Rip apart several new packages for inter-dependence

This will help make it clear what depends on what for rendering html
pages

config/config.go

@@ -0,0 +1,94 @@
+package config
+
+import (
+	"fmt"
+	"net/url"
+	"os"
+	"strconv"
+)
+
+var Bind, ClientID, ClientSecret, Environment, FieldseekerSchemaDirectory, MapboxToken, PGDSN, URLReport, URLSync, UserFilesDirectory string
+
+// Build the ArcGIS authorization URL with PKCE
+func BuildArcGISAuthURL(clientID string) string {
+	baseURL := "https://www.arcgis.com/sharing/rest/oauth2/authorize/"
+
+	params := url.Values{}
+	params.Add("client_id", clientID)
+	params.Add("redirect_uri", RedirectURL())
+	params.Add("response_type", "code")
+	//params.Add("code_challenge", generateCodeChallenge(codeVerifier))
+	//params.Add("code_challenge_method", "S256")
+
+	// See https://developers.arcgis.com/rest/users-groups-and-items/token/
+	// expiration is defined in minutes
+	var expiration int
+	if IsProductionEnvironment() {
+		// 2 weeks is the maximum allowed
+		expiration = 20160
+	} else {
+		expiration = 20
+	}
+	params.Add("expiration", strconv.Itoa(expiration))
+
+	return baseURL + "?" + params.Encode()
+}
+
+func IsProductionEnvironment() bool {
+	return Environment == "PRODUCTION"
+}
+
+func MakeURLSync(path string) string {
+	return fmt.Sprintf("https://%s%s", URLSync, path)
+}
+
+func Parse() error {
+	ClientID = os.Getenv("ARCGIS_CLIENT_ID")
+	if ClientID == "" {
+		return fmt.Errorf("You must specify a non-empty ARCGIS_CLIENT_ID")
+	}
+	ClientSecret = os.Getenv("ARCGIS_CLIENT_SECRET")
+	if ClientSecret == "" {
+		return fmt.Errorf("You must specify a non-empty ARCGIS_CLIENT_SECRET")
+	}
+	URLReport = os.Getenv("URL_REPORT")
+	if URLReport == "" {
+		return fmt.Errorf("You must specify a non-empty URL_REPORT")
+	}
+	URLSync = os.Getenv("URL_SYNC")
+	if URLSync == "" {
+		return fmt.Errorf("You must specify a non-empty URL_SYNC")
+	}
+	Bind = os.Getenv("BIND")
+	if Bind == "" {
+		Bind = ":9001"
+	}
+	Environment = os.Getenv("ENVIRONMENT")
+	if Environment == "" {
+		return fmt.Errorf("You must specify a non-empty ENVIRONMENT")
+	}
+	if !(Environment == "PRODUCTION" || Environment == "DEVELOPMENT") {
+		return fmt.Errorf("ENVIRONMENT should be either DEVELOPMENT or PRODUCTION")
+	}
+	MapboxToken = os.Getenv("MAPBOX_TOKEN")
+	if MapboxToken == "" {
+		return fmt.Errorf("You must specify a non-empty MAPBOX_TOKEN")
+	}
+	PGDSN = os.Getenv("POSTGRES_DSN")
+	if PGDSN == "" {
+		return fmt.Errorf("You must specify a non-empty POSTGRES_DSN")
+	}
+	FieldseekerSchemaDirectory = os.Getenv("FIELDSEEKER_SCHEMA_DIRECTORY")
+	if FieldseekerSchemaDirectory == "" {
+		return fmt.Errorf("You must specify a non-empty FIELDSEEKER_SCHEMA_DIRECTORY")
+	}
+	UserFilesDirectory = os.Getenv("USER_FILES_DIRECTORY")
+	if UserFilesDirectory == "" {
+		return fmt.Errorf("You must specify a non-empty USER_FILES_DIRECTORY")
+	}
+	return nil
+}
+
+func RedirectURL() string {
+	return MakeURLSync("/arcgis/oauth/callback")
+}