| 1 | const qs = require('qs')
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| 2 | const _ = require('lodash')
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| 3 |
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| 4 | /**
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| 5 | * @function
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| 6 | * @private
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| 7 | *
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| 8 | * @description
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| 9 | * Get parameter value based on the passed condition
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| 10 | *
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| 11 | * @param {*} param The parameter to be minimized
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| 12 | * @param {*} condition The condition to be checked for
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| 13 | * @returns {* | undefined} The minimized parameter value
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| 14 | */
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| 15 | function minimizeQueryParameter (param, condition) {
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| 16 | return param === condition ? undefined : param
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| 17 | }
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| 18 |
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| 19 | /**
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| 20 | * @function
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| 21 | * @private
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| 22 | *
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| 23 | * @description
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| 24 | * Halify links by converting them to objects
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| 25 | *
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| 26 | * @param {Object} links The links to be halified
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| 27 | * @returns {Object} The halified links object
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| 28 | */
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| 29 | function halifyLinks (links) {
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| 30 | _.forOwn(links, (href, entity) => {
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| 31 | links[entity] = { href }
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| 32 | })
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| 33 | }
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| 34 |
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| 35 | /**
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| 36 | * @function
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| 37 | * @private
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| 38 | *
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| 39 | * @description
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| 40 | * Get absolute/relative request url
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| 41 | *
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| 42 | * @param {Object} request The related request object
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| 43 | * @param {Object} pluginOptions The plugin related options
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| 44 | * @returns {string} The request url
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| 45 | */
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| 46 | function getRequestUrl (request, pluginOptions) {
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| 47 | const proxyProtocol = request.headers && request.headers['x-forwarded-proto']
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| 48 | const protocol = proxyProtocol || request.server.info.protocol || 'http'
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| 49 | let requestUrl = request.url.pathname
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| 50 |
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| 51 | if (pluginOptions.absolute) {
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| 52 | requestUrl = `${protocol}://${request.info.host}${requestUrl}`
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| 53 | }
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| 54 |
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| 55 | return requestUrl
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| 56 | }
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| 57 |
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| 58 | /**
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| 59 | * @function
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| 60 | * @private
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| 61 | *
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| 62 | * @description
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| 63 | * Get link of the requested resource itself
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| 64 | *
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| 65 | * @param {number} page The requested page
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| 66 | * @param {number} perPage The requested items per page
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| 67 | * @param {Object} request The related request object
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| 68 | * @param {Object} options The request related options
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| 69 | * @param {Object} pluginOptions The plugin related options
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| 70 | * @returns {string} The generated resource link
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| 71 | */
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| 72 | function getSelfLink (page, perPage, request, options, pluginOptions) {
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| 73 | const requestPath = getRequestUrl(request, pluginOptions)
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| 74 |
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| 75 | const paramNames = pluginOptions.paramNames
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| 76 | const query = qs.stringify(Object.assign({}, request.query, {
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| 77 | [paramNames.perPage]: minimizeQueryParameter(perPage, options.perPage),
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| 78 | [paramNames.page]: minimizeQueryParameter(page, 1)
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| 79 | }))
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| 80 |
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| 81 | return query ? `${requestPath}?${query}` : requestPath
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| 82 | }
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| 83 |
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| 84 | /**
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| 85 | * @function
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| 86 | * @private
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| 87 | *
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| 88 | * @description
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| 89 | * Get pagination link generator with predefined values
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| 90 | *
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| 91 | * @param {string} id The endpoint ID
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| 92 | * @param {number} perPage The number of entries per page
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| 93 | * @param {Object} options The related options
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| 94 | * @param {Object} requestObj The related query parameters
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| 95 | * @param {Function} aka The request bound akaya function for link building
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| 96 | * @param {boolean} absolute If the link should be an absolute one
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| 97 | * @param {Object} paramNames The names of the query params
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| 98 | * @returns {Function} The predefined pagination link generator
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| 99 | */
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| 100 | function getPaginationLink (id, perPage, options, requestObj, aka, absolute, paramNames) {
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| 101 | perPage = minimizeQueryParameter(perPage, options.perPage)
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| 102 |
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| 103 | return (page) => {
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| 104 | page = minimizeQueryParameter(page, 1)
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| 105 |
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| 106 | return aka(id, {
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| 107 | query: Object.assign({}, requestObj.query, {
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| 108 | [paramNames.page]: page,
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| 109 | [paramNames.perPage]: perPage
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| 110 | }),
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| 111 | params: requestObj.params
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| 112 | }, { rel: !absolute })
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| 113 | }
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| 114 | }
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| 115 |
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| 116 | /**
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| 117 | * @function
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| 118 | * @public
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| 119 | *
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| 120 | * @description
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| 121 | * Get entity/href mapping of necessary pagination links
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| 122 | *
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| 123 | * @param {string} id The endpoint ID
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| 124 | * @param {number} page The requested page
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| 125 | * @param {number} perPage The number of entries per page
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| 126 | * @param {number} total The total number of entries
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| 127 | * @param {Object} requestObj The related query parameters
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| 128 | * @param {Function} aka The request bound akaya function for link building
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| 129 | * @param {Object} options The related options
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| 130 | * @param {Object} pluginOptions The plugin related options
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| 131 | * @returns {Object.<?string>} The mapping of pagination links
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| 132 | */
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| 133 | function getPaginationLinks (id, page, perPage, total, requestObj, aka, options, pluginOptions) {
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| 134 | const getLink = getPaginationLink(
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| 135 | id, perPage, options, requestObj, aka, pluginOptions.absolute, pluginOptions.paramNames
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| 136 | )
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| 137 | const lastPage = Math.ceil(total / perPage)
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| 138 | const links = {}
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| 139 |
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| 140 | links.self = getSelfLink(page, perPage, requestObj, options, pluginOptions)
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| 141 | links.first = getLink(undefined)
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| 142 |
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| 143 | if (page > 1 && page <= lastPage) {
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| 144 | links.prev = getLink(page - 1)
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| 145 | }
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| 146 |
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| 147 | if (page < lastPage && page >= 1) {
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| 148 | links.next = getLink(page + 1)
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| 149 | }
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| 150 |
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| 151 | links.last = getLink(lastPage)
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| 152 |
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| 153 | halifyLinks(links)
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| 154 |
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| 155 | return links
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| 156 | }
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| 157 |
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| 158 | module.exports = {
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| 159 | getLinks: getPaginationLinks
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| 160 | }
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