Add Oauth2 TokenSource support

PagerDuty currently uses Oauth2 tokens that need to be acquired and
refreshed with some frequency. The current setup only supports static
string auth tokens.

While uses could do the Oauth2 handling themselves, it'd lead to a quite
challenging maneuvering to re-create the PagerDuty client with the new
token once the previous expires, which is unnecessary when there are
official canned libraries to do that for us.

Another option could almost be to just use the oauth2 created Client
[1], but the way `prepRequest` works would interfere with it.

Fixes PagerDuty#407

1: https://pkg.go.dev/golang.org/x/oauth2#Config.Client

client.go

@@ -22,6 +22,8 @@ import (
 	"strings"
 	"sync/atomic"
 	"time"
+
+	"golang.org/x/oauth2"
 )
 
 // Version is current version of this client.
@@ -270,7 +272,7 @@ type Client struct {
 	lastRequest  *atomic.Value
 	lastResponse *atomic.Value
 
-	authToken           string
+	oauthTokenSource    oauth2.TokenSource
 	apiEndpoint         string
 	v2EventsAPIEndpoint string
 
@@ -283,13 +285,12 @@ type Client struct {
 	HTTPClient HTTPClient
 }
 
-// NewClient creates an API client using an account/user API token
-func NewClient(authToken string, options ...ClientOptions) *Client {
+func newClient(oauthTokenSource oauth2.TokenSource, options ...ClientOptions) *Client {
 	client := Client{
 		debugFlag:           new(uint64),
 		lastRequest:         &atomic.Value{},
 		lastResponse:        &atomic.Value{},
-		authToken:           authToken,
+		oauthTokenSource:    oauthTokenSource,
 		apiEndpoint:         apiEndpoint,
 		v2EventsAPIEndpoint: v2EventsAPIEndpoint,
 		authType:            apiToken,
@@ -303,9 +304,19 @@ func NewClient(authToken string, options ...ClientOptions) *Client {
 	return &client
 }
 
+// NewClient creates an API client using an account/user API token
+func NewClient(authToken string, options ...ClientOptions) *Client {
+	return newClient(oauth2.StaticTokenSource(&oauth2.Token{AccessToken: authToken}), options...)
+}
+
 // NewOAuthClient creates an API client using an OAuth token
 func NewOAuthClient(authToken string, options ...ClientOptions) *Client {
-	return NewClient(authToken, WithOAuth())
+	return newClient(oauth2.StaticTokenSource(&oauth2.Token{AccessToken: authToken}), append(options, WithOAuth())...)
+}
+
+// NewOAuthClientWithTokenSource creates an API client using an OAuth token
+func NewOAuthClientWithTokenSource(authToken oauth2.TokenSource, options ...ClientOptions) *Client {
+	return newClient(authToken, append(options, WithOAuth())...)
 }
 
 // ClientOptions allows for options to be passed into the Client for customization
@@ -440,7 +451,9 @@ func (c *Client) LastAPIResponse() (*http.Response, bool) {
 // assumes any request body is in JSON format and sets the Content-Type to
 // application/json.
 func (c *Client) Do(r *http.Request, authRequired bool) (*http.Response, error) {
-	c.prepRequest(r, authRequired, nil)
+	if err := c.prepRequest(r, authRequired, nil); err != nil {
+		return nil, fmt.Errorf("failed to prepare request: %w", err)
+	}
 
 	return c.HTTPClient.Do(r)
 }
@@ -478,24 +491,29 @@ const (
 	contentTypeHeader = "application/json"
 )
 
-func (c *Client) prepRequest(req *http.Request, authRequired bool, headers map[string]string) {
+func (c *Client) prepRequest(req *http.Request, authRequired bool, headers map[string]string) error {
 	req.Header.Set("Accept", acceptHeader)
 
 	for k, v := range headers {
 		req.Header.Set(k, v)
 	}
 
 	if authRequired {
+		token, err := c.oauthTokenSource.Token()
+		if err != nil {
+			return err
+		}
 		switch c.authType {
 		case oauthToken:
-			req.Header.Set("Authorization", "Bearer "+c.authToken)
+			req.Header.Set("Authorization", "Bearer "+token.AccessToken)
 		default:
-			req.Header.Set("Authorization", "Token token="+c.authToken)
+			req.Header.Set("Authorization", "Token token="+token.AccessToken)
 		}
 	}
 
 	req.Header.Set("User-Agent", userAgentHeader)
 	req.Header.Set("Content-Type", contentTypeHeader)
+	return nil
 }
 
 func dupeRequest(r *http.Request) (*http.Request, error) {
@@ -541,7 +559,9 @@ func (c *Client) doWithEndpoint(ctx context.Context, endpoint, method, path stri
 		return nil, fmt.Errorf("failed to build request: %w", err)
 	}
 
