#!/usr/bin/env python3

import json
from itertools import tee, islice, chain
from os import scandir
import logging

logging.basicConfig()
logging.root.setLevel(logging.INFO)


def previous_and_next(some_iterable):
    prevs, items, nexts = tee(some_iterable, 3)
    prevs = chain([None], prevs)
    nexts = chain(islice(nexts, 1, None), [None])
    return zip(prevs, items, nexts)


def pretty_print(data, filename=None):
    if filename is None:
        logging.debug(json.dumps(data, sort_keys=True, indent=4))
    else:
        with open(filename, 'w') as outfile:
            json.dump(data, outfile, sort_keys=True, indent=4)


def add_docs(docs_in_order, doc):
    docs_in_order.append(doc)
    for doc in doc['children']:
        add_docs(docs_in_order, doc)


def create_previous_and_next(docs_in_order):
    for previous_doc, current_doc, next_doc in previous_and_next(docs_in_order):
        if previous_doc is not None:
            current_doc['previous_title'] = previous_doc['title']
            current_doc['previous_url'] = previous_doc['url']
        else:
            current_doc['previous_title'] = ''
            current_doc['previous_url'] = ''
        if next_doc is not None:
            current_doc['next_title'] = next_doc['title']
            current_doc['next_url'] = next_doc['url']
        else:
            current_doc['next_title'] = ''
            current_doc['next_url'] = ''


def create_breadcrumbs(docs_in_order, docs_by_title):
    for doc in docs_in_order:
        doc['breadcrumbs'] = []
        parent_title = doc.get('parent')
        while parent_title != '':
            parent = docs_by_title[parent_title]
            doc['breadcrumbs'].append(
                {'url': parent['url'], 'title': parent['title']})
            parent_title = parent.get('parent')


if __name__ == '__main__':
    langs = [f.name for f in scandir('_docs') if f.is_dir()]
    result = {}

    for lang in langs:
        # the fallback language, en, ends up at _site/ rather than _site/en/
        input_path = f'_site/{lang if lang != "en" else "."}/data/index.html'
        # input_path = f'_site/{lang}/data/index.html'
        output_path = '_data/docs.json'

        with open(input_path) as input_file:
            docs = json.load(input_file)

        docs_by_title = {}
        docs_in_order = []
        top_level_docs = []

        for doc in docs:
            docs_by_title[doc['title']] = doc
            doc['children'] = []

        for doc in docs:
            if doc['parent'] == '':
                top_level_docs.append(doc)
            else:
                try:
                    docs_by_title[doc['parent']]['children'].append(doc)
                except Exception as e:
                    msg = f'Error processing "{doc["title"]}", which has parent ' \
                        f'"{doc["parent"]}", for language {lang}.'

                    if lang != 'en':
                        msg += '  Once you\'ve given a translated _title_ to a parent page' \
                            ' you must create translations of all of its child pages' \
                            ' (which may be empty or contain the original English text)' \
                            ' and set their _parent_ to the new _title_ on the parent page'

                    logging.warn(msg)

        for doc in top_level_docs:
            add_docs(docs_in_order, doc)

        create_previous_and_next(docs_in_order)
        create_breadcrumbs(docs_in_order, docs_by_title)

        result[lang] = {'hierarchy': top_level_docs, 'by_title': docs_by_title}
        logging.info(f'Generated {len(docs_by_title)} doc entries for {lang}')

    pretty_print(result)
    pretty_print(result, output_path)