refactored flag/env loading

core/env/flags.go

@@ -9,8 +9,7 @@
 //
 // https://documize.com
 
-// Package env allow environment variables to be obtained from either the environment or the command line.
-// Environment variables are always uppercase, with the Prefix; flags are always lowercase without.
+// Package env provides runtime, server level setup and configuration
 package env
 
 import (
@@ -22,102 +21,125 @@ import (
 	"sync"
 )
 
-// CallbackT is the type signature of the callback function of GetString().
-type CallbackT func(*string, string) bool
+// Flags provides access to environment and command line switches for this program.
+type Flags struct {
+	DBConn            string // database connection string
+	Salt              string // the salt string used to encode JWT tokens
+	SSLCertFile       string // (optional) name of SSL certificate PEM file
+	SSLKeyFile        string // (optional) name of SSL key PEM file
+	HTTPPort          string // (optional) HTTP or HTTPS port
+	ForceHTTPPort2SSL string // (optional) HTTP that should be redirected to HTTPS
+	SiteMode          string // (optional) if 1 then serve offline web page
+}
 
-type varT struct {
+// SSLEnabled returns true if both cert and key were provided at runtime.
+func (f *Flags) SSLEnabled() bool {
+	return f.SSLCertFile != "" && f.SSLKeyFile != ""
+}
+
+type flagItem struct {
 	target              *string
 	name, setter, value string
 	required            bool
-	callback            CallbackT
 }
 
-type varsT struct {
-	vv []varT
+type progFlags struct {
+	items []flagItem
 }
 
-var vars varsT
-var varsMutex sync.Mutex
-
 // Len is part of sort.Interface.
-func (v *varsT) Len() int {
-	return len(v.vv)
+func (v *progFlags) Len() int {
+	return len(v.items)
 }
 
 // Swap is part of sort.Interface.
-func (v *varsT) Swap(i, j int) {
-	v.vv[i], v.vv[j] = v.vv[j], v.vv[i]
+func (v *progFlags) Swap(i, j int) {
+	v.items[i], v.items[j] = v.items[j], v.items[i]
 }
 
 // Less is part of sort.Interface.
-func (v *varsT) Less(i, j int) bool {
-	return v.vv[i].name < v.vv[j].name
+func (v *progFlags) Less(i, j int) bool {
+	return v.items[i].name < v.items[j].name
 }
 
-// Prefix provides the prefix for all Environment variables
-const Prefix = "DOCUMIZE"
-
+// prefix provides the prefix for all environment variables
+const prefix = "DOCUMIZE"
 const goInit = "(default)"
 
-// GetString sets-up the flag for later use, it must be called before ParseOK(), usually in an init().
-func GetString(target *string, name string, required bool, usage string, callback CallbackT) {
-	varsMutex.Lock()
-	defer varsMutex.Unlock()
+var flagList progFlags
+var loadMutex sync.Mutex
+
+// ParseFlags loads command line and OS environment variables required by the program to function.
+func ParseFlags() (f Flags) {
+	var dbConn, jwtKey, siteMode, port, certFile, keyFile, forcePort2SSL string
+
+	register(&jwtKey, "salt", false, "the salt string used to encode JWT tokens, if not set a random value will be generated")
+	register(&certFile, "cert", false, "the cert.pem file used for https")
+	register(&keyFile, "key", false, "the key.pem file used for https")
+	register(&port, "port", false, "http/https port number")
+	register(&forcePort2SSL, "forcesslport", false, "redirect given http port number to TLS")
+	register(&siteMode, "offline", false, "set to '1' for OFFLINE mode")
+	register(&dbConn, "db", true, `'username:password@protocol(hostname:port)/databasename" for example "fred:bloggs@tcp(localhost:3306)/documize"`)
+
+	parse("db")
+
+	f.DBConn = dbConn
+	f.ForceHTTPPort2SSL = forcePort2SSL
+	f.HTTPPort = port
+	f.Salt = jwtKey
+	f.SiteMode = siteMode
+	f.SSLCertFile = certFile
+	f.SSLKeyFile = keyFile
+
+	return f
+}
+
+// register prepares flag for subsequent parsing
+func register(target *string, name string, required bool, usage string) {
+	loadMutex.Lock()
+	defer loadMutex.Unlock()
+
 	name = strings.ToLower(strings.TrimSpace(name))
-	setter := Prefix + strings.ToUpper(name)
+	setter := prefix + strings.ToUpper(name)
+
 	value := os.Getenv(setter)
 	if value == "" {
 		value = *target // use the Go initialized value
 		setter = goInit
 	}
+
 	flag.StringVar(target, name, value, usage)
-	vars.vv = append(vars.vv, varT{target: target, name: name, required: required, callback: callback, value: value, setter: setter})
+	flagList.items = append(flagList.items, flagItem{target: target, name: name, required: required, value: value, setter: setter})
 }
 
-var showSettings = flag.Bool("showsettings", false, "if true, show settings in the log (WARNING: these settings may include passwords)")
+// parse loads flags from OS environment and command line switches
+func parse(doFirst string) {
+	loadMutex.Lock()
+	defer loadMutex.Unlock()
 
-// Parse calls flag.Parse() then checks that the required environment variables are all set.
-// It should be the first thing called by any main() that uses this library.
-// If all the required variables are not present, it prints an error and calls os.Exit(2) like flag.Parse().
-func Parse(doFirst string) {
-	varsMutex.Lock()
-	defer varsMutex.Unlock()
 	flag.Parse()
-	sort.Sort(&vars)
+	sort.Sort(&flagList)
+
 	for pass := 1; pass <= 2; pass++ {
-		for vi, v := range vars.vv {
+		for vi, v := range flagList.items {
 			if (pass == 1 && v.name == doFirst) || (pass == 2 && v.name != doFirst) {
-				typ := "Optional"
 				if v.value != *(v.target) || (v.value != "" && *(v.target) == "") {
-					vars.vv[vi].setter = "-" + v.name // v is a local copy, not the underlying data
-				}
-				if v.callback != nil {
-					if v.callback(v.target, v.name) {
-						vars.vv[vi].setter = "setting:" + v.name // v is a local copy, not the underlying data
-					}
+					flagList.items[vi].setter = "-" + v.name // v is a local copy, not the underlying data
 				}
 				if v.required {
 					if *(v.target) == "" {
 						fmt.Fprintln(os.Stderr)
 						fmt.Fprintln(os.Stderr, "In order to run", os.Args[0], "the following must be provided:")
-						for _, vv := range vars.vv {
+						for _, vv := range flagList.items {
 							if vv.required {
 								fmt.Fprintf(os.Stderr, "* setting from environment variable '%s' or flag '-%s' or an application setting '%s', current value: '%s' set by '%s'\n",
-									Prefix+strings.ToUpper(vv.name), vv.name, vv.name, *(vv.target), vv.setter)
+									prefix+strings.ToUpper(vv.name), vv.name, vv.name, *(vv.target), vv.setter)
 							}
 						}
 						fmt.Fprintln(os.Stderr)
 						flag.Usage()
-						os.Exit(2)
 						return
 					}
-					typ = "Required"
-				}
-				if *showSettings {
-					if *(v.target) != "" && vars.vv[vi].setter != goInit {
-						fmt.Fprintf(os.Stdout, "%s setting from '%s' is: '%s'\n",
-							typ, vars.vv[vi].setter, *(v.target))
-					}
 				}
 			}
 		}