import argparse
from functools import lru_cache
from jinja2 import Environment, FileSystemLoader, contextfilter
from pathlib import Path
from os import walk, makedirs, listdir, symlink, readlink
from os.path import join, exists, splitext, split, islink, isdir
from shutil import rmtree, copy2, copystat, Error
from time import sleep
from traceback import print_exc

#TODO: load from config file (and watch it too)
LANGUAGES = 'languages'
ROOT = 'root'
STATIC = 'static'
DEFAULT_LANG = 'en'
OTHER_LANGS = set(['es'])
WATCH_INTERVAL = 1 # in secs

# Utils

def copytree(src, dst, symlinks=False):
    names = listdir(src)
    makedirs(dst, exist_ok=True)
    # `exist_ok=True`, very important for hot reloading
    errors = []
    for name in names:
        srcname = join(src, name)
        dstname = join(dst, name)
        try:
            if symlinks and islink(srcname):
                linkto = readlink(srcname)
                symlink(linkto, dstname)
            elif isdir(srcname):
                copytree(srcname, dstname, symlinks)
            else:
                copy2(srcname, dstname)
            # XXX What about devices, sockets etc.?
        except OSError as why:
            errors.append((srcname, dstname, str(why)))
        # catch the Error from the recursive copytree so that we can
        # continue with other files
        except Error as err:
            errors.extend(err.args[0])
    try:
        copystat(src, dst)
    except OSError as why:
        # can't copy file access times on Windows
        if why.winerror is None:
            errors.extend((src, dst, str(why)))
    if errors:
        raise Error(errors)

def mtimes(target_dir):
    ''''get modification time of files in `target_dir`'''
    return { f: f.stat().st_mtime for f in Path(target_dir).rglob('*') }

def save_dic(lang, dic):
    with open(join(LANGUAGES, lang + '.txt'), 'w') as f:
        for key, value in dic.items():
            f.write(f"{key}:{value}\n")

@lru_cache(None)
def get_lang_dic(lang):
    makedirs(LANGUAGES, exist_ok=True)

    lang_file = join(LANGUAGES, lang + '.txt')

    if not exists(lang_file):
        return {}
    else:
        dic = {}
        with open(lang_file) as f:
            for line in f.readlines():
                key, value = line.strip('\n').split(':')
                dic[key] = value
        return dic

# Filters

def add_lang_prefix(lang, path):
    if lang == DEFAULT_LANG:
        return path

    if lang not in OTHER_LANGS:
        print(f"Not registered language: `{lang}`")

    return f"/{lang}{path}"

@contextfilter
def lang(ctx, value):
    lang = ctx.environment.globals['lang']

    if lang == DEFAULT_LANG:
        return value

    else:
        dic = get_lang_dic(lang)

        if value in dic and dic[value]:
            return dic[value]
        else:
            dic[value] = ""
            save_dic(lang, dic)
            print(f"Not translated phrase: `{value}`")
            return value

@contextfilter
def lang_url(ctx, lang):
    name, _ = splitext(ctx.name)
    if name.startswith('./'):
        name = name[2:]

    if name == 'index':
        name = ''

    return add_lang_prefix(lang, f"/{name}")

@contextfilter
def cur_lang(ctx, path):
    lang = ctx.environment.globals['lang']
    return add_lang_prefix(lang, path)

def static(value):
    return f"/static/{value}"

# Compiler

def compile(env, path, target):
    lang = env.globals['lang']

    for base, _, docs in walk(path):
        cur_base = Path(base)
        cur_base = Path(*cur_base.parts[1:])
        for doc in docs:
            if doc.startswith('_'):
                # Ignore this files
                continue

            src = join(base, doc)

            if args.with_index and doc != 'index.html':
                name, _ = splitext(doc)
                dst = join(cur_base, name, 'index.html')
            else:
                dst = join(cur_base, doc)

            if lang != DEFAULT_LANG:
                dst = join(lang, dst)

            dst = join(target, dst)
            dst_folder, _ = split(dst)

            makedirs(dst_folder, exist_ok=True)

            template = env.get_template(join(cur_base, doc))
            output = template.render()

            with open(dst, 'w') as f:
                f.write(output)

def init_gen(args):
    # Load layout
    file_loader = FileSystemLoader(args.source)
    env = args.env = Environment(loader=file_loader)

    # Init gobals
    env.globals['lang'] = DEFAULT_LANG

    # Add filters
    env.filters['lang'] = lang
    env.filters['lang_url'] = lang_url
    env.filters['cur_lang'] = cur_lang
    env.filters['static'] = static

    # Clean target
    if exists(args.target):
        rmtree(args.target)
    makedirs(args.target, exist_ok=True)

def gen_layout(args):
    env = args.env
    path = Path(args.source)

    # Reset gobals
    env.globals['lang'] = DEFAULT_LANG

    # compile
    compile(env, path, args.target)
    for other_lang in OTHER_LANGS:
        env.globals['lang'] = other_lang
        compile(env, path, args.target)

def gen_root(args):
    copytree(ROOT, args.target)

def gen_static(args):
    copytree(STATIC, join(args.target, 'static'))

def save_generate(generator, args, msg):
    print(f'* {msg}')
    try:
        generator(args)
        print('  done!')
    except:
        print_exc()
        return False
    return True

# Runtime

def run(args):
    print('initial compilation')
    init_gen(args)
    save_generate(gen_layout, args, 'generating layout')
    save_generate(gen_root, args, 'copying root files')
    save_generate(gen_static, args, 'copying static dir')

    if not args.watch:
        return

    print(f'watching {args.source}/*:{LANGUAGES}/*:{STATIC}/*:{ROOT}/*')
    while True:
        # take modification times
        source_mt = mtimes(args.source)
        source_mt.update(mtimes(LANGUAGES))
        static_mt = mtimes(STATIC)
        root_mt = mtimes(ROOT)

        sleep(WATCH_INTERVAL)

        # compare modification times and recompile if different
        new_source_mt = mtimes(args.source)
        new_source_mt.update(mtimes(LANGUAGES))
        if source_mt != new_source_mt:
            source_mt = new_source_mt
            save_generate(gen_layout, args, 'recompiling layout')

        new_root_mt = mtimes(ROOT)
        if root_mt != new_root_mt:
            root_mt = new_root_mt
            save_generate(gen_root, args, 'copying root files')

        new_static_mt = mtimes(STATIC)
        if static_mt != new_static_mt:
            static_mt = new_static_mt
            save_generate(gen_static, args, 'copying static files')

if __name__ == '__main__':
    parser = argparse.ArgumentParser("Site generator")

    parser.add_argument('--watch', action='store_true', default=False)
    parser.add_argument('--with-index', action='store_true', default=False)
    parser.add_argument('--source', default='layout')
    parser.add_argument('--target', default='build')

    args = parser.parse_args()
    run(args)