/null
+++ b/schema.go
@@ -0,0 +1,71 @@
+package dbschema
+
+import (
+	// External
+	_ "github.com/lib/pq"
+
+	// Standard
+	"database/sql"
+)
+
+type Upgrader struct {
+	schemaDb Database
+	databases map[string]Database
+	logCallback func(string, string)
+	sqlCallback func(string, int) ([]byte, bool)
+}
+
+type Database struct {
+	Host     string
+	Port     int
+	DbName   string
+	Username string
+	Password string
+
+	db *sql.DB
+	schemaDb *Database
+}
+
+/*
+func dbUpdate() (err error) {// {{{
+	var rows *sqlx.Rows
+	var schemaStr string
+	var schema int
+	rows, err = db.Queryx(`SELECT value FROM _internal.db WHERE "key"='schema'`)
+	if err != nil { return }
+	defer rows.Close()
+
+	if !rows.Next() {
+		return errors.New("Table _interval.db missing schema row")
+	}
+
+	if err = rows.Scan(&schemaStr); err != nil {
+		return
+	}
+
+	// Run updates
+	schema, err = strconv.Atoi(schemaStr)
+	if err != nil {
+		return err
+	}
+	for i := (schema+1); i <= DB_SCHEMA; i++ {
+		log.Printf("\x1b[32mNotes\x1b[0m Upgrading SQL schema to revision %d...", i)
+		sql, _ := embedded.ReadFile(
+			fmt.Sprintf("sql/%04d.sql", i),
+		)
+		_, err = db.Exec(string(sql))
+		if err != nil {
+			return
+		}
+		_, err = db.Exec(`UPDATE _internal.db SET "value"=$1 WHERE "key"='schema'`, i)
+		if err != nil {
+			return
+		}
+		log.Printf("\x1b[32mNotes\x1b[0m OK: %d", i)
+	}
+
+	return
+}// }}}
+*/
+
+// vim: foldmethod=marker
diff --git a/upgrader.go b/upgrader.go
new file mode 100644
index 0000000..27e4f4f
--- /dev/null
+++ b/upgrader.go
@@ -0,0 +1,154 @@
+package dbschema
+
+import (
+	// Standard
+	"database/sql"
+	"fmt"
+)
+
+func defaultCallback(topic, msg string) {// {{{
+	fmt.Printf("[%s] %s\n", topic, msg)
+}// }}}
+func NewUpgrader(host string, port int, dbName, user, pass string) (upgrader Upgrader, err error) {// {{{
+	upgrader.logCallback = defaultCallback
+	upgrader.databases = map[string]Database{}
+	upgrader.schemaDb, err = newDatabase(
+		host,
+		port,
+		dbName,
+		user,
+		pass,
+	)
+	err = upgrader.verifySchemaTable()
+	return
+}// }}}
+
+func (upgrader *Upgrader) SetLogCallback(callback func(string, string)) {// {{{
+	upgrader.logCallback = callback
+}// }}}
+func (upgrader *Upgrader) SetSqlCallback(callback func(string, int) ([]byte, bool)) {// {{{
+	upgrader.sqlCallback = callback
+}// }}}
+func (upgrader Upgrader) verifySchemaTable() (err error) {// {{{
+	var rows *sql.Rows
+	if rows, err = upgrader.schemaDb.db.Query(
+		`SELECT EXISTS (
+			SELECT FROM pg_catalog.pg_class c
+			JOIN   pg_catalog.pg_namespace n ON n.oid = c.relnamespace
+			WHERE  n.nspname = '_db'
+			AND    c.relname = 'schema'
+		)`,
+	); err != nil {
+		return
+	}
+	defer rows.Close()
+	var exists bool
+	rows.Next()
+	if err = rows.Scan(&exists); err != nil {
+		return
+	}
+
+	if !exists {
+		upgrader.logCallback("create", "_db.schema")
+		upgrader.schemaDb.db.Exec(`CREATE SCHEMA "_db"`)
+
+		if _, err = upgrader.schemaDb.db.Exec(`
+			CREATE TABLE "_db"."schema" (
+				database varchar   NOT NULL,
+				version  int4      NOT NULL,
+				updated  timestamp NOT NULL DEFAULT NOW(),
+
+				CONSTRAINT schema_pk PRIMARY KEY (database)
+			);
+			`,
+		); err != nil {
+			return
+		}
+	}
+	return
+}// }}}
+func (upgrader Upgrader) verifySchemaEntry(dbase Database) (err error) {// {{{
+	var rows *sql.Rows
+	rows, err = upgrader.schemaDb.db.Query(`SELECT version FROM _db.schema WHERE database=$1`, dbase.DbName)
+	if err != nil {
+		return
+	}
+	defer rows.Close()
+
+	if !rows.Next() {
+		upgrader.logCallback("initiate version", dbase.DbName)
+		_, err = upgrader.schemaDb.db.Exec(`INSERT INTO _db.schema(database, version) VALUES($1, 0)`, dbase.DbName)
+		if err != nil {
+			return
+		}
+	}
+
+	return
+}// }}}
+func (upgrader Upgrader) version(dbName string) (version int, err error) {// {{{
+	var rows *sql.Rows
+	rows, err = upgrader.schemaDb.db.Query(
+		`SELECT version FROM _db.schema WHERE database=$1`,
+		dbName,
+	)
+	if err != nil {
+		return
+	}
+	defer rows.Close()
+
+	if rows.Next() {
+		err = rows.Scan(&version)
+	} else {
+		err = fmt.Errorf(`Database "%s" is missing an entry in _db.schema`, dbName)
+	}
+	return
+}// }}}
+
+func (upgrader Upgrader) AddDatabase(host string, port int, dbName, user, pass string) (err error) {// {{{
+	var db Database
+	if db, err = newDatabase(host, port, dbName, user, pass); err != nil {
+		return
+	}
+	
+	upgrader.databases[dbName] = db
+
+	err = upgrader.verifySchemaEntry(db)
+	return
+}// }}}
+func (upgrader Upgrader) Run() (err error) {// {{{
+	var version int
+
+	for dbName, db := range upgrader.databases {
+		version, err = upgrader.version(dbName)
+		if err != nil {
+			return
+		}
+		upgrader.logCallback("version", fmt.Sprintf("%s: %d", dbName, version))
+
+		for {
+			version++
+			sql, found := upgrader.sqlCallback(dbName, version)
+			if !found {
+				break
+			}
+
+			upgrader.logCallback("exec", fmt.Sprintf("%s: %d", dbName, version))
+			if _, err = db.db.Exec(string(sql)); err != nil {
+				return
+			}
+			_, err = upgrader.schemaDb.db.Exec(`
+				UPDATE _db.schema
+				SET
+					version=$1,
+					updated=NOW()
+				WHERE database=$2
+			`, version, dbName)
+			if err != nil {
+				return
+			}
+		}
+	}
+	return
+}// }}}
+
+// vim: foldmethod=marker