Move to yaml-based configuration

This commit updates the configuration to be yaml-based and updates the
configuration to read in a yaml file.

internal/config/legacy/stringparser/stringparser.go

@@ -0,0 +1,125 @@
+// Package stringparser provides Parser.
+// It is deprecated and will be removed in a future release.
+package stringparser
+
+import (
+	"net/url"
+	"regexp"
+	"strconv"
+	"strings"
+	"time"
+
+	"github.com/FAU-CDI/wisski-distillery/pkg/environment"
+	"github.com/FAU-CDI/wisski-distillery/pkg/fsx"
+	"github.com/pkg/errors"
+)
+
+// Parser is used to read a value from a string and turn it into a golang value.
+// It is simultaniously used to validate particular setting.
+//
+// Parsers can be found in this package as functions called Parse*.
+// They are refered to by their name, e.g. ParseNonempty can be refered to by the name 'Nonempty'.
+// See [Parse].
+type Parser[T any] func(env environment.Environment, s string) (T, error)
+
+// ParseAbspath checks that s is an absolute path and returns it as-is
+func ParseAbspath(env environment.Environment, s string) (string, error) {
+	if !fsx.IsDirectory(env, s) {
+		return "", errors.Errorf("%q does not exist or is not a directory", s)
+	}
+	return s, nil
+}
+
+// ParseFile checks that s is a valid file and returns it as-is
+func ParseFile(env environment.Environment, s string) (string, error) {
+	if !fsx.IsFile(env, s) {
+		return "", errors.Errorf("%q does not exist or is not a regular file", s)
+	}
+	return s, nil
+}
+
+var errEmptyString = errors.New("value is empty")
+
+// ParseNonEmpty checks that s is a non-empty string and returns it as-is
+func ParseNonEmpty(env environment.Environment, s string) (string, error) {
+	if s == "" {
+		return "", errEmptyString
+	}
+	return s, nil
+}
+
+var regexpDomain = regexp.MustCompile(`^([a-zA-Z0-9][-a-zA-Z0-9]*\.)*[a-zA-Z0-9][-a-zA-Z0-9]*$`) // TODO: Make this regexp nicer!
+
+// ParseValidDomain checks that s is a valid domain and returns it in lowercase
+func ParseValidDomain(env environment.Environment, s string) (string, error) {
+	if !regexpDomain.MatchString(s) {
+		return "", errors.Errorf("%q is not a valid domain", s)
+	}
+	return strings.ToLower(s), nil
+}
+
+// ParseValidDomains checks that s is a comma-seperated list of valid domains and returns them in lower case
+func ParseValidDomains(env environment.Environment, s string) ([]string, error) {
+	if len(s) == 0 {
+		return []string{}, nil
+	}
+	domains := strings.Split(strings.ToLower(s), ",")
+	for _, d := range domains {
+		if !regexpDomain.MatchString(d) {
+			return nil, errors.Errorf("%q is not a valid domain", d)
+		}
+	}
+	return domains, nil
+}
+
+// ParseNumber parses s as a decimal integer
+func ParseNumber(env environment.Environment, s string) (int, error) {
+	value, err := strconv.ParseInt(s, 10, 64)
+	return int(value), err
+}
+
+// ParsePort parses s as a port
+func ParsePort(env environment.Environment, s string) (uint16, error) {
+	value, err := strconv.ParseUint(s, 10, 16)
+	return uint16(value), err
+}
+
+// ParseHttpsURL parses a string into a url that starts with 'https://'
+func ParseHttpsURL(env environment.Environment, s string) (*url.URL, error) {
+	url, err := url.Parse(s)
+	if err != nil {
+		return nil, errors.Wrapf(err, "%q is not a valid URL", s)
+	}
+	if url.Scheme != "https" {
+		return nil, errors.Errorf("%q is not a valid https URL (%q)", s, url.Scheme)
+	}
+	return url, nil
+}
+
+var regexpEmail = regexp.MustCompile(`^([-a-zA-Z0-9]+)\@([a-zA-Z0-9][-a-zA-Z0-9]*\.)*[a-zA-Z0-9][-a-zA-Z0-9]*$`) // TODO: Make this regexp nicer!
+
+// ParseEmail checks that s represents an email, and then returns it as is.
+func ParseEmail(env environment.Environment, s string) (string, error) {
+	if s == "" { // no email provided
+		return "", nil
+	}
+	if !regexpEmail.MatchString(s) {
+		return "", errors.Errorf("%q is not a valid email", s)
+	}
+	return s, nil
+}
+
+var regexpSlug = regexp.MustCompile(`^[a-zA-Z0-9][-a-zA-Z0-9]*$`) // TODO: Make this regexp nicer!
+
+// ParseSlug parses s as a slug and returns it as is.
+func ParseSlug(env environment.Environment, s string) (string, error) {
+	if !regexpSlug.MatchString(s) {
+		return "", errors.Errorf("%q is not a valid slug", s)
+	}
+	return s, nil
+}
+
+// ParseDuration parses a time.Duration
+func ParseDuration(env environment.Environment, s string) (time.Duration, error) {
+	return time.ParseDuration(s)
+}