Multiple provider support + OIDC provider

internal/provider/providers.go

@@ -1,16 +1,61 @@
 package provider
 
+import (
+	"context"
+	// "net/url"
+
+	"golang.org/x/oauth2"
+)
+
+// Providers contains all the implemented providers
 type Providers struct {
 	Google Google `group:"Google Provider" namespace:"google" env-namespace:"GOOGLE"`
+	OIDC   OIDC   `group:"OIDC Provider" namespace:"oidc" env-namespace:"OIDC"`
 }
 
-type Token struct {
+// Provider is used to authenticate users
+type Provider interface {
+	Name() string
+	GetLoginURL(redirectURI, state string) string
+	ExchangeCode(redirectURI, code string) (string, error)
+	GetUser(token string) (User, error)
+	Setup() error
+}
+
+type token struct {
 	Token string `json:"access_token"`
 }
 
+// User is the authenticated user
 type User struct {
-	Id       string `json:"id"`
+	ID       string `json:"id"`
 	Email    string `json:"email"`
 	Verified bool   `json:"verified_email"`
 	Hd       string `json:"hd"`
 }
+
+// OAuthProvider is a provider using the oauth2 library
+type OAuthProvider struct {
+	Config *oauth2.Config
+	ctx    context.Context
+}
+
+// ConfigCopy returns a copy of the oauth2 config with the given redirectURI
+// which ensures the underlying config is not modified
+func (p *OAuthProvider) ConfigCopy(redirectURI string) oauth2.Config {
+	config := *p.Config
+	config.RedirectURL = redirectURI
+	return config
+}
+
+// OAuthGetLoginURL provides a base "GetLoginURL" for proiders using OAauth2
+func (p *OAuthProvider) OAuthGetLoginURL(redirectURI, state string) string {
+	config := p.ConfigCopy(redirectURI)
+	return config.AuthCodeURL(state)
+}
+
+// OAuthExchangeCode provides a base "ExchangeCode" for proiders using OAauth2
+func (p *OAuthProvider) OAuthExchangeCode(redirectURI, code string) (*oauth2.Token, error) {
+	config := p.ConfigCopy(redirectURI)
+	return config.Exchange(p.ctx, code)
+}