ACF mvc.lua example

= Set the hostname with mvc.lua =
In this example we will create a simple hostname-setting command-line application using mvc.lua. Once the controller/model are built, you can use the same code to set the hostname via the web with a web-based application controller.
For this example, we will assume you have root access on the linux box you are running on (preferably an Alpine Linux box!)
== Get the mvc.lua module == 
Get the mvc.lua module from the git repository.
 wget https://gitlab.alpinelinux.org/acf/acf-core/-/blob/master/lua/mvc.lua
== Create a model and controller ==
Create a file hostname-controller.lua, defining the functions that an "end user" could run. We will only create one action, edithostname, which will be used to read and update the hostname. Since the action makes changes to the system, it naturally takes the form of a 'form':
=== hostname-controller.lua ===
 -- Controller for editing hostname
 local mymodule = {} 
 
 mymodule.edithostname = function (self)
 return self.handle_form(self, self.model.get_hostname, self.model.set_hostname, self.clientdata, "Update", "Edit Hostname", "Hostname Updated")
 end 
 
 return mymodule
Create a file hostname-model.lua, defining the model functions to get and set the hostname. We return a cfe table for each function including the form with the one entry for hostname:
=== hostname-model.lua ===
 -- Model functions for retrieving / setting the hostname
 local mymodule = {}
 
 -- Create a cfe defining the form for editing the hostname and containing the current value
 mymodule.get_hostname = function(self, clientdata)
 local retval = cfe({ type="group", value={}, label="Hostname" })
 
 -- Warning - io.popen has security risks, never pass user data to io.popen
 local f = io.popen ("/bin/hostname")
 local n = f:read("*a") or "none"
 f:close()
 n=string.gsub(n, "\n$", "")
 
 retval.value.hostname = cfe({ value=n, label="Hostname" })
 
 return retval
 end
 
 -- Set the hostname from the value contained in the cfe created by get_hostname
 mymodule.set_hostname = function(self, hostnameform, action)
 local success = true
 
 -- Check to make sure the name is valid
 if (hostnameform.value.hostname.value == "") then
 success = false
 hostnameform.value.hostname.errtxt = "Hostname must not be blank"
 elseif (#hostnameform.value.hostname.value > 16) then
 success = false
 hostnameform.value.hostname.errtxt = "Hostname must be 16 characters or less"
 elseif (string.find(hostnameform.value.hostname.value, "[^%w%_%-]")) then
 success = false
 hostnameform.value.hostname.errtxt = "Hostname can contain alphanumerics only"
 end
 
 -- If it is valid, set the hostname
 if ( success ) then
 local f = io.open("/etc/hostname", "w")
 if f then
 f:write(hostnameform.value.hostname.value .. "\n")
 f:close()
 end
 -- Warning - io.popen has security risks, never pass user data to io.popen
 f = io.popen ("/bin/hostname -F /etc/hostname")
 f:close()
 else
 hostnameform.errtxt = "Failed to set hostname"
 end
 
 return hostnameform
 end
 
 return mymodule
== Optionally test the model code (without mvc.lua) ==
If you want, you can create a test.lua script to validate the model code works on its own:
=== test.lua ===
 require("mvc") -- Needed for cfe function definition
 m=require("hostname-model")
 
 local form = m.get_hostname()
 form.value.hostname.value = arg[1] or ""
 form = m.set_hostname(nil, form)
 
