PoC to implement paged resource lists with lambda functions

.gitignore

@@ -1,3 +1,8 @@
+_dist/
+_functions/
+
+node_modules/
+
 .idea/
 
 *.py[cod]

build.sh

@@ -0,0 +1,11 @@
+#!/bin/bash
+
+set -e
+set -o pipefail
+set -x
+
+yarn install
+yarn run netlify-lambda build functions
+
+poetry install --no-dev
+poetry run ditto transform --base-url='https://pokeapi.netlify.com/' --dest-dir='_dist'

functions/resource-list.js

@@ -0,0 +1,103 @@
+import getJson from 'get-json'
+
+const baseUrl = "https://pokeapi.netlify.com";
+
+function targetUrlForPath(path) {
+    let target = baseUrl;
+    target += path;
+    if (!target.endsWith("/")) {
+        target += "/";
+    }
+    target += "index.json";
+    return target;
+}
+
+function extractParams(query) {
+    let defaults = {offset: 0, limit: 20};
+    return {
+        offset: parseInt(query.offset) || 0,
+        limit: parseInt(query.limit) || 20,
+    }
+}
+
+function getPageUrl(path, params) {
+    if (params == null) {
+        return null;
+    }
+    return baseUrl + path + "?offset=" + params.offset + "&limit=" + params.limit;
+}
+
+function getPreviousPage(params) {
+    let newPage = {
+        begin: params.offset - params.limit,
+        end: params.offset,
+    }
+
+    if (newPage.begin < 0) {
+        newPage.begin = 0;
+    }
+
+    // it's a prev page only if we've moved back
+    if (newPage.begin < params.offset) {
+        return {
+            offset: newPage.begin,
+            limit: newPage.end - newPage.begin,
+        };
+    }
+
+    return null;
+}
+
+function getNextPage(params, count) {
+    let newPage = {
+        begin: params.offset + params.limit,
+        end: params.offset + params.limit * 2,
+    }
+
+    if (newPage.end > count) {
+        newPage.end = count;
+    }
+
+    // it's a next page only if we've moved forward
+    if (newPage.end > params.offset + params.limit) {
+        return {
+            offset: newPage.begin,
+            limit: newPage.end - newPage.begin,
+        }
+    }
+
+    return null;
+}
+
+exports.handler = (event, context, callback) => {
+    if (event.httpMethod !== "GET") {
+        callback(null, {statusCode: 405, body: event.httpMethod + " not allowed"});
+        return;
+    }
+
+    let path = "/api/v2/" + event.queryStringParameters.endpoint + "/";
+
+    if (!path) {
+        callback(null, {statusCode: 400, body: "path must not be empty"});
+        return;
+    }
+
+    let url = targetUrlForPath(path);
+
+    getJson(url, (error, response) => {
+        if (error) {
+            callback(null, {statusCode: 400, body: "path must be a valid resource list"});
+            return;
+        }
+
+        let params = extractParams(event.queryStringParameters);
+        let resultSlice = response.results.slice(params.offset, params.offset + params.limit);
+        let finalResponse = Object.assign(response, {
+            next: getPageUrl(path, getNextPage(params, response.count)),
+            previous: getPageUrl(path, getPreviousPage(params)),
+            results: resultSlice,
+        });
+
+        callback(null, {statusCode: 200, body: JSON.stringify(finalResponse, null, 4)})
+    });
+};

netlify.toml

@@ -1,9 +1,7 @@
-[Settings]
-ID = "pokeapi"
-
 [build]
-publish = "dist"
-command = "pip install poetry && poetry install --no-dev && poetry run ditto transform --base-url='https://pokeapi.nelify.com/'"
+publish = "_dist"
+command = "pip install poetry && bash build.sh"
+functions = "_functions"
 
 [[redirects]]
 from = "/api/v2/"
@@ -12,25 +10,25 @@ status = 200
 
 [[redirects]]
 from = "/api/v2/:endpoint/"
-to = "https://pokeapi.co/api/v2/:endpoint/?limit=:limit&offset=:offset"
-status = 200
+to = "/.netlify/functions/resource-list/?endpoint=:endpoint&offset=:offset&limit=:limit"
 query = {offset = ":offset", limit = ":limit"}
+status = 200
 
 [[redirects]]
 from = "/api/v2/:endpoint/"
-to = "https://pokeapi.co/api/v2/:endpoint/?offset=:offset"
-status = 200
+to = "/.netlify/functions/resource-list/?endpoint=:endpoint&offset=:offset"
 query = {offset = ":offset"}
+status = 200
 
 [[redirects]]
 from = "/api/v2/:endpoint/"
-to = "https://pokeapi.co/api/v2/:endpoint/?limit=:limit"
-status = 200
+to = "/.netlify/functions/resource-list/?endpoint=:endpoint&limit=:limit"
 query = {limit = ":limit"}
+status = 200
 
 [[redirects]]
 from = "/api/v2/:endpoint/"
-to = "/api/v2/:endpoint/index.json"
+to = "/.netlify/functions/resource-list/?endpoint=:endpoint"
 status = 200
 
 [[redirects]]

package.json

@@ -0,0 +1,13 @@
+{
+  "devDependencies": {
+    "@babel/core": "^7.0.1",
+    "babel-loader": "^8.0.2",
+    "babel-plugin-transform-class-properties": "^6.24.1",
+    "babel-plugin-transform-object-assign": "^6.22.0",
+    "babel-plugin-transform-object-rest-spread": "^6.26.0",
+    "babel-preset-env": "^1.7.0",
+    "get-json": "^1.0.0",
+    "netlify-lambda": "^0.4.0"
+  },
+  "dependencies": {}
+}