#!/usr/bin/env python3

'''
Transforms a file into a web-servable file.

In most cases this entails either

  + just symlinking, or
  + transforming a page to html
'''

import sys
import os
import html
import subprocess

import yaml


def read(path):
    with open(path) as f:
        return f.read()

def write(path, text):
    with open(path, 'w') as f:
        f.write(text)


script_dir = os.path.dirname(__file__)
base_dir = os.path.split(script_dir)[0]
template_dir = os.path.join(base_dir, 'template')
template_base_file = os.path.join(template_dir, 'base.html')
template_base = read(template_base_file)
site_dir = os.path.join(base_dir, 'site')


def pandoc(filename):
    proc = subprocess.run(['pandoc', '-f', 'markdown+smart', filename],
                          stdout=subprocess.PIPE)
    return proc.stdout.decode('utf-8').strip()

def pandoc_stdin(text):
    out = subprocess.Popen(
        ['pandoc', '-f', 'markdown+smart'],
        stdin=subprocess.PIPE, stdout=subprocess.PIPE).communicate(text.encode('utf-8'))[0]
    return out.decode('utf-8').strip()

def extract_markdown_title(filename):
    with open(filename) as f:
        for line in f:
            if line.startswith('# '):
                return line[2:].strip()
    if filename.endswith('.md'):
        return os.path.basename(filename)[:-3]

def extract_markdown_abstract(filename):
    state = 0
    with open(filename) as f:
        for line in f:
            if state == 0 and line == '---\n':
                state = 1
                yaml_block = ''
            elif state == 1:
                if line == '---\n':
                    y = yaml.load(yaml_block)
                    if y is None:
                        return None
                    else:
                        return y.get('abstract').strip().replace('\n', ' ')
                else:
                    yaml_block += line

def markdown_to_html(input_file, output_dir):
    title = extract_markdown_title(input_file)
    title = html.escape(title)

    common = os.path.commonpath([input_file, output_dir])
    relpath = os.path.relpath(input_file, start=common)

    # Special cases
    if relpath == 'site/misc/index.md':
        top = read(input_file)

        pages = []
        for path, subdirs, subfiles in os.walk(site_dir):
            dir = path
            if dir.startswith('./'):
                dir = dir[1:]
            if dir.startswith('/site'):
                dir = dir[5:]
            if 'index.md' in subfiles:
                pages.append((dir + '/',
                              os.path.normpath(os.path.join(base_dir, path, 'index.md'))))
            for name in subfiles:
                if name.endswith('.md') and name != 'index.md':
                    uri = name[:-3]
                    pages.append((dir + '/' + uri,
                                  os.path.normpath(os.path.join(base_dir, path, name))))

        builtins = ['/', '/about/', '/about/niels', '/misc/', '/404']
        pages = filter(lambda t: t[0] not in builtins, pages)
        pages_new = []
        for page in pages:
            url, path = page
            ptitle = extract_markdown_title(path)
            pabstract = extract_markdown_abstract(path)
            pages_new.append((ptitle, pabstract, url, path))

        pages_new.append(('Potators', 'Do not look.', '/potator/', '/potator/'))

        pages_new.sort()
        md = ''
        for page in pages_new:
            ptitle, pabstract, url, _ = page
            if pabstract is None:
                pabstract = '(No description)'
            md += '[{}]({})\n  ~ {}\n\n'.format(ptitle, url, pabstract)
            
        bottom = md
        content = pandoc_stdin(top + '\n' + bottom)
    else:
        content = pandoc(input_file)

    html_out = template_base.format(title=title, content=content)
    output_file = os.path.join(
        output_dir,
        os.path.splitext(os.path.basename(input_file))[0]
        + '.html')
    write(output_file, html_out)

def symlink_relative(input_file, output_dir):
    in_path_abs = os.path.abspath(input_file)
    os.chdir(output_dir)
    in_path_rel = os.path.relpath(in_path_abs)
    output_file = os.path.basename(input_file)
    os.symlink(in_path_rel, output_file)

def get_extension(filename):
    _, extension = os.path.splitext(filename)
    extension = extension[1:]
    return extension
    
def transform(input_file, output_dir):
    extension = get_extension(input_file)

    actions = {
        'md': lambda: markdown_to_html(input_file, output_dir)
    }
    try:
        action = actions[extension]
    except KeyError:
        action = lambda: symlink_relative(input_file, output_dir)
    action()
    return 0

def main(args):
    try:
        [input_file, output_dir] = args
    except ValueError:
        print_usage()
        return 1

    transform(input_file, output_dir)

def print_usage():
    print('''\
usage: transform-file.py INPUT_FILE OUTPUT_DIRECTORY
''')
    
if __name__ == '__main__':
    sys.exit(main(sys.argv[1:]))