vendor/github.com/hashicorp/terraform/helper/schema/field_reader_multi.go

   1 package schema
   2
   3 import (
   4         "fmt"
   5 )
   6
   7 // MultiLevelFieldReader reads from other field readers,
   8 // merging their results along the way in a specific order. You can specify
   9 // "levels" and name them in order to read only an exact level or up to
  10 // a specific level.
  11 //
  12 // This is useful for saying things such as "read the field from the state
  13 // and config and merge them" or "read the latest value of the field".
  14 type MultiLevelFieldReader struct {
  15         Readers map[string]FieldReader
  16         Levels  []string
  17 }
  18
  19 func (r *MultiLevelFieldReader) ReadField(address []string) (FieldReadResult, error) {
  20         return r.ReadFieldMerge(address, r.Levels[len(r.Levels)-1])
  21 }
  22
  23 func (r *MultiLevelFieldReader) ReadFieldExact(
  24         address []string, level string) (FieldReadResult, error) {
  25         reader, ok := r.Readers[level]
  26         if !ok {
  27                 return FieldReadResult{}, fmt.Errorf(
  28                         "Unknown reader level: %s", level)
  29         }
  30
  31         result, err := reader.ReadField(address)
  32         if err != nil {
  33                 return FieldReadResult{}, fmt.Errorf(
  34                         "Error reading level %s: %s", level, err)
  35         }
  36
  37         return result, nil
  38 }
  39
  40 func (r *MultiLevelFieldReader) ReadFieldMerge(
  41         address []string, level string) (FieldReadResult, error) {
  42         var result FieldReadResult
  43         for _, l := range r.Levels {
  44                 if r, ok := r.Readers[l]; ok {
  45                         out, err := r.ReadField(address)
  46                         if err != nil {
  47                                 return FieldReadResult{}, fmt.Errorf(
  48                                         "Error reading level %s: %s", l, err)
  49                         }
  50
  51                         // TODO: computed
  52                         if out.Exists {
  53                                 result = out
  54                         }
  55                 }
  56
  57                 if l == level {
  58                         break
  59                 }
  60         }
  61
  62         return result, nil
  63 }