#!/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.

# ## 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

# The detected application type (`Python`|`Python/Django`).
NAME=$($BIN_DIR/detect $BUILD_DIR)

# Where to store the Pip download cache.
PIP_DOWNLOAD_CACHE=${PIP_DOWNLOAD_CACHE:-$CACHE_DIR/pip_downloads}

# The directories to include in the cache.
VIRTUALENV_DIRS="bin include lib"

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

# The slug compiler doesn't do a very good job of sanitizing environment variables.
unset GIT_DIR

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

# Syntax sugar.
indent() {
  RE="s/^/       /"
  [ $(uname) == "Darwin" ] && sed -l "$RE" || sed -u "$RE"
}

function virtualenv (){
  python "$ROOT_DIR/vendor/virtualenv-1.7/virtualenv.py" "$@"
}

function puts-step (){
  echo "-----> $@"
}

function puts-warn (){
  echo " !     $@"
}

# ## Build Time
# 

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

# ### Sanity Checks
# 
# Just a little peace of mind.

# 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

# Reject a Django app that appears to be packaged incorrectly.
if [ "$NAME" = "Python" ]; then
  [ -f settings.py ] && { puts-warn "Django settings must be in a package subdirectory"; exit 1; }

  (grep -Fiq "django" requirements.txt) && [ -f settings.py ] && { puts-warn "Django app must be in a package subdirectory"; exit 1; }
fi

# Warn for a checked-in virtualenv.
if [ -d "lib" ] || [ -d "bin" ]; then
  puts-warn "You have a virtualenv checked in. You should ignore the appropriate paths in your repo. See http://devcenter.heroku.com/articles/gitignore for more info.";
fi

# Reject a conflicting checked-in virtualenv.
if [ -f "lib/python2.7" ]; then
  puts-warn "Checked-in virtualenv conflict."
  exit 1;
fi

# Copy old artifacts out of the cache.
mkdir -p $CACHE_DIR
for dir in $VIRTUALENV_DIRS; do
  cp -R $CACHE_DIR/$dir . &> /dev/null || true
done

# ### 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 version $(virtualenv --version)"

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

# If there's an error, purge and recreate.
[ $? -ne 0 ] && {
  puts-warn "Virtualenv corrupt, rebuilding."
  for dir in $VIRTUALENV_DIRS; do
    rm -fr $dir &> /dev/null || true
  done
  OUT=$(virtualenv --python $PYTHON_EXE --distribute --never-download  --prompt=venv . )
}
echo "$OUT" | indent

set -e

# Create set-aside `.heroku` folder.
mkdir -p .heroku

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

# Activate the Virtualenv.
puts-step "Activating virtualenv"
source bin/activate

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

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

# Do additional application hackery if applications appears to be a Django app.
# Optionally, disable all Django-specific changes with `DISABLE_INJECTION` env.
# 
# See [`bin/steps/django`](django.html).

if [ "$NAME" = "Python/Django" ] && ! [ "$DISABLE_INJECTION" ]; then
  source $BIN_DIR/steps/django
fi

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

# ### Finalize
#

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

# ### Fin.