//! **This module is deprecated by the [crate::zc_parser] module** and is only kept for
//! compatibility with existing parsers.
//!
//! This module implements the parsing routines that uses the state machine
//! generated by rustlr.  The main structure here is [RuntimeParser].
//! All parsing functions are organized around the [RuntimeParser::parse_base]
//! function, which implements the basic LR parsing algorithm.  This function
//! expects dynamic [Lexer] and [ErrHandler] trait-objects. 
//! This module provides generic
//! parsing and parser-training routines that use stdio for interface, but
//! the [ErrHandler] trait allows custom user interfaces to be build separately.

#![allow(dead_code)]
#![allow(unused_variables)]
#![allow(non_snake_case)]
#![allow(non_camel_case_types)]
#![allow(unused_parens)]
#![allow(unused_mut)]
#![allow(unused_assignments)]
#![allow(unused_doc_comments)]
#![allow(unused_imports)]
use std::fmt::Display;
use std::default::Default;
use std::collections::{HashMap,HashSet,BTreeSet};
use std::io::{self,Read,Write,BufReader,BufRead};
use std::cell::{RefCell,Ref,RefMut};
use std::hash::{Hash,Hasher};
use std::any::Any;
use std::fs::File;
use std::io::prelude::*;
use std::path::Path;
use std::mem;
use crate::{TRACE,Lexer,Lextoken,Stateaction,Statemachine};
use crate::{LBox,LRc};
use crate::Stateaction::*;

/// this structure is only exported because it is required by the generated parsers.
/// There is no reason to use it in other programs.
#[derive(Clone)]
pub struct RProduction<AT:Default,ET:Default>  // runtime rep of grammar rule
{
  pub lhs: &'static str, // left-hand side nonterminal of rule
  pub Ruleaction : fn(&mut RuntimeParser<AT,ET>) -> AT, //parser as arg
}
impl<AT:Default,ET:Default> RProduction<AT,ET>
{
  pub fn new_skeleton(lh:&'static str) -> RProduction<AT,ET>
  {
     RProduction {
       lhs : lh,
       Ruleaction : |p|{<AT>::default()},
     }
  }
}//impl RProduction

pub struct Stackelement<AT:Default>
{
   pub si : usize, // state index
   pub value : AT, // semantic value (don't clone grammar symbols)
   //pub line: usize,  // line and column
   //pub column: usize, 
}

/// this is the structure created by the generated parser.  The generated parser
/// program will contain a make_parser function that returns this structure.
/// Most of the pub items are, however, only exported to support the operation
/// of the parser, and should not be accessed directly.  Only the functions
/// [RuntimeParser::parse], [RuntimeParser::report], [RuntimeParser::abort]
/// and [RuntimeParser::error_occurred] should be called directly 
/// from user programs.  Only the field [RuntimeParser::exstate] should be accessed
/// by user programs.
pub struct RuntimeParser<AT:Default,ET:Default>  
{
  /// this is the "external state" structure, with type ET defined by the grammar.
  /// The semantic actions associated with each grammar rule, which are written
  /// in the grammar, have ref mut access to the RuntimeParser structure, which
  /// allows them to read and change the external state object.  This gives
  /// the parsers greater flexibility and capability, including the ability to
  /// parse some non-context free languages.  See 
  /// [this sample grammar](<https://cs.hofstra.edu/~cscccl/rustlr_project/ncf.grammar>).
  /// The exstate is initialized to ET::default().
  pub exstate : ET,  // external state structure, usage optional
  /// used only by generated parser: do not reference
  pub RSM : Vec<HashMap<&'static str,Stateaction>>,  // runtime state machine
  // do not reference
  //pub Expected : Vec<Vec<&'static str>>,
  /// do not reference
  pub Rules : Vec<RProduction<AT,ET>>, //rules with just lhs and delegate function
  ////// this value should be set through abort or report
  stopparsing : bool,
  /// do not reference  
  pub stack :  Vec<Stackelement<AT>>, // parse stack
//  pub recover : HashSet<&'static str>, // for error recovery
  pub resynch : HashSet<&'static str>,
  pub Errsym : &'static str,
  err_occurred : bool,
  pub linenum : usize,
  pub column : usize,
  pub src_id : usize,
  report_line : usize,
//  training : bool,
//  pub trained: HashMap<(usize,String),String>,
  /// Hashset containing all grammar symbols (terminal and non-terminal). This is used for error reporting and training.
  pub Symset : HashSet<&'static str>,
}//struct RuntimeParser

impl<AT:Default,ET:Default> RuntimeParser<AT,ET>
{
    /// this is only called by the make_parser function in the machine-generated
    /// parser program.  *Do not call this function in other places* as it
    /// only generates a skeleton.
    pub fn new(rlen:usize, slen:usize) -> RuntimeParser<AT,ET>
    {  // given number of rules and number states
       let mut p = RuntimeParser {
         RSM : Vec::with_capacity(slen),
         //Expected : Vec::with_capacity(slen),
         Rules : Vec::with_capacity(rlen),
         stopparsing : false,
         exstate : ET::default(),
         stack : Vec::with_capacity(1024),
         Errsym : "",
         err_occurred : false,
         linenum : 0,
         column : 0,
         src_id : 0,
         report_line : 0,
         resynch : HashSet::new(),
         //added for training
         //training : false,
         //trained : HashMap::new(),
         Symset : HashSet::with_capacity(64),
       };
       for _ in 0..slen {
         p.RSM.push(HashMap::with_capacity(16));
         //p.Expected.push(Vec::new());
       }
       return p;
    }//new

