Add migration system and initial migration

migration/2021-03-09T06:47:20Z CreateEverything.go

@@ -1,25 +0,0 @@
-package migration
-
-import (
-	"time"
-
-	"github.com/jackc/pgx/v4"
-)
-
-func init() {
-	registerMigration(CreateEverything{})
-}
-
-type CreateEverything struct{}
-
-func (m CreateEverything) Date() time.Time {
-	return time.Date(2021, 3, 9, 6, 53, 0, 0, time.UTC)
-}
-
-func (m CreateEverything) Up(conn *pgx.Conn) {
-
-}
-
-func (m CreateEverything) Down(conn *pgx.Conn) {
-
-}

migration/migration.go

@@ -2,45 +2,257 @@ package migration
 
 import (
 	"context"
+	_ "embed"
+	"fmt"
+	"os"
+	"path/filepath"
+	"sort"
+	"strings"
 	"time"
 
 	"git.handmade.network/hmn/hmn/db"
+	"git.handmade.network/hmn/hmn/migration/migrations"
+	"git.handmade.network/hmn/hmn/migration/types"
 	"git.handmade.network/hmn/hmn/website"
 	"github.com/jackc/pgx/v4"
 	"github.com/spf13/cobra"
 )
 
-var migrations map[time.Time]Migration = make(map[time.Time]Migration)
-
-type Migration interface {
-	Date() time.Time
-	Up(conn *pgx.Conn)
-	Down(conn *pgx.Conn)
-}
-
-func registerMigration(m Migration) {
-	migrations[m.Date()] = m
-}
+var listMigrations bool
 
 func init() {
 	migrateCommand := &cobra.Command{
-		Use:   "migrate",
+		Use:   "migrate [target migration id]",
 		Short: "Run database migrations",
 		Run: func(cmd *cobra.Command, args []string) {
-			Migrate()
+			if listMigrations {
+				ListMigrations()
+				return
+			}
+
+			targetVersion := time.Time{}
+			if len(args) > 0 {
+				var err error
+				targetVersion, err = time.Parse(time.RFC3339, args[0])
+				if err != nil {
+					fmt.Printf("ERROR: bad version string: %v", err)
+					os.Exit(1)
+				}
+			}
+			Migrate(types.MigrationVersion(targetVersion))
+		},
+	}
+	migrateCommand.Flags().BoolVar(&listMigrations, "list", false, "List available migrations")
+
+	makeMigrationCommand := &cobra.Command{
+		Use:   "makemigration <name> <description>...",
+		Short: "Create a new database migration file",
+		Run: func(cmd *cobra.Command, args []string) {
+			if len(args) < 2 {
+				fmt.Println("You must provide a name and a description.")
+				os.Exit(1)
+			}
+
+			name := args[0]
+			description := strings.Join(args[1:], " ")
+
+			MakeMigration(name, description)
 		},
 	}
 
 	website.WebsiteCommand.AddCommand(migrateCommand)
+	website.WebsiteCommand.AddCommand(makeMigrationCommand)
 }
 
-func Migrate() {
+func getSortedMigrationVersions() []types.MigrationVersion {
+	var allVersions []types.MigrationVersion
+	for migrationTime, _ := range migrations.All {
+		allVersions = append(allVersions, migrationTime)
+	}
+	sort.Slice(allVersions, func(i, j int) bool {
+		return allVersions[i].Before(allVersions[j])
+	})
+
+	return allVersions
+}
+
+func getCurrentVersion(conn *pgx.Conn) (types.MigrationVersion, error) {
+	var currentVersion time.Time
+	row := conn.QueryRow(context.Background(), "SELECT version FROM hmn_migration")
+	err := row.Scan(&currentVersion)
+	if err != nil {
+		return types.MigrationVersion{}, err
+	}
+	currentVersion = currentVersion.UTC()
+
+	return types.MigrationVersion(currentVersion), nil
+}
+
+func ListMigrations() {
 	conn := db.NewConn()
 	defer conn.Close(context.Background())
 
