scripts/build_web_assets.py

#! /usr/bin/python3

import argparse
import os
import gzip
import hashlib
from subprocess import Popen, PIPE
import re

THIS_DIR = os.path.dirname(os.path.realpath(__file__))

ENABLE_CACHING = True

# TODO(ed) this needs to be better
CONTENT_TYPES = {
    '.css': "text/css;charset=UTF-8",
    '.html': "text/html;charset=UTF-8",
    '.js': "text/html;charset=UTF-8",
    '.png': "image/png;charset=UTF-8",
    '.woff': "application/x-font-woff",
}

CPP_BEGIN_BUFFER = """
#include <webassets.hpp>

"""

ROUTE_DECLARATION = """

void crow::webassets::request_routes(BmcAppType& app){
"""

CACHE_FOREVER_HEADER = """
    res.add_header("Cache-Control", "public, max-age=31556926");
"""

CPP_MIDDLE_BUFFER = """
    CROW_ROUTE(app, "{relative_path_sha1}")([](const crow::request& req, crow::response& res) {{
        {CACHE_FOREVER_HEADER}

        res.add_header("ETag", "{sha1}");
        if (req.headers.count("If-None-Match") == 1) {{
            if (req.get_header_value("If-None-Match") == "{sha1}"){{
                res.code = 304;
                res.end();
                return;
            }}
        }}

        res.code = 200;
        // TODO, if you have a browser from the dark ages that doesn't support gzip,
        // unzip it before sending based on Accept-Encoding header
        res.add_header("Content-Encoding", "{content_encoding}");
        res.add_header("Content-Type", "{content_type}");

        res.write({relative_path_escaped});
        
        res.end();
    }});
"""


def twos_comp(val, bits):
    """compute the 2's compliment of int value val"""
    if (val & (1 << (bits - 1))) != 0: # if sign bit is set e.g., 8bit: 128-255
        val = val - (1 << bits)        # compute negative value
    return val                         # return positive value as is

CPP_END_BUFFER = """
}
"""

CPP_END_BUFFER2 = """const static std::string {relative_path_escaped}{{{file_bytes}}};
"""

def get_relative_path(full_filepath):
    pathsplit = full_filepath.split(os.path.sep)
    relative_path = os.path.sep.join(pathsplit[pathsplit.index("static") + 1:])

    relative_path_escaped = relative_path
    for character in ['/', '.', '-']:
        relative_path_escaped = relative_path_escaped.replace(character, "_")

    relative_path = "static/" + relative_path

    return relative_path, relative_path_escaped

def get_sha1_path_from_relative(relative_path, sha1):
    if sha1 != "":
        path, extension = os.path.splitext(relative_path)
        return path + "-" + sha1[:10] + extension
    else:
        return relative_path

def filter_html(sha1_list, file_content):
    string_content = file_content.decode()
    for key, value in sha1_list.items():
        replace_name = get_sha1_path_from_relative(key, value)
        string_content_new = re.sub("((src|href)=[\"'])(" + re.escape(key) + ")([\"'])", "\\1" + replace_name + "\\4", string_content)
        if string_content_new != string_content:
            print("    Replaced {}".format(key))
            print("    With {}".format(replace_name))
            string_content = string_content_new

    return string_content.encode()

def filter_js(sha1_list, file_content):

    string_content = file_content.decode()
    for key, value in sha1_list.items():
        replace_name = get_sha1_path_from_relative(key, value)

        string_content_new = re.sub(key, replace_name, string_content)
        if string_content_new != string_content:
            print("    Replaced {}".format(key))
            print("    With {}".format(replace_name))
            string_content = string_content_new
    return string_content.encode()

def compute_sha1_and_update_dict(sha1_list, file_content, relative_path):
    sha = hashlib.sha1()
    sha.update(file_content)
    sha_bytes = sha.digest()

    sha_text = "".join("{:02x}".format(x) for x in sha_bytes)
    sha1_list[relative_path] = sha_text

FILE_PRECIDENCE = ['.woff', '.png' ,'.css', '.js', '.html']
def sort_order(full_filepath):
    # sort list based on users
    path, ext = os.path.splitext(full_filepath)
    if ext in FILE_PRECIDENCE:
        return FILE_PRECIDENCE.index(ext) + 1
    else:
        return 0


def get_dependencies(dependency_list, full_filepath):
    r = []
    my_dependencies = dependency_list[full_filepath]
    r.extend(my_dependencies)
    sub_deps = []
    for dependency in my_dependencies:
        sub_deps += get_dependencies(dependency_list, dependency)
    r.extend(sub_deps)
    return r

def remove_duplicates_preserve_order(seq):
    seen = set()
    seen_add = seen.add
    return [x for x in seq if not (x in seen or seen_add(x))]

