#!/bin/sh

proc throw {
  echo "$ifsjoin(Argv)" > !2
  exit 1
}

setglobal BRIEF = '0'
setglobal LEAFONLY = '0'
setglobal PRUNE = '0'
setglobal NO_HEAD = '0'
setglobal NORMALIZE_SOLIDUS = '0'

proc usage {
  echo
  echo "Usage: JSON.sh [-b] [-l] [-p] [-s] [-h]"
  echo
  echo "-p - Prune empty. Exclude fields with empty values."
  echo "-l - Leaf only. Only show leaf nodes, which stops data duplication."
  echo "-b - Brief. Combines 'Leaf only' and 'Prune empty' options."
  echo "-n - No-head. Do not show nodes that have no path (lines that start with [])."
  echo "-s - Remove escaping of the solidus symbol (straight slash)."
  echo "-h - This help text."
  echo
}

proc parse_options {
  set -- @Argv
  local ARGN=$Argc
  while [ "$ARGN" -ne 0 ]
  {
    match $1 {
      with -h usage
          exit 0
      
      with -b setglobal BRIEF = '1'
          setglobal LEAFONLY = '1'
          setglobal PRUNE = '1'
      
      with -l setglobal LEAFONLY = '1'
      
      with -p setglobal PRUNE = '1'
      
      with -n setglobal NO_HEAD = '1'
      
      with -s setglobal NORMALIZE_SOLIDUS = '1'
      
      with ?* echo "ERROR: Unknown option."
          usage
          exit 0
      
    }
    shift 1
    setglobal ARGN = $shExpr('ARGN-1')
  }
}

proc awk_egrep {
  local pattern_string=$1

  gawk '{
    while ($0) {
      start=match($0, pattern);
      token=substr($0, start, RLENGTH);
      print token;
      $0=substr($0, start+RLENGTH);
    }
  }' pattern="$pattern_string"
}

proc tokenize {
  local GREP
  local ESCAPE
  local CHAR

  if echo "test string" | egrep -ao --color=never "test" >/dev/null !2 > !1
  {
    setglobal GREP = ''egrep -ao --color=never''
  } else {
    setglobal GREP = ''egrep -ao''
  }

  if echo "test string" | egrep -o "test" >/dev/null !2 > !1
  {
    setglobal ESCAPE = ''(\\[^u[:cntrl:]]|\\u[0-9a-fA-F]{4})''
    setglobal CHAR = ''[^[:cntrl:]"\\]''
  } else {
    setglobal GREP = 'awk_egrep'
    setglobal ESCAPE = ''(\\\\[^u[:cntrl:]]|\\u[0-9a-fA-F]{4})''
    setglobal CHAR = ''[^[:cntrl:]"\\\\]''
  }

  local STRING="\"$CHAR*($ESCAPE$CHAR*)*\""
  local NUMBER='-?(0|[1-9][0-9]*)([.][0-9]*)?([eE][+-]?[0-9]*)?'
  local KEYWORD='null|false|true'
  local SPACE='[[:space:]]+'

  # Force zsh to expand $A into multiple words
  local is_wordsplit_disabled=$[unsetopt !2 >/dev/null | grep -c '^shwordsplit$]
  if test $is_wordsplit_disabled != 0 { setopt shwordsplit; }
  $GREP "$STRING|$NUMBER|$KEYWORD|$SPACE|." | egrep -v "^$SPACE$"
  if test $is_wordsplit_disabled != 0 { unsetopt shwordsplit; }
}

proc parse_array {
  local index=0
  local ary=''
  read -r token
  match $token {
    with ']' 
    with *
      while :
      {
        parse_value $1 $index
        setglobal index = $shExpr('index+1')
        setglobal ary = ""$ary""$value"" 
        read -r token
        match $token {
          with ']' break 
          with ',' setglobal ary = ""$ary,"" 
          with * throw "EXPECTED , or ] GOT $(token:-EOF)" 
        }
        read -r token
      }
      
  }
  test $BRIEF -eq 0 && setglobal value = $[printf '[%s]' $ary] || setglobal value = ''
  :
}

proc parse_object {
  local key
  local obj=''
  read -r token
  match $token {
    with '}' 
    with *
      while :
      {
        match $token {
          with '"'*'"' setglobal key = $token 
          with * throw "EXPECTED string GOT $(token:-EOF)" 
        }
        read -r token
        match $token {
          with ':' 
          with * throw "EXPECTED : GOT $(token:-EOF)" 
        }
        read -r token
        parse_value $1 $key
        setglobal obj = ""$obj$key:$value""        
        read -r token
        match $token {
          with '}' break 
          with ',' setglobal obj = ""$obj,"" 
          with * throw "EXPECTED , or } GOT $(token:-EOF)" 
        }
        read -r token
      }
    
  }
  test $BRIEF -eq 0 && setglobal value = $[printf '{%s}' $obj] || setglobal value = ''
  :
}

proc parse_value {
  local jpath="$(1:+$1,)$2" isleaf=0 isempty=0 print=0
  match $token {
    with '{' parse_object $jpath 
    with '[' parse_array  $jpath 
    # At this point, the only valid single-character tokens are digits.
    with ''|[!0-9] throw "EXPECTED value GOT $(token:-EOF)" 
    with * setglobal value = $token
       # if asked, replace solidus ("\/") in json strings with normalized value: "/"
       test $NORMALIZE_SOLIDUS -eq 1 && setglobal value = $[echo $value | sed 's#\\/#/#g]
       setglobal isleaf = '1'
       test $value = '""' && setglobal isempty = '1'
       
  }
  test $value = '' && return
  test $NO_HEAD -eq 1 && test -z $jpath && return

  test $LEAFONLY -eq 0 && test $PRUNE -eq 0 && setglobal print = '1'
  test $LEAFONLY -eq 1 && test $isleaf -eq 1 && test $PRUNE -eq 0 && setglobal print = '1'
  test $LEAFONLY -eq 0 && test $PRUNE -eq 1 && test $isempty -eq 0 && setglobal print = '1'
  test $LEAFONLY -eq 1 && test $isleaf -eq 1 && \
    test $PRUNE -eq 1 && test $isempty -eq 0 && setglobal print = '1'
  test $print -eq 1 && printf "[%s]\t%s\n" $jpath $value
  :
}

proc parse {
  read -r token
  parse_value
  read -r token
  match $token {
    with '' 
    with * throw "EXPECTED EOF GOT $token" 
  }
}

if shell {test $0 = $BASH_SOURCE || ! test -n $BASH_SOURCE}
{
  parse_options @Argv
  tokenize | parse
}

# vi: expandtab sw=2 ts=2