/
tpl.go
87 lines (79 loc) · 1.67 KB
/
tpl.go
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package configure
import (
"bytes"
"fmt"
"io/ioutil"
"os"
"strings"
"text/template"
"github.com/gravitational/configure/cstrings"
"github.com/gravitational/trace"
)
func renderTemplate(data []byte) ([]byte, error) {
t := template.New("tpl")
c, err := newCtx()
if err != nil {
return nil, trace.Wrap(err)
}
t.Funcs(map[string]interface{}{
"env": c.Env,
"file": c.File,
})
t, err = t.Parse(string(data))
if err != nil {
return nil, trace.Wrap(err)
}
buf := &bytes.Buffer{}
if err := t.Execute(buf, nil); err != nil {
return nil, trace.Wrap(err)
}
return buf.Bytes(), nil
}
func newCtx() (*ctx, error) {
values := os.Environ()
c := &ctx{
env: make(map[string]string, len(values)),
}
for _, v := range values {
vals := strings.SplitN(v, "=", 2)
if len(vals) != 2 {
return nil, trace.Errorf("failed to parse variable: '%v'", v)
}
c.env[vals[0]] = vals[1]
}
return c, nil
}
type ctx struct {
env map[string]string
}
func (c *ctx) File(path string) (string, error) {
o, err := ioutil.ReadFile(path)
if err != nil {
return "", trace.Wrap(err, fmt.Sprintf("reading file: %v", path))
}
return string(o), nil
}
func (c *ctx) Env(key string) (string, error) {
v, ok := c.env[key]
if !ok {
return "", trace.Errorf("environment variable '%v' is not set", key)
}
values := cstrings.SplitComma(v)
out := make([]string, len(values))
for i, p := range values {
out[i] = quoteYAML(p)
}
return strings.Join(out, ","), nil
}
func quoteYAML(val string) string {
if len(val) == 0 {
return val
}
if strings.HasPrefix(val, "'") && strings.HasSuffix(val, "'") {
return val
}
if strings.ContainsAny(val, ":") {
return "'" + val + "'"
}
return val
}