#!/usr/bin/env python
#
# heron.cgi - generic RESTful services for Heron
#
# This CGI provides Heron services that can only/better be handled
# within a server. The setup is generic: a parameter 'action' determines
# which function is to be called. The other parameters are specific to
# each handler.
import cgi
import cgitb
import base64

cgitb.enable()

# Get form/query params
params = cgi.FieldStorage()

def param_available(param_names):
	for param_name in param_names:
		if param_name not in params:
			print('Content-Type: text/html')
			print('')
			print('<h2>Heron Export - Error</h2>')
			print('Please supply query parameter <i>%s</i>.' % param_name )
			return False

	return True

# Echo data back to client forcing a download to file in the browser.
def download():
	if not param_available(['mime', 'data', 'filename']):
		return

	# Get the form-based data values
	filename = params.getvalue('filename')
	mime = params.getvalue('mime')
	data = params.getvalue('data')
	encoding = params.getvalue('encoding', 'base64')
	if encoding == 'base64':
		data = base64.b64decode(data)

	# Echo back to client
	print('Content-Type: %s' % mime)
	# Forces download in browser
	print('Content-Disposition: attachment; filename="%s"' % filename)
	print('')
	print(data)

# Echo uploaded file back to client as data.
def upload():
	if not param_available(['mime', 'file']):
		return

	# Get the form-based data values
	mime = params.getvalue('mime')
	fileitem = params['file']
	encoding = params.getvalue('encoding', 'none')

	# Start echo back
	print('Content-Type: %s' % mime)
	print('')

	# Test if the file was uploaded
	if fileitem.filename:
		# strip leading path from file name to avoid directory traversal attacks
		# fn = os.path.basename(fileitem.filename)
		# open('files/' + fn, 'wb').write(fileitem.file.read())
		# Echo back file content to client
		data = fileitem.value
		if encoding == 'escape':
			data = cgi.escape(data)
		print(data)
	else:
		print(' ')

# Convert data to shape file and force a download to file in the browser.
def to_shape():
	if not param_available(['data']):
		return

	print('Content-Type: text/html')
	print('')
	print('ESRI Shapefile export not yet implemented')

# Action handlers: jump table with function pointers
handlers = {
	'download': download,
	'upload': upload,
	'to_shape': to_shape
}

handlers[params.getvalue('action', 'download')]()