    /// this function can be called from with the "semantic" actions attached
    /// to grammar production rules that are executed for each
    /// "reduce" action of the parser.
    pub fn abort(&mut self, msg:&str)
    {
       eprintln!("\n!!!Parsing Aborted: {}",msg);
       self.err_occurred = true;
       self.stopparsing=true;
    }

    /// may be called from grammar semantic actions to report error.
    /// this report function will print to stdout. 
    pub fn report(&mut self, errmsg:&str)  
    {      // linenum must be set prior to call
       if (self.report_line != self.linenum || self.linenum==0)  {
//         eprint!("ERROR on line {}, column {}:\n{}\n",self.linenum,self.column,tokenizer.current_line());         
         eprintln!("ERROR on line {}, column {}: {}",self.linenum,self.column,errmsg);
         self.report_line = self.linenum;
       }
       else {
         eprint!(" {} ",errmsg);
       }
       self.err_occurred = true;
    }// report

    /// this function is only exported to support the generated code
    pub fn bad_pattern(&mut self,pattern:&str) -> AT
    {
       let msg = format!("pattern {} failed to bind to stacked values\n",pattern);
       self.report(&msg);
       AT::default()
    }

    /// sets an index that index source information, such as the source file
    /// when compiling multiple sources. This information must be maintained externally.
    /// The source id will also be passed on to the [LBox] and [LRc] smartpointers by
    /// the [RuntimeParser::lb] function.
    pub fn set_src_id(&mut self, id:usize)
    { self.src_id =id; }

    //called to simulate a shift
    fn errshift(&mut self, sym:&str) -> bool
    {
       let csi = self.stack[self.stack.len()-1].si; // current state
       let actionopt = self.RSM[csi].get(sym);
       if let Some(Shift(ni)) = actionopt {
         self.stack.push(Stackelement{si:*ni,value:AT::default()}); true
       }
       else {false}
    }

  // this is the LR parser shift action: push the next state, along with the
  // value of the current lookahead token onto the parse stack, returns the
  // next token
  fn shift(&mut self, nextstate:usize, lookahead:Lextoken<AT>, tokenizer:&mut dyn Lexer<AT>) -> Lextoken<AT>
  {
     self.stack.push(Stackelement{si:nextstate,value:lookahead.value});
     self.nexttoken(tokenizer)
  }

    fn reduce(&mut self, ri:&usize)
    {
              let rulei = &self.Rules[*ri];
              let ruleilhs = rulei.lhs; // &'static : Copy
              let val = (rulei.Ruleaction)(self); // calls delegate function
              let newtop = self.stack[self.stack.len()-1].si; 
              let goton = self.RSM[newtop].get(ruleilhs).unwrap();
//              if TRACE>1 {println!(" ..performing Reduce({}), new state {}, action on {}: {:?}..",ri,newtop,ruleilhs,goton);}
              if let Stateaction::Gotonext(nsi) = goton {
                self.stack.push(Stackelement{si:*nsi,value:val});
                // DO NOT CHANGE LOOKAHEAD AFTER REDUCE!
              }// goto next state after reduce
              else {
                self.report("state transition table corrupted: no suitable action after reduce");
                self.stopparsing=true;
              }
    }//reduce

    /// can be called to determine if an error occurred during parsing.  The parser
    /// will not panic.
    pub fn error_occurred(&self) -> bool {self.err_occurred}

    fn nexttoken(&self, tokenizer:&mut dyn Lexer<AT>) -> Lextoken<AT>
    {
       if let Some(tok) = tokenizer.nextsym() {tok}
        else { Lextoken{sym:"EOF".to_owned(),  value:AT::default()} } 
    }


    /// *this function is equivalent to [RuntimeParser::parse_stdio_train]*.
    pub fn parse_train(&mut self, tokenizer:&mut dyn Lexer<AT>, parserfile:&str) -> AT
    {
      self.parse_stdio_train(tokenizer,parserfile)
    }//parse_train

    /// creates a [LBox] smart pointer that includes line/column/src information;
    /// should be called from the semantic actions of a grammar rule, e.g.
    ///```ignore
    ///   E --> E:a + E:b {PlusExpr(parser.lb(a),parser.lb(b))}
    ///```
    pub fn lb<T>(&self,e:T) -> LBox<T> { LBox::new(e,self.linenum,self.column /*,self.src_id*/) }
    /// creates a `LBox<dyn Any>`, which allows attributes of different types to
    /// be associated with grammar symbols.  Use in conjuction with [LBox::downcast], [LBox::upcast] and the [lbdown], [lbup] macros.
    pub fn lba<T:'static>(&self,e:T) -> LBox<dyn Any> { LBox::upcast(LBox::new(e,self.linenum,self.column /*,self.src_id*/)) }
    /// similar to [RuntimeParser::lb], but creates a [LRc] instead of [LBox]
    pub fn lrc<T>(&self,e:T) -> LRc<T> { LRc::new(e,self.linenum,self.column /*,self.src_id*/) }
    /// similar to [RuntimeParser::lba] but creates a [LRc]
    pub fn lrca<T:'static>(&self,e:T) -> LRc<dyn Any> { LRc::upcast(LRc::new(e,self.linenum,self.column /*,self.src_id*/)) }        
}// impl RuntimeParser


