to build or not to build is the question

example/main.go

@@ -10,6 +10,26 @@ import (
 func main() {
 	m := testMachine()
 	testPackages(m)
+
+	loop := m.Packages.SortByName()
+	for loop.Scan() {
+		p := loop.Package()
+		log.Info("installed package:", p.Name, p.Version, p.PkgName)
+	}
+
+	if m.IsInstalled("bash") {
+		log.Info("bash installed check worked")
+	} else {
+		log.Info("bash installed check failed")
+		panic("bash")
+	}
+
+	if m.IsInstalled("foo") {
+		log.Info("foo not-installed check failed")
+		panic("foo")
+	} else {
+		log.Info("foo not-installed check worked")
+	}
 }
 
 func testMachine() *zoopb.Machine {
@@ -20,14 +40,13 @@ func testMachine() *zoopb.Machine {
 }
 
 func testPackages(m *zoopb.Machine) {
-	var all *zoopb.Packages
-	all = new(zoopb.Packages)
+	m.Packages = new(zoopb.Packages)
 	// r = zoopb.LoadJSON("go.wit.com/lib/protobuf/zoopb")
 
 	new1 := new(zoopb.Package)
 	new1.Name = "bash"
 	new1.Version = "5.2.21"
-	if all.Append(new1) {
+	if m.Packages.Append(new1) {
 		log.Info("added", new1.Name, "ok")
 	} else {
 		log.Info("added", new1.Name, "failed")
@@ -36,17 +55,17 @@ func testPackages(m *zoopb.Machine) {
 	new2 := new(zoopb.Package)
 	new2.Name = "go-clone"
 	new2.Version = "0.6.8" // good version of the macos
-	if all.Append(new2) {
+	if m.Packages.Append(new2) {
 		log.Info("added", new2.Name, "ok")
 	} else {
 		log.Info("added", new2.Name, "failed")
 	}
 
-	if all.Append(new2) {
+	if m.Packages.Append(new2) {
 		log.Info("added", new2.Name, "ok (this is bad)")
 	} else {
 		log.Info("added", new2.Name, "failed (but ok)")
 	}
 
-	fmt.Println("packages are:", len(all.Packages))
+	fmt.Println("package count = ", m.Packages.Len())
 }

wit.go

@@ -11,9 +11,70 @@ var VERSION string
 var BUILDTIME string
 
 func (m *Machine) IsInstalled(name string) bool {
+	loop := m.Packages.SortByName()
+	for loop.Scan() {
+		p := loop.Package()
+		if name == p.Name {
+			// log.Info("package installed:", p.Name, p.Version, p.PkgName)
+			return true
+		}
+	}
+
+	// log.Info("package not-installed:", name)
 	return false
 }
 
+func (m *Machine) FindInstalledByName(name string) *Package {
+	loop := m.Packages.SortByName()
+	for loop.Scan() {
+		p := loop.Package()
+		if name == p.Name {
+			// log.Info("package installed:", p.Name, p.Version, p.PkgName)
+			return p
+		}
+	}
+
+	// log.Info("package not-installed:", name)
+	return nil
+}
+
+// looks to see if any package matches a name and version
+// if version == "", return the first name found
+func (m *Machine) FindVersion(name string, version string) *Package {
+	// first check all installed versions
+	loop := m.Packages.SortByName()
+	for loop.Scan() {
+		p := loop.Package()
+		if name == p.Name {
+			if version == "" {
+				return p
+			} else {
+				if version == p.Version {
+					return p
+				}
+			}
+		}
+	}
+
+	// check all wit packages
+	loop = m.Wit.SortByName()
+	for loop.Scan() {
+		p := loop.Package()
+		if name == p.Name {
+			if version == "" {
+				return p
+			} else {
+				if version == p.Version {
+					return p
+				}
+			}
+		}
+	}
+
+	// log.Info("package not-installed:", name)
+	return nil
+}
+
 // read the package list file from mirrors.wit.com
 func (m *Machine) InitWit() error {
 	if m.Wit == nil {
@@ -117,10 +178,10 @@ func parsePackageInfo(lines string) *Package {
 	}
 
 	p := Package{
-		Name:     name,
-		Version:  version,
+		Name:    name,
+		Version: version,
 		PkgName: filename,
-		SrcPath:   gopath,
+		SrcPath: gopath,
 	}
 
 	return &p