def main():
    """ Main Function """

    parser = argparse.ArgumentParser()
    parser.add_argument('-i', '--input', nargs='+', type=str)
    parser.add_argument('-o', '--output', type=str)
    parser.add_argument('-d', '--debug', action='store_true')
    args = parser.parse_args()

    file_list = args.input

    file_list = [os.path.realpath(f) for f in file_list]

    sha1_list = {}

    file_list.sort(key=sort_order)
    from collections import defaultdict
    depends_on = {}

    for full_filepath in file_list:
        relative_path, relative_path_escaped = get_relative_path(full_filepath)
        text_file_types = ['.css', '.js', '.html']
        ext = os.path.splitext(relative_path)[1]
        depends_on[full_filepath] = []
        if ext in text_file_types:
            with open(full_filepath, 'r') as input_file:
                file_content = input_file.read()
            for full_replacename in file_list:
                relative_replacename, _ = get_relative_path(full_replacename)
                if ext == ".html":
                    match = re.search("((src|href)=[\"'])(" + relative_replacename + ")([\"'])", file_content)
                    if match:
                        depends_on[full_filepath].append(full_replacename)

                elif ext == ".js":
                    match = re.search("([\"'])(" + relative_replacename + ")([\"'])", file_content)
                    if match:
                        depends_on[full_filepath].append(full_replacename)

    dependency_ordered_file_list = []
    for full_filepath in file_list:
        relative_path, relative_path_escaped = get_relative_path(full_filepath)
        deps = get_dependencies(depends_on, full_filepath)
        dependency_ordered_file_list.extend(deps)
        dependency_ordered_file_list.append(full_filepath)

    dependency_ordered_file_list = remove_duplicates_preserve_order(dependency_ordered_file_list)

    with open(args.output, 'w') as cpp_output:
        cpp_output.write(CPP_BEGIN_BUFFER)

        for full_filepath in dependency_ordered_file_list:
            # make sure none of the files are hidden
            with open(full_filepath, 'rb') as input_file:
                file_content = input_file.read()
            relative_path, relative_path_escaped = get_relative_path(full_filepath)

            print("Including {:<40} size {:>7}".format(relative_path, len(file_content)))

            if relative_path.endswith(".html") or relative_path == "/":
                new_file_content = filter_html(sha1_list, file_content)
            elif relative_path.endswith(".js"):
                new_file_content = filter_js(sha1_list, file_content)
            else:
                new_file_content = file_content

            file_content = new_file_content

            if not args.debug:
                file_content = gzip.compress(file_content)
                #file_content = file_content[:10]
                # compute the 2s complement.  If you don't, you get narrowing warnings from gcc/clang

            compute_sha1_and_update_dict(sha1_list, file_content, relative_path)
            array_binary_text = ', '.join(str(twos_comp(x, 8)) for x in file_content)

            cpp_output.write(
                CPP_END_BUFFER2.format(
                    relative_path=relative_path,
                    file_bytes=array_binary_text,
                    relative_path_escaped=relative_path_escaped
                )
            )

        cpp_output.write(ROUTE_DECLARATION)

        for full_filepath in dependency_ordered_file_list:
            relative_path, relative_path_escaped = get_relative_path(full_filepath)
            sha1 = sha1_list.get(relative_path, '')

            content_type = CONTENT_TYPES.get(os.path.splitext(relative_path)[1], "")
            if content_type == "":
                print("unknown content type for {}".format(relative_path))

            # handle the default routes
            if relative_path == "static/index.html":
                relative_path = "/"
                relative_path_sha1 = "/"
            # TODO(ed), handle woff files better.  They are referenced in CSS, which at this
            # point isn't scrubbed with a find and replace algorithm
            elif relative_path.endswith(".woff"):
                relative_path_sha1 = relative_path
            else:
                relative_path_sha1 = "/" + get_sha1_path_from_relative(relative_path, sha1)

            content_encoding = 'none' if args.debug else 'gzip'

            environment = {
                'relative_path':relative_path,
                'relative_path_escaped': relative_path_escaped,
                'relative_path_sha1': relative_path_sha1,
                'sha1': sha1,
                'sha1_short': sha1[:20],
                'content_type': content_type,
                'content_encoding': content_encoding
            }
            environment["CACHE_FOREVER_HEADER"] = ""
            if ENABLE_CACHING:
                # if we have a valid sha1, and we have a unique path to the resource
                # it can be safely cached forever
                if sha1 != "" and relative_path != relative_path_sha1:
                    environment["CACHE_FOREVER_HEADER"] = CACHE_FOREVER_HEADER      

            content = CPP_MIDDLE_BUFFER.format(
                **environment
            )
            cpp_output.write(content)

        cpp_output.write(CPP_END_BUFFER)



if __name__ == "__main__":
    main()