//////////////////////////////////////////////////////////////////
//////////////////////////////////////////////////////////////////
//// new version of write_fsm:

impl Statemachine
{
  pub fn writeparser(&self, filename:&str)->Result<(),std::io::Error>
  {
    let mut fd = File::create(filename)?;
    write!(fd,"//Parser generated by rustlr\n
#![allow(unused_variables)]
#![allow(non_snake_case)]
#![allow(non_camel_case_types)]
#![allow(unused_parens)]
#![allow(unused_mut)]
#![allow(unused_imports)]
#![allow(unused_assignments)]
#![allow(irrefutable_let_patterns)]
extern crate rustlr;
use rustlr::{{RuntimeParser,RProduction,Stateaction,decode_action}};\n")?;

    write!(fd,"{}\n",&self.Gmr.Extras)?; // use clauses

    // write static array of symbols
    write!(fd,"const SYMBOLS:[&'static str;{}] = [",self.Gmr.Symbols.len())?;
    for i in 0..self.Gmr.Symbols.len()-1
    {
      write!(fd,"\"{}\",",&self.Gmr.Symbols[i].sym)?;
    }
    write!(fd,"\"{}\"];\n\n",&self.Gmr.Symbols[self.Gmr.Symbols.len()-1].sym)?;
    // position of symbols must be inline with self.Gmr.Symhash

    // record table entries in a static array
    let mut totalsize = 0;
    for i in 0..self.FSM.len() { totalsize+=self.FSM[i].len(); }
    write!(fd,"const TABLE:[u64;{}] = [",totalsize)?;
    // generate table to represent FSM
    let mut encode:u64 = 0;
    for i in 0..self.FSM.len() // for each state index i
    {
      let row = &self.FSM[i];
      for key in row.keys()
      { // see function decode for opposite translation
        let k = *self.Gmr.Symhash.get(key).unwrap(); // index of symbol
        encode = ((i as u64) << 48) + ((k as u64) << 32);
        match row.get(key) {
          Some(Shift(statei)) => { encode += (*statei as u64) << 16; },
          Some(Gotonext(statei)) => { encode += ((*statei as u64) << 16)+1; },
          Some(Reduce(rulei)) => { encode += ((*rulei as u64) << 16)+2; },
          Some(Accept) => {encode += 3; },
          _ => {encode += 4; },  // 4 indicates Error
        }//match
        write!(fd,"{},",encode)?;
      } //for symbol index k
    }//for each state index i
    write!(fd,"];\n\n")?;

    // must know what absyn type is when generating code.
    let ref absyn = self.Gmr.Absyntype;
    let ref extype = self.Gmr.Externtype;
    write!(fd,"pub fn make_parser() -> RuntimeParser<{},{}>",absyn,extype)?; 
    write!(fd,"\n{{\n")?;
    // write code to pop stack, assign labels to variables.
    write!(fd," let mut parser1:RuntimeParser<{},{}> = RuntimeParser::new({},{});\n",absyn,extype,self.Gmr.Rules.len(),self.States.len())?;
    // generate rules and Ruleaction delegates, must pop values from runtime stack
    write!(fd," let mut rule = RProduction::<{},{}>::new_skeleton(\"{}\");\n",absyn,extype,"start")?;
    for i in 0..self.Gmr.Rules.len() 
    {
      write!(fd," rule = RProduction::<{},{}>::new_skeleton(\"{}\");\n",absyn,extype,self.Gmr.Rules[i].lhs.sym)?;      
      write!(fd," rule.Ruleaction = |parser|{{ ")?;
      let mut k = self.Gmr.Rules[i].rhs.len();

      //form if-let labels and patterns as we go...
      let mut labels = String::from("(");
      let mut patterns = String::from("(");
      while k>0
      {
        let gsym = &self.Gmr.Rules[i].rhs[k-1];
	if gsym.label.len()>1 && gsym.label.find('@').is_some() { // if-let pattern
	  let atindex = gsym.label.find('@').unwrap();
	  let varlab = if atindex>0 {gsym.label[0..atindex].to_string()} 
	      else {format!("_vflab_{}",k-1)};
 	  if atindex>0 {labels.push_str("&mut ");}
	  labels.push_str(&varlab); labels.push(',');
	  patterns.push_str(&gsym.label[atindex+1..]); patterns.push_str(",");
	  write!(fd," let mut {}=",&varlab)?;	  
	}
	else if gsym.label.len()>0 { // simple pattern, no need for if-let
	  if gsym.rusttype.len()>=3 && &gsym.rusttype[0..3]=="mut" {
	    write!(fd," let mut {}:{}=",&gsym.label,absyn)?;
	  }
          else {write!(fd," let {}:{}=",&gsym.label,absyn)?;}
	}
        write!(fd,"parser.stack.pop()")?; 
        if gsym.label.len()>0 { write!(fd,".unwrap().value;  ")?;}
        else {write!(fd,";  ")?;}
        k -= 1;      
      }// for each symbol on right hand side of rule
      // form if-let clause
      let defaultaction = format!("return <{}>::default();}}",absyn);
      let mut semaction = &self.Gmr.Rules[i].action; //string that ends with }
      if semaction.len()<=1 {semaction = &defaultaction;}
      if labels.len()<2 { write!(fd,"{};\n",semaction.trim_end())?; } //empty pattern
      else { // write an if-let
        labels.push(')');  patterns.push(')');
	write!(fd,"\n  if let {}={} {{ {}  else {{parser.bad_pattern(\"{}\")}} }};\n",&patterns,&labels,semaction.trim_end(),&patterns)?;
      }// if-let semantic action

