Add config file support

options.go

@@ -0,0 +1,67 @@
+package main
+
+import (
+	"errors"
+	"fmt"
+	"net/url"
+	"time"
+)
+
+// Configuration Options that can be set by Command Line Flag, or Config File
+type Options struct {
+	HttpAddress             string        `flag:"http-address" cfg:"http_address"`
+	RedirectUrl             string        `flag:"redirect-url" cfg:"redirect_url"`
+	ClientID                string        `flag:"client-id" cfg:"client_id"`
+	ClientSecret            string        `flag:"client-secret" cfg:"client_secret"`
+	PassBasicAuth           bool          `flag:"pass-basic-auth" cfg:"pass_basic_auth"`
+	HtpasswdFile            string        `flag:"htpasswd-file" cfg:"htpasswd_file"`
+	CookieSecret            string        `flag:"cookie-secret" cfg:"cookie_secret"`
+	CookieDomain            string        `flag:"cookie-domain" cfg:"cookie_domain"`
+	CookieExpire            time.Duration `flag:"cookie-expire" cfg:"cookie_expire"`
+	CookieHttpsOnly         bool          `flag:"cookie-https-only" cfg:"cookie_https_only"`
+	AuthenticatedEmailsFile string        `flag:"authenticated-emails-file" cfg:"authenticated_emails_file"`
+	GoogleAppsDomains       []string      `flag:"google-apps-domain" cfg:"google_apps_domains"`
+	Upstreams               []string      `flag:"upstream" cfg:"upstreams"`
+
+	// internal values that are set after config validation
+	redirectUrl *url.URL
+	proxyUrls   []*url.URL
+}
+
+func NewOptions() *Options {
+	return &Options{}
+}
+
+func (o *Options) Validate() error {
+	if len(o.Upstreams) < 1 {
+		return errors.New("missing -upstream")
+	}
+	if o.CookieSecret == "" {
+		errors.New("missing -cookie-secret")
+	}
+	if o.ClientID == "" {
+		return errors.New("missing -client-id")
+	}
+	if o.ClientSecret == "" {
+		return errors.New("missing -client-secret")
+	}
+
+	redirectUrl, err := url.Parse(o.RedirectUrl)
+	if err != nil {
+		return fmt.Errorf("error parsing -redirect-url=%q %s", o.RedirectUrl, err)
+	}
+	o.redirectUrl = redirectUrl
+
+	for _, u := range o.Upstreams {
+		upstreamUrl, err := url.Parse(u)
+		if err != nil {
+			return fmt.Errorf("error parsing -upstream=%q %s", upstreamUrl, err)
+		}
+		if upstreamUrl.Path == "" {
+			upstreamUrl.Path = "/"
+		}
+		o.proxyUrls = append(o.proxyUrls, upstreamUrl)
+	}
+
+	return nil
+}