juliankoehn · October 30, 2020 13:56 · Oct 30, 2020
diff --git a/env.go b/env.go
@@ -0,0 +1,205 @@
+package env
+
+import (
+	"bufio"
+	"errors"
+	"fmt"
+	"io"
+	"os"
+	"regexp"
+	"strings"
+)
+
+func init() {
+	fmt.Println("trying to load environemtn from .env")
+	loadFile(".env", false)
+}
+
+func loadFile(filename string, overload bool) error {
+	envMap, err := readFile(filename)
+	if err != nil {
+		return err
+	}
+
+	currentEnv := map[string]bool{}
+	rawEnv := os.Environ()
+	for _, rawEnvLine := range rawEnv {
+		key := strings.Split(rawEnvLine, "=")[0]
+		currentEnv[key] = true
+	}
+
+	for key, value := range envMap {
+		if !currentEnv[key] || overload {
+			os.Setenv(key, value)
+		}
+	}
+
+	return nil
+}
+
+func readFile(filename string) (envMap map[string]string, err error) {
+	file, err := os.Open(filename)
+	if err != nil {
+		return
+	}
+	defer file.Close()
+
+	return Parse(file)
+}
+
+// Parse reads an env file from io.Reader, returning a map of keys and values.
+func Parse(r io.Reader) (envMap map[string]string, err error) {
+	envMap = make(map[string]string)
+
+	var lines []string
+	scanner := bufio.NewScanner(r)
+	for scanner.Scan() {
+		lines = append(lines, scanner.Text())
+	}
+
+	if err = scanner.Err(); err != nil {
+		return
+	}
+
+	for _, fullLine := range lines {
+		if !isIgnoredLine(fullLine) {
+			var key, value string
+			key, value, err = parseLine(fullLine, envMap)
+
+			if err != nil {
+				return
+			}
+			envMap[key] = value
+		}
+	}
+	return
+}
+
+func isIgnoredLine(line string) bool {
+	trimmedLine := strings.TrimSpace(line)
+	return len(trimmedLine) == 0 || strings.HasPrefix(trimmedLine, "#")
+}
+
+var exportRegex = regexp.MustCompile(`^\s*(?:export\s+)?(.*?)\s*$`)
+
+func parseLine(line string, envMap map[string]string) (key string, value string, err error) {
+	if len(line) == 0 {
+		err = errors.New("zero length string")
+		return
+	}
+
+	// ditch the comments (but keep quoted hashes)
+	if strings.Contains(line, "#") {
+		segmentsBetweenHashes := strings.Split(line, "#")
+		quotesAreOpen := false
+		var segmentsToKeep []string
+		for _, segment := range segmentsBetweenHashes {
+			if strings.Count(segment, "\"") == 1 || strings.Count(segment, "'") == 1 {
+				if quotesAreOpen {
+					quotesAreOpen = false
+					segmentsToKeep = append(segmentsToKeep, segment)
+				} else {
+					quotesAreOpen = true
+				}
+			}
+
+			if len(segmentsToKeep) == 0 || quotesAreOpen {
+				segmentsToKeep = append(segmentsToKeep, segment)
+			}
+		}
+
+		line = strings.Join(segmentsToKeep, "#")
+	}
+
+	firstEquals := strings.Index(line, "=")
+	firstColon := strings.Index(line, ":")
+	splitString := strings.SplitN(line, "=", 2)
+	if firstColon != -1 && (firstColon < firstEquals || firstEquals == -1) {
+		//this is a yaml-style line
+		splitString = strings.SplitN(line, ":", 2)
+	}
+
+	if len(splitString) != 2 {
+		err = errors.New("Can't separate key from value")
+		return
+	}
+
+	// Parse the key
+	key = splitString[0]
+	if strings.HasPrefix(key, "export") {
+		key = strings.TrimPrefix(key, "export")
+	}
+	key = strings.TrimSpace(key)
+
+	key = exportRegex.ReplaceAllString(splitString[0], "$1")
+
+	// Parse the value
+	value = parseValue(splitString[1], envMap)
+	return
+}
+
+var (
+	singleQuotesRegex  = regexp.MustCompile(`\A'(.*)'\z`)
+	doubleQuotesRegex  = regexp.MustCompile(`\A"(.*)"\z`)
+	escapeRegex        = regexp.MustCompile(`\\.`)
+	unescapeCharsRegex = regexp.MustCompile(`\\([^$])`)
+)
+
+func parseValue(value string, envMap map[string]string) string {
+
+	// trim
+	value = strings.Trim(value, " ")
+
+	// check if we've got quoted values or possible escapes
+	if len(value) > 1 {
+		singleQuotes := singleQuotesRegex.FindStringSubmatch(value)
+
+		doubleQuotes := doubleQuotesRegex.FindStringSubmatch(value)
+
+		if singleQuotes != nil || doubleQuotes != nil {
+			// pull the quotes off the edges
+			value = value[1 : len(value)-1]
+		}
+
+		if doubleQuotes != nil {
+			// expand newlines
+			value = escapeRegex.ReplaceAllStringFunc(value, func(match string) string {
+				c := strings.TrimPrefix(match, `\`)
+				switch c {
+				case "n":
+					return "\n"
+				case "r":
+					return "\r"
+				default:
+					return match
+				}
+			})
+			// unescape characters
+			value = unescapeCharsRegex.ReplaceAllString(value, "$1")
+		}
+
+		if singleQuotes == nil {
+			value = expandVariables(value, envMap)
+		}
+	}
+
+	return value
+}
+
+var expandVarRegex = regexp.MustCompile(`(\\)?(\$)(\()?\{?([A-Z0-9_]+)?\}?`)
+
+func expandVariables(v string, m map[string]string) string {
+	return expandVarRegex.ReplaceAllStringFunc(v, func(s string) string {
+		submatch := expandVarRegex.FindStringSubmatch(s)
+
+		if submatch == nil {
+			return s
+		}
+		if submatch[1] == "\\" || submatch[2] == "(" {
+			return submatch[0][1:]
+		} else if submatch[4] != "" {
+			return m[submatch[4]]
+		}
+		return s
+	})
+}