 if form.errtxt then
 print("FAILED: "..form.value.hostname.errtxt or form.errtxt)
 end
 form = m.get_hostname()
 print(form.value.hostname.value)
You can then test this with:
 #lua test.lua "Alpine"
 Alpine
 #lua test.lua "Invalid Name"
 FAILED: Hostname can contain alphanumerics only
 Alpine
== Add the package to the ACF framework ==
To make the model and controller work within the ACF mvc.lua framework, we must do several things. 
1. Install the ACF core package:
 apk add acf-core
Optionally, you can add the entire web-based ACF framework:
 setup-acf
2. Modify the ACF configuration file to look in /etc/acf/app/ for additional packages. Edit the /etc/acf/acf.conf file to add the /etc/acf/app/ directory to the appdir comma-separated list:
 appdir=/etc/acf/app/,/usr/share/acf/app/
3. Move the model and controller to the new package directory. We will call the package "test":
 mkdir -p /etc/acf/app/test
 mv hostname-*.lua /etc/acf/app/test
4. Test the new package using the acf-cli application:
 # acf-cli /test/hostname/edithostname
 result = {}
 result["label"] = "Edit Hostname"
 result["option"] = "Edit"
 result["type"] = "form"
 result["value"] = {}
 result["value"]["hostname"] = {}
 result["value"]["hostname"]["label"] = "Hostname"
 result["value"]["hostname"]["type"] = "text"
 result["value"]["hostname"]["value"] = "Alpine"
 # acf-cli /test/hostname/edithostname hostname=test submit=true
 result = {}
 result["descr"] = "Hostname Updated"
 result["label"] = "Edit Hostname"
 result["option"] = "Edit"
 result["type"] = "form"
 result["value"] = {}
 result["value"]["hostname"] = {}
 result["value"]["hostname"]["label"] = "Hostname"
 result["value"]["hostname"]["type"] = "text"
 result["value"]["hostname"]["value"] = "test"
Note that the action string passed to acf-cli is of the form "/prefix/controller/action". The prefix is the path within /etc/acf/app where the controller may be found, so "/test/" for our case. The controller is determined from the controller file name, so "hostname" for our case. And, the action corresponds to the function within the controller to call, so "edithostname" for our case. Also note that, in the two examples above, the first case reads the existing hostname and the second case updates it. The output of the acf-cli application is a serialized version of the cfe form, which is good for testing but not too useful in real life.
== Enable the package in the ACF web interface ==
1. Add the web-based ACF framework:
 setup-acf
2. Configure all users to have access to the new hostname action. Edit "/etc/acf/app/test/hostname.roles" file and add GUEST permission for the edithostname action:
 echo "GUEST=hostname/edithostname" > /etc/acf/app/test/hostname.roles
The new action should now be visible by browsing to https://IP-of-host/cgi-bin/acf/test/hostname/edithostname. Obviously you might want to reconsider providing GUEST access to this action, because this allows unauthenticated users to modify your hostname.
3. Add the new hostname action to the ACF menu. Edit "/etc/acf/app/test/hostname.menu" file and add a menu item:
 echo "Test Hostname Edit edithostname" > /etc/acf/app/test/hostname.menu
You will need to log off from the ACF interface (or delete the session cookie) before the new menu item will be visible.
== Make an MVC based application ==
You have two options for creating an MVC based application of your own.
1. Use the dispatch function. This is the method used by the web interface and the acf-cli application. The action to be dispatched is passed in a string format /prefix/controller/action and the input values are passed in as a clientinfo table. Output is determined by the view.
2. Use the new function to load the desired controller and then directly call the controller actions or model functions. Using the controller actions requires use of the clientdata structure to pass parameters. For calling the model functions, the application will call the get function to retrieve the form cfe, fill in the desired input values into the cfe, and then call the set function to submit the form and perform the desired action. The MVC application is responsible for any user interaction and display of the results.
=== Use the Dispatch method ===
==== test_dispatch ====
 #!/usr/bin/lua
 -- Simple CLI based mvc application
 
 -- load the mvc module
 mvc = require("acf.mvc")
 
 -- create an new "mvc object"
 MVC=mvc:new()
 
 -- load the config file so we can find the appdir
 MVC:read_config("acf")
 
 -- dispatch the request
 local clientdata = {hostname=arg[1], viewtype=arg[2], submit="Update"}
 MVC:dispatch("/test/", "hostname", "edithostname", clientdata)
 
 -- destroy the mvc object
 MVC:destroy()
Test the application. As can be seen in the code above, the first argument is the new hostname and the second is a viewtype.
 alpine:~# chmod 755 test_dispatch 
 alpine:~# ./test_dispatch test
 test:~# ./test_dispatch alpine
 alpine:~#
Note that the application functions, but there is no output. This is because there is no viewtype supplied. There is built-in support for these standard viewtypes (not all apply): html, json, stream, serialized
 alpine:~# ./test_dispatch test serialized
 result = {}
 result["descr"] = "Hostname Updated"
 result["label"] = "Edit Hostname"
 result["option"] = "Update"
 result["type"] = "form"
 result["value"] = {}
 result["value"]["hostname"] = {}
 result["value"]["hostname"]["label"] = "Hostname"
 result["value"]["hostname"]["type"] = "text"
 result["value"]["hostname"]["value"] = "test"
 test:~# ./test_dispatch alpine json
 {"type":"form","label":"Edit Hostname","value":{"hostname":{"value":"alpine","type":"text","label":"Hostname"}},"option":"Update","descr":"Hostname Updated"}
 alpine:~# 
You can also use a custom viewtype and/or view to customize the output. This relies on haserl to parse the view file, and haserl lua functions are only available when launched from haserl scripts (it would be nice if haserl were available as a standalone lua library). Haserl scripts expect to be launched by a web browser to handle CGI data, so passing input is trickier. I'm sure there is a better way to do this, but this is just an example:
==== test_haserl ====
 #!/usr/bin/haserl-lua5.2 --shell=lua
 <%
 -- Simple CLI based mvc application
 
 -- load the mvc module
 mvc = require("acf.mvc")
 
 -- create an new "mvc object"
 MVC=mvc:new()
 
 -- load the config file so we can find the appdir
 MVC:read_config("acf")
 
 -- dispatch the request
 local clientdata = {hostname=FORM.hostname, viewtype=FORM.viewtype, submit="Update"}
 MVC:dispatch("/test/", "hostname", "edithostname", clientdata)
 
 -- destroy the mvc object
 MVC:destroy()
 %>
==== /etc/acf/app/test/hostname-edithostname-text.lsp ====
 <%
 local data, viewlibrary, page_info, session = ... 
 
