misc: refactored caplets code in a dedicated package

caplets/caplet.go

@@ -0,0 +1,53 @@
+package caplets
+
+import (
+	"fmt"
+	"os"
+	"path/filepath"
+	"strings"
+)
+
+type Caplet struct {
+	Name string
+	Path string
+	Size int64
+	Code []string
+}
+
+func (cap *Caplet) Eval(argv []string, lineCb func(line string) error) error {
+	// the caplet might include other files (include directive, proxy modules, etc),
+	// temporarily change the working directory
+	cwd, err := os.Getwd()
+	if err != nil {
+		return fmt.Errorf("error while getting current working directory: %v", err)
+	}
+
+	capPath := filepath.Dir(cap.Path)
+	if err := os.Chdir(capPath); err != nil {
+		return fmt.Errorf("error while changing current working directory: %v", err)
+	}
+
+	defer func() {
+		if err := os.Chdir(cwd); err != nil {
+			fmt.Printf("error while restoring working directory: %v\n", err)
+		}
+	}()
+
+	if argv == nil {
+		argv = []string{}
+	}
+
+	for _, line := range cap.Code {
+		// replace $0 with argv[0], $1 with argv[1] and so on
+		for i, arg := range argv {
+			what := fmt.Sprintf("$%d", i)
+			line = strings.Replace(line, what, arg, -1)
+		}
+
+		if err = lineCb(line); err != nil {
+			return err
+		}
+	}
+
+	return nil
+}