From da36030846d068c4643f1e609c3119bad3a4b329 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Piotr=20Koz=C5=82owski?= <piotr@pkozlowski.pl>
Date: Fri, 17 Mar 2017 14:44:22 +0100
Subject: [PATCH] Support for migrating up/down to a specific version

---
 down.go    | 39 +++++++++++++++++++++++++++++++++++++++
 goose.go   | 25 +++++++++++++++++++++++++
 migrate.go | 10 ++++++++++
 up.go      |  8 ++++++--
 4 files changed, 80 insertions(+), 2 deletions(-)

diff --git a/down.go b/down.go
index e5e819a..2c92937 100644
--- a/down.go
+++ b/down.go
@@ -23,3 +23,42 @@ func Down(db *sql.DB, dir string) error {
 
 	return current.Down(db)
 }
+
+func DownTo(db *sql.DB, dir string, version int64) error {
+	migrations, err := collectMigrations(dir, minVersion, maxVersion)
+	if err != nil {
+		return err
+	}
+
+	for {
+		currentVersion, err := GetDBVersion(db)
+		if err != nil {
+			return err
+		}
+
+		prev, err := migrations.Previous(currentVersion)
+		if err != nil {
+			if err == ErrNoNextVersion {
+				fmt.Printf("goose: no migrations to run. current version: %d\n", currentVersion)
+				return nil
+			}
+			return err
+		}
+
+		if prev.Version < version {
+			fmt.Printf("goose: no migrations to run. current version: %d\n", currentVersion)
+			return nil
+		}
+
+		current, err := migrations.Current(currentVersion)
+		if err != nil {
+			return fmt.Errorf("no migration %v", currentVersion)
+		}
+
+		if err = current.Down(db); err != nil {
+			return err
+		}
+	}
+
+	return nil
+}
diff --git a/goose.go b/goose.go
index 604e29f..3573a31 100644
--- a/goose.go
+++ b/goose.go
@@ -4,6 +4,7 @@ import (
 	"database/sql"
 	"fmt"
 	"sync"
+	"strconv"
 )
 
 var (
@@ -22,6 +23,18 @@ func Run(command string, db *sql.DB, dir string, args ...string) error {
 		if err := UpByOne(db, dir); err != nil {
 			return err
 		}
+	case "up-to":
+		if len(args) == 0 {
+			return fmt.Errorf("up-to must be of form: goose [OPTIONS] DRIVER DBSTRING up-to VERSION")
+		}
+
+		version, err := strconv.ParseInt(args[0], 10, 64)
+		if err != nil {
+			return fmt.Errorf("version must be a number (got '%s')", args[0])
+		}
+		if err := UpTo(db, dir, version); err != nil {
+			return err
+		}
 	case "create":
 		if len(args) == 0 {
 			return fmt.Errorf("create must be of form: goose [OPTIONS] DRIVER DBSTRING create NAME [go|sql]")
@@ -38,6 +51,18 @@ func Run(command string, db *sql.DB, dir string, args ...string) error {
 		if err := Down(db, dir); err != nil {
 			return err
 		}
+	case "down-to":
+		if len(args) == 0 {
+			return fmt.Errorf("down-to must be of form: goose [OPTIONS] DRIVER DBSTRING down-to VERSION")
+		}
+
+		version, err := strconv.ParseInt(args[0], 10, 64)
+		if err != nil {
+			return fmt.Errorf("version must be a number (got '%s')", args[0])
+		}
+		if err := DownTo(db, dir, version); err != nil {
+			return err
+		}
 	case "redo":
 		if err := Redo(db, dir); err != nil {
 			return err
diff --git a/migrate.go b/migrate.go
index b9474c3..26ce946 100644
--- a/migrate.go
+++ b/migrate.go
@@ -51,6 +51,16 @@ func (ms Migrations) Next(current int64) (*Migration, error) {
 	return nil, ErrNoNextVersion
 }
 
+func (ms Migrations) Previous(current int64) (*Migration, error) {
+	for i := len(ms)-1; i >= 0; i-- {
+		if ms[i].Version < current {
+			return ms[i], nil
+		}
+	}
+
+	return nil, ErrNoNextVersion
+}
+
 func (ms Migrations) Last() (*Migration, error) {
 	if len(ms) == 0 {
 		return nil, ErrNoNextVersion
diff --git a/up.go b/up.go
index 0c79ec5..d785686 100644
--- a/up.go
+++ b/up.go
@@ -5,8 +5,8 @@ import (
 	"fmt"
 )
 
-func Up(db *sql.DB, dir string) error {
-	migrations, err := collectMigrations(dir, minVersion, maxVersion)
+func UpTo(db *sql.DB, dir string, version int64) error {
+	migrations, err := collectMigrations(dir, minVersion, version)
 	if err != nil {
 		return err
 	}
@@ -34,6 +34,10 @@ func Up(db *sql.DB, dir string) error {
 	return nil
 }
 
+func Up(db *sql.DB, dir string) error {
+	return UpTo(db, dir, maxVersion)
+}
+
 func UpByOne(db *sql.DB, dir string) error {
 	migrations, err := collectMigrations(dir, minVersion, maxVersion)
 	if err != nil {