Initial commit.

sec.go

@@ -0,0 +1,93 @@
+package sec
+
+import (
+	// stdlib
+	"errors"
+	"log"
+	"os"
+	"reflect"
+	"strconv"
+	"strings"
+)
+
+var (
+	// Errors.
+	errNotPTR       = errors.New("passed data is not a pointer")
+	errNotStructure = errors.New("passed data is not a structure")
+
+	// Debug flag.
+	debugFlagEnvName = "SEC_DEBUG"
+	debug            bool
+
+	// Parsed structure fields.
+	parsedTree []*field
+
+	// Options for current run.
+	options *Options
+)
+
+// Parse parses environment variables into passed structure.
+func Parse(structure interface{}, config *Options) error {
+	parsedTree = []*field{}
+
+	options = config
+	if config == nil {
+		options = defaultOptions
+	}
+
+	// Set debug flag if defined in environment.
+	debugFlagRaw, found := os.LookupEnv(debugFlagEnvName)
+	if found {
+		var err error
+		debug, err = strconv.ParseBool(debugFlagRaw)
+		if err != nil {
+			log.Println("Invalid '" + debugFlagEnvName + "' environment variable data: '" + debugFlagRaw + "'. Error: " + err.Error())
+			if options.ErrorsAreCritical {
+				return err
+			}
+		} else {
+			printDebug("Debug mode activated")
+		}
+	}
+
+	printDebug("Parsing started with configuration: %+v", options)
+
+	value := reflect.ValueOf(structure)
+
+	// Figure out passed data type. We should accept ONLY pointers
+	// to structure.
+	printDebug("Passed structure kind: %s, want: %s", value.Type().Kind().String(), reflect.Ptr.String())
+
+	// If passed data isn't a pointer - return error in any case because
+	// we can't support anything except pointer.
+	if value.Type().Kind() != reflect.Ptr {
+		return errNotPTR
+	}
+
+	printDebug("Passed data kind: %s, want: %s", value.Elem().Type().Kind().String(), reflect.Struct.String())
+
+	value = value.Elem()
+
+	// Passed data should be a pointer to structure. Otherwise we should
+	// return error in any case.
+	if value.Type().Kind() != reflect.Struct {
+		return errNotStructure
+	}
+
+	// Parse structure.
+	composeTree(value, strings.ToUpper(value.Type().Name()))
+
+	return parseEnv()
+}
+
+// Produces debug output into stdout using standard log module if debug
+// mode was activated by setting SEC_DEBUG environment variable to true.
+func printDebug(text string, params ...interface{}) {
+	if debug {
+		if len(params) == 0 {
+			log.Println(text)
+		} else {
+			log.Printf(text, params...)
+		}
+	}
+}