-	// check for existence of database??
+	currentVersion, _ := getCurrentVersion(conn)
+	for _, version := range getSortedMigrationVersions() {
+		migration := migrations.All[version]
+		indicator := "  "
+		if version.Equal(currentVersion) {
+			indicator = "✔ "
+		}
+		fmt.Printf("%s%v (%s: %s)\n", indicator, version, migration.Name(), migration.Description())
+	}
+}
 
-	// check for migration data, create it if missing
+func Migrate(targetVersion types.MigrationVersion) {
+	conn := db.NewConn()
+	defer conn.Close(context.Background())
+
+	// create migration table
+	_, err := conn.Exec(context.Background(), `
+		CREATE TABLE IF NOT EXISTS hmn_migration (
+			version		TIMESTAMP WITH TIME ZONE
+		)
+	`)
+	if err != nil {
+		panic(fmt.Errorf("failed to create migration table: %w", err))
+	}
+
+	// ensure there is a row
+	row := conn.QueryRow(context.Background(), "SELECT COUNT(*) FROM hmn_migration")
+	var numRows int
+	err = row.Scan(&numRows)
+	if err != nil {
+		panic(err)
+	}
+	if numRows < 1 {
+		_, err := conn.Exec(context.Background(), "INSERT INTO hmn_migration (version) VALUES ($1)", time.Time{})
+		if err != nil {
+			panic(fmt.Errorf("failed to insert initial migration row: %w", err))
+		}
+	}
 
 	// run migrations
+	currentVersion, err := getCurrentVersion(conn)
+	if err != nil {
+		panic(fmt.Errorf("failed to get current version: %w", err))
+	}
+	if currentVersion.IsZero() {
+		fmt.Println("This is the first time you have run database migrations.")
+	} else {
+		fmt.Printf("Current version: %s\n", currentVersion.String())
+	}
+
+	allVersions := getSortedMigrationVersions()
+	if targetVersion.IsZero() {
+		targetVersion = allVersions[len(allVersions)-1]
+	}
+
+	currentIndex := -1
+	targetIndex := -1
+	for i, version := range allVersions {
+		if currentVersion.Equal(version) {
+			currentIndex = i
+		}
+		if targetVersion.Equal(version) {
+			targetIndex = i
+		}
+	}
+
+	if targetIndex < 0 {
+		fmt.Printf("ERROR: Could not find migration with version %v\n", targetVersion)
+		return
+	}
+
+	if currentIndex < targetIndex {
+		// roll forward
+		for i := currentIndex + 1; i <= targetIndex; i++ {
+			version := allVersions[i]
+			fmt.Printf("Applying migration %v\n", version)
+			migration := migrations.All[version]
+
+			tx, err := conn.Begin(context.Background())
+			if err != nil {
+				panic(fmt.Errorf("failed to start transaction: %w", err))
+			}
+			defer tx.Rollback(context.Background())
+
+			err = migration.Up(tx)
+			if err != nil {
+				fmt.Printf("MIGRATION FAILED for migration %v.\n", version)
+				fmt.Printf("Error: %v\n", err)
+				return
+			}
+
+			_, err = tx.Exec(context.Background(), "UPDATE hmn_migration SET version = $1", version)
+			if err != nil {
+				panic(fmt.Errorf("failed to update version in migrations table: %w", err))
+			}
+
+			err = tx.Commit(context.Background())
+			if err != nil {
+				panic(fmt.Errorf("failed to commit transaction: %w", err))
+			}
+		}
+	} else if currentIndex > targetIndex {
+		// roll back
+		for i := currentIndex; i > targetIndex; i-- {
+			version := allVersions[i]
+			previousVersion := types.MigrationVersion{}
+			if i > 0 {
+				previousVersion = allVersions[i-1]
+			}
+
+			tx, err := conn.Begin(context.Background())
+			if err != nil {
+				panic(fmt.Errorf("failed to start transaction: %w", err))
+			}
+			defer tx.Rollback(context.Background())
+
+			fmt.Printf("Rolling back migration %v\n", version)
+			migration := migrations.All[version]
+			err = migration.Down(tx)
+			if err != nil {
+				fmt.Printf("MIGRATION FAILED for migration %v.\n", version)
+				fmt.Printf("Error: %v\n", err)
+				return
+			}
+
+			_, err = tx.Exec(context.Background(), "UPDATE hmn_migration SET version = $1", previousVersion)
+			if err != nil {
+				panic(fmt.Errorf("failed to update version in migrations table: %w", err))
+			}
+
+			err = tx.Commit(context.Background())
+			if err != nil {
+				panic(fmt.Errorf("failed to commit transaction: %w", err))
+			}
+		}
+	} else {
+		fmt.Println("Already migrated; nothing to do.")
+	}
+}
+
+//go:embed migrationTemplate.txt
+var migrationTemplate string
+
+func MakeMigration(name, description string) {
+	result := migrationTemplate
+	result = strings.ReplaceAll(result, "%NAME%", name)
+	result = strings.ReplaceAll(result, "%DESCRIPTION%", fmt.Sprintf("%#v", description))
+
+	now := time.Now().UTC()
+	nowConstructor := fmt.Sprintf("time.Date(%d, %d, %d, %d, %d, %d, 0, time.UTC)", now.Year(), now.Month(), now.Day(), now.Hour(), now.Minute(), now.Second())
+	result = strings.ReplaceAll(result, "%DATE%", nowConstructor)
+
+	safeVersion := strings.ReplaceAll(types.MigrationVersion(now).String(), ":", "")
+	filename := fmt.Sprintf("%v_%v.go", safeVersion, name)
+	path := filepath.Join("migration", "migrations", filename)
+
+	err := os.WriteFile(path, []byte(result), 0644)
+	if err != nil {
+		panic(fmt.Errorf("failed to write migration file: %w", err))
+	}
+
+	fmt.Println("Successfully created migration file:")
+	fmt.Println(path)
 }