/*
      while k>0 // k-1 indexes backwards rhs of grammar rule
      {
        let gsym = &self.Gmr.Rules[i].rhs[k-1];
        if gsym.label.len()>0 && &gsym.rusttype[0..3]=="mut"
          { write!(fd," let mut {}:{}=",gsym.label,absyn)?; }        
        else if gsym.label.len()>0
          { write!(fd," let {}:{}=",gsym.label,absyn)?; }
        write!(fd,"parser.stack.pop()")?; 
        if gsym.label.len()>0 { write!(fd,".unwrap().value;  ")?;}
        else {write!(fd,";  ")?;}
        k -= 1;
      } // for each symbol on right hand side of rule  
      let mut semaction = &self.Gmr.Rules[i].action; //this is a string
      if semaction.len()>1 {write!(fd,"{};\n",semaction.trim_end())?;}
      else {write!(fd," return <{}>::default();}};\n",absyn)?;}
*/

      write!(fd," parser1.Rules.push(rule);\n")?;
    }// for each rule
    write!(fd," parser1.Errsym = \"{}\";\n",&self.Gmr.Errsym)?;
    // resynch vector
    for s in &self.Gmr.Resynch {write!(fd," parser1.resynch.insert(\"{}\");\n",s)?;}

    // generate code to load RSM from TABLE
    write!(fd,"\n for i in 0..{} {{\n",totalsize)?;
    write!(fd,"   let symi = ((TABLE[i] & 0x0000ffff00000000) >> 32) as usize;\n")?;
    write!(fd,"   let sti = ((TABLE[i] & 0xffff000000000000) >> 48) as usize;\n")?;
    write!(fd,"   parser1.RSM[sti].insert(SYMBOLS[symi],decode_action(TABLE[i]));\n }}\n\n")?;
//    write!(fd,"\n for i in 0..{} {{for k in 0..{} {{\n",rows,cols)?;
//    write!(fd,"   parser1.RSM[i].insert(SYMBOLS[k],decode_action(TABLE[i*{}+k]));\n }}}}\n",cols)?;
    write!(fd," for s in SYMBOLS {{ parser1.Symset.insert(s); }}\n\n")?;

    write!(fd," load_extras(&mut parser1);\n")?;
    write!(fd," return parser1;\n")?;
    write!(fd,"}} //make_parser\n\n")?;

    ////// Augment!
    write!(fd,"fn load_extras(parser:&mut RuntimeParser<{},{}>)\n{{\n",absyn,extype)?;
    write!(fd,"}}//end of load_extras: don't change this line as it affects augmentation\n")?;
    Ok(())
  }//writeparser


//////////////
///////////////// non-binary version (no augmentation) //////////////////
pub fn write_verbose(&self, filename:&str)->Result<(),std::io::Error>
  {
    let mut fd = File::create(filename)?;
    write!(fd,"//Parser generated by rustlr\n
#![allow(unused_variables)]
#![allow(non_snake_case)]
#![allow(non_camel_case_types)]
#![allow(unused_parens)]
#![allow(unused_mut)]
#![allow(unused_assignments)]
extern crate rustlr;
use rustlr::{{RuntimeParser,RProduction,Stateaction}};\n")?;

    write!(fd,"{}\n",&self.Gmr.Extras)?; // use clauses
    let ref absyn = self.Gmr.Absyntype;
    let ref extype = self.Gmr.Externtype;
    write!(fd,"pub fn make_parser() -> RuntimeParser<{},{}>",absyn,extype)?; 
    write!(fd,"\n{{\n")?;
    // write code to pop stack, assign labels to variables.
    write!(fd," let mut parser1:RuntimeParser<{},{}> = RuntimeParser::new({},{});\n",absyn,extype,self.Gmr.Rules.len(),self.States.len())?;
    // generate rules and Ruleaction delegates, must pop values from runtime stack
    write!(fd," let mut rule = RProduction::<{},{}>::new_skeleton(\"{}\");\n",absyn,extype,"start")?;
    for i in 0..self.Gmr.Rules.len() 
    {
      write!(fd," rule = RProduction::<{},{}>::new_skeleton(\"{}\");\n",absyn,extype,self.Gmr.Rules[i].lhs.sym)?;      
      write!(fd," rule.Ruleaction = |parser|{{ ")?;
      let mut k = self.Gmr.Rules[i].rhs.len();
      while k>0
      {
        let gsym = &self.Gmr.Rules[i].rhs[k-1];
        if gsym.label.len()>0 && &gsym.rusttype[0..3]=="mut"
          { write!(fd," let mut {}:{}=",gsym.label,absyn)?; }        
        else if gsym.label.len()>0
          { write!(fd," let {}:{}=",gsym.label,absyn)?; }
        write!(fd,"parser.stack.pop()")?; 
        if gsym.label.len()>0 { write!(fd,".unwrap().value;  ")?;}
        else {write!(fd,";  ")?;}
        k -= 1;
      } // for each symbol on right hand side of rule  
      let mut semaction = &self.Gmr.Rules[i].action; //this is a string
      //if semaction.len()<1 {semaction = "}}";}
      //if al>1 {semaction = semaction.substring(0,al-1);}
      if semaction.len()>1 {write!(fd,"{};\n",semaction.trim_end())?;}
      else {write!(fd," return <{}>::default();}};\n",absyn)?;}
      write!(fd," parser1.Rules.push(rule);\n")?;
    }// for each rule
    write!(fd," parser1.Errsym = \"{}\";\n",&self.Gmr.Errsym)?;
    // resynch vector
    for s in &self.Gmr.Resynch {write!(fd," parser1.resynch.insert(\"{}\");\n",s)?;}
    
