#!/bin/dash

# Syntax scheme:
#
# hemar
#   elements
# 
# elements
#   element
#   element ws elements
# 
# element
#   tag
#   text
# 
# text
#   text-item
#   text-item text
# 
# text-item
#   '0020' . '10FFFF' - '{'
#   nopatern
# 
# tag
#   '{[' ws path           ws ']}'
#   '{[' ws loop-statement ws ']}'
#   '{[' ws include-header ws ']}'
#   '{[' ws "end"          ws ']}'
#   '{[' ws function       ws ']}'
# 
# # loop tag
# loop-statemant
#   "for" string "in" path
# 
# # include tag
# include-header
#   "include" path
# 
# # fucntion tag
# function
#   "compute" language function-body
#   "compute" - function-body
# 
# language
#   "dash"
#   "plpgsql"
# 
# function-body
#   ""
#   '0020' . '10FFFF', function-body
# 
# function-character
#   '0020' . '10FFFF' - ']'
#   ncpatern
# 
# # path
# path
#   "."
#   segmented-path
# 
# segmented-path
#   segment
#   segment "." segmented-path
# 
# segment
#   string
#   index
# 
# index
#   '\'     digit
#   '\'     onenine digits
#   '\' '-' digit
#   '\' '-' onenine digits
# 
# # types
# string
#   character
#   character string
# 
# character
#   '0020' . '10FFFF' - '"' - '\' - '.' - ']'
#   '\' escape
#   ncpatern
# 
# escape
#   '.'
#   ']}'
#   '"'
#   '\'
#   '/'
#   'b'
#   'f'
#   'n'
#   'r'
#   't'
#   'u' hex hex hex hex
# 
# hex
#   digit
#   'A' . 'F'
#   'a' . 'f'
# 
# digits
#   digit
#   digit digits
# 
# digit
#   '0'
#   onenine
# 
# onenine
#   '1' . '9'
# 
# # paterns
# ws
#   ""
#   '0020' ws
#   '000A' ws
#   '000D' ws
#   '0009' ws
# 
# nopatern
#   '{' '0020' . '10FFFF' - '['
# 
# ncpatern
#   ']' '0020' . '10FFFF' - '}'


# AST Plex:
#
# Type = 0..=5
#
# Text = string            # just a text body
#
# Interpolation = string   # path to variable 
#
# Include = string         # path to include data
#
# Section = {
#   v = string      # item variable name for loop
#   p = string      # path to array for iteration
#   b = [Element]   # section body
#    
# }
#
# End = null
#
# Compute = {
#   l     = string  # programing language
#   b     = string  # function body
# }
#
# Element = {
#   t = Type        # element type
#   b = Text        # element body
#       | Interpolation 
#       | Section 
#       | End 
#       | Include 
#       | Compute 
# }
#
# AbstarctSyntaxTree (ATS) = {
#    e = [Element]  # elements array
#}
AST=''

# 0 - text
# 1 - deside tag type
# 2 - interpolation
# 3 - section
# 4 - include
# 5 - compute
STAGE=0
STAGE_BUFFER="$(mktemp)"
open_tag_flag=0

# finds close pattern and store the char to the STAGE_BUFFER
find_close_pattern() {
  char="${1:?}"
  if   [ "${close_tag_flag:?}" -eq 0 ] && [ "$char" = ']' ]; then
    close_tag_flag=1
  elif [ "${close_tag_flag:?}" -eq 1 ] && [ "$char" = '}' ]; then
    close_tag_flag=0

    # removes first and last white spaces from the buffer
    sed -i 's/[[:space:]]$//g' "$STAGE_BUFFER"
    sed -i 's/^[[:space:]]//g' "$STAGE_BUFFER"
    
    # removes last char from buffer (]) is part of close pattern
    truncate -s -1 "$STAGE_BUFFER"
    return 0
  else
    printf '%s' "$char" >> "$STAGE_BUFFER"
  fi

  return 1
}

# finds open pattern and stores the char to the STAGE_BUFFER
find_open_pattern() {
  char="${1:?}"
  if   [ "${open_tag_flag:?}" -eq 0 ] && [ "$char" = '{' ]; then
    open_tag_flag=1
  elif [ "${open_tag_flag:?}" -eq 1 ] && [ "$char" = '[' ]; then
    open_tag_flag=0

    # removes last char from buffer ({) is part of open pattern
    truncate -s -1 "$STAGE_BUFFER"
    return 0
  else
    printf '%s' "$char" >> "$STAGE_BUFFER"
  fi

  return 1
}

parse() {
  char="$1"

  case "$STAGE" in
    0)
      if find_open_pattern "$char"; then
	plex_set "$data_pointer"''
        STAGE=1
      fi
      ;;
    1)
      if find_close_pattern "$char"; then
        STAGE=0
      fi
      ;;
    2)

      ;;
    3)
    
      ;;
    4)

      ;;
    *)

      ;;
  esac
}

# Using dd to read one character at a time
input=$(cat)
i=1
while :; do
    char=$(printf '%s' "$input" | dd bs=1 skip=$((i-1)) count=1 2>/dev/null)
    [ -z "$char" ] && break

    parse "$char"

    i=$((i+1))
done