1// Copyright The OpenTelemetry Authors
2//
3// Licensed under the Apache License, Version 2.0 (the "License");
4// you may not use this file except in compliance with the License.
5// You may obtain a copy of the License at
6//
7//     http://www.apache.org/licenses/LICENSE-2.0
8//
9// Unless required by applicable law or agreed to in writing, software
10// distributed under the License is distributed on an "AS IS" BASIS,
11// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
12// See the License for the specific language governing permissions and
13// limitations under the License.
14
15package attribute // import "go.opentelemetry.io/otel/attribute"
16
17// Iterator allows iterating over the set of labels in order,
18// sorted by key.
19type Iterator struct {
20	storage *Set
21	idx     int
22}
23
24// MergeIterator supports iterating over two sets of labels while
25// eliminating duplicate values from the combined set.  The first
26// iterator value takes precedence.
27type MergeIterator struct {
28	one     oneIterator
29	two     oneIterator
30	current KeyValue
31}
32
33type oneIterator struct {
34	iter  Iterator
35	done  bool
36	label KeyValue
37}
38
39// Next moves the iterator to the next position. Returns false if there
40// are no more labels.
41func (i *Iterator) Next() bool {
42	i.idx++
43	return i.idx < i.Len()
44}
45
46// Label returns current KeyValue. Must be called only after Next returns
47// true.
48func (i *Iterator) Label() KeyValue {
49	kv, _ := i.storage.Get(i.idx)
50	return kv
51}
52
53// Attribute is a synonym for Label().
54func (i *Iterator) Attribute() KeyValue {
55	return i.Label()
56}
57
58// IndexedLabel returns current index and attribute. Must be called only
59// after Next returns true.
60func (i *Iterator) IndexedLabel() (int, KeyValue) {
61	return i.idx, i.Label()
62}
63
64// Len returns a number of labels in the iterator's `*Set`.
65func (i *Iterator) Len() int {
66	return i.storage.Len()
67}
68
69// ToSlice is a convenience function that creates a slice of labels
70// from the passed iterator. The iterator is set up to start from the
71// beginning before creating the slice.
72func (i *Iterator) ToSlice() []KeyValue {
73	l := i.Len()
74	if l == 0 {
75		return nil
76	}
77	i.idx = -1
78	slice := make([]KeyValue, 0, l)
79	for i.Next() {
80		slice = append(slice, i.Label())
81	}
82	return slice
83}
84
85// NewMergeIterator returns a MergeIterator for merging two label sets
86// Duplicates are resolved by taking the value from the first set.
87func NewMergeIterator(s1, s2 *Set) MergeIterator {
88	mi := MergeIterator{
89		one: makeOne(s1.Iter()),
90		two: makeOne(s2.Iter()),
91	}
92	return mi
93}
94
95func makeOne(iter Iterator) oneIterator {
96	oi := oneIterator{
97		iter: iter,
98	}
99	oi.advance()
100	return oi
101}
102
103func (oi *oneIterator) advance() {
104	if oi.done = !oi.iter.Next(); !oi.done {
105		oi.label = oi.iter.Label()
106	}
107}
108
109// Next returns true if there is another label available.
110func (m *MergeIterator) Next() bool {
111	if m.one.done && m.two.done {
112		return false
113	}
114	if m.one.done {
115		m.current = m.two.label
116		m.two.advance()
117		return true
118	}
119	if m.two.done {
120		m.current = m.one.label
121		m.one.advance()
122		return true
123	}
124	if m.one.label.Key == m.two.label.Key {
125		m.current = m.one.label // first iterator label value wins
126		m.one.advance()
127		m.two.advance()
128		return true
129	}
130	if m.one.label.Key < m.two.label.Key {
131		m.current = m.one.label
132		m.one.advance()
133		return true
134	}
135	m.current = m.two.label
136	m.two.advance()
137	return true
138}
139
140// Label returns the current value after Next() returns true.
141func (m *MergeIterator) Label() KeyValue {
142	return m.current
143}
144