    for i in 0..self.FSM.len()
    {
      let row = &self.FSM[i];
      for key in row.keys()
      {
        write!(fd," parser1.RSM[{}].insert(\"{}\",Stateaction::{:?});\n",i,key,row.get(key).unwrap())?;
      } //for each string key in row
    }//for each state index i

    write!(fd," return parser1;\n")?;
    write!(fd,"}} //make_parser\n")?;
    Ok(())
  }//write_verbose

} // impl Statemachine


//// independent function
    fn iserror(actionopt:&Option<&Stateaction>) -> bool
    {
       match actionopt {
           None => true,
           Some(Error(_)) => true,
           _ => false,
         }
    }//iserror





///////////////////////////////////////////////////////////////////////////
////// reimplementing the parsing algorithm more modularly, with aim of
////// allowing custom parsers
//////////// errors should compile a report

impl<AT:Default,ET:Default> RuntimeParser<AT,ET>
{
  /// this function is used to invoke the generated parser returned by
  /// the generated parser program's make_parser function.  *This function
  /// is equivalent to [RuntimeParser::parse_stdio]*.
  pub fn parse(&mut self, tokenizer:&mut dyn Lexer<AT>) -> AT
  {
     self.parse_stdio(tokenizer)
  }

  /// Error recovery routine of rustlr, separate from error_reporter.
  /// This function will modify the parser and lookahead symbol and return
  /// either the next action the parser should take (if recovery succeeded)
  /// or None if recovery failed.
  pub fn error_recover<'t>(&mut self, lookahead:&mut Lextoken<AT>,tokenizer:&mut dyn Lexer<AT>) -> Option<Stateaction>
  {
    let mut erraction = None;
    ///// prefer to ue Errsym method
    if self.Errsym.len()>0 {
      let errsym = self.Errsym;
      // lookdown stack for state with trainsiton on Errsym
      // but that could be current state too (start at top)
      let mut k = self.stack.len(); // offset by 1 because of usize
      let mut spos = k+1;
      while k>0 && spos>k
      {
        let ksi = self.stack[k-1].si;
        erraction = self.RSM[ksi].get(errsym);
        if let None = erraction {k-=1;} else {spos=k;}
      }//while k>0
      if spos==k { self.stack.truncate(k); } // new current state revealed
      // run all reduce actions that are valid before the Errsym:
      while let Some(Reduce(ri)) = erraction // keep reducing
      {
       //self.reduce(ri); // borrow error- only need mut self.stack
              let rulei = &self.Rules[*ri];
              let ruleilhs = rulei.lhs; // &'static : Copy
              let val = (rulei.Ruleaction)(self); // calls delegate function
              let newtop = self.stack[self.stack.len()-1].si; 
              let gotonopt = self.RSM[newtop].get(ruleilhs);
              match gotonopt {
                Some(Gotonext(nsi)) => { 
                  self.stack.push(Stackelement{si:*nsi,value:val});
                },// goto next state after reduce
                _ => {self.abort("recovery failed"); },
              }//match
              // end reduce
              let tos=self.stack[self.stack.len()-1].si;
              erraction = self.RSM[tos].get(self.Errsym);
      } // while let erraction is reduce
      // remaining defined action on Errsym must be shift
      if let Some(Shift(i)) = erraction { // simulate shift errsym 
          self.stack.push(Stackelement{si:*i,value:AT::default()});
          // keep lookahead until action is found that transitions from
          // current state (i). but skipping ahead without reducing
          // the error production is not a good idea
          while let None = self.RSM[*i].get(&lookahead.sym[..]) {
            if &lookahead.sym[..]=="EOF" {break;}
            *lookahead = self.nexttoken(tokenizer);
          }//while let
          // either at end of input or found action on next symbol
          erraction = self.RSM[*i].get(&lookahead.sym[..]);
      } // if shift action found down under stack
    }//errsym exists

    // at this point, if erraction is None, then Errsym failed to recover,
    // try the resynch symbol method next ...
    if iserror(&erraction) && self.resynch.len()>0 {
      while &lookahead.sym!="EOF" &&
        !self.resynch.contains(&lookahead.sym[..]) {
        self.linenum = tokenizer.linenum(); self.column = tokenizer.column();
        *lookahead = self.nexttoken(tokenizer);
      }//while
      if &lookahead.sym!="EOF" {
        // look for state on stack that has action defined on next symbol
        self.linenum = tokenizer.linenum(); self.column = tokenizer.column();    
        *lookahead = self.nexttoken(tokenizer); // skipp err-causing symbol
      }
      let mut k = self.stack.len()-1; // offset by 1 because of usize
      let mut position = 0;
      while k>0 && erraction==None
      {
         let ksi = self.stack[k-1].si;
         erraction = self.RSM[ksi].get(&lookahead.sym[..]);
         if let None=erraction {k-=1;}
      }//while k>0 && erraction==None
      match erraction {
        None => {}, // do nothing, whill shift next symbol
        _ => { self.stack.truncate(k);},//pop stack
      }//match
   }// there are resync symbols

