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{}: for _, element := range val { result = append(result, element) } default: result = append(result, v) } } w.replaceCurrent(reflect.ValueOf(result)) }