tvl-depot/ops/kontemplate/templater/templater.go

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// Copyright (C) 2016-2019 Vincent Ambo <mail@tazj.in>
//
// This file is part of Kontemplate.
//
// Kontemplate is free software: you can redistribute it and/or modify
// it under the terms of the GNU General Public License as published by
// the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.
package templater
import (
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"bytes"
"encoding/json"
"fmt"
"io/ioutil"
"os"
"os/exec"
"path"
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"strings"
"text/template"
"github.com/Masterminds/sprig/v3"
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"github.com/tazjin/kontemplate/context"
"github.com/tazjin/kontemplate/util"
)
const failOnMissingKeys string = "missingkey=error"
type RenderedResource struct {
Filename string
Rendered string
}
type RenderedResourceSet struct {
Name string
Resources []RenderedResource
Args []string
}
func LoadAndApplyTemplates(include *[]string, exclude *[]string, c *context.Context) ([]RenderedResourceSet, error) {
limitedResourceSets := applyLimits(&c.ResourceSets, include, exclude)
renderedResourceSets := make([]RenderedResourceSet, 0)
if len(*limitedResourceSets) == 0 {
return renderedResourceSets, fmt.Errorf("No valid resource sets included!")
}
for _, rs := range *limitedResourceSets {
set, err := processResourceSet(c, &rs)
if err != nil {
return nil, err
}
renderedResourceSets = append(renderedResourceSets, *set)
}
return renderedResourceSets, nil
}
func processResourceSet(ctx *context.Context, rs *context.ResourceSet) (*RenderedResourceSet, error) {
fmt.Fprintf(os.Stderr, "Loading resources for %s\n", rs.Name)
fileInfo, err := os.Stat(rs.Path)
if err != nil {
return nil, err
}
var files []os.FileInfo
var resources []RenderedResource
// Treat single-file resource paths separately from resource
// sets containing multiple templates
if fileInfo.IsDir() {
// Explicitly discard this error, which will give us an empty
// list of files instead.
// This will end up printing a warning to the user, but it
// won't stop the rest of the process.
files, _ = ioutil.ReadDir(rs.Path)
resources, err = processFiles(ctx, rs, files)
if err != nil {
return nil, err
}
} else {
resource, err := templateFile(ctx, rs, rs.Path)
if err != nil {
return nil, err
}
resources = []RenderedResource{resource}
}
return &RenderedResourceSet{
Name: rs.Name,
Resources: resources,
Args: rs.Args,
}, nil
}
func processFiles(ctx *context.Context, rs *context.ResourceSet, files []os.FileInfo) ([]RenderedResource, error) {
resources := make([]RenderedResource, 0)
for _, file := range files {
if !file.IsDir() && isResourceFile(file) {
path := path.Join(rs.Path, file.Name())
res, err := templateFile(ctx, rs, path)
if err != nil {
return resources, err
}
resources = append(resources, res)
}
}
return resources, nil
}
func templateFile(ctx *context.Context, rs *context.ResourceSet, filepath string) (RenderedResource, error) {
var resource RenderedResource
tpl, err := template.New(path.Base(filepath)).Funcs(templateFuncs(ctx, rs)).Option(failOnMissingKeys).ParseFiles(filepath)
if err != nil {
return resource, fmt.Errorf("Could not load template %s: %v", filepath, err)
}
var b bytes.Buffer
err = tpl.Execute(&b, rs.Values)
if err != nil {
return resource, fmt.Errorf("Error while templating %s: %v", filepath, err)
}
resource = RenderedResource{
Filename: path.Base(filepath),
Rendered: b.String(),
}
return resource, nil
}
// Applies the limits of explicitly included or excluded resources and returns the updated resource set.
// Exclude takes priority over include
func applyLimits(rs *[]context.ResourceSet, include *[]string, exclude *[]string) *[]context.ResourceSet {
if len(*include) == 0 && len(*exclude) == 0 {
return rs
}
// Exclude excluded resource sets
excluded := make([]context.ResourceSet, 0)
for _, r := range *rs {
if !matchesResourceSet(exclude, &r) {
excluded = append(excluded, r)
}
}
// Include included resource sets
if len(*include) == 0 {
return &excluded
}
included := make([]context.ResourceSet, 0)
for _, r := range excluded {
if matchesResourceSet(include, &r) {
included = append(included, r)
}
}
return &included
}
// Check whether an include/exclude string slice matches a resource set
func matchesResourceSet(s *[]string, rs *context.ResourceSet) bool {
for _, r := range *s {
r = strings.TrimSuffix(r, "/")
if r == rs.Name || r == rs.Parent {
return true
}
}
return false
}
func templateFuncs(c *context.Context, rs *context.ResourceSet) template.FuncMap {
m := sprig.TxtFuncMap()
m["json"] = func(data interface{}) string {
b, _ := json.Marshal(data)
return string(b)
}
m["passLookup"] = GetFromPass
m["gitHEAD"] = func() (string, error) {
out, err := exec.Command("git", "-C", c.BaseDir, "rev-parse", "HEAD").Output()
if err != nil {
return "", err
}
output := strings.TrimSpace(string(out))
return output, nil
}
m["lookupIPAddr"] = GetIPsFromDNS
m["insertFile"] = func(file string) (string, error) {
data, err := ioutil.ReadFile(path.Join(rs.Path, file))
if err != nil {
return "", err
}
return string(data), nil
}
m["insertTemplate"] = func(file string) (string, error) {
data, err := templateFile(c, rs, path.Join(rs.Path, file))
if err != nil {
return "", err
}
return data.Rendered, nil
}
m["default"] = func(defaultVal interface{}, varName string) interface{} {
if val, ok := rs.Values[varName]; ok {
return val
}
return defaultVal
}
return m
}
// Checks whether a file is a resource file (i.e. is YAML or JSON) and not a default values file.
func isResourceFile(f os.FileInfo) bool {
for _, defaultFile := range util.DefaultFilenames {
if f.Name() == defaultFile {
return false
}
}
return strings.HasSuffix(f.Name(), "yaml") ||
strings.HasSuffix(f.Name(), "yml") ||
strings.HasSuffix(f.Name(), "json")
}