   // at this point, if erraction is None, then resynch recovery failed too.
   // only action left is to skip ahead...
   let mut eofcx = 0;
   while iserror(&erraction) && eofcx<1 { //skip input
      self.linenum = tokenizer.linenum(); self.column = tokenizer.column();
      *lookahead = self.nexttoken(tokenizer);
      if &lookahead.sym=="EOF" {eofcx+=1;}
      let csi =self.stack[self.stack.len()-1].si;
      erraction = self.RSM[csi].get(&lookahead.sym[..]);
   }// skip ahead
   match erraction {
     None => None,
     Some(act) => Some(*act),
   }//return match
  }//error_recover function

}//impl RuntimeParser 2


/////////////////////////////////////////////////////////////////////////
/////////////// new approach using more flexible trait object

/// A trait object that implements ErrHandler is expected by the [RuntimeParser::parse_base]
/// function, which implements the basic LR parsing algorithm using the
/// generated state machine.  The struct [StandardReporter] is provided as
/// the default ErrHandler that uses standard I/O as interface and has the
/// ability to train the parser.  But other implementations of the trait
/// can be created that use different interfaces, such as a graphical IDE.
pub trait ErrHandler<AT:Default,ET:Default> // not same as error recovery
{
  fn err_reporter(&mut self, parser:&mut RuntimeParser<AT,ET>, lookahead:&Lextoken<AT>, erropt:&Option<Stateaction>);
  fn report_err(&self, parser:&mut RuntimeParser<AT,ET>, msg:&str) { parser.report(msg) }
//  fn training_mode(&self, parser:&RuntimeParser<AT,ET>) -> bool {false}
//  fn interactive_mode(&self, parser:&RuntimeParser<AT,ET>) -> bool {false}
}// ErrHandler trait

/*
The structure here is a bit strange.  The script file is written to in
interactive training mode and read from in script-training mode.  However,
the actual modification of the parser file is done after the training, by
the augmenter module.  Thus there's another wrapper function that's needed
besides the creation of the right kind of StandardReporter.
*/

/// these objects implement the [ErrHandler] trait.  They are used in the
/// [RuntimeParser::parse_stdio], [RuntimeParser::parse_stdio_train] and
/// [RuntimeParser::train_from_script] functions.
pub struct StandardReporter
{
  pub  training : bool,
  //    pub  interactive : bool,  scriptinopt==None
  pub  trained : HashMap<(usize,String),String>,
  pub scriptinopt:  Option<BufReader<File>>,   // for training from script
  pub scriptoutopt: Option<File>,   // created during interactive training
}
impl StandardReporter
{
  /// creates default standard reporter, used by parse_stdio (does not train)
  pub fn new() -> StandardReporter
  {
    StandardReporter {
      training:false, trained:HashMap::new(), scriptinopt:None, scriptoutopt:None,}
  }
  /// creates a stdio error handler with interactive training, takes as
  /// argument parser file name, to create script for future retraining.
  pub fn new_interactive_training(existingparser:&str) -> StandardReporter
  {
    let outfile =  format!("{}_script.txt", existingparser);
    let mut fout = File::create(outfile).expect("failed to create training script file");
    let _ = write!(fout,"# Rustlr training script for {}\n\n",existingparser);
    StandardReporter {
      training:true, trained:HashMap::with_capacity(8),
      scriptoutopt:Some(fout), scriptinopt:None,}     
  }
  /// creates a stdio error handler that trains (non-interactively) from
  /// a previously created script.  It's the user's responsibility to match
  /// the script file with the input source.
  pub fn new_script_training(existingparser:&str,scriptfile:&str) -> StandardReporter
  {
    let fin = BufReader::new(File::open(scriptfile).expect("failed to open training script file"));
    StandardReporter {
      training:true, trained:HashMap::with_capacity(32),
      scriptoutopt:None,
      scriptinopt:Some(fin), }     
  }  
  // augment_train implemented in augmenter.rs
}//impl StandardReporter

impl<AT:Default,ET:Default> ErrHandler<AT,ET> for StandardReporter
{
  // this function will be able to write training script to file
  fn err_reporter(&mut self, parser:&mut RuntimeParser<AT,ET>, lookahead:&Lextoken<AT>, erropt:&Option<Stateaction>)
 { 
  let mut wresult:std::io::Result<()> = Err(std::io::Error::new(std::io::ErrorKind::Other,"")); // dummy
  // known that actionop is None or Some(Error(_))
  let cstate = parser.stack[parser.stack.len()-1].si; // current state
  let mut actionopt = if let Some(act)=erropt {Some(act)} else {None};
  let lksym = &lookahead.sym[..];
  // is lookahead recognized as a grammar symbol?
  // if actionopt is NONE, check entry for ANY_ERROR            
  if parser.Symset.contains(lksym) {
     if let None=actionopt {
        actionopt = parser.RSM[cstate].get("ANY_ERROR");
     }
  }// lookahead is recognized grammar sym
  else {
     actionopt = parser.RSM[cstate].get("ANY_ERROR");
  }// lookahead is not a grammar sym
  let errmsg = if let Some(Error(em)) = &actionopt {
    format!("unexpected symbol {}, ** {} ** ..",lksym,em.trim())
  } else {format!("unexpected symbol {} .. ",lksym)};

