1+ import { stringify } from '../../utils/stringify' ;
2+ import getExpressionPrecedence from '../../utils/getExpressionPrecedence' ;
3+ import Node from './shared/Node' ;
4+ import Block from '../dom/Block' ;
5+
6+ export default class Title extends Node {
7+ build (
8+ block : Block ,
9+ parentNode : string ,
10+ parentNodes : string
11+ ) {
12+ const isDynamic = ! ! this . children . find ( node => node . type !== 'Text' ) ;
13+
14+ if ( isDynamic ) {
15+ let value ;
16+
17+ const allDependencies = new Set ( ) ;
18+ let shouldCache ;
19+
20+ // TODO some of this code is repeated in Tag.ts — would be good to
21+ // DRY it out if that's possible without introducing crazy indirection
22+ if ( this . children . length === 1 ) {
23+ // single {{tag}} — may be a non-string
24+ const { expression } = this . children [ 0 ] ;
25+ const { indexes } = block . contextualise ( expression ) ;
26+ const { dependencies, snippet } = this . children [ 0 ] . metadata ;
27+
28+ value = snippet ;
29+ dependencies . forEach ( d => {
30+ allDependencies . add ( d ) ;
31+ } ) ;
32+
33+ shouldCache = (
34+ expression . type !== 'Identifier' ||
35+ block . contexts . has ( expression . name )
36+ ) ;
37+ } else {
38+ // '{{foo}} {{bar}}' — treat as string concatenation
39+ value =
40+ ( this . children [ 0 ] . type === 'Text' ? '' : `"" + ` ) +
41+ this . children
42+ . map ( ( chunk : Node ) => {
43+ if ( chunk . type === 'Text' ) {
44+ return stringify ( chunk . data ) ;
45+ } else {
46+ const { indexes } = block . contextualise ( chunk . expression ) ;
47+ const { dependencies, snippet } = chunk . metadata ;
48+
49+ dependencies . forEach ( d => {
50+ allDependencies . add ( d ) ;
51+ } ) ;
52+
53+ return getExpressionPrecedence ( chunk . expression ) <= 13 ? `(${ snippet } : snippet ;
54+ }
55+ } )
56+ . join ( ' + ' ) ;
57+
58+ shouldCache = true ;
59+ }
60+
61+ const last = shouldCache && block . getUniqueName (
62+ `title_value`
63+ ) ;
64+
65+ if ( shouldCache ) block . addVariable ( last ) ;
66+
67+ let updater ;
68+ const init = shouldCache ? `${ last } ${ value } : value ;
69+
70+ block . builders . init . addLine (
71+ `document.title = ${ init }
72+ ) ;
73+ updater = `document.title = ${ shouldCache ? last : value } ;
74+
75+ if ( allDependencies . size ) {
76+ const dependencies = Array . from ( allDependencies ) ;
77+ const changedCheck = (
78+ ( block . hasOutroMethod ? `#outroing || ` : '' ) +
79+ dependencies . map ( dependency => `changed.${ dependency } ) . join ( ' || ' )
80+ ) ;
81+
82+ const updateCachedValue = `${ last } ${ last } ${ value } ;
83+
84+ const condition = shouldCache ?
85+ ( dependencies . length ? `(${ changedCheck } ${ updateCachedValue } : updateCachedValue ) :
86+ changedCheck ;
87+
88+ block . builders . update . addConditional (
89+ condition ,
90+ updater
91+ ) ;
92+ }
93+ } else {
94+ const value = stringify ( this . children [ 0 ] . data ) ;
95+ block . builders . hydrate . addLine ( `document.title = ${ value } ) ;
96+ }
97+ }
98+ }
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