-	c.prepRequest(req, authRequired, headers)
+	if err := c.prepRequest(req, authRequired, headers); err != nil {
+		return nil, fmt.Errorf("failed to prepare request: %w", err)
+	}
 
 	// if in debug mode, copy request before making it
 	if c.debugCaptureRequest() {

client_test.go

@@ -14,6 +14,7 @@ import (
 	"testing"
 
 	"github.com/google/go-cmp/cmp"
+	"golang.org/x/oauth2"
 )
 
 var (
@@ -42,7 +43,7 @@ func defaultTestClient(serverURL, authToken string) *Client {
 	return &Client{
 		v2EventsAPIEndpoint: serverURL,
 		apiEndpoint:         serverURL,
-		authToken:           authToken,
+		oauthTokenSource:    oauth2.StaticTokenSource(&oauth2.Token{AccessToken: authToken}),
 		HTTPClient:          defaultHTTPClient,
 		debugFlag:           new(uint64),
 		lastRequest:         &atomic.Value{},

go.mod

@@ -18,6 +18,7 @@ require (
 	github.com/armon/go-radix v0.0.0-20180808171621-7fddfc383310 // indirect
 	github.com/bgentry/speakeasy v0.1.0 // indirect
 	github.com/fatih/color v1.7.0 // indirect
+	github.com/golang/protobuf v1.5.2 // indirect
 	github.com/google/uuid v1.1.2 // indirect
 	github.com/hashicorp/errwrap v1.0.0 // indirect
 	github.com/hashicorp/go-multierror v1.0.0 // indirect
@@ -31,5 +32,9 @@ require (
 	github.com/shopspring/decimal v1.2.0 // indirect
 	github.com/spf13/cast v1.3.1 // indirect
 	golang.org/x/crypto v0.0.0-20200820211705-5c72a883971a // indirect
-	golang.org/x/sys v0.0.0-20220715151400-c0bba94af5f8 // indirect
+	golang.org/x/net v0.6.0 // indirect
+	golang.org/x/oauth2 v0.5.0 // indirect
+	golang.org/x/sys v0.5.0 // indirect
+	google.golang.org/appengine v1.6.7 // indirect
+	google.golang.org/protobuf v1.28.0 // indirect
 )

