# mockup: a function to mockup other commands/functions
#
# this can be used to simulate a program that records calling arguments,
# provided input, produces specified output/errors, and exits with a specified 
# return code.  very useful for unit testing!
#
# simple usage:
#  $ echo file1 file2 file3 > ls.output.txt
#  $ mockup -o ls.output.txt ls
#  $ ls
#  file1 file2 file3
#
# more advanced features are possible, such as multiple different invocations
# and support for running in parallel under pipes.  see the nonexistant 
# documentation for examples
set -u

MOCKUP_WORKDIR=${MOCKUP_WORKDIR:-${TMPDIR}/mockup-$$}

# record internal mockup program failure
mockup_fail(){
  echo "MOCKUP ERROR: $@" >> "${errorfile:-/dev/stderr}"
  return 127
}

# helpful usage stmts
mockup_help(){
  cat << EOF
mockup: create "mock" programs/functions for unit testing shell scripts.

usage:
  mockup -h
  mockup [-i] [-o file] [-e file] [-r code] command

  command:   command-line program or shell function to override.

  options:
  -h:        print this useful help message.
  -i:        record the input provided on stdin (to mockup.<n>.input.<cmd>)
  -o FILE:   print the contents of FILE on standard output.
  -e FILE:   print the contents of FILE on standard error.
  -r CODE:   return with status CODE.
EOF
}

# main function, called from test suite
mockup(){
  local args efile input ofile rcode
  local n cmd envfile
  args=`getopt -o e:hio:r: -n mockup -- "$@"`
  test $? = 0 || mockup_fail invalid options passed to mockup
  eval set -- "$args"

  # do something that will always be true without using true
  # thus allowing even the "true" command to be mocked up :)
  while [ "true" ]; do
    case "$1" in
    -e)
      efile="$2"
      shift
      ;;
    -h) 
      mockup_help
      return 0
      ;;
    -i)
      input=yes
      ;;
    -o)
      ofile="$2"
      shift
      ;;
    -r)
      rcode="$2"
      shift
      ;;
    --)
      shift
      break
      ;;
    *) 
      mockup_help >&2; 
      mockup_fail invalid arguments passed to mockup
      return 127
      ;;
    esac
    shift
  done
  if [ ! -e "$MOCKUP_WORKDIR" ]; then
    mockup_fail "${MOCKUP_WORKDIR} not found, create or set MOCKUP_WORKDIR"
    return 127
  elif [ $# -ne 1 ]; then 
    mockup_help 2>&1
    mockup_fail "$# $* need command name to mockup"
    return 127
  fi

  cmd=$1

  # to support multiple invokations, organize filenames in a queue
  n=`mockup_next_available "$MOCKUP_WORKDIR" "$cmd"`

  mockup_print "$cmd" "$n"

  envfile=$MOCKUP_WORKDIR/$n.env.$cmd
  if [ -f "$envfile" ]; then
    . "$envfile"
  else
    mockup_fail "env file for $cmd (iteration $n) not found"
    return 127
  fi

  return 0
}

# utility function for the case where a program might be called
# multiple times in the same test suite but it's desired to
# have different behaviours on each invokation
mockup_next_available(){
  local wd="$1"
  local cmd="$2"
  local n=0;
  while [ -f "$wd/$n.script.$cmd" ] || [ -f "$wd/done.$n.script.$cmd" ]; do
    n=`expr $n + 1`
  done
  echo $n
}

  # likewise but opposite: find the next to be evaluated
mockup_next_evaluated(){
  local wd="$1"
  local cmd="$2"
  local n=0;
  local next oldnext

  n=`ls "$wd" | grep -E "^[0-9]*.script.$cmd" 2>/dev/null | head -1`
  n=`basename "$n" ".script.$cmd"`
  echo ${n:-0}
}

# utility function to quote cmdline arguments distinctly wrt whitespace
# it can also replace certain environment variables with a template value,
# i.e. s/$TMPDIR/<TMPDIR>/ for easy comparison
mockup_escape(){
  local esc_tmpdir
  esc_tmpdir=`echo $TMPDIR | sed -e 's,\\\\,\\\\\\\\,g'`
  sed -e "s,$esc_tmpdir,<TMPDIR>,g" 2>"$errorfile" -e "s/'/'\\\\''/g" << EOF
$1
EOF
}

# create the mock wrappers etc for the selected program/function
mockup_print(){
  local n scriptfile cmdlinefile errorfile mockup_control envfile
  local cmd="$1"
  local next oldnext
  n="$2"