 if data.errtxt then
 print(data:print_errtxt())
 else
 print(data.descr)
 end
 %>
Test the application
 test:~# chmod 755 test_haserl 
 test:~# QUERY_STRING='hostname=alpine&viewtype=text' REQUEST_METHOD=GET ./test_haserl
 Hostname Updated
 alpine:~# QUERY_STRING='hostname=asdfasdfasdfasdfasdf&viewtype=text' REQUEST_METHOD=GET ./test_haserl
 Failed to set hostname
 hostname: Hostname must be 16 characters or less
 alpine:~# 
You can further customize the application by creating your own application-specific controller. This is how the web interface and the acf-cli application are written. In both cases, a simple application is written to load not just an mvc:new() reference, but an application-specific controller to wrap the mvc:new() object. The dispatch function is then called on the application-specific controller object, which can override any function in mvc.lua to add a customized implementation. For example, both applications override the handle_clientdata function to customize the way input data is provided in the clientdata structure, and the web interface-specific controller contains a lot of code to handle features such as menus, templates, skins, authentication, redirection, ... The best way to understand this is to just read the code.
* Web application
** Application - acf
** Controller - acf_www-controller.lua
* acf-cli
** Application - acf-cli
** Controller - acf_cli-controller.lua
=== Use the New method ===
==== test_new ====
 #!/usr/bin/lua
 -- Simple CLI based mvc application
 
 -- load the mvc module
 mvc = require("acf.mvc")
 
 -- create an new "mvc object"
 MVC=mvc:new()
 
 -- load the config file so we can find the appdir
 MVC:read_config("acf")
 
 -- load the hostname controller
 HOSTNAME=MVC:new("/test/hostname")
 
 local hostname
 
 -- METHOD 1 - controller action
 HOSTNAME.clientdata = {hostname=arg[1], submit="Update"}
 hostname = HOSTNAME:edithostname()
 
 -- METHOD 2 - model functions
 hostname = HOSTNAME.model:get_hostname()
 hostname.value.hostname.value = arg[1]
 hostname = HOSTNAME.model:set_hostname(hostname)
 
 if hostname.errtxt then
 print(hostname:print_errtxt())
 else
 print(hostname.descr or "Hostname Updated")
 end
 
 HOSTNAME:destroy()
 MVC:destroy()
Once you have a hostname controller object, you can access its actions, passing data through clientdata, or you can directly access the get/set functions of the model. Test the app:
 test:~# chmod 755 test_new
 test:~# ./test_new alpine
 Hostname Updated
 alpine:~# ./test_new asdfasdfasdfasdfasdf
 Failed to set hostname
 hostname: Hostname must be 16 characters or less
 alpine:~# 
= mvc load & exec special functions =
The mvc.lua module has a provision for executing code on module load, prior to executing the controller's action, just after executing the controller's action, and on module unload.
This is done with the mvc table in the controller. To demonstrate, let's add a few functions to helloworld/app/app-controller.lua
 mvc = {}
 mvc.on_load = function (self, parent)
 print ("This is the app controller's on_load function")
 end
 
 mvc.pre_exec = function (self)
 print ("This is the app controller's pre_exec function")
 end 
 
 mvc.post_exec = function (self)
 print ("This is the app controller's post_exec function")
 end
 mvc.on_unload = function (self)
 print ("This is the app controller's on_unload function")
 end
 
Now running our script shows when the functions get called:
 # lua helloworld.lua update "Alpine"
 This is the app controller's on_load function
 This is the app controller's pre_exec function
 This is the app controller's post_exec function
 Controller: hostname Action: update
 Returned a table with the following values:
 value Alpine
 type string
 This is the app controller's on_unload function
We can add mvc functions to a specific controller, as well. Add this to helloworld/app/hostname-controller.lua
 mvc = {}
 mvc.on_load = function (self, parent)
 print ("This is the hostname controller's on_load function")
 end
 
 mvc.pre_exec = function (self)
 print ("This is the hostname controller's pre_exec function")
 end 
 
 mvc.post_exec = function (self)
 print ("This is the hostname controller's post_exec function")
 end
 
 mvc.on_unload = function (self)
 print ("This is the hostname controller's on_unload function")
 end
 
And this happens:
 # lua helloworld.lua update "Alpine"
 This is the app controller's on_load function
 This is the hostname controller's on_load function
 This is the hostname controller's pre_exec function
 This is the hostname controller's post_exec function
 This is the hostname controller's on_unload function
 Controller: hostname Action: update
 Returned a table with the following values:
 value Alpine
 type string
 This is the app controller's on_unload function
Note that both the app and hostname on_load and on_unload functions were run, but only the hostname pre_exec and post_exec functions ran. This is because the pre and post exec functions are run as part of the "action", and the dispatch function looks in the lowest-level controller for the pre/post_exec function. Since hostname now defines those functions, it runs them.
To run both the hostname and app pre_exec function, you must arrange for the hostname pre_exec function to call it's parent pre_exec:
 mvc = {}
 mvc.on_load = function (self, parent)
 print ("This is the hostname controller's on_load function")
 mvc.parent_pre_exec = parent.worker.mvc.pre_exec
 end
 
 mvc.pre_exec = function (self)
 mvc.parent_pre_exec (self)
 print ("This is the hostname controller's pre_exec function")
 end
Category:ACF Category:Lua