#!/usr/bin/env python

# Minifies JavaScripts, creating source maps

from __future__ import absolute_import

import os
from glob import glob
import subprocess
import optparse
import sys

parser = optparse.OptionParser()
parser.add_option('--prev-deploy', nargs=1, metavar='DIR',
                  help='A previous deploy from which to reuse files if possible')
(options, args) = parser.parse_args()
prev_deploy = options.prev_deploy

# We have to pull out JS_SPECS, defined in our settings file, so we know what
# JavaScript source files to minify (and what output files to create).
sys.path.insert(0, os.path.join(os.path.dirname(__file__), '..'))
os.environ['DJANGO_SETTINGS_MODULE'] = 'zproject.settings'
from django.conf import settings

os.chdir(settings.DEPLOY_ROOT)

STATIC_PATH = 'static/'

# Compile Handlebars templates
subprocess.check_call(['tools/node', 'node_modules/.bin/handlebars']
    + glob(os.path.join(STATIC_PATH, 'templates/*.handlebars'))
    + ['--output', os.path.join(STATIC_PATH, 'templates/compiled.js'),
       '--known', 'if,unless,each,with'])

def get_changed_source_files(other_checkout):
    """ Get list of changed static files since other_checkout.
    If git fails to return a reasonable looking list, this returns None,
    in which case it should be assumed no files can be reused from
    other_checkout. """

    try:
        git_dir = os.path.join(other_checkout, '.git')
        old_commit_sha1 = subprocess.check_output(['git', 'rev-parse', 'HEAD'],
                                                  env={'GIT_DIR': git_dir})
        old_commit_sha1 = old_commit_sha1.rstrip()

        git_diff = subprocess.check_output(['git', 'diff', '--name-only',
                                            old_commit_sha1])
    except subprocess.CalledProcessError:
        # If git returned an error, assume we can't reuse any files, and
        # regenerate everything.
        print "Warning: git returned an error when comparing to the previous"
        print ("deploy in %s. Will re-minify JavaScript instead of reusing"
               % other_checkout)
        return None

    changed = set()
    for filename in git_diff.split('\n'):
        if not filename.startswith(STATIC_PATH):
            continue  # Ignore non-static files.

        if filename.endswith('.handlebars'):
            # Since Handlebars templates are compiled, treat this as if the
            # compiled .js file changed (which it did).
            changed.add(os.path.join(STATIC_PATH, 'templates/compiled.js'))
            continue

        changed.add(filename)

    return changed


changed_files = set()
if prev_deploy:
    changed_files = get_changed_source_files(prev_deploy)
    if changed_files is None:
        prev_deploy = None

JS_SPECS = settings.JS_SPECS
CLOSURE_BINARY = 'tools/closure-compiler/run'

# Where to put minified JS and source maps
MIN_DIR = os.path.join(STATIC_PATH, 'min/')
MAP_DIR = os.path.join(STATIC_PATH, 'source-map/')
subprocess.check_call(['mkdir', '-p', MIN_DIR, MAP_DIR])

for js_group, filespec in JS_SPECS.iteritems():
    #      JS_SPECS look like        'js/foobar.js'.
    # changed_files look like 'static/js/foobar.js'.
    # So we prepend 'static/' to the JS_SPECS so these match up.
    in_files = [os.path.join(STATIC_PATH, filename)
                for filename in filespec['source_filenames']]

    out_file = os.path.join(MIN_DIR, os.path.basename(filespec['output_filename']))
    map_file = os.path.join(MAP_DIR, os.path.basename(filespec['output_filename'])
                                     + '.map')

    if (not 'force_minify' in filespec) and (prev_deploy and len(set(in_files) & changed_files) == 0):
        # Try to reuse the output file from previous deploy
        try:
            for dest in [out_file, map_file]:
                src = os.path.join(prev_deploy, dest)
                os.path.getsize(src)  # Just to throw error if it doesn't exist.
                if os.path.abspath(src) != os.path.abspath(dest):
                    subprocess.check_call(['cp', src, dest])
            continue  # Copy succeeded, so go on to next file.
        except (subprocess.CalledProcessError, OSError):
            pass  # Copy failed, so fall through to minification instead.

    # No previous deploy, or a source file has changed, or copying was
    # supposed to work but failed.  Thus, minify the JS anew.
    # (N.B. we include STATIC_HEADER_FILE before the JavaScripts.
    #  This way it doesn't throw off the source map.)
    cmd = '%s --language_in ECMASCRIPT5 --create_source_map %s %s %s' % (
            CLOSURE_BINARY, map_file,
            settings.STATIC_HEADER_FILE, ' '.join(in_files))
    js = subprocess.check_output(cmd, shell=True)

    # Write out the JS
    with open(out_file, 'w') as fp:
        fp.write(js)