  # the actual hook
  scriptfile="$MOCKUP_WORKDIR/$n.script.$cmd"
  donescriptfile="$MOCKUP_WORKDIR/done.$n.script.$cmd"
  # where any received input is put
  inputfile="$MOCKUP_WORKDIR/$n.input.$cmd"
  doneinputfile="$MOCKUP_WORKDIR/done.$n.input.$cmd"
  # where the cmdline with which the hook was called is stored
  cmdlinefile="$MOCKUP_WORKDIR/$n.cmdline.$cmd"
  donecmdlinefile="$MOCKUP_WORKDIR/done.$n.cmdline.$cmd"
  # where the mockup-internal errors are stored
  errorfile="$MOCKUP_WORKDIR/$n.errors.$cmd"
  doneerrorfile="$MOCKUP_WORKDIR/done.$n.errors.$cmd"
  # env file (see below)
  envfile="$MOCKUP_WORKDIR/$n.env.$cmd"
  doneenvfile="$MOCKUP_WORKDIR/done.$n.env.$cmd"
  # master hook function control file for mockup scripts
  mockup_control="$MOCKUP_WORKDIR/mockup.control"

  # create an environment file to store all of this, but in the
  # form of after it's run (so it can be sourced for comparisons later)
  cat << EOF >"$envfile"
mockup_cmdline="$donecmdlinefile"
mockup_scriptfile="$donescriptfile"
mockup_errorfile="$doneerrorfile"
mockup_inputfile="$doneinputfile"
EOF

  # see if the mockup script already has a mockup hook registered
  # and if not, add it, and re-source it.  this hook doesn't actually
  # do the real work, as there's an extra level of indirection (argh,
  # meta-meta-shell programming makes teh hedz hurt) to support
  # multiple sequential invokations
  if ! grep -q "^$cmd(){" "$mockup_control" 2>/dev/null; then
    cat << EOF >> "${mockup_control}"

$cmd(){
  local next n oldnext ret
  local errorfile
  errorfile="$errorfile"
  unset -f mock_$cmd >/dev/null 2>&1
  n="\`mockup_next_evaluated \"\$MOCKUP_WORKDIR\" \"$cmd\"\`"
  if [ \$? -ne 0 ] || [ -z "\$n" ]; then
    mockup_fail "no mockup script to execute for $cmd"
    return 127
  fi
  next="\$MOCKUP_WORKDIR/\$n.script.$cmd"
  if [ -f  "\$next" ]; then
    . "\${next}"
  else
    mockup_fail "sourcing \${next}"
    return 127
  fi
  mock_$cmd "\$@"
  ret=\$?
  (
  cd \$MOCKUP_WORKDIR
  for f in \$n.*.$cmd; do
    mv "\$f" "done.\$f"
    if [ \$? -ne 0 ]; then
      mockup_fail "rotating out \${next}"
      return 127
    fi
  done
  )
  return \$ret
}

EOF
  fi
  . "$mockup_control"

  # okay, now this is the real meat and potatoes of the mockup work
  # this gets put into the sequential script file, and is called by
  # the main hook above.
  cat << EOF > "$scriptfile"
mock_$cmd(){
  local escaped cmdline
  local errorfile="$errorfile"

  # record the cmdline
  set $cmd "\$@"
  while [ \$# -gt 0 ]; do
    escaped="\`mockup_escape \"\$1\"\`"
    if [ -n "\${cmdline:-}" ]; then
      cmdline="\$cmdline '\$escaped'"
    else
      cmdline="'\$escaped'"
    fi
    shift
  done
  set "\$cmdline"
  echo "\$@" > "$cmdlinefile"
  if [ \$? -ne 0 ]; then
    mockup_fail failed recording cmdlinefile
    return 127
  fi

  # record input
  if [ -n "${input:-}" ]; then
    cat > "${inputfile:-}" 2>>"$errorfile"
    if [ \$? -ne 0 ]; then
      mockup_fail failed recording input
      return 127
    fi
  fi

  # produce output
  if [ -n "${ofile:-}" ]; then
    cat < "${ofile:-}" 2>>"$errorfile"
    if [ \$? -ne 0 ]; then
      mockup_fail failed producing output
      return 127
    fi
  fi

  # produce errors
  if [ -n "${efile:-}" ]; then
    if [ ! -f "${efile:-}" ]; then
      mockup_fail failed to find error output file
      return 127
    else
      cat < "${efile:-}" >&2 
    fi
    if [ \$? -ne 0 ]; then
      mockup_fail failed producing error output
      return 127
    fi
  fi

  # and return requested value
  return ${rcode:-0}
}
EOF
}

