1package schema
2
3import (
4	"fmt"
5)
6
7// DataSourceResourceShim takes a Resource instance describing a data source
8// (with a Read implementation and a Schema, at least) and returns a new
9// Resource instance with additional Create and Delete implementations that
10// allow the data source to be used as a resource.
11//
12// This is a backward-compatibility layer for data sources that were formerly
13// read-only resources before the data source concept was added. It should not
14// be used for any *new* data sources.
15//
16// The Read function for the data source *must* call d.SetId with a non-empty
17// id in order for this shim to function as expected.
18//
19// The provided Resource instance, and its schema, will be modified in-place
20// to make it suitable for use as a full resource.
21func DataSourceResourceShim(name string, dataSource *Resource) *Resource {
22	// Recursively, in-place adjust the schema so that it has ForceNew
23	// on any user-settable resource.
24	dataSourceResourceShimAdjustSchema(dataSource.Schema)
25
26	dataSource.Create = CreateFunc(dataSource.Read)
27	dataSource.Delete = func(d *ResourceData, meta interface{}) error {
28		d.SetId("")
29		return nil
30	}
31	dataSource.Update = nil // should already be nil, but let's make sure
32
33	// FIXME: Link to some further docs either on the website or in the
34	// changelog, once such a thing exists.
35	dataSource.DeprecationMessage = fmt.Sprintf(
36		"using %s as a resource is deprecated; consider using the data source instead",
37		name,
38	)
39
40	return dataSource
41}
42
43func dataSourceResourceShimAdjustSchema(schema map[string]*Schema) {
44	for _, s := range schema {
45		// If the attribute is configurable then it must be ForceNew,
46		// since we have no Update implementation.
47		if s.Required || s.Optional {
48			s.ForceNew = true
49		}
50
51		// If the attribute is a nested resource, we need to recursively
52		// apply these same adjustments to it.
53		if s.Elem != nil {
54			if r, ok := s.Elem.(*Resource); ok {
55				dataSourceResourceShimAdjustSchema(r.Schema)
56			}
57		}
58	}
59}
60