Add endpoint and link for retrieving a thumbnail (#341)

Author: Phil Varner

CHANGELOG.md

@@ -25,6 +25,7 @@ and this project adheres to [Semantic Versioning](http://semver.org/spec/v2.0.0.
 - POST /collections endpoint to create collections
 - Configuration of shards and replicas for the indices containing Items can now be done
   with environment variables ITEMS_INDICIES_NUM_OF_SHARDS and ITEMS_INDICIES_NUM_OF_REPLICAS.
+- (Experimental) Adds Item 'thumbnail' link to presign an s3 protocol thumbnail asset ARN
 
 ### Changed
 

src/lambdas/api/app.js

@@ -321,6 +321,31 @@ app.delete('/collections/:collectionId/items/:itemId', async (req, res, next) =>
   }
 })
 
+app.get('/collections/:collectionId/items/:itemId/thumbnail', async (req, res, next) => {
+  try {
+    const { itemId, collectionId } = req.params
+
+    const response = await api.getItemThumbnail(
+      collectionId,
+      itemId,
+      database,
+    )
+
+    if (response instanceof Error) {
+      if (response.message === 'Item not found'
+          || response.message === 'Thumbnail not found') {
+        next(createError(404))
+      } else {
+        next(createError(500))
+      }
+    } else {
+      res.redirect(response.location)
+    }
+  } catch (error) {
+    next(error)
+  }
+})
+
 // catch 404 and forward to error handler
 app.use((_req, _res, next) => {
   next(createError(404))

src/lib/api.js

@@ -1,6 +1,7 @@
 const { pickBy, assign, get: getNested } = require('lodash')
 const extent = require('@mapbox/extent')
 const { DateTime } = require('luxon')
+const AWS = require('aws-sdk')
 const { isIndexNotFoundError } = require('./database')
 const logger = console
 
@@ -374,6 +375,10 @@ const addItemLinks = function (results, endpoint) {
       type: 'application/geo+json',
       href: `${endpoint}`
     })
+    links.push({
+      rel: 'thumbnail',
+      href: `${endpoint}/collections/${collection}/items/${id}/thumbnail`
+    })
     result.type = 'Feature'
     return result
   })
@@ -862,6 +867,39 @@ const deleteItem = async function (collectionId, itemId, backend) {
   return new Error(`Error deleting item ${collectionId}/${itemId}`)
 }
 
+const getItemThumbnail = async function (collectionId, itemId, backend) {
+  const itemQuery = { collections: [collectionId], id: itemId }
+  const { results } = await backend.search(itemQuery)
+  const [item] = results
+  if (!item) {
+    return new Error('Item not found')
+  }
+
+  const thumbnailAsset = Object.values(item.assets || []).find((x) => x.roles.includes('thumbnail'))
+  if (!thumbnailAsset) {
+    return new Error('Thumbnail not found')
+  }
+
+  let location
+  if (thumbnailAsset.href && thumbnailAsset.href.startsWith('http')) {
+    location = thumbnailAsset.href
+  } else if (thumbnailAsset.href && thumbnailAsset.href.startsWith('s3')) {
+    const withoutProtocol = thumbnailAsset.href.substring(5) // chop off s3://
+    const [bucket, ...keyArray] = withoutProtocol.split('/')
+    const key = keyArray.join('/')
+    location = new AWS.S3().getSignedUrl('getObject', {
+      Bucket: bucket,
+      Key: key,
+      Expires: 60 * 5, // expiry in seconds
+      RequestPayer: 'requester'
+    })
+  } else {
+    return new Error('Thumbnail not found')
+  }
+
+  return { location }
+}
+
 const healthCheck = async function (backend) {
   const response = await backend.healthCheck()
   logger.debug(`Health check: ${response}`)
@@ -890,5 +928,6 @@ module.exports = {
   extractLimit,
   extractDatetime,
   aggregate,
-  healthCheck
+  getItemThumbnail,
+  healthCheck,
 }