from collections import defaultdict
from dataclasses import dataclass, field
from itertools import chain
from os import environ, path
from pathlib import Path
from subprocess import CalledProcessError, run
from tempfile import NamedTemporaryFile
from typing import Dict, Iterator, Union


@dataclass
class Directory:
    files: Iterator[str] = field(default_factory=list)
    subfolders: Iterator[str] = field(default_factory=set)

    def serialize(self):
        return {
            'files': sorted(self.files),
            'subfolders': sorted(self.subfolders)
        }

    @classmethod
    def deserialize(cls, d):
        return cls(**d)


def _find_files(extensions, repository):
    patterns = (f'**.{ext}' for ext in extensions)
    zero = '\x00'
    return repository.git.ls_files('-z', *patterns).strip(zero).split(zero)


def _fill_directories(files, top_dir):
    directories = defaultdict(Directory)

    for f in files:
        fdir, fname = path.split(f)

        directories[fdir].files.append(fname)

        while fdir:
            parent, child = path.split(fdir)
            directories[parent].subfolders.add(child)
            fdir = parent

    return directories


def compute_directories(extensions, repository):
    files = _find_files(extensions, repository)
    top_dir = path.relpath(repository.working_dir, path.curdir)
    return _fill_directories(files, top_dir)


def deserialize_directories(directories):
    return {
        k: Directory.deserialize(v) for k, v in directories.items()
    }


class _NullPreprocessor:
    def __init__(self, source_path):
        self._source_path = source_path

    def __enter__(self):
        self.output = self._source_path
        return self

    def __exit__(self, *args):
        pass

class _OrgPreprocessor:
    def __init__(self, source_path):
        self._source_path = source_path

    def __enter__(self):
        self._output = NamedTemporaryFile(mode='w+', suffix='.org')
        try:
            run((
                'emacs', '-Q', '--batch', '--load', 'preprocess-org.el',
                '--eval', f'(preprocess-org "{self._source_path}")'
            ), check=True, stdout=self._output)
        except CalledProcessError:
            self._output.close()
            raise

        self.output = self._output.name
        return self

    def __exit__(self, *args):
        self._output.close()

_PREPROCESSORS = defaultdict(lambda: _NullPreprocessor,
                             (('org', _OrgPreprocessor),))


_PathArg = Union[Path, str, bytes]

@dataclass
class PandocRunner:
    output: _PathArg
    template: _PathArg
    filters: Iterator[_PathArg]
    stylesheets: Iterator[_PathArg]
    variables: Dict[str, str] = field(default_factory=dict)

    def run(self, page, include_after=(), metadata=None):
        cmd = (
            'pandoc', '-s', '-o', self.output, '--template', self.template,
            *chain(*(('--lua-filter', f) for f in self.filters)),
            *chain(*(('--css', s) for s in self.stylesheets)),
            *chain(*(('--include-after-body', f) for f in include_after))
        )

        cmd += tuple(chain(
            *(('-V', f'{k}={v}') for k, v in self.variables.items())
        ))
        if metadata is not None:
            cmd += tuple(chain(
                *(('-M', f'{k}={v}') for k, v in metadata.items())
            ))

        environ['LUA_PATH'] = '.cache/?.lua;;'

        _, ext = path.splitext(page)
        preprocessor = _PREPROCESSORS[ext[1:]]

        with preprocessor(page) as preproc:
            cmd = cmd + (preproc.output,)
            run(cmd, check=True)


def generate_crumbs(target):
    parts = ('(top)', *target.parts)

    if parts[-1] == 'index':
        *crumbs, current = parts[:-1]
    else:
        crumbs = parts[:-1]
        current, _ = path.splitext(parts[-1])

    crumbs_li = (
        '<li><a href="{link}">{crumb}</a></li>'.format(
            link=(path.relpath(path.join(*crumbs[1:i], 'index.html'),
                               start=target.parent)),
            crumb=crumb
        )
        for i, crumb in enumerate(crumbs, start=1)
    )

    current_li = f'<li aria-current="page">{current}</li>'

    return '\n'.join((*crumbs_li, current_li))