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package templatebuilder
import (
"bytes"
"embed"
"encoding/json"
"io/fs"
"path"
"strings"
"sync"
"text/template"
"golang.org/x/xerrors"
)
// BaseOS enumerates operating systems for base template filtering.
type BaseOS string
const (
BaseOSLinux BaseOS = "linux"
BaseOSWindows BaseOS = "windows"
)
// validBaseOS maps base.json os strings to their typed equivalents.
var validBaseOS = map[string]BaseOS{
"linux": BaseOSLinux,
"windows": BaseOSWindows,
}
//go:embed bases
var basesFS embed.FS
const basesDir = "bases"
// templateSuffix identifies Go template files that are pre-parsed at load time.
// Terraform templatefile() inputs (.tftpl) are not Go templates and are left
// as raw files in the embedded FS.
const templateSuffix = ".tf.tmpl"
// BaseManifest is the on-disk schema for a base.json file.
type BaseManifest struct {
ID string `json:"id"`
DisplayName string `json:"display_name"`
OS string `json:"os"`
DefaultContext BaseDefaultContext `json:"default_context"`
Variables []ModuleVariable `json:"variables"`
}
// BaseDefaultContext holds default render values stored in base.json.
type BaseDefaultContext struct {
ContainerImage string `json:"container_image,omitempty"`
}
// parsedBase holds the result of loading and pre-parsing a single base
// template directory.
type parsedBase struct {
Manifest BaseManifest
Templates map[string]*template.Template
FS fs.FS
Readme string // full README.md content (including frontmatter)
Prerequisites string // content between prerequisite comment markers
ExtraFiles map[string][]byte // non-template, non-manifest files (e.g. .tftpl)
}
var loadBases = sync.OnceValues(func() (map[string]*parsedBase, error) {
return parseBasesFromFS(basesFS)
})
// parseBasesFromFS reads and validates all base.json manifests and pre-parses
// Go template files from the given filesystem. Most callers should use the
// exported accessors, which read from the cached embedded catalog.
func parseBasesFromFS(fsys fs.FS) (map[string]*parsedBase, error) {
sub, err := fs.Sub(fsys, basesDir)
if err != nil {
return nil, xerrors.Errorf("open embedded base catalog: %w", err)
}
dirs, err := fs.ReadDir(sub, ".")
if err != nil {
return nil, xerrors.Errorf("list base catalog entries: %w", err)
}
bases := make(map[string]*parsedBase)
for _, dir := range dirs {
if !dir.IsDir() {
continue
}
base, err := parseBaseDir(sub, dir.Name())
if err != nil {
return nil, err
}
if bases[base.Manifest.ID] != nil {
return nil, xerrors.Errorf("duplicate base id %q", base.Manifest.ID)
}
bases[base.Manifest.ID] = base
}
return bases, nil
}
// parseBaseDir loads a single base template directory: reads the
// manifest, pre-parses Go templates, reads the README, and collects
// extra files.
func parseBaseDir(parent fs.FS, dirName string) (*parsedBase, error) {
manifest, err := parseManifest(parent, dirName)
if err != nil {
return nil, err
}
baseFS, err := fs.Sub(parent, dirName)
if err != nil {
return nil, xerrors.Errorf("sub fs for %s: %w", dirName, err)
}
templates, err := parseTemplatesFromFS(baseFS)
if err != nil {
return nil, xerrors.Errorf("parse templates for base %q: %w", manifest.ID, err)
}
readmeData, err := fs.ReadFile(baseFS, "README.md")
if err != nil {
return nil, xerrors.Errorf("read README.md for base %q: %w", manifest.ID, err)
}
readme := string(readmeData)
extraFiles, err := collectExtraFilesFromFS(baseFS)
if err != nil {
return nil, xerrors.Errorf("collect extra files for base %q: %w", manifest.ID, err)
}
return &parsedBase{
Manifest: manifest,
Templates: templates,
FS: baseFS,
Readme: readme,
Prerequisites: ExtractPrerequisites(readme),
ExtraFiles: extraFiles,
}, nil
}
// parseManifest reads and validates a base.json file from the given
// directory within parent.
func parseManifest(parent fs.FS, dirName string) (BaseManifest, error) {
manifestPath := path.Join(dirName, "base.json")
data, err := fs.ReadFile(parent, manifestPath)
if err != nil {
return BaseManifest{}, xerrors.Errorf("read %s: %w", manifestPath, err)
}
var manifest BaseManifest
dec := json.NewDecoder(bytes.NewReader(data))
dec.DisallowUnknownFields()
if err := dec.Decode(&manifest); err != nil {
return BaseManifest{}, xerrors.Errorf("decode %s: %w", manifestPath, err)
}
if manifest.ID == "" {
return BaseManifest{}, xerrors.Errorf("base in %s has empty id", dirName)
}
if _, ok := validBaseOS[manifest.OS]; !ok && manifest.OS != "" {
return BaseManifest{}, xerrors.Errorf("base %q has unknown os %q", manifest.ID, manifest.OS)
}
return manifest, nil
}
// parseTemplatesFromFS walks the filesystem and pre-parses all .tf.tmpl files
// into Go templates. Returned keys are paths relative to the FS root.
