forked from rancher/rancher-compose-executor
/
interpolation.go
157 lines (123 loc) · 3.12 KB
/
interpolation.go
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package config
import (
"bytes"
"fmt"
"strings"
"github.com/Sirupsen/logrus"
)
func isNum(c uint8) bool {
return c >= '0' && c <= '9'
}
func validVariableNameChar(c uint8) bool {
return c == '_' ||
c >= 'A' && c <= 'Z' ||
c >= 'a' && c <= 'z' ||
isNum(c)
}
func parseVariable(line string, pos int, mapping func(string) string) (string, int, bool) {
var buffer bytes.Buffer
for ; pos < len(line); pos++ {
c := line[pos]
switch {
case validVariableNameChar(c):
buffer.WriteByte(c)
default:
return mapping(buffer.String()), pos - 1, true
}
}
return mapping(buffer.String()), pos, true
}
func parseVariableWithBraces(line string, pos int, mapping func(string) string) (string, int, bool) {
var buffer bytes.Buffer
for ; pos < len(line); pos++ {
c := line[pos]
switch {
case c == '}':
bufferString := buffer.String()
if bufferString == "" {
return "", 0, false
}
return mapping(buffer.String()), pos, true
case validVariableNameChar(c):
buffer.WriteByte(c)
default:
return "", 0, false
}
}
return "", 0, false
}
func parseInterpolationExpression(line string, pos int, mapping func(string) string) (string, int, bool) {
c := line[pos]
switch {
case c == '$':
return "$", pos, true
case c == '{':
return parseVariableWithBraces(line, pos+1, mapping)
case !isNum(c) && validVariableNameChar(c):
// Variables can't start with a number
return parseVariable(line, pos, mapping)
default:
return "", 0, false
}
}
func parseLine(line string, mapping func(string) string) (string, bool) {
var buffer bytes.Buffer
for pos := 0; pos < len(line); pos++ {
c := line[pos]
switch {
case c == '$':
var replaced string
var success bool
replaced, pos, success = parseInterpolationExpression(line, pos+1, mapping)
if !success {
return "", false
}
buffer.WriteString(replaced)
default:
buffer.WriteByte(c)
}
}
return buffer.String(), true
}
func parseConfig(key string, data *interface{}, mapping func(string) string) error {
switch typedData := (*data).(type) {
case string:
var success bool
*data, success = parseLine(typedData, mapping)
if !success {
return fmt.Errorf("Invalid interpolation format for key \"%s\": \"%s\"", key, typedData)
}
case []interface{}:
for k, v := range typedData {
err := parseConfig(key, &v, mapping)
if err != nil {
return err
}
typedData[k] = v
}
case map[interface{}]interface{}:
for k, v := range typedData {
err := parseConfig(key, &v, mapping)
if err != nil {
return err
}
typedData[k] = v
}
}
return nil
}
// Interpolate replaces variables in a map entry
func Interpolate(key string, data *interface{}, environmentLookup EnvironmentLookup) error {
return parseConfig(key, data, func(s string) string {
values := environmentLookup.Lookup(s, nil)
if len(values) == 0 {
logrus.Warnf("The %s variable is not set. Substituting a blank string.", s)
return ""
}
// Use first result if many are given
value := values[0]
// Environment variables come in key=value format
// Return everything past first '='
return strings.SplitN(value, "=", 2)[1]
})
}