#!/bin/bash

################################################################################

# Notes         :

# Preconditions:

# - Packages doxygen doxygen-doc doxygen-latex doxygen-gui graphviz

#   must be installed.

# - Doxygen configuration file must have the destination directory empty and

#   source code directory.

# - A gh-pages branch should already exist.

#

# Required global variables:

# - DOXYFILE            : The Doxygen configuration file.

# - GH_REPO_NAME        : The name of the repository.

# - GH_REPO_REF         : The GitHub reference to the repository.

# - GH_REPO_TOKEN       : The GitHub application token.

#

# This script will generate Doxygen documentation and push the documentation to

# the gh-pages branch of a repository specified by GH_REPO_REF.

# Before this script is used there should already be a gh-pages branch in the

# repository.

#

################################################################################

################################################################################

##### Setup this script and get the current gh-pages branch.               #####

echo 'Setting up the script...'

# Exit with nonzero exit code if anything fails

set -e

GH_REPO_NAME=

GH_REPO_REF=

GH_REPO_TOKEN=

usage() { echo "Usage: `basename $0` options (-n value) (-r value) (-t value)" 1>&2; exit 1; }

if ( ! getopts ":n:r:t:" opt); then

      usage

fi

while getopts :n:r:t: opt; do

  case $opt in

  n)

      GH_REPO_NAME=$OPTARG

      ;;

  r)

      GH_REPO_REF=$OPTARG

      ;;

  t)

      GH_REPO_TOKEN=$OPTARG

      ;;

  *)

      usage

      ;;

  esac

done

shift $((OPTIND - 1))

[ -n "$GH_REPO_NAME" ] || {

    echo "ERROR: -n GH_REPO_NAME is not defined" >/dev/stderr

    exit 1

}

[ -n "$GH_REPO_REF" ] || {

    echo "ERROR: -r GH_REPO_REF is not defined" >/dev/stderr

    exit 1

}

[ -n "$GH_REPO_TOKEN" ] || {

    echo "ERROR: -t GH_REPO_TOKEN is not defined" >/dev/stderr

    exit 1

}

################################################################################

##### Upload the documentation to the gh-pages branch of the repository.   #####

# Only upload if Doxygen successfully created the documentation.

# Check this by verifying that the html directory and the file html/index.html

# both exist. This is a good indication that Doxygen did it's work.

if [ -d "html-out" ] && [ -f "html-out/index.html" ]; then

    # Create a clean working directory for this script.

    mkdir code_docs

    cd code_docs

    # Get the current gh-pages branch

    git clone -b gh-pages https://git@$GH_REPO_REF

    cd $GH_REPO_NAME

    ##### Configure git.

    # Set the push default to simple i.e. push only the current branch.

    git config --global push.default simple

    # Remove everything currently in the gh-pages branch.

    # GitHub is smart enough to know which files have changed and which files have

    # stayed the same and will only update the changed files. So the gh-pages branch

    # can be safely cleaned, and it is sure that everything pushed later is the new

    # documentation.

    CURRENTCOMMIT=`git rev-parse HEAD`

    git reset --hard `git rev-list HEAD | tail -n 1` # Reset working tree to initial commit

    git reset --soft $CURRENTCOMMIT # Move HEAD back to where it was

    # Move doxy files into local gh-pages branch folder

    mv ../../html-out/* .

    # Need to create a .nojekyll file to allow filenames starting with an underscore

    # to be seen on the gh-pages site. Therefore creating an empty .nojekyll file.

    # Presumably this is only needed when the SHORT_NAMES option in Doxygen is set

    # to NO, which it is by default. So creating the file just in case.

    echo "" > .nojekyll

    echo 'Uploading documentation to the gh-pages branch...'

    # Add everything in this directory (the Doxygen code documentation) to the

    # gh-pages branch.

    # GitHub is smart enough to know which files have changed and which files have

    # stayed the same and will only update the changed files.

    git add --all

    # Commit the added files with a title and description containing the Travis CI

    # build number and the GitHub commit reference that issued this build.

    git commit -m "Deploy code docs to GitHub Pages"

    # Force push to the remote gh-pages branch.

    # The ouput is redirected to /dev/null to hide any sensitive credential data

    # that might otherwise be exposed.

    git push --force "https://${GH_REPO_TOKEN}@${GH_REPO_REF}" > /dev/null 2>&1

else

    echo '' >&2

    echo 'Warning: No documentation (html) files have been found!' >&2

    echo 'Warning: Not going to push the documentation to GitHub!' >&2

    exit 1

fi