  parser.report(&errmsg);

  if self.training {          ////// Training mode
    let csym = lookahead.sym.clone();
    let mut inp = String::from("");    
   if let None=self.scriptinopt {  // interactive mode
   if let Some(outfd1) = &self.scriptoutopt {
    let mut outfd = outfd1;
    print!("\n>>>TRAINER: if this message is not adequate (for state {}), enter a replacement (default no change): ",cstate);
    let rrrflush = io::stdout().flush();
    if let Ok(n) = io::stdin().read_line(&mut inp) {
       if inp.len()>5 && parser.Symset.contains(lksym) {
         print!(">>>TRAINER: should this message be given for all unexpected symbols in the current state? (default yes) ");
        let rrrflush2 = io::stdout().flush();
        let mut inp2 = String::new();
        if let Ok(n) = io::stdin().read_line(&mut inp2) {
            if inp2.trim()=="no" || inp2.trim()=="No" {
               wresult = write!(outfd,"{}\t{}\t{} ::: {}\n",parser.linenum,parser.column,&csym,inp.trim());
               self.trained.insert((cstate,csym),inp);
            }
            else  {// insert for any error
               wresult = write!(outfd,"{}\t{}\t{} ::: {}\n",parser.linenum,parser.column,"ANY_ERROR",inp.trim());
               self.trained.insert((cstate,String::from("ANY_ERROR")),inp);
            }
        }// read ok
       }// unexpected symbol is grammar sym
       else if inp.len()>5 && !parser.Symset.contains(lksym) {
         wresult = write!(outfd,"{}\t{}\t{} ::: {}\n",parser.linenum,parser.column,"ANY_ERROR",inp.trim());
         self.trained.insert((cstate,String::from("ANY_ERROR")),inp);
       }
    }// process user response
   }}// interactive mode
   else { // training from script mode (non-interactive)
    if let Some(brfd) = &mut self.scriptinopt {
     let mut scin = brfd;
     let mut readn = 0;
     while readn < 1
     {
       inp = String::new();
       match scin.read_line(&mut inp) {
         Ok(n) if n>1 && &inp[0..1]!="#" && inp.trim().len()>0 => {readn=n;},
         Ok(n) if n>0 => { readn=0; }, // keep reading
         _ => {readn = 1; } // stop - this means End of Stream
       }//match
       if readn>1 { // read something
         let inpsplit:Vec<&str> = inp.split_whitespace().collect();
         if inpsplit.len()>4 && inpsplit[3].trim()==":::" {
           let inline = inpsplit[0].trim().parse::<usize>().unwrap();
           let incolumn = inpsplit[1].trim().parse::<usize>().unwrap();
           let insym = inpsplit[2].trim();
           if parser.linenum==inline && parser.column==incolumn {
             if &csym==insym || insym=="ANY_ERROR" {
               let posc = inp.find(":::").unwrap()+4;
               println!("\n>>>Found matching entry from training script for {}, error message: {}",insym,&inp[posc..]);
               self.trained.insert((cstate,String::from(insym)),String::from(&inp[posc..]));
             } // unexpected symbol match
           }// line/column match
         }//inpsplit check
       }// valid training line read
     }//while readn<2
   }}//training from script mode
  }//if training   //// END TRAINING MODE
  
 }// standardreporter function
}// impl ErrHandler for StandardReporter


//////////////// temporary: live side by side with parse_core (tobe replaced)
impl<AT:Default,ET:Default> RuntimeParser<AT,ET>
{
  /// Core parser (temporarily lives side by side with parse_core) that
  /// takes dynamic trait objects for lexical scanning and err_reporting.
  /// This design makes it possible to create a custom error reporting
  /// interface.
  pub fn parse_base(&mut self, tokenizer:&mut dyn Lexer<AT>, err_handler:&mut dyn ErrHandler<AT,ET>) -> AT
  {
    self.stack.clear();
    self.err_occurred = false;
    let mut result = AT::default();
    self.stack.push(Stackelement {si:0, value:AT::default()});
    self.stopparsing = false;
    let mut action = Stateaction::Error("");
    let mut lookahead = Lextoken{sym:"EOF".to_owned(),value:AT::default()};
    if let Some(tok) = tokenizer.nextsym() {lookahead=tok;}
    else {self.stopparsing=true;}

    while !self.stopparsing
    {
      self.linenum = tokenizer.linenum(); self.column=tokenizer.column();
      let currentstate = self.stack[self.stack.len()-1].si;
      let mut actionopt = self.RSM[currentstate].get(lookahead.sym.as_str());
      let actclone:Option<Stateaction> = match actionopt {
        Some(a) => Some(*a),
        None => None,
      };
      if iserror(&actionopt) {  // either None or Error
        if !self.err_occurred {self.err_occurred = true;}
        
        err_handler.err_reporter(self,&lookahead,&actclone);
        //err_reporter(self,&lookahead,&actclone);
        
        match self.error_recover(&mut lookahead,tokenizer) {
          None => { self.stopparsing=true; break; }
          Some(act) => {action = act;},
        }//match
      }// iserror
      else { action = actclone.unwrap(); }
      match &action {
        Shift(nextstate) => {
           lookahead = self.shift(*nextstate,lookahead,tokenizer);
        },
        Reduce(rulei) => { self.reduce(rulei); },
        Accept => {
          self.stopparsing=true;
          if self.stack.len()>0 {result = self.stack.pop().unwrap().value;}
          else {self.err_occurred=true;}
        },
        _ => {}, // continue
      }//match action
    }// main parse loop
    return result;
  }//parse_base

