"""Automate creation of standard header for Summaries.

Expected usage is to redirect output of this script to ``cat - <summary>`` to
then be redirected to a file: ``python makeheader.py summary | cat - summary >
summary``.

Uses basic %()s substitution to creation which is printed to stdout.  See
docstring for createheader for supported %-escapes.

XXX: To Do:
    * Be able to specify header text file to use
    * Specify final output file to skip need to use 'cat'

"""
import os
import datetime


# Simple functions for creating filenames with .ht and .html extensions
htname = lambda start, end: start.isoformat() + '_' + end.isoformat() + ".ht"
htmlname = lambda start, end: htname(start, end) + "ml"

def createheader(start_date, end_date,
                 last_start_date, last_end_date,
                 header_text):
    """Replace %-escaped values in header_text with proper information as
    generated using the start and end dates of coverage for this summary and
    the start and end dates of the last summary (all passed in as datetime.date
    objects).

    %-escaped values:
    + start_ISO_date
          Output start_date formatted as yyy-mm-dd
    + end_ISO_date
          Same as start_ISO_date except end_date is used
    + start_traditional_date
          start_date formatted as "%B %d, %Y"
    + end_traditional_date
          Same as start_traditional_date except with end_date
    + ht_name
          The expected name of the summary when saved as an .ht file
    + html_prev_summary
          The expected name of the last summary when save as a .html file

    """
    subst_dict = dict(
                        start_ISO_date = start_date.isoformat(),
                        end_ISO_date = end_date.isoformat(),
                        start_traditional_date = start_date.strftime("%B %d, %Y"),
                        end_traditional_date = end_date.strftime("%B %d, %Y"),
                        ht_name = htname(start_date, end_date),
                        html_prev_summary = htmlname(last_start_date,
                                                     last_end_date)
                    )
    if "XXX" in header_text:
        print>>sys.stderr, ("NOTE: 'XXX' markers found in header; " +
                            "make sure to replace them")
    return header_text % subst_dict

def lastsummary(directory, this_summary_start, file_ending=".ht"):
    """Figure out the start and end dates of the last summary as found in
    'directory', excluding the newest one if exclude_newest is true."""
    summary_files = os.listdir(os.getcwd())
    # In case directory contains various versions of the summaries (.txt,
    #   .html, etc.), filter on only a single file extension known to be there
    summary_files = [filename
                        for filename in summary_files
                            if (filename.endswith(file_ending) and
                                len(filename) == (21 + len(file_ending))) and
                                not filename.startswith(this_summary_start)
                    ]
    # Can do a standard sort since filenames all in ISO format
    summary_files.sort()
    last_summary = summary_files[-1]
    start_date_text = last_summary[:10] # "yyyy-mm-dd" = 10 characters
    end_date_text = last_summary[11:21]
    return (convertISO(start_date_text), convertISO(end_date_text))

def convertISO(text):
    """Convert 'text', which is an ISO date string, into a datetime.date
    object."""
    year = int(text[:4])
    month = int(text[5:7])
    day = int(text[8:])
    return datetime.date(year, month, day)



if __name__ == "__main__":
    import sys

    try:
        filename = sys.argv[1]
    except IndexError:
        print>>sys.stderr, "ERROR: You must specify the summary to use."
        print>>sys.stderr, ("Usage: python makeheader.py summary.txt | "
                            "cat - summary.txt > summary.ht")
        sys.exit(1)
    start_date_text, end_date_text = os.path.splitext(filename)[0].split('_')
    start_date = convertISO(start_date_text)
    end_date = convertISO(end_date_text)
    last_start_date, last_end_date = lastsummary(os.getcwd(), start_date_text)
    # XXX: can make a command-line argument
    header_FILE = file("header.txt")
    try:
        header_text = header_FILE.read()
    finally:
        header_FILE.close()
    # Printed so that you can do ``cat - <new summary>``
    print createheader(start_date, end_date,
                       last_start_date, last_end_date,
                       header_text)