| aicra |

Aicra is a configuration-driven web framework written in Go that allows you to create a fully featured REST API.

The whole management is done for you from a configuration file describing your API, you're left with implementing :

• controllers
• optionnally middle-wares (e.g. authentication, csrf)
• and optionnally type checkers to check input parameters

The aicra server fulfills the net/http Server interface.

A example project is available here

Table of contents

• I/ Installation
• II/ Development
  • 1) Main executable
  • 2) API Configuration
    • Definition
    • Input Arguments
      • 1. Input types
      • 2. Global Format
• III/ Change Log

I/ Installation

You need a recent machine with go installed. This package has not been tested under the version 1.10.

go get -u git.xdrm.io/go/aicra/cmd/aicra

The library should now be available as git.xdrm.io/go/aicra in your imports.

II/ Development

1) Main executable

The main executable will declare and run the aicra server, it might look quite like the code below.

package main
import (
    "log"
    "net/http"

    "git.xdrm.io/go/aicra"
    "git.xdrm.io/go/aicra/typecheck/builtin"
    "git.xdrm.io/go/aicra/api"
)

func main() {

    // 1. build server
    server, err := aicra.New("path/to/your/api/definition.json");
    if err != nil {
        log.Fatalf("Cannot build the aicra server: %v\n", err)
    }

    // 2. add type checkers
    server.Checkers.Add( builtin.NewAny() );
    server.Checkers.Add( builtin.NewString() );
    server.Checkers.Add( builtin.NewFloat64() );

    // 3. bind your implementations
    server.HandleFunc(http.MethodGet, func(req api.Request, res *api.Response){
        // ... process stuff ...
        res.SetError(api.ErrorSuccess());
    })

    // 4. launch server
    log.Fatal( http.ListenAndServer("localhost:8181", server) )
}

2) API Configuration

The whole project behavior is described inside a json file (e.g. usually api.json) file. For a better understanding of the format, take a look at this working template. This file defines :

• resource routes and their methods
• every input for each method (called argument)
• every output for each method
• scope permissions (list of permissions needed for clients to use which method)
• input policy :
  • type of argument (i.e. for type checkers)
  • required/optional
  • default value
  • variable renaming

Definition

At the root of the json file are available 5 field names :

1. GET - to define what to do when receiving a request with a GET HTTP method at the root URI
2. POST - to define what to do when receiving a request with a POST HTTP method at the root URI
3. PUT - to define what to do when receiving a request with a PUT HTTP method at the root URI
4. DELETE - to define what to do when receiving a request with a DELETE HTTP method at the root URI
5. / - to define children URIs ; each will have the same available fields

For each method you will have to create fields described in the table above.

field path	description	example
info	A short human-readable description of what the method does	create a new user
scope	A 2-dimensional array of permissions. The first dimension can be translated to a or operator, the second dimension as a and. It allows you to combine permissions in complex ways.	[["A", "B"], ["C", "D"]] can be translated to : this method needs users to have permissions (A and B) or (C and D)
in	The list of arguments that the clients will have to provide. See here for details.
out	The list of output data that will be returned by your controllers. It has the same syntax as the in field but is only use for readability purpose and documentation.

Input Arguments

1. Input types

Input arguments defines what data from the HTTP request the method needs. Aicra is able to extract 3 types of data :

• URI - Slash-separated strings right after the resource URI. For instance, if your controller is bound to the /user URI, you can use the URI slot right after to send the user ID ; Now a client can send requests to the URI /user/:id where :id is a number sent by the client. This kind of input cannot be extracted by name, but rather by index in the URL (begins at 0).
• Query - data formatted at the end of the URL following the standard HTTP Query syntax.
• URL encoded - data send inside the body of the request but following the HTTP Query syntax.
• Multipart - data send inside the body of the request with a dedicated format. This format is not very lightweight but allows you to receive data as well as files.
• JSON - data send inside the body as a json object ; each key being a variable name, each value its content. Note that the HTTP header 'Content-Type' must be set to application/json for the API to use it.

2. Global Format

The in field in each method contains as list of arguments where the key is the argument name, and the value defines how to manage the variable.

Variable names must be prefixed when requesting URI or Query input types.

• The first URI data has to be named URL#0, the second one URL#1 and so on...
• The variable named somevar in the Query has to be named GET@somvar in the configuration.

Example

In this example we want 3 arguments :

• the 1^st^ one is send at the end of the URI and is a number compliant with the int type checker (else the controller will not be run). It is renamed uri-param, this new name will be sent to the controller.
• the 2^nd^ one is send in the query (e.g. http://host/uri?get-var=value). It must be a valid int or not given at all (the ? at the beginning of the type tells that the argument is optional) ; it will be named get-param.
• the 3^rd^ can be send with a JSON body, in multipart or URL encoded it makes no difference and only give clients a choice over the technology to use. If not renamed, the variable will be given to the controller with the name multipart-var.

"in": {
    // arg 1
    "URL#0": {
        "info": "some integer in the URI",
        "type": "int",
        "name": "uri-param"
    },
    // arg 2
    "GET@get-var": {
        "info": "some Query OPTIONAL variable",
        "type": "?int",
        "name": "get-param"
    },
    // arg 3
    "multipart-var": { /* ... */ }
}

III/ Change Log

• human-readable json configuration
• nested routes (i.e. /user/:id: and /user/post/:id:)
• nested URL arguments (i.e. /user/:id: and /user/:id:/post/​:id:​)
• useful http methods: GET, POST, PUT, DELETE
• manage URL, query and body arguments:
  • multipart/form-data (variables and file uploads)
  • application/x-www-form-urlencoded
  • application/json
• required vs. optional parameters with a default value
• parameter renaming
• generic type check (i.e. implement custom types alongside built-in ones)
• built-in types
  • any - wildcard matching all values
  • int - see go types
  • uint - see go types
  • float - see go types
  • string - any text
  • string(min, max) - any string with a length between min and max
  • [a] - array containing only elements matching a type
  • [a:b] - map containing only keys of type a and values of type b (a or b can be ommited)
• generic controllers implementation (shared objects)
• response interface
• log bound resources when building the aicra server
• fail on check for unimplemented resources at server boot.
• fail on check for unavailable types in api.json at server boot.