func parseTemplatesFromFS(fsys fs.FS) (map[string]*template.Template, error) {
templates := make(map[string]*template.Template)
err := fs.WalkDir(fsys, ".", func(p string, d fs.DirEntry, err error) error {
if err != nil {
return err
}
if d.IsDir() || !strings.HasSuffix(p, templateSuffix) {
return nil
}
raw, err := fs.ReadFile(fsys, p)
if err != nil {
return xerrors.Errorf("read %s: %w", p, err)
}
tmpl, err := template.New(p).Parse(string(raw))
if err != nil {
return xerrors.Errorf("parse %s: %w", p, err)
}
templates[p] = tmpl
return nil
})
if err != nil {
return nil, err
}
return templates, nil
}
// BaseTemplateOS resolves the OS for a given example ID.
// Returns empty string if the example is not a known base template.
func BaseTemplateOS(exampleID string) BaseOS {
bases, err := loadBases()
if err != nil || bases[exampleID] == nil {
return ""
}
return validBaseOS[bases[exampleID].Manifest.OS]
}
// DefaultBaseRenderContext returns the render context that produces the
// canonical default output for a base template.
func DefaultBaseRenderContext(exampleID string) BaseRenderContext {
bases, err := loadBases()
if err != nil || bases[exampleID] == nil {
return BaseRenderContext{}
}
base := bases[exampleID]
dc := base.Manifest.DefaultContext
// Populate Variables from manifest defaults so that Go template
// rendering succeeds even without caller-supplied values.
vars := make(map[string]string, len(base.Manifest.Variables))
for _, v := range base.Manifest.Variables {
if v.Computed || v.Sensitive {
continue
}
if len(v.Default) > 0 && isSimpleJSONValue(v.Default) {
vars[v.Name] = string(v.Default)
}
}
return BaseRenderContext{
ContainerImage: dc.ContainerImage,
Variables: vars,
}
}
// BaseTemplateIDs returns the set of known base template example IDs.
func BaseTemplateIDs() []string {
bases, err := loadBases()
if err != nil {
return nil
}
ids := make([]string, 0, len(bases))
for id := range bases {
ids = append(ids, id)
}
return ids
}
// BaseVariables returns the user-facing variables for a given base
// template ID. Computed variables are excluded. Returns nil if the
// base is unknown or has no variables.
func BaseVariables(exampleID string) []ModuleVariable {
bases, err := loadBases()
if err != nil || bases[exampleID] == nil {
return nil
}
return bases[exampleID].Manifest.Variables
}
// BaseTemplateFS returns a filesystem rooted at the given base template
// directory within the embedded bases catalog. Returns an error if
// exampleID is not a known base template.
func BaseTemplateFS(exampleID string) (fs.FS, error) {
bases, err := loadBases()
if err != nil {
return nil, xerrors.Errorf("load base catalog: %w", err)
}
base, ok := bases[exampleID]
if !ok {
return nil, xerrors.Errorf("unknown base template %q", exampleID)
}
return base.FS, nil
}
// BaseReadme returns the full README.md content for a base template.
// Returns an empty string if the base is unknown or has no README.
func BaseReadme(exampleID string) string {
bases, err := loadBases()
if err != nil || bases[exampleID] == nil {
return ""
}
return bases[exampleID].Readme
}
// BasePrerequisites returns the prerequisites section extracted from
// the base template README. Returns an empty string if the base is
// unknown or has no prerequisites markers.
func BasePrerequisites(exampleID string) string {
bases, err := loadBases()
if err != nil || bases[exampleID] == nil {
return ""
}
return bases[exampleID].Prerequisites
}
// BaseExtraFiles returns the non-template, non-manifest files embedded
// in the base template directory (e.g. cloud-init .tftpl files). Returns
// nil if the base is unknown or has no extra files.
func BaseExtraFiles(exampleID string) map[string][]byte {
bases, err := loadBases()
if err != nil || bases[exampleID] == nil {
return nil
}
return bases[exampleID].ExtraFiles
}
// collectExtraFilesFromFS walks a base template filesystem and returns
// all files that are not Go templates (.tf.tmpl), the manifest
// (base.json), or the README. These are raw files that must be included
// in the output archive (e.g. Terraform templatefile() inputs).
func collectExtraFilesFromFS(baseFS fs.FS) (map[string][]byte, error) {
files := make(map[string][]byte)
err := fs.WalkDir(baseFS, ".", func(p string, d fs.DirEntry, err error) error {
if err != nil {
return err
}
if d.IsDir() {
return nil
}
if p == "base.json" || p == "README.md" || strings.HasSuffix(p, ".tf.tmpl") {
return nil
}
data, err := fs.ReadFile(baseFS, p)
if err != nil {
return xerrors.Errorf("read %s: %w", p, err)
}
files[p] = data
return nil
})
if err != nil {
return nil, err
}
return files, nil
}