stream/mts/meta.go: added Format func, but need to complete later once specs are clarified

stream/mts/meta.go

@@ -0,0 +1,82 @@
+/*
+NAME
+  meta.go
+
+DESCRIPTION
+  See Readme.md
+
+AUTHOR
+  Saxon Nelson-Milton <saxon@ausocean.org>
+
+LICENSE
+  meta.go is Copyright (C) 2017-2019 the Australian Ocean Lab (AusOcean)
+
+  It is free software: you can redistribute it and/or modify them
+  under the terms of the GNU General Public License as published by the
+  Free Software Foundation, either version 3 of the License, or (at your
+  option) any later version.
+
+  It is distributed in the hope that it will be useful, but WITHOUT
+  ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+  FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
+ for more details.
+
+  You should have received a copy of the GNU General Public License
+  along with revid in gpl.txt. If not, see http://www.gnu.org/licenses.
+*/
+
+package mts
+
+import (
+	"errors"
+	"fmt"
+	"sync"
+)
+
+type Meta struct {
+	mu   sync.RWMutex
+	data map[string]string
+}
+
+// Add adds metadata with key and val, if already exists return error
+func (m *Meta) Add(key, val string) error {
+	m.mu.Lock()
+	if _, exists := m.data[key]; !exists {
+		return errors.New(fmt.Sprintf("Metadata for: %v already exists", key))
+	}
+	m.data[key] = val
+	m.mu.Unlock()
+	return nil
+}
+
+// All returns the a copy of the map containing the meta data
+func (m *Meta) All() map[string]string {
+	var cpy map[string]string
+	for k, v := range m.data {
+		cpy[k] = v
+	}
+	return cpy
+}
+
+// Get returns the meta data for the passed key
+func (m *Meta) Get(key string) (string, error) {
+	val, ok := m.data[key]
+	if !ok {
+		return "", errors.New("Key does not exist in metadata map")
+	}
+	return val, nil
+}
+
+// Remove deletes a meta entry in the map and returns error if it doesn’t exist
+func (m *Meta) Delete(key string) error {
+	if _, ok := m.data[key]; ok {
+		delete(m.data, key)
+		return nil
+	}
+	return errors.New("Trying to delete map entry that doesn't exist")
+}
+
+func (m *Meta) Format() []byte {
+	// TODO: complete this
+	return []byte("someData")
+}