Node selection capability (#541)

* add flag

* add node selection capability

* run tidy

* add Marshal for node structs

* Fixup info command filtering implementation

* Check filters for validity before attempting to use
* Accept filters that start with a '.' character (jq-style)
* Check validity of field at each step, to avoid reflect-related panics
* Minor refactoring to pull filtering into a separate function

---------

Co-authored-by: Angel Misevski <amisevsk@gmail.com>

go.mod

@@ -13,6 +13,7 @@ require (
 	golang.org/x/sync v0.8.0
 	golang.org/x/sys v0.26.0
 	golang.org/x/term v0.25.0
+	golang.org/x/text v0.19.0
 	gopkg.in/yaml.v3 v3.0.1
 	oras.land/oras-go/v2 v2.5.0
 )

go.sum

@@ -39,6 +39,8 @@ golang.org/x/sys v0.26.0 h1:KHjCJyddX0LoSTb3J+vWpupP9p0oznkqVk/IfjymZbo=
 golang.org/x/sys v0.26.0/go.mod h1:/VUhepiaJMQUp4+oa/7Zr1D23ma6VTLIYjOOTFZPUcA=
 golang.org/x/term v0.25.0 h1:WtHI/ltw4NvSUig5KARz9h521QvRC8RmF/cuYqifU24=
 golang.org/x/term v0.25.0/go.mod h1:RPyXicDX+6vLxogjjRxjgD2TKtmAO6NZBsBRfrOLu7M=
+golang.org/x/text v0.19.0 h1:kTxAhCbGbxhK0IwgSKiMO5awPoDQ0RpfiVYBfK860YM=
+golang.org/x/text v0.19.0/go.mod h1:BuEKDfySbSR4drPmRPG/7iBdf8hvFMuRexcpahXilzY=
 gopkg.in/check.v1 v0.0.0-20161208181325-20d25e280405 h1:yhCVgyC4o1eVCa2tZl7eS0r+SDo693bJlVdllGtEeKM=
 gopkg.in/check.v1 v0.0.0-20161208181325-20d25e280405/go.mod h1:Co6ibVJAznAaIkqp8huTwlJQCZ016jof/cbN4VW5Yz0=
 gopkg.in/yaml.v3 v3.0.1 h1:fxVm/GzAzEWqLHuvctI91KS9hhNmmWOoWu0XTYJS7CA=

pkg/cmd/info/cmd.go

@@ -17,19 +17,27 @@
 package info
 
 import (
+	"bytes"
 	"context"
 	"errors"
 	"fmt"
+	"reflect"
+	"regexp"
 	"strings"
 
+	"kitops/pkg/artifact"
 	"kitops/pkg/cmd/options"
 	"kitops/pkg/lib/constants"
 	"kitops/pkg/lib/repo/util"
 	"kitops/pkg/output"
 
 	"github.com/spf13/cobra"
+	"gopkg.in/yaml.v3"
 	"oras.land/oras-go/v2/errdef"
 	"oras.land/oras-go/v2/registry"
+
+	"golang.org/x/text/cases"
+	"golang.org/x/text/language"
 )
 
 const (
@@ -49,11 +57,15 @@ kit info mymodel@sha256:44136fa355b3678a1146ad16f7e8649e94fb4fc21fe77e8310c060f6
 kit info --remote registry.example.com/my-model:1.0.0`
 )
 
+// Currently supported filter syntax: alphanumeric (plus dashes and underscores), dot-delimited fields
+var validFilterRegexp = regexp.MustCompile(`^\.?[a-zA-Z0-9_-]+(\.[a-zA-Z0-9_-]+)*$`)
+
 type infoOptions struct {
 	options.NetworkOptions
 	configHome  string
 	checkRemote bool
 	modelRef    *registry.Reference
+	filter      string
 }
 
 func InfoCommand() *cobra.Command {
@@ -70,6 +82,7 @@ func InfoCommand() *cobra.Command {
 
 	opts.AddNetworkFlags(cmd)
 	cmd.Flags().BoolVarP(&opts.checkRemote, "remote", "r", false, "Check remote registry instead of local storage")
+	cmd.Flags().StringVarP(&opts.filter, "filter", "f", "", "filter with node selectors")
 	cmd.Flags().SortFlags = false
 
 	return cmd
@@ -87,11 +100,21 @@ func runCommand(opts *infoOptions) func(*cobra.Command, []string) error {
 			}
 			return output.Fatalf("Error resolving modelkit: %s", err)
 		}
-		yamlBytes, err := config.MarshalToYAML()
-		if err != nil {
-			return output.Fatalf("Error formatting manifest: %w", err)
+
+		if len(opts.filter) > 0 {
+			filteredOutput, err := filterKitfile(config, opts.filter)
+			if err != nil {
+				return output.Fatalln(err)
+			}
+			fmt.Print(string(filteredOutput))
+		} else {
+			yamlBytes, err := config.MarshalToYAML()
+			if err != nil {
+				return output.Fatalf("Error formatting manifest: %w", err)
+			}
+			fmt.Print(string(yamlBytes))
 		}
-		fmt.Println(string(yamlBytes))
+
 		return nil
 	}
 }
@@ -122,3 +145,43 @@ func (opts *infoOptions) complete(ctx context.Context, args []string) error {
 
 	return nil
 }
+
+func filterKitfile(config *artifact.KitFile, filter string) ([]byte, error) {
+	if err := checkFilterIsValid(filter); err != nil {
+		return nil, fmt.Errorf("invalid filter: %w", err)
+	}
+	// Accept filters that start (jq-style) and don't start with a '.'; we need to trim as otherwise we start the list
+	// with an empty string
+	filter = strings.TrimPrefix(filter, ".")
+
+	var filterSlice = strings.Split(filter, ".")
+	value := reflect.ValueOf(config)
+	for _, str := range filterSlice {
+		if value.Kind() == reflect.Ptr {
+			value = value.Elem()
+		}
+		field := value.FieldByName(cases.Title(language.Und, cases.NoLower).String(str))
+		if !field.IsValid() {
+			return nil, fmt.Errorf("error filtering output: cannot find required node")
+		}
+		value = field
+	}
+
+	buf := new(bytes.Buffer)
+	enc := yaml.NewEncoder(buf)
+	enc.SetIndent(2)
+	if err := enc.Encode(value.Interface()); err != nil {
+		return nil, fmt.Errorf("error formatting manifest: %w", err)
+	}
+	return buf.Bytes(), nil
+}
+
+func checkFilterIsValid(filter string) error {
+	if strings.Contains(filter, "[") {
+		return fmt.Errorf("array access using '[]' is not currently supported")
+	}
+	if !validFilterRegexp.MatchString(filter) {
+		return fmt.Errorf("invalid filter: %s", filter)
+	}
+	return nil
+}