#!/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


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)


def pandoc(filename):
    proc = subprocess.run(['pandoc', '--smart', filename], stdout=subprocess.PIPE)
    return proc.stdout.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 markdown_to_html(input_file, output_dir):
    title = extract_markdown_title(input_file)
    title = html.escape(title)
    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:]))