// vue compiler module for transforming `img:srcset` to a number of `require`s
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import { urlToRequire, ASTNode } from './utils'
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import { TransformAssetUrlsOptions } from './assetUrl'
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interface ImageCandidate {
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require: string
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descriptor: string
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}
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export default (transformAssetUrlsOptions?: TransformAssetUrlsOptions) => ({
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postTransformNode: (node: ASTNode) => {
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transform(node, transformAssetUrlsOptions)
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}
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})
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// http://w3c.github.io/html/semantics-embedded-content.html#ref-for-image-candidate-string-5
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const escapedSpaceCharacters = /( |\\t|\\n|\\f|\\r)+/g
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function transform(
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node: ASTNode,
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transformAssetUrlsOptions?: TransformAssetUrlsOptions
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) {
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const tags = ['img', 'source']
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if (tags.indexOf(node.tag) !== -1 && node.attrs) {
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node.attrs.forEach(attr => {
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if (attr.name === 'srcset') {
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// same logic as in transform-require.js
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const value = attr.value
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const isStatic =
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value.charAt(0) === '"' && value.charAt(value.length - 1) === '"'
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if (!isStatic) {
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return
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}
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const imageCandidates: ImageCandidate[] = value
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.substr(1, value.length - 2)
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.split(',')
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.map(s => {
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// The attribute value arrives here with all whitespace, except
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// normal spaces, represented by escape sequences
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const [url, descriptor] = s
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.replace(escapedSpaceCharacters, ' ')
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.trim()
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.split(' ', 2)
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return {
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require: urlToRequire(url, transformAssetUrlsOptions),
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descriptor
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}
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})
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// "require(url1)"
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// "require(url1) 1x"
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// "require(url1), require(url2)"
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// "require(url1), require(url2) 2x"
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// "require(url1) 1x, require(url2)"
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// "require(url1) 1x, require(url2) 2x"
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const code = imageCandidates
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.map(
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({ require, descriptor }) =>
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`${require} + "${descriptor ? ' ' + descriptor : ''}, " + `
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)
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.join('')
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.slice(0, -6)
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.concat('"')
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.replace(/ \+ ""$/, '')
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attr.value = code
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}
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})
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}
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}
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