env.go

package devstatscode

import (
	"bufio"
	"fmt"
	"os"
	"sort"
	"strings"
	"time"
)

var gEnvMap map[string]string = make(map[string]string)

// EnvSyncer - support auto updating env variables via "env.env" file
func EnvSyncer() {
	for {
		time.Sleep(30 * time.Second)
		UpdateEnv(true)
	}
}

// UpdateEnv - update (eventually) env using env.env file
func UpdateEnv(useLog bool) {
	ef, err := os.Open("env.env")
	if err != nil {
		return
	}
	defer ef.Close()
	sc := bufio.NewScanner(ef)
	for sc.Scan() {
		line := sc.Text()
		ary := strings.Split(line, "=")
		if len(ary) < 2 {
			continue
		}
		k := strings.TrimSpace(ary[0])
		if k == "" {
			continue
		}
		// v := strings.TrimSpace(ary[1])
		v := strings.TrimSpace(strings.Join(ary[1:], "="))
		os.Setenv(k, v)
		cv, ok := gEnvMap[k]
		if !ok || cv != v {
			if useLog {
				if IsLogInitialized() {
					Printf("new environment overwrite: '%s' --> '%s'\n", k, v)
				}
			} else {
				fmt.Printf("new environment overwrite: '%s' --> '%s'\n", k, v)
			}
		}
		gEnvMap[k] = v
	}
}

// EnvReplace - replace all environment variables starting with "prefix"
// with contents of variables with "suffix" added - if defined
// If prefix is "DB_" and suffix is "_SRC" then:
// So if there is "DB_HOST_SRC" variable defined - it will replace "DB_HOST" and so on
func EnvReplace(prefix, suffix string) map[string]string {
	if suffix == "" {
		return map[string]string{}
	}
	oldEnv := make(map[string]string)
	var environ []string
	for _, e := range os.Environ() {
		environ = append(environ, e)
	}
	sort.Strings(environ)
	pLen := len(prefix)
	for _, e := range environ {
		l := pLen
		eLen := len(e)
		if l > eLen {
			l = eLen
		}
		if pLen == 0 || e[0:l] == prefix {
			pair := strings.SplitN(e, "=", 2)
			eSuff := os.Getenv(pair[0] + suffix)
			if eSuff != "" {
				oldEnv[pair[0]] = pair[1]
				FatalOnError(os.Setenv(pair[0], eSuff))
			}
		}
	}
	sLen := len(suffix)
	for _, e := range environ {
		pair := strings.SplitN(e, "=", 2)
		eLen := len(pair[0])
		lS := eLen - sLen
		if lS <= 0 {
			continue
		}
		lP := pLen
		if lP > eLen {
			lP = eLen
		}
		if (pLen == 0 || e[0:lP] == prefix) && pair[0][lS:] == suffix {
			eName := pair[0][:lS]
			_, ok := oldEnv[eName]
			if !ok {
				oldEnv[eName] = Unset
				FatalOnError(os.Setenv(eName, pair[1]))
			}
		}
	}
	return oldEnv
}

// EnvRestore - restores all environment variables given in the map
func EnvRestore(env map[string]string) {
	for envName, envValue := range env {
		if envValue == Unset {
			FatalOnError(os.Unsetenv(envName))
		} else {
			FatalOnError(os.Setenv(envName, envValue))
		}
	}
}