#!/usr/bin/python

import argparse
import os
import sys

import docx


def expand_chapter_range(chapter_request):
    if '-' not in chapter_request:
        return (int(chapter_request),)

    chapter_range = chapter_request.split('-')

    return tuple(range(int(chapter_range[0]), int(chapter_range[1]) + 1))


def filter_chapters(document, chapter_requests):
    if not chapter_requests:
        return

    chapter_numbers = {
        chapter_number
        for request in chapter_requests
        for chapter_number in expand_chapter_range(request)
    }

    current_chapter_number = 0

    for paragraph in document.paragraphs:
        if paragraph.style.name.startswith('Heading'):
            current_chapter_number += 1

        if current_chapter_number not in chapter_numbers:
            element = paragraph._element
            element.getparent().remove(element)


def set_default_font(document):
    document.styles['Normal'].font.name = 'Times New Roman'


def add_header_text(document, text):
    document.sections[0].header.paragraphs[0].text = text


def create_element(name):
    return docx.oxml.OxmlElement(name)


def create_attribute(element, name, value):
    element.set(docx.oxml.ns.qn(name), value)


def add_header_page_number(document):
    run = document.sections[0].header.paragraphs[0].add_run()

    fldChar1 = create_element('w:fldChar')
    create_attribute(fldChar1, 'w:fldCharType', 'begin')

    instrText = create_element('w:instrText')
    create_attribute(instrText, 'xml:space', 'preserve')
    instrText.text = "PAGE"

    fldChar2 = create_element('w:fldChar')
    create_attribute(fldChar2, 'w:fldCharType', 'end')

    run._r.append(fldChar1)
    run._r.append(instrText)
    run._r.append(fldChar2)


def skip_page_number_on_first_page(document):
    document.sections[0].different_first_page_header_footer = True
    page_number_type = docx.oxml.OxmlElement('w:pgNumType')
    page_number_type.set(docx.oxml.ns.qn('w:start'), "0")
    document.sections[0]._sectPr.append(page_number_type)


def right_align_header(document):
    header_paragraph = document.sections[0].header.paragraphs[0]
    header_paragraph.paragraph_format.alignment = docx.enum.text.WD_ALIGN_PARAGRAPH.RIGHT


def double_space_and_indent(paragraphs, format_all):
    previous_paragraph = None
    this_paragraph_plaintext = False
    previous_paragraph_plaintext = None
    reached_first_heading = False

    for paragraph in paragraphs:
        this_paragraph_plaintext = not (
            paragraph.style.name.startswith('Heading')
            or paragraph.style.name == '0 Block'
            or paragraph.text == '#'
            or paragraph.style.paragraph_format.left_indent
            or paragraph.style.paragraph_format.right_indent
        )
        if not this_paragraph_plaintext:
            reached_first_heading = True

        # Skip past the title page until we reach the first chapter/other heading.
        if not reached_first_heading and not format_all:
            continue

        paragraph.paragraph_format.line_spacing = 2
        paragraph.paragraph_format.space_before = docx.shared.Inches(0)
        paragraph.paragraph_format.space_after = docx.shared.Inches(0)

        # To reduce page count, allow splitting paragraphs across pages.
        paragraph.paragraph_format.widow_control = False

        # Indent first lines of paragraphs except for styled ones (headings, etc.) and initial
        # paragraphs.
        if this_paragraph_plaintext and previous_paragraph_plaintext:
            paragraph.paragraph_format.first_line_indent = docx.shared.Inches(0.5)

        if (
            previous_paragraph
            and paragraph.style == previous_paragraph.style
            and not paragraph.text
            and not previous_paragraph.text
        ):
            previous_paragraph._element.getparent().remove(previous_paragraph._element)

        previous_paragraph = paragraph
        previous_paragraph_plaintext = this_paragraph_plaintext


def parse_arguments(unparsed_arguments):
    parser = argparse.ArgumentParser(add_help=True)
    parser.add_argument(
        metavar='FILENAME', dest='document_filename', help='Novel document to format',
    )
    parser.add_argument(
        '-c',
        '--chapters',
        metavar='CHAPTER',
        nargs='+',
        help='Chapter numbers or ranges to include in output, defaults to all',
    )
    parser.add_argument(
        '-a',
        '--author',
        metavar='LAST NAME',
        help='Author last name to show in page headers, defaults to parsing the first line of the manuscript for the name',
    )
    parser.add_argument(
        '-t',
        '--title',
        help='Project title to show in page headers, defaults to the manuscript filename without the file extension',
    )
    parser.add_argument(
        '-f',
        '--format-all',
        help='Format the whole document, even the title page (if any)',
        action='store_true',
        default=False,
    )

    return parser.parse_args(unparsed_arguments)


def main():
    arguments = parse_arguments(sys.argv[1:])
    document = docx.Document(arguments.document_filename)
    author_last_name = arguments.author or document.paragraphs[0].text.split('\n')[0].split(' ')[-1]
    project_title = arguments.title or os.path.splitext(arguments.document_filename)[0]

    filter_chapters(document, arguments.chapters)
    set_default_font(document)
    add_header_text(document, f'{author_last_name} / {project_title} / ')
    add_header_page_number(document)

    if not arguments.chapters:
        skip_page_number_on_first_page(document)

    right_align_header(document)
    double_space_and_indent(document.paragraphs, arguments.format_all)

    document.save(arguments.document_filename)


if __name__ == '__main__':
    main()