migration/migrationTemplate.txt

@@ -0,0 +1,34 @@
+package migrations
+
+import (
+	"time"
+
+	"git.handmade.network/hmn/hmn/migration/types"
+	"github.com/jackc/pgx/v4"
+)
+
+func init() {
+	registerMigration(%NAME%{})
+}
+
+type %NAME% struct{}
+
+func (m %NAME%) Version() types.MigrationVersion {
+	return types.MigrationVersion(%DATE%)
+}
+
+func (m %NAME%) Name() string {
+	return "%NAME%"
+}
+
+func (m %NAME%) Description() string {
+	return %DESCRIPTION%
+}
+
+func (m %NAME%) Up(tx pgx.Tx) error {
+	panic("Implement me")
+}
+
+func (m %NAME%) Down(tx pgx.Tx) error {
+	panic("Implement me")
+}

migration/migrations/migrations.go

@@ -0,0 +1,9 @@
+package migrations
+
+import "git.handmade.network/hmn/hmn/migration/types"
+
+var All map[types.MigrationVersion]types.Migration = make(map[types.MigrationVersion]types.Migration)
+
+func registerMigration(m types.Migration) {
+	All[m.Version()] = m
+}

migration/types/types.go

@@ -0,0 +1,33 @@
+package types
+
+import (
+	"time"
+
+	"github.com/jackc/pgx/v4"
+)
+
+type Migration interface {
+	Version() MigrationVersion
+	Name() string
+	Description() string
+	Up(conn pgx.Tx) error
+	Down(conn pgx.Tx) error
+}
+
+type MigrationVersion time.Time
+
+func (v MigrationVersion) String() string {
+	return time.Time(v).Format(time.RFC3339)
+}
+
+func (v MigrationVersion) Before(other MigrationVersion) bool {
+	return time.Time(v).Before(time.Time(other))
+}
+
+func (v MigrationVersion) Equal(other MigrationVersion) bool {
+	return time.Time(v).Equal(time.Time(other))
+}
+
+func (v MigrationVersion) IsZero() bool {
+	return time.Time(v).IsZero()
+}