  ///provided generic parsing function that reports errors on std::io. This
  ///function is equivalent to [RuntimeParser::parse].
  pub fn parse_stdio(&mut self, tokenizer:&mut dyn Lexer<AT>) -> AT
  {
    let mut stdeh = StandardReporter::new();
    self.parse_base(tokenizer,&mut stdeh) 
  }//parse_stdio

  ///Parses in interactive training mode with provided path to parserfile.
  ///The parser file will be modified and a training script file will be
  ///created for future retraining after grammar is modified. This function
  ///is equivalent to [RuntimeParser::parse_train].
  ///
  /// When an error occurs, the parser will
    /// ask the human trainer for an appropriate error message: it will
    /// then insert an entry into its state transition table to
    /// give the same error message on future errors of the same type.
    /// If the error is caused by an unexpected token that is recognized
    /// as a terminal symbol of the grammar, the trainer can select to
    /// enter the entry 
    /// under the reserved ANY_ERROR symbol. If the unexpected token is
    /// not recognized as a grammar symbol, then the entry will always
    /// be entered under ANY_ERROR.  ANY_ERROR entries for a state will match
    /// all future unexpected symbols for that state: however, entries for
    /// valid grammar symbols will still override the generic entry.
    ///
    /// Example: with the parser for this [toy grammar](https://cs.hofstra.edu/~cscccl/rustlr_project/cpm.grammar), parse_train can run as follows:
    ///```ignore
    ///  Write something in C+- : cout << x y ;   
    ///  ERROR on line 1, column 0: unexpected symbol y ..
    ///  >>>TRAINER: is this error message adequate? If not, enter a better one: need another <<                   
    ///  >>>TRAINER: should this message be given for all unexpected symbols in the current state? (default yes) yes
    ///```
    /// (ignore the column number as the lexer for this toy language does not implement it)
    ///
    /// parse_train will then produced a [modified parser](https://cs.hofstra.edu/~cscccl/rustlr_project/cpmparser.rs) as specified
    /// by the filename (path) argument.  When the augmented parser is used, it will
    /// give a more helpful error message:
    ///```
    /// Write something in C+- : cout << x endl
    /// ERROR on line 1, column 0: unexpected symbol endl, ** need another << ** ..
    ///```
    ///
    /// parse_stdio_train calls parse_stdio, which uses stdin/stdout for user interface.
    /// Parsing in interactive training mode also produces a [training script file](http://cs.hofstra.edu/~cscccl/rustlr_project/cpmparser.rs_script.txt) which can
    /// be used to re-train a parser using [RuntimeParser::train_from_script]. 
    /// This is useful after a grammar is modified with extensions to a language.
  pub fn parse_stdio_train(&mut self, tokenizer:&mut dyn Lexer<AT>, parserfile:&str) -> AT
    {
      let mut stdtrainer = StandardReporter::new_interactive_training(parserfile);
      let result = self.parse_base(tokenizer,&mut stdtrainer);
      if let Err(m) = stdtrainer.augment_training(parserfile) {
        eprintln!("Error in augmenting parser: {:?}",m)
      }

      return result;
    }//parse_stdio_train

  /// trains parser from a [training script](https://cs.hofstra.edu/~cscccl/rustlr_project/cpmparser.rs_script.txt)
  /// created by interactive training.  This
  /// is intended to be used after a grammar has been modified and the parser
  /// is regenerated with different state numbers.  It is the user's
  /// responsibility to keep consistent the parser file, script file, and sample
  /// input that was used when the script was created.  The script contains
  /// the line and column numbers of each error encountered, along with either
  /// the unexpected symbol that caused the error, or the reserved ANY_ERROR
  /// symbol if the error message is to be applied to all unexpected symbols.
  /// These entries must match, in sequence, the errors encountered during
  /// retraining - it is therefore recommended that the same tokenizer be used
  /// during retraining so that the same line/column information are given.
  /// The trainer will augment the parser (parserfile) with new Error
  /// entries, overriding any previous ones.  It is also recommended that the
  /// user examines the "load_extras" function that appears at the end of
  /// the [augmented parser](https://cs.hofstra.edu/~cscccl/rustlr_project/cpmparser.rs).
  /// The train_from_script function does not return
  /// a value, unlike [RuntimeParser::parse_stdio] and [RuntimeParser::parse_stdio_train].
  pub fn train_from_script(&mut self, tokenizer:&mut dyn Lexer<AT>, parserfile:&str, scriptfile:&str)
  {
      let mut stdtrainer = StandardReporter::new_script_training(parserfile,scriptfile);
      let result = self.parse_base(tokenizer,&mut stdtrainer);
      if let Err(m) = stdtrainer.augment_training(parserfile) {
        eprintln!("Error in augmenting parser: {:?}",m)
      }
      if !self.err_occurred {println!("no errors encountered during parsing");}
  }//train_from_script

}// 3rd impl RuntimeParser