,                     _
                          /   _, _   /  _/ _,   / ) _  _,
                         (__ (/ //) () (/ (/   (__ //)_)

                   developer friendly :: type safe :: performant

Rationale

LambdaCms is a set of packaged libraries —containing subsites for the Yesod application framework— which allow rapid development of robust and highly performant websites with content management functionality.

The lambdacms-* packages each provide some functionality and can depend on eachother as they depend on other packages. The only mandatory package is lambdacms-core (this package), it provides functionality that all other lambdacms-* packages depend on.

As mentioned, each lambdacms-* package contains a subsite which is "mounted" in a standard Yesod application, which we will refer to as "the base application" or simply "base". Before a packaged subsite can be mounted, the package needs to be included as a dependency to the base app's .cabal file. After that some glue code needs to be added to the base app, as explained below.

In the base app we have to:

• configure a database connection,
• organize the admin backend's menu,
• specify the authentication strategies for admins, and
• define admin user roles and their permissions.

In the base app we optionally may also:

• override default behavior,
• override UI texts,
• provide a means to send email notifications, and last but not least,
• write the themes so the website can actually be visited (recommended).

Setting up a site with LambdaCms

This section walk through the steps of setting up a site with LambdaCms.

Prerequisites

You need to be reasonably acquinted with Haskell in order to follow along with this guide. To learn basic Haskell skills we recommend Brent Yorgey's excellent Introduction to Haskell course.

Besides Haskell you need to be somewhat familliar with:

• the web technologies (HTTP, HTML, CSS, JS, REST),
• RDBMS/SQL (LambdaCms makes use of a relational database), and
• the Yesod web application framework (for which an awesome book exists).

Non-Haskell dependencies

For the connection with the database, Haskell libraries typically compile against non-Haskell libraries. One of the following libraries needs to be available:

• For Postgres:

  • Debian/Ubuntu: libpq-dev
  • CentOS/Fedora/RHEL: postgresql-devel
  • Homebrew (OSX): postgres

• For Mysql:

  • Debian/Ubuntu: libmysqlclient-dev
  • CentOS/Fedora/RHEL: mysql-devel
  • Homebrew (OSX): mysql

• For Sqlite

  • Debian/Ubuntu: libsqlite3-dev
  • CentOS/Fedora/RHEL: sqlite-devel
  • Homebrew (OSX): sqlite

On other platforms these packages might have different names, but are most likely available.

If you are going to use a database other than Sqlite (which directly writes to a file), you need to have a database accessible from where you run your site. This means you might have to install and setup a database server locally.

The tool chain

Make sure to have GHC 7.8.3+, cabal-install 1.20+, happy and alex installed; and their binaries available from your shell's $PATH.

Use the following command to check your system meets the requirements:

for c in ghc cabal happy alex; do $c -V | head -n1; done

When good to go the output should be similar to:

The Glorious Glasgow Haskell Compilation System, version 7.8.4
cabal-install version 1.20.0.3
Happy Version 1.19.5 Copyright (c) 1993-1996 Andy Gill, Simon Marlow (c) 1997-2005 Simon Marlow
Alex version 3.1.4, (c) 2003 Chris Dornan and Simon Marlow

In case you are not good to go, you may want to follow the per operating system installation guides on the haskell.org website which provides instructions for installing the tool chain and setting up your $PATH.

Create a project folder

Choose a name for your project. In below we chose mysite, which you probably want to change. Make sure to choose a valid unix file name to avoid naming issues. Now create a directory for your project and cd into it, by running the following commands:

export PROJECT_NAME=mysite; mkdir $PROJECT_NAME; cd $PROJECT_NAME

Initialize a cabal sandbox

To avoid running into version conflicts with other Haskell projects you might be working on from the same system, we setup a cabal sandbox.

From within your project's folder run the following commmand:

cabal sandbox init

Using LTS Haskell

To avoid spending too much time on build issues we use and recommend LTS Haskell.

Currently we develop and test LambdaCms only against the 2.x LTS Haskell releases. As minor releases of LTS Haskell should never contain breaking changes, you can safely use the latest release of a major LTS version.

Run the following commands from within your project's folder, to install the most recent LTS Haskell package set in the 2.x series.

wget http://www.stackage.org/lts/2/cabal.config
cabal update

Initializing the base application

First we need to install the yesod command, this command requires a lot of dependent packages to be downloaded and build (may a while). Run this from your project's folder:

cabal install yesod-bin

With the following command you create a "scaffolded" Yesod application. The command is interactive; you need to supply some configuration values. Pick the database of your choice, and choose a project name:

yesod init --bare

If you have chosen a database other than Sqlite, you need to create a database and a sufficiently priviledged database user, and set these credentials in the config/setting.yml file.

This installs all dependencies and builds the scaffoled application (may take a while):

cabal install -j --enable-tests --max-backjumps=-1 --reorder-goals

In case you experience problems with cabal install try changing -j into -j1 to prevents concurrent building, and/or simply retry the command until you consistently run into the same error.

When you experience problems during builds, while using LTS 2.x, we consider this a bug. Please raise an issue.

Testing your Yesod app

The following commands will run your scaffolded Yesdo application in development mode.

yesod devel

Now test it by pointing the browser to: http://localhost:3000

If all went well you are ready to add LambdaCms to your app.

Patching a freshly init'ed Yesod app to use lambdacms-core

To add lambdacms-core to a freshly initialized Yesod application a number of files need to be edited. We have prepared a patch-set to simplify this process into a couple of commands.

First we need to download the patches by cloning the repository, we do so in /tmp. Then we apply the patches with the good old patch command.

Run the following from the root of your newly created Yesod project:

(cd /tmp; git clone https://github.com/lambdacms/lambdacms-patches.git)
patch -p1 < /tmp/lambdacms-patches/all_patches_combined.patch

Because the cabal file has a different name for each project (i.e. <project_name>.cabal) the patch command will notice a patched file is missing (we named it project_name.cabal). When the patch command tries to patch this file you will be prompted for the name of your projects cabal file, after providing the name it will successfully complete patching.

Alternatives to the patch set

There are two alternatives to using the patch set:

1. Patch files individually, how to do so is explained in the lambdacms-patches README.
2. Follow the Getting Started Manually guide on the wiki.

Configure the initial administrator

By default the application uses Mozilla's Persona to log in: the email address used to log in need to be registered with Persona. It is recommended to use an email address of a Persona account for development as it simplifies logging in during development.

Edit config/settings.yml to insert a valid email address.

admin: "_env:LAMBDACMS_ADMIN:<email address>"

Replace <email address> with the email address of an initial administrator or developer, so the admin inteface can be accessed.

Enjoy!

After applying the patches lambdacms-core is installed in your Yesod application. Run cabal install (possibly with -j1) to fetch and build the dependencies. Then run the development server.

yesod devel

Now point your browser to http://localhost:3000/admin and you will be prompted to login. The setup as described above has selected Mozilla's Persona as the only means of authentication. In config/settings.yml you have provided an email address for the admin user that is created if no users exist. If this email address is known to Mozilla Persona then you can procede to log in.

License

All code in this repository is released under the MIT license, as specified in the LICENSE file.