#!/usr/bin/env bash

# This script serves as the
# [**Python Buildpack**](https://github.com/heroku/heroku-buildpack-python)
# compiler.
#
# A [buildpack](http://devcenter.heroku.com/articles/buildpacks) is an
# adapter between a Python application and Heroku's runtime.
#
# You can intreract with the Heroku API directly with [heroku.py](https://github.com/heroku/heroku.py/).
#
# See also: [Release history](/changelog.html), [Detection](/detect.html).
#
# ## Usage
# Compiling an app into a slug is simple:
#
#     $ bin/compile <build-dir> <cache-dir>


# ## Assumptions
#
# This buildpack makes the following assumptions:
#
# - The desired Python VM is available on the base system.
# - Library dependencies are available on the base system.
# - Django applications should not require any platform-specific configuration.

# <hr />

# ## Context

# Fail fast and fail hard.
set -eo pipefail

# Prepend proper path for virtualenv hackery. This will be deprecated soon.
export PATH=:/usr/local/bin:$PATH

# Paths.
BIN_DIR=$(cd $(dirname $0); pwd) # absolute path
ROOT_DIR=$(dirname $BIN_DIR)
BUILD_DIR=$1
CACHE_DIR=$2

# Where to store the pip download cache.
CACHED_DIRS=".heroku"
PIP_DOWNLOAD_CACHE=${PIP_DOWNLOAD_CACHE:-$CACHE_DIR/pip_downloads}

# Static configurations for virtualenv caches.
VIRTUALENV_LOC=".heroku/venv"
LEGACY_TRIGGER="lib/python2.7"
PROFILE_PATH="$BUILD_DIR/.profile.d/python.sh"

# Python version. This will be used in the future to specify custom Pythons.
PYTHON_VERSION="2.7.2"
PYTHON_EXE="python2.7"

# Sanitizing environment variables.
unset GIT_DIR PYTHONHOME PYTHONPATH LD_LIBRARY_PATH LIBRARY_PATH

# We'll need to send these statics to other scripts we `source`.
export PIP_DOWNLOAD_CACHE BUILD_DIR CACHE_DIR BIN_DIR PROFILE_PATH

# Syntax sugar.
source $BIN_DIR/utils

# ## Build Time
#

# Switch to the repo's context.
cd $BUILD_DIR

# Experimental pre_compile hook.
source $BIN_DIR/steps/hooks/pre_compile

# If no requirements given, assume `setup.py develop`.
if [ ! -f requirements.txt ]; then
  puts-step "No requirements.txt provided; assuming dist package."
  echo "-e ." > requirements.txt
fi

# ### The Cache
mkdir -p $CACHE_DIR
[ ! "$(ls -A $CACHE_DIR)" ] && export FRESH_APP=1

# Purge "old-style" virtualenvs.
[ -d $CACHE_DIR/$LEGACY_TRIGGER ] && rm -fr $CACHE_DIR/*

# Restore old artifacts from the cache.
for dir in $CACHED_DIRS; do
  cp -R $CACHE_DIR/$dir . &> /dev/null || true
done

set +e
# Create set-aside `.heroku` folder.
mkdir .heroku &> /dev/null
set -e

# Buildpack profile init script
mkdir -p $(dirname $PROFILE_PATH)

# ### Virtualenv Setup
#

# Create the virtualenv. Rebuild if corrupt.
# TODO: Bootstrap a bottled Python VM...

set +e
puts-step "Preparing Python interpreter ($PYTHON_VERSION)"
puts-step "Creating Virtualenv ($(virtualenv --version))"

# Try to create the virtualenv.
OUT=$(virtualenv --python $PYTHON_EXE --distribute --never-download --prompt='(venv) ' $VIRTUALENV_LOC 2>&1)

[ $? -ne 0 -o -n "$CLEAN_VIRTUALENV" ] && {
  if [ -n "$CLEAN_VIRTUALENV" ]
    then echo " !     CLEAN_VIRTUALENV set, rebuilding virtualenv."
    else echo " !     Virtualenv corrupt, rebuilding."
  fi

  rm -fr $VIRTUALENV_LOC &> /dev/null || true

  OUT=$(virtualenv --python $PYTHON_EXE --distribute --never-download  --prompt='(venv) ' $VIRTUALENV_LOC )
}
echo "$OUT"  | cleanup | indent
set -e

# Pylibmc support.
# See [`bin/steps/pylibmc`](pylibmc.html).
source $BIN_DIR/steps/pylibmc

# Activate the Virtualenv.
source $VIRTUALENV_LOC/bin/activate

# Install Mercurial if it appears to be required.
if (grep -Fiq "hg+" requirements.txt) then
  pip install --use-mirrors mercurial | cleanup | indent
fi

# Install dependencies with Pip.
puts-step "Installing dependencies using pip ($(pip --version | awk '{print $2}'))"
pip install --use-mirrors -r requirements.txt --exists-action=w --src=./.heroku/src | cleanup | indent

# Django collectstatic support.
source $BIN_DIR/steps/collectstatic

# Make Virtualenv's paths relative for portability.
set +e
OUT=$(virtualenv --python $PYTHON_EXE  --relocatable $VIRTUALENV_LOC)
[ $? -ne 0 ] && {
  puts-warn "Error making virtualenv relocatable"
  echo "$OUT" | indent
  exit 1
}
set -e

# ### Finalize
#

# Store new artifacts in cache.
for dir in $CACHED_DIRS; do
  rm -rf $CACHE_DIR/$dir
  cp -R $dir $CACHE_DIR/
done

# Set context environment variables.
set-env PATH '$HOME/.heroku/venv/bin:$PATH'
set-default-env PYTHONUNBUFFERED true
set-default-env LIBRARY_PATH /app/.heroku/vendor/lib
set-default-env LD_LIBRARY_PATH /app/.heroku/vendor/lib
set-default-env LANG en_US.UTF-8
set-default-env PYTHONHASHSEED random
set-default-env PYTHONHOME /app/.heroku/venv/
set-default-env PYTHONPATH /app/


# ### Fin.

# Experimental post_compile hook.
source $BIN_DIR/steps/hooks/post_compile

# <a href="http://github.com/heroku/heroku-buildpack-python"><img style="position: absolute; top: 0; right: 0; border: 0;" src="https://d3nwyuy0nl342s.cloudfront.net/img/7afbc8b248c68eb468279e8c17986ad46549fb71/687474703a2f2f73332e616d617a6f6e6177732e636f6d2f6769746875622f726962626f6e732f666f726b6d655f72696768745f6461726b626c75655f3132313632312e706e67" alt="Fork me on GitHub"></a>