fix: add basic <wutta-autocomplete> component

this probably needs improvement yet but we'll see

src/wuttaweb/templates/wutta-components.mako

@@ -1,6 +1,7 @@
 
 <%def name="make_wutta_components()">
   ${self.make_wutta_request_mixin()}
+  ${self.make_wutta_autocomplete_component()}
   ${self.make_wutta_button_component()}
   ${self.make_wutta_datepicker_component()}
   ${self.make_wutta_timepicker_component()}
@@ -86,6 +87,150 @@
   </script>
 </%def>
 
+<%def name="make_wutta_autocomplete_component()">
+  <script type="text/x-template" id="wutta-autocomplete-template">
+    <div>
+      <b-autocomplete ref="autocomplete"
+                      v-show="!value"
+                      v-model="entry"
+                      :data="data"
+                      @typing="getAsyncData"
+                      @select="selectionMade"
+                      keep-first>
+        <template slot-scope="props">
+          {{ props.option.label }}
+        </template>
+      </b-autocomplete>
+      <b-button v-if="value"
+                @click="clearValue(true, true)">
+        {{ recordLabel }} (click to change)
+      </b-button>
+    </div>
+  </script>
+  <script>
+    const WuttaAutocomplete = {
+        template: '#wutta-autocomplete-template',
+
+        props: {
+
+            // callers do not specify this directly but rather by way
+            // of the `v-model` directive.  the component will emit
+            // `input` events when this value changes
+            value: String,
+
+            // caller must specify initial display string, if the
+            // (v-model) value is not empty when component loads
+            display: String,
+
+            // the url from which search results are obtained.  the
+            // endpoint should expect a GET with single `term` param
+            // in query string, and return list of objects, each with
+            // (at least) `value` and `label` properties.
+            serviceUrl: String,
+        },
+
+        data() {
+            return {
+
+                // user search input
+                entry: null,
+
+                // display label for button, when value is set
+                recordLabel: this.display,
+
+                // this contains the latest search results; it will
+                // change over time as user types.  when an option is
+                // selected, it will be an element from this list.
+                data: [],
+            }
+        },
+
+        watch: {
+
+            value(val) {
+                // reset ourself when model value is cleared
+                if (!val) {
+                    this.clearValue()
+                }
+            },
+        },
+
+        methods: {
+
+            focus() {
+                this.$refs.autocomplete.focus()
+            },
+
+            // convenience for parent component to fetch current label
+            getLabel() {
+                return this.recordLabel
+            },
+
+            // fetch new search results from server.  this is invoked
+            // when user types new input
+            getAsyncData(entry) {
+
+                // nb. skip search until we have at least 3 chars of input
+                if (entry.length < 3) {
+                    this.data = []
+                    return
+                }
+
+                // search results become autocomplete options
+                this.$http.get(this.serviceUrl + '?term=' + encodeURIComponent(entry))
+                    .then(({ data }) => {
+                        this.data = data
+                    })
+                    .catch((error) => {
+                        this.data = []
+                        throw error
+                    })
+            },
+
+            // handle selection change.  this is invoked when user
+            // chooses an autocomplete option
+            selectionMade(option) {
+
+                // reset user input
+                this.entry = null
+
+                // nb. this method can be triggered when a selection
+                // is made *or cleared* - if the latter then we do not
+                // want to emit event for the empty value; that part
+                // is handled in clearValue()
+                if (option) {
+                    this.recordLabel = option.label
+                    this.$emit('input', option.value)
+                } else {
+                    this.recordLabel = null
+                }
+            },
+
+            // clear the component value
+            clearValue(emit, focus) {
+
+                // clear autocomplete selection
+                this.$refs.autocomplete.setSelected(null)
+
+                // maybe emit event for new value
+                if (emit) {
+                    this.$emit('input', null)
+                }
+
+                // maybe set focus to autocomplete
+                if (focus) {
+                    this.$nextTick(function() {
+                        this.focus()
+                    })
+                }
+            },
+        },
+
+    }
+    Vue.component('wutta-autocomplete', WuttaAutocomplete)
+  </script>
+</%def>
+
 <%def name="make_wutta_button_component()">
   <script type="text/x-template" id="wutta-button-template">
     <b-button :type="type"