Specialized client for interacting with Consul keys

This deals with some of the quirks of interacting with the Consul API,
with the goal of making the consul_keys resource implementation, and
later the consul_keys data source, less noisy to read.

builtin/providers/consul/key_client.go

@@ -0,0 +1,66 @@
+package consul
+
+import (
+	"fmt"
+	"log"
+
+	consulapi "github.com/hashicorp/consul/api"
+)
+
+// keyClient is a wrapper around the upstream Consul client that is
+// specialized for Terraform's manipulations of the key/value store.
+type keyClient struct {
+	client *consulapi.KV
+	qOpts  *consulapi.QueryOptions
+	wOpts  *consulapi.WriteOptions
+}
+
+func newKeyClient(realClient *consulapi.KV, dc, token string) *keyClient {
+	qOpts := &consulapi.QueryOptions{Datacenter: dc, Token: token}
+	wOpts := &consulapi.WriteOptions{Datacenter: dc, Token: token}
+
+	return &keyClient{
+		client: realClient,
+		qOpts:  qOpts,
+		wOpts:  wOpts,
+	}
+}
+
+func (c *keyClient) Get(path string) (string, error) {
+	log.Printf(
+		"[DEBUG] Reading key '%s' in %s",
+		path, c.qOpts.Datacenter,
+	)
+	pair, _, err := c.client.Get(path, c.qOpts)
+	if err != nil {
+		return "", fmt.Errorf("Failed to read Consul key '%s': %s", path, err)
+	}
+	value := ""
+	if pair != nil {
+		value = string(pair.Value)
+	}
+	return value, nil
+}
+
+func (c *keyClient) Put(path, value string) error {
+	log.Printf(
+		"[DEBUG] Setting key '%s' to '%v' in %s",
+		path, value, c.wOpts.Datacenter,
+	)
+	pair := consulapi.KVPair{Key: path, Value: []byte(value)}
+	if _, err := c.client.Put(&pair, c.wOpts); err != nil {
+		return fmt.Errorf("Failed to write Consul key '%s': %s", path, err)
+	}
+	return nil
+}
+
+func (c *keyClient) Delete(path string) error {
+	log.Printf(
+		"[DEBUG] Deleting key '%s' in %s",
+		path, c.wOpts.Datacenter,
+	)
+	if _, err := c.client.Delete(path, c.wOpts); err != nil {
+		return fmt.Errorf("Failed to delete Consul key '%s': %s", path, err)
+	}
+	return nil
+}