#!/bin/bash

# timein--Shows the current time in the specified time zone or 
#   geographic zone. Without any argument, this shows UTC/GMT. Use
#   the word "list" to see a list of known geographic regions.
#   Note that it's possible to match zone directories (regions),
#   but that only time zone files (cities) are valid specifications.

#   Time zone database ref: http://www.twinsun.com/tz/tz-link.htm

setglobal zonedir = '"/usr/share/zoneinfo'"

if test ! -d $zonedir  {
  echo "No time zone database at $zonedir." > !2 ; exit 1
}

if test -d "$zonedir/posix"  {
  setglobal zonedir = "$zonedir/posix"        # modern Linux systems
}

if test $Argc -eq 0  {
  setglobal timezone = '"UTC'"
  setglobal mixedzone = '"UTC'"
} elif test $1 = "list"  {
  shell { echo "All known time zones and regions defined on this system:"
    cd $zonedir
    find -L * -type f -print | xargs -n 2 | \
      awk '{ printf "  %-38s %-38s\n", $1, $2 }' 
  } | more
  exit 0
} else {

  setglobal region = $[dirname $1]
  setglobal zone = $[basename $1]

  # Is the given time zone a direct match? If so, we're good to go. 
  #   Otherwise we need to dig around a bit to find things. Start by 
  #   just counting matches.

  setglobal matchcnt = $[find -L $zonedir -name $zone -type f -print |
        wc -l | sed 's/[^[:digit:]]//g]

  # Check if at least one file matches
  if test $matchcnt -gt 0  {
    # But exit if more than one file matches
    if test $matchcnt -gt 1  {
      echo "\"$zone\" matches more than one possible time zone record." > !2
      echo "Please use 'list' to see all known regions and time zones" > !2
      exit 1
    }
    setglobal match = $[find -L $zonedir -name $zone -type f -print]
    setglobal mixedzone = $zone 
  } else { # maybe we can find a matching time zone region, rather than a specific time zone
    # First letter capitalized, rest of word lowercase for region + zone
    setglobal mixedregion = ""$[echo $(region%${region#?}) \
                 | tr '[[:lower:]]' '[[:upper:]]]\
                 $[echo $(region#?) | tr '[[:upper:]]' '[[:lower:]]]""
    setglobal mixedzone = ""$[echo $(zone%${zone#?}) | tr '[[:lower:]]' '[[:upper:]]] \
               $[echo $(zone#?) | tr '[[:upper:]]' '[[:lower:]]]""
    
    if test $mixedregion != "."  {
      # Only look for specified zone in specified region
      # to let users specify unique matches when there's more than one
      # possibility (e.g., "Atlantic")
      setglobal match = $[find -L $zonedir/$mixedregion -type f -name $mixedzone -print]
    } else {
      setglobal match = $[find -L $zonedir -name $mixedzone -type f -print]
    }

    # If file exactly matched the specified pattern
    if test -z $match  {
      # Check if the pattern was too ambiguous
      if test ! -z $[find -L $zonedir -name $mixedzone -type d -print]  {
         echo "The region \"$1\" has more than one time zone. " > !2
      } else {  # Or if it just didn't produce any matches at all
        echo "Can't find an exact match for \"$1\". " > !2
      }
      echo "Please use 'list' to see all known regions and time zones." > !2
      exit 1
    }
  }
  setglobal timezone = $match
}

setglobal nicetz = $[echo $timezone | sed "s|$zonedir/||g]    # pretty up the output

echo It'''s $[env TZ=$timezone date '+%A, %B %e, %Y, at %l:%M %p] in $nicetz

exit 0