reorg: breaking out functionality into separate subcommands

cmd.go

@@ -0,0 +1,35 @@
+package main
+
+import (
+	"flag"
+	// "fmt"
+	"os"
+)
+
+// shamelessly snagged from the go tool
+// each command gets its own set of args,
+// defines its own entry point, and provides its own help
+type Command struct {
+	Run  func(cmd *Command, args ...string)
+	Flag flag.FlagSet
+
+	Name  string
+	Usage string
+
+	Summary string
+	Help    string
+}
+
+func (c *Command) Exec(args []string) {
+	c.Flag.Usage = func() {
+		// helpFunc(c, c.Name)
+	}
+	c.Flag.Parse(args)
+	defer func() {
+		if r := recover(); r != nil {
+			panic(r)
+		}
+		os.Exit(1)
+	}()
+	c.Run(c, c.Flag.Args()...)
+}

dbconf.go

@@ -0,0 +1,37 @@
+package main
+
+import (
+	"fmt"
+	"github.com/kylelemons/go-gypsy/yaml"
+)
+
+type DBConf struct {
+	Name    string
+	Driver  string
+	OpenStr string
+}
+
+// extract configuration details from the given file
+func dbConfFromFile(path, envtype string) (*DBConf, error) {
+
+	f, err := yaml.ReadFile(path)
+	if err != nil {
+		return nil, err
+	}
+
+	drv, derr := f.Get(fmt.Sprintf("%s.driver", envtype))
+	if derr != nil {
+		return nil, derr
+	}
+
+	open, oerr := f.Get(fmt.Sprintf("%s.open", envtype))
+	if oerr != nil {
+		return nil, oerr
+	}
+
+	return &DBConf{
+		Name:    envtype,
+		Driver:  drv,
+		OpenStr: open,
+	}, nil
+}

main.go

@@ -3,53 +3,39 @@ package main
 import (
 	"flag"
 	"fmt"
-	"github.com/kylelemons/go-gypsy/yaml"
-	"log"
-	"path"
+	"os"
+	"strings"
 )
 
-type DBConf struct {
-	Name    string
-	Driver  string
-	OpenStr string
+var commands = []*Command{
+	upCmd,
 }
 
-var dbFolder = flag.String("db", "db", "folder containing db info")
-var dbConfName = flag.String("config", "development", "which DB configuration to use")
-var targetVersion = flag.Int("target", -1, "which DB version to target (defaults to latest version)")
-
 func main() {
+
+	// XXX: create a flag.Usage that dumps all commands
 	flag.Parse()
 
-	conf, err := dbConfFromFile(path.Join(*dbFolder, "dbconf.yml"), *dbConfName)
-	if err != nil {
-		log.Fatal(err)
+	args := flag.Args()
+	if len(args) == 0 {
+		flag.Usage()
+		return
 	}
 
-	runMigrations(conf, path.Join(*dbFolder, "migrations"), *targetVersion)
-}
-
-// extract configuration details from the given file
-func dbConfFromFile(path, envtype string) (*DBConf, error) {
-
-	f, err := yaml.ReadFile(path)
-	if err != nil {
-		return nil, err
-	}
-
-	drv, derr := f.Get(fmt.Sprintf("%s.driver", envtype))
-	if derr != nil {
-		return nil, derr
-	}
-
-	open, oerr := f.Get(fmt.Sprintf("%s.open", envtype))
-	if oerr != nil {
-		return nil, oerr
-	}
-
-	return &DBConf{
-		Name:    envtype,
-		Driver:  drv,
-		OpenStr: open,
-	}, nil
+	var cmd *Command
+	name := args[0]
+	for _, c := range commands {
+		if strings.HasPrefix(c.Name, name) {
+			cmd = c
+			break
+		}
+	}
+
+	if cmd == nil {
+		fmt.Printf("error: unknown command %q\n", name)
+		flag.Usage()
+		os.Exit(1)
+	}
+
+	cmd.Exec(args[1:])
 }

migrate.go

@@ -41,7 +41,7 @@ func runMigrations(conf *DBConf, migrationsDir string, target int) {
 
 	current, e := ensureDBVersion(db)
 	if e != nil {
-		log.Fatal("couldn't get/set DB version")
+		log.Fatalf("couldn't get DB version: %v", e)
 	}
 
 	mm, err := collectMigrations(migrationsDir, current, target)
@@ -97,12 +97,6 @@ func collectMigrations(dirpath string, current, target int) (mm *MigrationMap, e
 		Migrations: make(map[int]Migration),
 	}
 
-	// if target is the default -1,
-	// we need to find the most recent possible version to target
-	if target < 0 {
-		target = mostRecentVersionAvailable(names)
-	}
-
 	// extract the numeric component of each migration,
 	// filter out any uninteresting files,
 	// and ensure we only have one file per migration version.
@@ -134,31 +128,6 @@ func collectMigrations(dirpath string, current, target int) (mm *MigrationMap, e
 	return mm, nil
 }
 
-// helper to identify the most recent possible version
-// within a folder of migration scripts
-func mostRecentVersionAvailable(names []string) int {
-
-	mostRecent := -1
-
-	for _, name := range names {
-
-		if ext := path.Ext(name); ext != ".go" && ext != ".sql" {
-			continue
-		}
-
-		v, e := numericComponent(name)
-		if e != nil {
-			continue
-		}
-
-		if v > mostRecent {
-			mostRecent = v
-		}
-	}
-
-	return mostRecent
-}
-
 func versionFilter(v, current, target int) bool {
 
 	// special case - default target value

up.go

@@ -0,0 +1,68 @@
+package main
+
+import (
+	"log"
+	"os"
+	"path"
+)
+
+var upCmd = &Command{
+	Name:    "up",
+	Usage:   "",
+	Summary: "Migrate the DB to the most recent version available",
+	Help:    `up extended help here...`,
+}
+
+var dbFolder = upCmd.Flag.String("db", "db", "folder containing db info")
+var dbConfName = upCmd.Flag.String("config", "development", "which DB configuration to use")
+
+func upRun(cmd *Command, args ...string) {
+
+	conf, err := dbConfFromFile(path.Join(*dbFolder, "dbconf.yml"), *dbConfName)
+	if err != nil {
+		log.Fatal(err)
+	}
+
+	folder := path.Join(*dbFolder, "migrations")
+	target := mostRecentVersionAvailable(folder)
+	runMigrations(conf, folder, target)
+}
+
+// helper to identify the most recent possible version
+// within a folder of migration scripts
+func mostRecentVersionAvailable(dirpath string) int {
+
+	dir, err := os.Open(dirpath)
+	if err != nil {
+		log.Fatal(err)
+	}
+
+	names, err := dir.Readdirnames(0)
+	if err != nil {
+		log.Fatal(err)
+	}
+
+	mostRecent := -1
+
+	for _, name := range names {
+
+		if ext := path.Ext(name); ext != ".go" && ext != ".sql" {
+			continue
+		}
+
+		v, e := numericComponent(name)
+		if e != nil {
+			continue
+		}
+
+		if v > mostRecent {
+			mostRecent = v
+		}
+	}
+
+	return mostRecent
+}
+
+func init() {
+	upCmd.Run = upRun
+}