#!/usr/bin/env python3
"""Simple tex jinja2 Precompiler.
With slightly different syntax:
{{ ... }} => \VAR{ ... }   for Expressions to print to the template output
{% ... %} => \BLOCK{ ... } for Statements
{# ... #} => \#{ ... }     for Comments not included in the template output
#  ... ## => %$ ... %#     for Line Statements

Usage:
  pretex [<templates>] [options]

Arguments:
  <templates>          Compiles every given file ending with ".j2.tex" into
                       respective ".tex" file. [default: "**/*.j2.tex"]

Options:
  -h --help            Show this screen.
  -p --pdf             Also compiles rendered ".tex" file to pdf.
  -o --out=<file>      Save output to file.
  -d --data=<yamlfile> YAML files with data for the template.
  -t --tex=<compiler>  LaTeX compiler to use [default: pdflatex]
  -a --arg=<args>      LaTeX compiler arguments
                       [default: -synctex=1 -interaction=nonstopmode -file-line-error]
  -b --bib=<bib>       bibTeX compiler to use. [default: bibtex]
  -c --copy=<dir>      Gather copies of all resulting pdf files in a folder.
  --chain=<chain>      Define the render command.
                       [default: {TEX} {ARG} {document}.tex, {BIB} {document}, {TEX} {ARG} {document}.tex, {TEX} {ARG} {document}.tex]
  --clean              Clean aux files.
  -f --files=<end>     Files to clean.
                       [default: *.aux, *.bbl, *.blg, *.idx, *.ind, *.lof, *.lot, *.out, *.toc, *.acn, *.acr, *.alg, *.glg, *.glo, *.gls, *.ist, *.fls, *.log, *.fdb_latexmk]
"""

import yaml
import glob
import jinja2
import os
from docopt import docopt
import dateparser
import datetime
import subprocess
import functools
import shlex
from shutil import copyfile


class RelEnvironment(jinja2.Environment):
    """Override join_path() to enable relative template paths."""
    def join_path(self, template, parent):
        return os.path.normpath(os.path.join(os.path.dirname(parent), template))


def datetime_filter(dt, format=None):
    """Jinja template filter to format a datetime object."""
    if dt is None:
        # By default, render an empty string.
        return ''
    if not isinstance(dt, datetime.datetime):
        dt = dateparser.parse(dt, settings={'DATE_ORDER': 'DMY'})
    if format is None:
        # No format is given in the template call.
        # Use a default format.
        formatted_date = dt.strftime('%Y-%m-%d - %A')
        formatted_time =\
          dt.strftime('%I:%M%p').lstrip('0').lower()
        formatted = '%s at %s' %\
          (formatted_date, formatted_time)
    else:
        formatted = dt.strftime(format)
    return formatted


def get_latex_toolchain(arguments, document):
    return arguments["--chain"].format(
        TEX=arguments["--tex"],
        ARG=arguments["--arg"],
        BIB=arguments["--bib"],
        document=document).split(",")


def compile_all(data, templates, pdf, cmd, copy, clean):
    if templates is None:
        templates = "**/*.j2.tex"
    for tex_file in glob.glob(templates, recursive=True):
        if tex_file[-7:] == ".j2.tex":
            compiled_file = f"{tex_file[:-7]}.tex"
            print(compile_file(tex_file, data, compiled_file))

            if not pdf:
                continue
            path, filename = os.path.split(compiled_file)
            for command in cmd(filename[:-4]):
                cwd = path
                if cwd == '':
                    cwd = None
                subprocess.call(shlex.split(command), cwd=cwd, stdout=subprocess.DEVNULL, stderr=subprocess.DEVNULL)

            if copy:
                if not os.path.exists(copy):
                    os.makedirs(copy)
                copyfile(f"{tex_file[:-7]}.pdf", os.path.join(copy, f"{filename[:-4]}.pdf"))

            if clean:
                for ending in clean.split(","):
                    for file in glob.glob(os.path.join(path, ending.strip()), recursive=True):
                        os.remove(file)


def compile_file(tex_file, data, file=None):
    template = latex_jinja_env.get_template(os.path.abspath(tex_file))

    path, filename = os.path.split(tex_file)
    rendered = template.render(**data, load_yaml=functools.partial(load_yaml, path=path))
    if file is None:
        return rendered
    f = open(file, 'w')
    f.write(rendered)
    f.close()
    return f'"{tex_file}" successful rendered into "{file}"'

def load_yaml(filename, path=""):
    with open(os.path.join(path,filename)) as file:
        data = yaml.load(file, Loader=yaml.FullLoader)
    return data

if __name__ == '__main__':
    arguments = docopt(__doc__)

    latex_jinja_env = RelEnvironment(
        block_start_string = '\\BLOCK{',
        block_end_string = '}',
        variable_start_string = '\\VAR{',
        variable_end_string = '}',
        comment_start_string = '\\#{',
        comment_end_string = '}',
        line_statement_prefix = '%§',
        line_comment_prefix = '%#',
        trim_blocks = True,
        autoescape = False,
        loader = jinja2.FileSystemLoader(os.path.abspath('/')),
    )

    latex_jinja_env.filters['datetime'] = datetime_filter

    if arguments['--data']:
        data = load_yaml(arguments["--data"])
    else:
        data = {}

    cmd = functools.partial(get_latex_toolchain, arguments)
    compile_all(data, arguments['<templates>'], arguments['--pdf'], cmd, arguments['--copy'], arguments['--clean'] and arguments['--files'])