package config
import (
"fmt"
"reflect"
"strings"
"github.com/hashicorp/hil"
"github.com/hashicorp/hil/ast"
"github.com/mitchellh/reflectwalk"
)
// interpolationWalker implements interfaces for the reflectwalk package
// (github.com/mitchellh/reflectwalk) that can be used to automatically
// execute a callback for an interpolation.
type interpolationWalker struct {
// F is the function to call for every interpolation. It can be nil.
//
// If Replace is true, then the return value of F will be used to
// replace the interpolation.
F interpolationWalkerFunc
Replace bool
// ContextF is an advanced version of F that also receives the
// location of where it is in the structure. This lets you do
// context-aware validation.
ContextF interpolationWalkerContextFunc
key []string
lastValue reflect.Value
loc reflectwalk.Location
cs []reflect.Value
csKey []reflect.Value
csData interface{}
sliceIndex []int
unknownKeys []string
}
// interpolationWalkerFunc is the callback called by interpolationWalk.
// It is called with any interpolation found. It should return a value
// to replace the interpolation with, along with any errors.
//
// If Replace is set to false in interpolationWalker, then the replace
// value can be anything as it will have no effect.
type interpolationWalkerFunc func(ast.Node) (interface{}, error)
// interpolationWalkerContextFunc is called by interpolationWalk if
// ContextF is set. This receives both the interpolation and the location
// where the interpolation is.
//
// This callback can be used to validate the location of the interpolation
// within the configuration.
type interpolationWalkerContextFunc func(reflectwalk.Location, ast.Node)
func (w *interpolationWalker) Enter(loc reflectwalk.Location) error {
w.loc = loc
return nil
}
func (w *interpolationWalker) Exit(loc reflectwalk.Location) error {
w.loc = reflectwalk.None
switch loc {
case reflectwalk.Map:
w.cs = w.cs[:len(w.cs)-1]
case reflectwalk.MapValue:
w.key = w.key[:len(w.key)-1]
w.csKey = w.csKey[:len(w.csKey)-1]
case reflectwalk.Slice:
// Split any values that need to be split
w.splitSlice()
w.cs = w.cs[:len(w.cs)-1]
case reflectwalk.SliceElem:
w.csKey = w.csKey[:len(w.csKey)-1]
w.sliceIndex = w.sliceIndex[:len(w.sliceIndex)-1]
}
return nil
}
func (w *interpolationWalker) Map(m reflect.Value) error {
w.cs = append(w.cs, m)
return nil
}
func (w *interpolationWalker) MapElem(m, k, v reflect.Value) error {
w.csData = k
w.csKey = append(w.csKey, k)
if l := len(w.sliceIndex); l > 0 {
w.key = append(w.key, fmt.Sprintf("%d.%s", w.sliceIndex[l-1], k.String()))
} else {
w.key = append(w.key, k.String())
}
w.lastValue = v
return nil
}
func (w *interpolationWalker) Slice(s reflect.Value) error {
w.cs = append(w.cs, s)
return nil
}
func (w *interpolationWalker) SliceElem(i int, elem reflect.Value) error {
w.csKey = append(w.csKey, reflect.ValueOf(i))
w.sliceIndex = append(w.sliceIndex, i)
return nil
}
func (w *interpolationWalker) Primitive(v reflect.Value) error {
setV := v
// We only care about strings
if v.Kind() == reflect.Interface {
setV = v
v = v.Elem()
}
if v.Kind() != reflect.String {
return nil
}
astRoot, err := hil.Parse(v.String())
if err != nil {
return err
}
// If the AST we got is just a literal string value with the same
// value then we ignore it. We have to check if its the same value
// because it is possible to input a string, get out a string, and
// have it be different. For example: "foo-$${bar}" turns into
// "foo-${bar}"
if n, ok := astRoot.(*ast.LiteralNode); ok {
if s, ok := n.Value.(string); ok && s == v.String() {
return nil
}
}
if w.ContextF != nil {
w.ContextF(w.loc, astRoot)
}
if w.F == nil {
return nil
}
replaceVal, err := w.F(astRoot)
if err != nil {
return fmt.Errorf(
"%s in:\n\n%s",
err, v.String())
}
if w.Replace {
// We need to determine if we need to remove this element
// if the result contains any "UnknownVariableValue" which is
// set if it is computed. This behavior is different if we're
// splitting (in a SliceElem) or not.
remove := false
if w.loc == reflectwalk.SliceElem {
switch typedReplaceVal := replaceVal.(type) {
case string:
if typedReplaceVal == UnknownVariableValue {
remove = true
}
case []interface{}:
if hasUnknownValue(typedReplaceVal) {
remove = true
}
}
} else if replaceVal == UnknownVariableValue {
remove = true
}
if remove {
w.unknownKeys = append(w.unknownKeys, strings.Join(w.key, "."))
}
resultVal := reflect.ValueOf(replaceVal)
switch w.loc {
case reflectwalk.MapKey:
m := w.cs[len(w.cs)-1]
// Delete the old value
var zero reflect.Value
m.SetMapIndex(w.csData.(reflect.Value), zero)
// Set the new key with the existing value
m.SetMapIndex(resultVal, w.lastValue)
// Set the key to be the new key
w.csData = resultVal
case reflectwalk.MapValue:
// If we're in a map, then the only way to set a map value is
// to set it directly.
m := w.cs[len(w.cs)-1]
mk := w.csData.(reflect.Value)
m.SetMapIndex(mk, resultVal)
default:
// Otherwise, we should be addressable
setV.Set(resultVal)
}
}
return nil
}
func (w *interpolationWalker) replaceCurrent(v reflect.Value) {
// if we don't have at least 2 values, we're not going to find a map, but
// we could panic.
if len(w.cs) < 2 {
return
}
c := w.cs[len(w.cs)-2]
switch c.Kind() {
case reflect.Map:
// Get the key and delete it
k := w.csKey[len(w.csKey)-1]
c.SetMapIndex(k, v)
}
}
func hasUnknownValue(variable []interface{}) bool {
for _, value := range variable {
if strVal, ok := value.(string); ok {
if strVal == UnknownVariableValue {
return true
}
}
}
return false
}
func (w *interpolationWalker) splitSlice() {
raw := w.cs[len(w.cs)-1]
var s []interface{}
switch v := raw.Interface().(type) {
case []interface{}:
s = v
case []map[string]interface{}:
return
}
split := false
for _, val := range s {
if varVal, ok := val.(ast.Variable); ok && varVal.Type == ast.TypeList {
split = true
}
if _, ok := val.([]interface{}); ok {
split = true
}
}
if !split {
return
}
result := make([]interface{}, 0)
for _, v := range s {
switch val := v.(type) {
case ast.Variable:
switch val.Type {
case ast.TypeList:
elements := val.Value.([]ast.Variable)
for _, element := range elements {
result = append(result, element.Value)
}
default:
result = append(result, val.Value)
}
case []interface{}:
result = append(result, val...)
default:
result = append(result, v)
}
}
w.replaceCurrent(reflect.ValueOf(result))
}
