Caption support (#2462)

Co-authored-by: WithoutPants <53250216+WithoutPants@users.noreply.github.com>

vendor/github.com/asticode/go-astikit/map.go

@@ -0,0 +1,67 @@
+package astikit
+
+import (
+	"fmt"
+	"sync"
+)
+
+// BiMap represents a bidirectional map
+type BiMap struct {
+	forward map[interface{}]interface{}
+	inverse map[interface{}]interface{}
+	m       *sync.Mutex
+}
+
+// NewBiMap creates a new BiMap
+func NewBiMap() *BiMap {
+	return &BiMap{
+		forward: make(map[interface{}]interface{}),
+		inverse: make(map[interface{}]interface{}),
+		m:       &sync.Mutex{},
+	}
+}
+
+func (m *BiMap) get(k interface{}, i map[interface{}]interface{}) (v interface{}, ok bool) {
+	m.m.Lock()
+	defer m.m.Unlock()
+	v, ok = i[k]
+	return
+}
+
+// Get gets the value in the forward map based on the provided key
+func (m *BiMap) Get(k interface{}) (interface{}, bool) { return m.get(k, m.forward) }
+
+// GetInverse gets the value in the inverse map based on the provided key
+func (m *BiMap) GetInverse(k interface{}) (interface{}, bool) { return m.get(k, m.inverse) }
+
+// MustGet gets the value in the forward map based on the provided key and panics if key is not found
+func (m *BiMap) MustGet(k interface{}) interface{} {
+	v, ok := m.get(k, m.forward)
+	if !ok {
+		panic(fmt.Sprintf("astikit: key %+v not found in foward map", k))
+	}
+	return v
+}
+
+// MustGetInverse gets the value in the inverse map based on the provided key and panics if key is not found
+func (m *BiMap) MustGetInverse(k interface{}) interface{} {
+	v, ok := m.get(k, m.inverse)
+	if !ok {
+		panic(fmt.Sprintf("astikit: key %+v not found in inverse map", k))
+	}
+	return v
+}
+
+func (m *BiMap) set(k, v interface{}, f, i map[interface{}]interface{}) *BiMap {
+	m.m.Lock()
+	defer m.m.Unlock()
+	f[k] = v
+	i[v] = k
+	return m
+}
+
+// Set sets the value in the forward and inverse map for the provided forward key
+func (m *BiMap) Set(k, v interface{}) *BiMap { return m.set(k, v, m.forward, m.inverse) }
+
+// SetInverse sets the value in the forward and inverse map for the provided inverse key
+func (m *BiMap) SetInverse(k, v interface{}) *BiMap { return m.set(k, v, m.inverse, m.forward) }