Simple-Web Framework

Easy, simple websites with Prolog.

Simply declare your routes as predicates and run the server. Simple-Web aims to help make web development simpler and easier. It does this by being opinionated. The scope of SWI-Prolog's capabilities are narrowed to a core subset, it requires a wise directory structure for static files, and it expects that you'll use simple_template for clever work with HTML.

Setup

Simple-Web depends on simple-templates, this can be installed via

?- pack_install(simple_template).

Example Basic Use

Create a directory with app.pl

:- use_module(sw/simple_web).

sw:route(home, '/', _Request) :-
    reply_html("<h1>Hello, world!</h1>
                <img src='static/images/logo.jpg' alt='logo'/>").

sw:route(templates_test, '/test', _Request) :-
    Data = data{ title: 'Hello'
               , items: [ item{ title: 'Item 1', content: 'Abc 1' }
                        , item{ title: 'Item 1', content: 'Abc 2' }
                        ]
               },
    reply_template(test, Data, options{cache:true}).

sw:route(termarized_test, root(termerized), _Request) :-
    reply_html([title('Termerized')], [h1('Termerized Example'), p('With some text')]).

sw:route(api, '/api', method(get), _Request) :-
    reply_json_dict(data{example: "Hello, world!"}).

:- run([port(5000)]).

Inside this root directory, create a folder called static to save your static files, such as your css, javascript and images. Place an image called logo.jpg into static/images/.

Also inside the root directory, create a folder called templates, inside this place test.html

<html>
  <head>
    <title>Test</title>
  </head>
  <body>
    <h1>{{= title }}</h1>
    {{ each items, item }}
        <h2>{{= item.title }}</h2>
        <div class="content">{{- item.content }}</div>
    {{ end }}
        <ul>
          <li><a href="{{ url_for("templates_test")}}"</a></li>
          <li><a href="{{ url_for("termarized_test")}}"</a></li>
          <li><a href="{{ url_for("api")}}"</a></li>
        </ul>
  </body>
</html>

Finally, run app.pl and navigate to http://localhost:5000

:~$ swipl app.pl

More Examples

A repository of examples, including using static, templates and creating an API can be found in the simple_web_examples repository.

Predicates

run/0: run the webserver on a random, free, high numbered port
run/1: run the server with options as per http_server/3
route/3: Declare a route: sw:route(Name, Path, Request) where Request is a list of attr(val)
route/4: Declare a route: sw:route(Name, Path, method(M), Request)
reply_html/1: Reply with a string assumed to be valid html
reply_template/2: Use simple_template to reply: reply_template(Template, DataDict)
read_json_dict/2 &/3: Read request JSON into dict. See http_read_json_dict.
reply_json_dict/1 & 2: Convert dict to JSON and reply. See read_json_dict
reply_file/3: Reply with a file. See http_reply_file/3
location/2 &/3: Define a new URL location, as per http:location(api, "/api", []), allows you to declare routes with sw:route(all_data, api(all_data), method(get), _Request), where api(all_data) is equivalent to `/api/all_data`. See http:location/3
reply_404/1 &/2: Return a 404, eg: reply_404(Request). See http_404/2
reply_redirect/3: Redirect to another page, eg: reply_redirect(How, Where, Request). How is one of moved, moved_temporary or see_other. Where can be an atom ('/some/page'), or an aliased path (root(some/page)). See http_redirect/3

Config Options

You can optionally create a config.pl file in the root directory of your application to change the default values:

For simple_web:

config(debug, true). Turn on http/http_error. Default false
config(static_dir, "/static"). Name of the directory in the web application root directory to serve static files from. Default "/static"
config(templates_dir, "/templates"). Name of the directory in the root directory in which templates are stored. *Default "/templates"*
For simple_template, these are set to the same default's as simple_template and are documented by simple_template:
config(st_encoding, utf8).
config(st_extension, html).
config(st_cache, false).
config(st_strip, false).
config(st_frontend, simple).
config(st_undefined, error).