major package structure refactoring

core/env/flags.go

@@ -0,0 +1,125 @@
+// Copyright 2016 Documize Inc. <legal@documize.com>. All rights reserved.
+//
+// This software (Documize Community Edition) is licensed under
+// GNU AGPL v3 http://www.gnu.org/licenses/agpl-3.0.en.html
+//
+// You can operate outside the AGPL restrictions by purchasing
+// Documize Enterprise Edition and obtaining a commercial license
+// by contacting <sales@documize.com>.
+//
+// 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
+
+import (
+	"flag"
+	"fmt"
+	"os"
+	"sort"
+	"strings"
+	"sync"
+)
+
+// CallbackT is the type signature of the callback function of GetString().
+type CallbackT func(*string, string) bool
+
+type varT struct {
+	target              *string
+	name, setter, value string
+	required            bool
+	callback            CallbackT
+}
+
+type varsT struct {
+	vv []varT
+}
+
+var vars varsT
+var varsMutex sync.Mutex
+
+// Len is part of sort.Interface.
+func (v *varsT) Len() int {
+	return len(v.vv)
+}
+
+// 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]
+}
+
+// Less is part of sort.Interface.
+func (v *varsT) Less(i, j int) bool {
+	return v.vv[i].name < v.vv[j].name
+}
+
+// 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()
+	name = strings.ToLower(strings.TrimSpace(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})
+}
+
+var showSettings = flag.Bool("showsettings", false, "if true, show settings in the log (WARNING: these settings may include passwords)")
+
+// 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)
+	for pass := 1; pass <= 2; pass++ {
+		for vi, v := range vars.vv {
+			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
+					}
+				}
+				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 {
+							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)
+							}
+						}
+						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))
+					}
+				}
+			}
+		}
+	}
+}