capsule/pkg/template/unstructured.go

// Copyright 2020-2026 Project Capsule Authors
// SPDX-License-Identifier: Apache-2.0

package template

import (
	"bytes"
	"errors"
	"fmt"
	"io"
	"strings"
	"text/template"

	"k8s.io/apimachinery/pkg/apis/meta/v1/unstructured"
	kyaml "k8s.io/apimachinery/pkg/util/yaml"

	"github.com/projectcapsule/capsule/pkg/template/functions"
)

// RenderUnstructuredItems attempts to render a given string template into a list of unstructured resources.
func RenderUnstructuredItems(
	context ReferenceContext,
	key MissingKeyOption,
	tplString string,
) (items []*unstructured.Unstructured, err error) {
	tmpl, err := template.New("tpl").Option("missingkey=" + key.String()).Funcs(functions.ExtraFuncMap()).Parse(tplString)
	if err != nil {
		return
	}

	var rendered bytes.Buffer
	if err = tmpl.Execute(&rendered, context); err != nil {
		return
	}

	dec := kyaml.NewYAMLOrJSONDecoder(bytes.NewReader(rendered.Bytes()), 4096)

	var out []*unstructured.Unstructured

	for {
		var obj map[string]any
		if err := dec.Decode(&obj); err != nil {
			if errors.Is(err, io.EOF) {
				break
			}

			// Skip pure whitespace/--- separators that decode to nil/empty.
			return nil, fmt.Errorf("decode yaml: %w\nrendered template:\n%s", err, withLineNumbers(rendered.String()))
		}

		if len(obj) == 0 {
			continue
		}

		u := &unstructured.Unstructured{Object: obj}
		if u.GetAPIVersion() == "" && u.GetKind() == "" {
			continue
		}

		out = append(out, u)
	}

	return out, nil
}

func withLineNumbers(s string) string {
	lines := strings.Split(s, "\n")

	width := len(fmt.Sprintf("%d", len(lines)))

	var b strings.Builder

	for i, line := range lines {
		fmt.Fprintf(&b, "%*d | %s\n", width, i+1, line)
	}

	return b.String()
}