From 21942591240f66936b1e98d63749e6800125d6f0 Mon Sep 17 00:00:00 2001
From: Simon Ser <contact@emersion.fr>
Date: Fri, 10 Apr 2020 22:45:02 +0200
Subject: [PATCH] Set up DB migration infrastructure

The database is now initialized automatically on first run. The schema
version is stored in SQLite's user_version special field. Migrations are
stored in an array and applied based on the schema version.
---
 README.md  |  1 -
 db.go      | 88 ++++++++++++++++++++++++++++++++++++++++++++++++++++--
 schema.sql | 29 ------------------
 3 files changed, 86 insertions(+), 32 deletions(-)
 delete mode 100644 schema.sql

diff --git a/README.md b/README.md
index 0a4a8cd..1d19739 100644
--- a/README.md
+++ b/README.md
@@ -10,7 +10,6 @@ A user-friendly IRC bouncer.
 
 ## Usage
 
-    sqlite3 soju.db <schema.sql
     go run ./cmd/sojuctl create-user <username>
     go run ./cmd/soju
 
diff --git a/db.go b/db.go
index 782358b..9bb08ab 100644
--- a/db.go
+++ b/db.go
@@ -48,17 +48,59 @@ type Channel struct {
 
 var ErrNoSuchChannel = fmt.Errorf("soju: no such channel")
 
+const schema = `
+CREATE TABLE User (
+	username VARCHAR(255) PRIMARY KEY,
+	password VARCHAR(255) NOT NULL
+);
+
+CREATE TABLE Network (
+	id INTEGER PRIMARY KEY,
+	name VARCHAR(255),
+	user VARCHAR(255) NOT NULL,
+	addr VARCHAR(255) NOT NULL,
+	nick VARCHAR(255) NOT NULL,
+	username VARCHAR(255),
+	realname VARCHAR(255),
+	pass VARCHAR(255),
+	sasl_mechanism VARCHAR(255),
+	sasl_plain_username VARCHAR(255),
+	sasl_plain_password VARCHAR(255),
+	FOREIGN KEY(user) REFERENCES User(username),
+	UNIQUE(user, addr, nick)
+);
+
+CREATE TABLE Channel (
+	id INTEGER PRIMARY KEY,
+	network INTEGER NOT NULL,
+	name VARCHAR(255) NOT NULL,
+	key VARCHAR(255),
+	FOREIGN KEY(network) REFERENCES Network(id),
+	UNIQUE(network, name)
+);
+`
+
+var migrations = []string{
+	"", // migration #0 is reserved for schema initialization
+}
+
 type DB struct {
 	lock sync.RWMutex
 	db   *sql.DB
 }
 
 func OpenSQLDB(driver, source string) (*DB, error) {
-	db, err := sql.Open(driver, source)
+	sqlDB, err := sql.Open(driver, source)
 	if err != nil {
 		return nil, err
 	}
-	return &DB{db: db}, nil
+
+	db := &DB{db: sqlDB}
+	if err := db.upgrade(); err != nil {
+		return nil, err
+	}
+
+	return db, nil
 }
 
 func (db *DB) Close() error {
@@ -67,6 +109,48 @@ func (db *DB) Close() error {
 	return db.Close()
 }
 
+func (db *DB) upgrade() error {
+	db.lock.Lock()
+	defer db.lock.Unlock()
+
+	var version int
+	if err := db.db.QueryRow("PRAGMA user_version").Scan(&version); err != nil {
+		return fmt.Errorf("failed to query schema version: %v", err)
+	}
+
+	if version == len(migrations) {
+		return nil
+	} else if version > len(migrations) {
+		return fmt.Errorf("soju (version %d) older than schema (version %d)", len(migrations), version)
+	}
+
+	tx, err := db.db.Begin()
+	if err != nil {
+		return err
+	}
+	defer tx.Rollback()
+
+	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)
+			}
+		}
+	}
+
+	// For some reason prepared statements don't work here
+	_, err = tx.Exec(fmt.Sprintf("PRAGMA user_version = %d", len(migrations)))
+	if err != nil {
+		return fmt.Errorf("failed to bump schema version: %v", err)
+	}
+
+	return tx.Commit()
+}
+
 func fromStringPtr(ptr *string) string {
 	if ptr == nil {
 		return ""
diff --git a/schema.sql b/schema.sql
deleted file mode 100644
index a778b9c..0000000
--- a/schema.sql
+++ /dev/null
@@ -1,29 +0,0 @@
-CREATE TABLE User (
-	username VARCHAR(255) PRIMARY KEY,
-	password VARCHAR(255) NOT NULL
-);
-
-CREATE TABLE Network (
-	id INTEGER PRIMARY KEY,
-	name VARCHAR(255),
-	user VARCHAR(255) NOT NULL,
-	addr VARCHAR(255) NOT NULL,
-	nick VARCHAR(255) NOT NULL,
-	username VARCHAR(255),
-	realname VARCHAR(255),
-	pass VARCHAR(255),
-	sasl_mechanism VARCHAR(255),
-	sasl_plain_username VARCHAR(255),
-	sasl_plain_password VARCHAR(255),
-	FOREIGN KEY(user) REFERENCES User(username),
-	UNIQUE(user, addr, nick)
-);
-
-CREATE TABLE Channel (
-	id INTEGER PRIMARY KEY,
-	network INTEGER NOT NULL,
-	name VARCHAR(255) NOT NULL,
-	key VARCHAR(255),
-	FOREIGN KEY(network) REFERENCES Network(id),
-	UNIQUE(network, name)
-);