go.sum

@@ -13,7 +13,12 @@ github.com/davecgh/go-spew v1.1.1 h1:vj9j/u1bqnvCEfJOwUhtlOARqs3+rkHYY13jYWTU97c
 github.com/davecgh/go-spew v1.1.1/go.mod h1:J7Y8YcW2NihsgmVo/mv3lAwl/skON4iLHjSsI+c5H38=
 github.com/fatih/color v1.7.0 h1:DkWD4oS2D8LGGgTQ6IvwJJXSL5Vp2ffcQg58nFV38Ys=
 github.com/fatih/color v1.7.0/go.mod h1:Zm6kSWBoL9eyXnKyktHP6abPY2pDugNf5KwzbycvMj4=
+github.com/golang/protobuf v1.3.1/go.mod h1:6lQm79b+lXiMfvg/cZm0SGofjICqVBUtrP5yJMmIC1U=
+github.com/golang/protobuf v1.5.0/go.mod h1:FsONVRAS9T7sI+LIUmWTfcYkHO4aIWwzhcaSAoJOfIk=
+github.com/golang/protobuf v1.5.2 h1:ROPKBNFfQgOUMifHyP+KYbvpjbdoFNs+aK7DXlji0Tw=
+github.com/golang/protobuf v1.5.2/go.mod h1:XVQd3VNwM+JqD3oG2Ue2ip4fOMUkwXdXDdiuN0vRsmY=
 github.com/google/go-cmp v0.5.2/go.mod h1:v8dTdLbMG2kIc/vJvl+f65V22dbkXbowE6jgT/gNBxE=
+github.com/google/go-cmp v0.5.5/go.mod h1:v8dTdLbMG2kIc/vJvl+f65V22dbkXbowE6jgT/gNBxE=
 github.com/google/go-cmp v0.5.9 h1:O2Tfq5qg4qc4AmwVlvv0oLiVAGB7enBSJ2x2DqQFi38=
 github.com/google/go-cmp v0.5.9/go.mod h1:17dUlkBOakJ0+DkrSSNjCkIjxS6bF9zb3elmeNGIjoY=
 github.com/google/go-querystring v1.1.0 h1:AnCroh3fv4ZBgVIf1Iwtovgjaw/GiKJo8M8yD/fhyJ8=
@@ -63,12 +68,27 @@ golang.org/x/crypto v0.0.0-20200414173820-0848c9571904/go.mod h1:LzIPMQfyMNhhGPh
 golang.org/x/crypto v0.0.0-20200820211705-5c72a883971a h1:vclmkQCjlDX5OydZ9wv8rBCcS0QyQY66Mpf/7BZbInM=
 golang.org/x/crypto v0.0.0-20200820211705-5c72a883971a/go.mod h1:LzIPMQfyMNhhGPhUkYOs5KpL4U8rLKemX1yGLhDgUto=
 golang.org/x/net v0.0.0-20190404232315-eb5bcb51f2a3/go.mod h1:t9HGtf8HONx5eT2rtn7q6eTqICYqUVnKs3thJo3Qplg=
+golang.org/x/net v0.0.0-20190603091049-60506f45cf65/go.mod h1:HSz+uSET+XFnRR8LxR5pz3Of3rY3CfYBVs4xY44aLks=
+golang.org/x/net v0.6.0 h1:L4ZwwTvKW9gr0ZMS1yrHD9GZhIuVjOBBnaKH+SPQK0Q=
+golang.org/x/net v0.6.0/go.mod h1:2Tu9+aMcznHK/AK1HMvgo6xiTLG5rD5rZLDS+rp2Bjs=
+golang.org/x/oauth2 v0.5.0 h1:HuArIo48skDwlrvM3sEdHXElYslAMsf3KwRkkW4MC4s=
+golang.org/x/oauth2 v0.5.0/go.mod h1:9/XBHVqLaWO3/BRHs5jbpYCnOZVjj5V0ndyaAM7KB4I=
 golang.org/x/sys v0.0.0-20190215142949-d0b11bdaac8a/go.mod h1:STP8DvDyc/dI5b8T5hshtkjS+E42TnysNCUPdjciGhY=
 golang.org/x/sys v0.0.0-20190412213103-97732733099d/go.mod h1:h1NjWce9XRLGQEsW7wpKNCjG9DtNlClVuFLEZdDNbEs=
 golang.org/x/sys v0.0.0-20220715151400-c0bba94af5f8 h1:0A+M6Uqn+Eje4kHMK80dtF3JCXC4ykBgQG4Fe06QRhQ=
 golang.org/x/sys v0.0.0-20220715151400-c0bba94af5f8/go.mod h1:oPkhp1MJrh7nUepCBck5+mAzfO9JrbApNNgaTdGDITg=
+golang.org/x/sys v0.5.0 h1:MUK/U/4lj1t1oPg0HfuXDN/Z1wv31ZJ/YcPiGccS4DU=
+golang.org/x/sys v0.5.0/go.mod h1:oPkhp1MJrh7nUepCBck5+mAzfO9JrbApNNgaTdGDITg=
 golang.org/x/text v0.3.0/go.mod h1:NqM8EUOU14njkJ3fqMW+pc6Ldnwhi/IjpwHt7yyuwOQ=
+golang.org/x/text v0.3.2/go.mod h1:bEr9sfX3Q8Zfm5fL9x+3itogRgK3+ptLWKqgva+5dAk=
+golang.org/x/tools v0.0.0-20180917221912-90fa682c2a6e/go.mod h1:n7NCudcB/nEzxVGmLbDWY5pfWTLqBcC2KZ6jyYvM4mQ=
 golang.org/x/xerrors v0.0.0-20191204190536-9bdfabe68543/go.mod h1:I/5z698sn9Ka8TeJc9MKroUUfqBBauWjQqLJ2OPfmY0=
+google.golang.org/appengine v1.6.7 h1:FZR1q0exgwxzPzp/aF+VccGrSfxfPpkBqjIIEq3ru6c=
+google.golang.org/appengine v1.6.7/go.mod h1:8WjMMxjGQR8xUklV/ARdw2HLXBOI7O7uCIDZVag1xfc=
+google.golang.org/protobuf v1.26.0-rc.1/go.mod h1:jlhhOSvTdKEhbULTjvd4ARK9grFBp09yW+WbY/TyQbw=
+google.golang.org/protobuf v1.26.0/go.mod h1:9q0QmTI4eRPtz6boOQmLYwt+qCgq0jsYwAQnmE0givc=
+google.golang.org/protobuf v1.28.0 h1:w43yiav+6bVFTBQFZX0r7ipe9JQ1QsbMgHwbBziscLw=
+google.golang.org/protobuf v1.28.0/go.mod h1:HV8QOd/L58Z+nl8r43ehVNZIU/HEI6OcFqwMG9pJV4I=
 gopkg.in/check.v1 v0.0.0-20161208181325-20d25e280405 h1:yhCVgyC4o1eVCa2tZl7eS0r+SDo693bJlVdllGtEeKM=
 gopkg.in/check.v1 v0.0.0-20161208181325-20d25e280405/go.mod h1:Co6ibVJAznAaIkqp8huTwlJQCZ016jof/cbN4VW5Yz0=
 gopkg.in/yaml.v2 v2.2.2/go.mod h1:hI93XBmqTisBFMUTm0b8Fm+jr3Dg1NNxqwp+5A1VGuI=