Orbit
MVC for Lua Web Development

## Orbit Pages

Orbit Pages is a PHP-like programming environment built on top of Orbit. Orbit pages are HTML pages (but using the extension .op in a typical Orbit installation) that get dynamically converted into Orbit apps. They are launched by the op.cgi, op.fcgi and ophandler.lua launchers, for CGI, FastCGI, and Xavante, respectively. A standard Kepler installation includes support for Orbit pages by default.

An Orbit page is also a template that uses the Cosmo template language. The environment of this template is a sandbox that wraps the global environment and is recreated on each request. The main variable in this environment is the `web` variable, which is an Orbit request/response object. Other variables of note:

mapper - an instance of the default Orbit ORM

model(name, dao) - same as mapper:new(name, dao), except that if name is a tabel then calls mapper:new(name[1], name[2]), so you can use this in the template as `$model{ name, dao }`

app - the application's global environment, to be used as a session cache (for DB connections, for example) for persistent launchers

finish(res) - suspends the execution of the current page, and sends res as a response instead of the page's contents

redirect(target) - same as web:redirect(target) followed by finish(). If target is a table does web:redirect(target[1]), so you can use this in the template as `$redirect{ target }`

include(page, [env]) - evaluates the Orbit page in the file page (relative to the current page's path), optionally using the extra variables in env in the template's environment. Can also be used in the template as `$include{ page, env }`

forward(page, [env]) - aborts the execution of the current page and evaluates and sends the page in file page instead; otherwise same as include

There also a few more variables that should be used only in the template:

$lua{ code } - runs code in the same environment as the page, so code can change the template's variables and even define new ones

$if{ condition }[[ then-part ]],[[ else-part ]] - if condition is true then is replaced by the template evaluation of then-part, otherwise else-part. else-part is optional, defaulting to blank

$fill{ ... }[[ template ]] - replaced by the evaluation of template using the environment passed to fill (template does not inherit the variables of the page)

Below is a very simple Orbit page that shows most of the concepts above (including Cosmo concepts, see the Cosmo documentation for that):

        #!/usr/bin/env op.cgi
        <html>
        <body>
        <p>Hello Orbit!</p>
        <p>I am in $web|real_path, and the script is
        $web|script_name.</p>
        $lua{[[
          if not web.input.msg then
            web.input.msg = "nothing"
          end
        ]]}
        <p>You passed: $web|input|msg.</p>
        $include{ "bar.op" }
        </body>
        </html>

The `bar.op` page it includes is this:

        #!/usr/bin/env op.cgi
        <p>This is bar, and you passed $web|input|msg!</p>

The Kepler distribution has a more complete example that has database access, POST, and even some simple AJAX.

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