Initial version

.eslintignore

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+coverage

.eslintrc.json

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+{
+  "env": {
+    "node": true
+  },
+  "extends": [
+    "bloq",
+    "bloq/experimental"
+  ]
+}

.gitignore

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+.eslintcache
+.nyc_output
+coverage
+node_modules
+npm-debug.log

.npmrc

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+save-exact = true

.travis.yml

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+language: node_js
+node_js:
+  - "6"
+  - "7"
+  - "8"
+

LICENSE

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+The MIT License (MIT)
+
+Copyright (c) Bloq, Inc.
+
+Permission is hereby granted, free of charge, to any person obtaining a copy of
+this software and associated documentation files (the "Software"), to deal in
+the Software without restriction, including without limitation the rights to
+use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of
+the Software, and to permit persons to whom the Software is furnished to do so,
+subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in all
+copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS
+FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR
+COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER
+IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
+CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.

README.md

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+# http-json-proxy
+
+[![Build Status](https://travis-ci.org/bloq/http-json-proxy.svg?branch=master)](https://travis-ci.org/bloq/http-json-proxy)
+[![bitHound Overall Score](https://www.bithound.io/github/bloq/http-json-proxy/badges/score.svg)](https://www.bithound.io/github/bloq/http-json-proxy)
+[![bitHound Dependencies](https://www.bithound.io/github/bloq/http-json-proxy/badges/dependencies.svg)](https://www.bithound.io/github/bloq/http-json-proxy/master/dependencies/npm)
+[![bitHound Code](https://www.bithound.io/github/bloq/http-json-proxy/badges/code.svg)](https://www.bithound.io/github/bloq/http-json-proxy)
+
+Simple HTTP JSON proxy.
+
+This proxy can be used as a middleman in between a HTTP JSON API server and a client to monitor the requests, responses and even modify on the fly any of those.
+
+## Installation
+
+```bash
+$ npm install --global http-json-proxy
+```
+
+## Usage
+
+The following command will spin up a proxy server that will forward all requests to a locally installed Ethereum node and will log to console each JSON RPC call with the corresponding response:
+
+```
+$ http-json-proxy -p 18545 -t http://localhost:8545
+Proxy for http://localhost:8545 listening on port 18545
+```
+
+Then, each call will be logged as follows:
+
+```
+--> POST / {"jsonrpc":"2.0","id":3,"method":"eth_gasPrice","params":[]}
+<-- {"jsonrpc":"2.0","result":"0x2e90edd000","id":3}
+```
+
+### Options
+
+```
+$ http-json-proxy
+Start a HTTP JSON proxy server.
+
+Options:
+  --version     Show version number                                    [boolean]
+  --port, -p    the port the server should listen to                    [number]
+  --target, -t  the proxied API server URL                   [string] [required]
+  --help        Show help                                              [boolean]
+```
+
+## API
+
+The module can also be used programmatically as follows:
+
+```js
+const createProxy = require('http-json-proxy')
+
+const options = {
+  port: 18545,
+  target: 'http://localhost:8545',
+  onReq: function (req) {
+    console.log('-->', req.method, req.url, JSON.stringify(req.body))
+    return req
+  },
+  onRes: function (body) {
+    console.log('<--', JSON.stringify(body))
+    return body
+  }
+}
+
+const proxy = createProxy(options)
+```
+
+### `createProxy(options)`
+
+Creates a new proxy that starts listening on the specified port, forwarding all requests to the target server. It returns an [`http.Server`](https://nodejs.org/api/http.html#http_class_http_server) instance.
+
+#### `options.port`
+
+Is the port the proxy will listen on. If not specified, the proxy will start listening to a random unused port.
+
+#### `options.host`
+
+Is the host the proxy will listen on. If not specified, the proxy will listen in all interfaces.
+
+#### `options.target`
+
+Is the proxied API server URL.
+
+#### `options.onReq`
+
+Will be called on each request with the `req` object that will be forwarded to the target server and shall return that `req`. Any of the properties of the `req` object can be altered to modify the actual request that is sent to the target server. Defaults to the identity function.
+
+#### `options.onRes`
+
+Will be called on each response with the `body` of the response and shall return the actual `body` to be provided to the client. It can be altered to provide a different response too. Defaults to the identity function.
+
+#### `options.onErr`
+
+Will be called on each request error with the corresponding `err` object and shall return the same, altered or different `err` object that will be returned to the client along with a 500 status code. Defaults to the identity function.
+
+## License
+
+MIT

bin/.eslintrc.json

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+{
+  "rules": {
+    "max-len": "off",
+    "no-console": "off"
+  }
+}

bin/proxy.js

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+#!/usr/bin/env node
+
+'use strict'
+
+const yargs = require('yargs')
+
+const createProxy = require('..')
+
+const argv = yargs
+  .version()
+  .usage('Start a HTTP JSON proxy server.')
+  .options('port', {
+    alias: 'p',
+    describe: 'the port the server should listen to',
+    type: 'number'
+  })
+  .options('target', {
+    alias: 't',
+    describe: 'the proxied API server URL',
+    demandOption: true,
+    type: 'string'
+  })
+  .help()
+  .parse()
+
+const { port, target } = argv
+
+const proxy = createProxy({
+  port,
+  target,
+  onReq (req) {
+    console.log('-->', req.method, req.url, JSON.stringify(req.body))
+    return req
+  },
+  onRes (body) {
+    console.log('<--', JSON.stringify(body))
+    return body
+  },
+  onErr (err) {
+    console.warn('<-- ERROR', err.message)
+    return err
+  }
+})
+
+proxy.on('listening', function () {
+  console.log(`Proxy for ${target} listening on port ${proxy.address().port}`)
+})

lib/identity/index.js

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+'use strict'
+
+/**
+ * Returns the first parameter it receives.
+ *
+ * @param {*} x Any value.
+ * @returns {*} the received value.
+ */
+const identity = x => x
+
+module.exports = identity