#!/usr/bin/env python

import pyfits
import argparse

def formatVisits(visits):
    """Format a set of visits into the format used for an --id argument"""
    visits = sorted(set(visits))

    visitSummary = []
    i = 0
    while i < len(visits):
        v0 = -1

        while i < len(visits):
            v = visits[i]; i += 1
            if v0 < 0:
                v0 = v
                dv = -1                 # visit stride
                continue

            if dv < 0:
                dv = v - v0

            if visits[i - 2] + dv != v:
                i -= 1                  # process this visit again later
                v = visits[i - 1]       # previous value of v
                break

        if v0 == v:
            vstr = "%d" % v
        else:
            if v == v0 + dv:
                vstr = "%d^%d" % (v0, v)
            else:
                vstr = "%d..%d" % (v0, v)
                if dv > 1:
                    vstr += ":%d" % dv

        visitSummary.append(vstr)

    return "^".join(visitSummary)

def getVisitsForCalib(filename):
    fits = pyfits.open(filename)
    header = fits[0].header
    pattern = "HIERARCH CALIB_INPUT_%04d"
    index = 0
    visits = []
    while pattern % index in header:
        visits.append(header[pattern % index])
        index += 1
    return visits

if __name__ == "__main__":
    parser = argparse.ArgumentParser()
    parser.add_argument("filename", help="Calib filename")
    args = parser.parse_args()
    visits = getVisitsForCalib(args.filename)
    print args.filename, formatVisits(visits)