1 files changed, 232 insertions, 0 deletions
diff --git a/internal/wireguard/ini/ini.go b/internal/wireguard/ini/ini.go
new file mode 100644
index 0000000..6791336
--- /dev/null
+++ b/internal/wireguard/ini/ini.go
@@ -0,0 +1,232 @@
+// package ini implements an opinionated ini parser that only implements what we exactly need for WireGuard configs
+// - key/values MUST live under a section
+// - empty section names are NOT allowed
+// - comments are indicated with a #
+package ini
+
+import (
+	"errors"
+	"fmt"
+	"strings"
+)
+
+// shouldSkip returns whether or not a line should be skipped, empty line (after whitespace omitting) or a comment
+func shouldSkip(f string) bool {
+	return f == "" || strings.HasPrefix(f, "#")
+}
+
+// isSection returns whether a line is a section
+// this happens when it begins with [ and ends with ]
+func isSection(f string) bool {
+	return strings.HasPrefix(f, "[") && strings.HasSuffix(f, "]")
+}
+
+// sectionName extracts the section name from a line by removing the [ and ] prefix and suffix
+func sectionName(f string) string {
+	name := strings.TrimSuffix(strings.TrimPrefix(f, "["), "]")
+	return strings.TrimSpace(name)
+}
+
+// keyValue extracts a key and a value from a line
+// if no 2 components are found (separated by =), we will return an error
+// the key and value have their spaces trimmed
+func keyValue(f string) (string, string, error) {
+	sl := strings.SplitN(f, "=", 2)
+	if len(sl) < 2 {
+		return "", "", errors.New("no key/value found")
+	}
+	k := strings.TrimSpace(sl[0])
+	if k == "" {
+		return "", "", errors.New("key cannot be empty")
+	}
+	v := strings.TrimSpace(sl[1])
+	return k, v, nil
+}
+
+// OrderedKeys is a slice of strings that is used for an ordered map
+type OrderedKeys []string
+
+func (ok *OrderedKeys) find(name string) int {
+	if ok == nil {
+		return -1
+	}
+	for i, v := range *ok {
+		if v == name {
+			return i
+		}
+	}
+	return -1
+}
+
+// Remove removes a `name` from the OrderedKeys slice by finding the name
+// It is a no-op if the key does not exist
+func (ok *OrderedKeys) Remove(name string) {
+	idx := ok.find(name)
+	if idx == -1 {
+		return
+	}
+	*ok = append((*ok)[:idx], (*ok)[idx+1:]...)
+}
+
+// Section represents a single section within an ini file
+// It consists of multiple key and values
+type Section struct {
+	keyValues map[string]string
+	keys      OrderedKeys
+}
+
+// KeyValue gets a value for key `key`
+// It returns an error if the key does not exist
+func (sec *Section) KeyValue(key string) (string, error) {
+	if v, ok := sec.keyValues[key]; ok {
+		return v, nil
+	}
+	return "", fmt.Errorf("key: '%s' does not exist", key)
+}
+
+func (sec *Section) newKeyValue(key string, value string) {
+	if sec.keyValues == nil {
+		sec.keyValues = make(map[string]string)
+	}
+	sec.keyValues[key] = value
+	sec.keys = append(sec.keys, key)
+}
+
+// AddOrReplaceKeyValue adds a key `key` with value `value`
+// If the key already exists it modifies the value
+func (sec *Section) AddOrReplaceKeyValue(key string, value string) {
+	_, err := sec.KeyValue(key)
+	if err == nil {
+		sec.keyValues[key] = value
+		return
+	}
+	sec.newKeyValue(key, value)
+}
+
+// AddKeyValue adds a new key `key` with value `value`
+// It returns an error if the key already exists
+func (sec *Section) AddKeyValue(key string, value string) error {
+	// get an existing key
+	_, err := sec.KeyValue(key)
+	if err == nil {
+		return fmt.Errorf("key: '%s' already exists", key)
+	}
+	sec.newKeyValue(key, value)
+	return nil
+}
+
+// RemoveKey removes a key `key` from the section
+// It returns an error if the key cannot be found
+func (sec *Section) RemoveKey(key string) (string, error) {
+	if v, ok := sec.keyValues[key]; ok {
+		sec.keys.Remove(key)
+		delete(sec.keyValues, key)
+		return v, nil
+	}
+	return "", fmt.Errorf("no key to remove with name: '%s'", key)
+}
+
+// INI is the struct for a ini file
+type INI struct {
+	sections map[string]*Section
+	keys     OrderedKeys
+}
+
+// Empty returns true if there are no sections defined in the INI
+func (i *INI) Empty() bool {
+	return len(i.keys) == 0
+}
+
+// Section gets a section from the ini file
+func (i *INI) Section(name string) (*Section, error) {
+	if _, ok := i.sections[name]; ok {
+		return i.sections[name], nil
+	}
+	return nil, fmt.Errorf("section: '%s' does not exist", name)
+}
+
+// AddSection adds a section with name `name` and returns an error if the section already exists
+func (i *INI) AddSection(name string) error {
+	// get an existing section
+	_, err := i.Section(name)
+	if err == nil {
+		return errors.New("section: '%s' already exists")
+	}
+	if i.sections == nil {
+		i.sections = make(map[string]*Section)
+	}
+	i.sections[name] = &Section{}
+	i.keys = append(i.keys, name)
+	return nil
+}
+
+// String returns the representation of the ini as a string
+func (i *INI) String() string {
+	var out strings.Builder
+	for _, s := range i.keys {
+		sec, err := i.Section(s)
+		if err != nil {
+			continue
+		}
+		out.WriteString(fmt.Sprintf("[%s]\n", s))
+
+		for _, k := range sec.keys {
+			v, err := sec.KeyValue(k)
+			if err != nil {
+				continue
+			}
+			delim := ""
+			if v != "" {
+				delim = " "
+			}
+			out.WriteString(fmt.Sprintf("%s =%s%s\n", k, delim, v))
+		}
+	}
+	return out.String()
+}
+
+// Parse returns a slice of sections
+// we do not return a map as we want to ensure the same ordering of sections, keys and values
+func Parse(f string) INI {
+	lines := strings.Split(f, "\n")
+
+	var secs INI
+	sec := ""
+	for _, line := range lines {
+		// clean the line
+		line = strings.TrimSpace(line)
+
+		if shouldSkip(line) {
+			continue
+		}
+
+		if isSection(line) {
+			name := sectionName(line)
+			// we do not allow sections with empty names
+			if name == "" {
+				continue
+			}
+			_ = secs.AddSection(name)
+			sec = name
+			continue
+		}
+
+		// no section has been parsed yet
+		// we will ignore the rest of the values
+		if sec == "" {
+			continue
+		}
+
+		// split key and value
+		key, value, err := keyValue(line)
+		if err != nil {
+			continue
+		}
+
+		csec := secs.sections[sec]
+		// This adds a new key and value to the section
+		// If it already exists it ignores it as this function would return an error
+		_ = csec.AddKeyValue(key, value)
+	}
+	return secs
+}