/*
Copyright 2015-2022 Ian Jauslin

Licensed under the Apache License, Version 2.0 (the "License");
you may not use this file except in compliance with the License.
You may obtain a copy of the License at

    http://www.apache.org/licenses/LICENSE-2.0

Unless required by applicable law or agreed to in writing, software
distributed under the License is distributed on an "AS IS" BASIS,
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
See the License for the specific language governing permissions and
limitations under the License.
*/

#include "symbolic_parser.h"
#include <stdlib.h>
#include <stdio.h>
#include "tree.h"
#include "definitions.cpp"
#include "array.h"
#include "istring.h"
#include "fields.h"
#include "polynomial.h"

#define SP_NULL_MODE 0
#define SP_FUNCTION_MODE 1

// parse a symbolic expression from a char_array
int parse_symbolic_expression(Char_Array str, Fields_Table fields, Variables variables, Polynomial* polynomial){
  Tree symbol_tree;
  char_array_to_symbol_tree(str, &symbol_tree);
  resolve_symbol_tree(symbol_tree, fields, variables, polynomial);
  free_Tree(symbol_tree);
  return(0);
}
// from char*
int parse_symbolic_expression_str(char* str, Fields_Table fields, Variables variables, Polynomial* polynomial){
  Char_Array char_array;
  str_to_char_array(str,&char_array);
  parse_symbolic_expression(char_array, fields, variables, polynomial);
  free_Char_Array(char_array);
  return(0);
}

// compute the symbol tree from a string
int char_array_to_symbol_tree(Char_Array str, Tree* symbol_tree){
  // buffer
  char* buffer=calloc(str.length+1,sizeof(char));
  char* buffer_ptr=buffer;
  Tree child;
  int match;
  Char_Array nodestr;
  Char_Array label;
  Char_Array str_clean;
  int mode;
  int comment=0;
  int j;
  int gotanode=0;

  // allocate memory
  init_Tree(symbol_tree,SYMBOL_TREE_SIZE, SYMBOL_TREE_LABEL_SIZE);

  // remove comments, ' ' and '\n'
  init_Char_Array(&str_clean,str.length);
  for(j=0;j<str.length;j++){
    if(comment==1){
      if(str.str[j]=='\n'){
	comment=0;
      }
    }
    else{
      switch(str.str[j]){
      case ' ':break;
      case '\n':break;
      // comments
      case '#':
	comment=1;
	break;
      default:
	char_array_append(str.str[j],&str_clean);
	break;
      }
    }
  }

  // if the string contains no '<', then trivial tree
  for(j=0;j<str_clean.length;j++){
    if(str_clean.str[j]=='<'){
      break;
    }
  }
  // no '<': trivial tree
  if(j==str_clean.length){
    tree_set_label(str_clean, symbol_tree);
    free(buffer);
    free_Char_Array(str_clean);
    return(0);
  }

  *buffer_ptr='\0';
  // loop over the input string
  // start in null mode
  mode=SP_NULL_MODE;
  for(j=0;j<str_clean.length;j++){
    switch(str_clean.str[j]){
    // new node
    case '<':
      // find matching bracket
      match=matching_bracket(str_clean,j);
      // check whether it exists
      if(match<0){
	fprintf(stderr,"syntax error: unmatched brackets in %s\n",char_array_to_str_noinit(&str));
	exit(-1);
      }
      // extract substring until bracket
      char_array_substring(str_clean,j+1,match-1,&nodestr);

      // check whether node is trivial
      if(j==0 && match==str_clean.length-1){
	free_Tree(*symbol_tree);
	char_array_to_symbol_tree(nodestr, symbol_tree);
	free_Char_Array(nodestr);
	j=match;
	break;
      }

      // parse subexpression
      char_array_to_symbol_tree(nodestr, &child);
      free_Char_Array(nodestr);
      // add child to tree
      tree_append_child_noinit(child, symbol_tree);
      // boolean indicating a node has been found
      gotanode=1;
      // set next position after the node
      j=match;

      // if function mode, then check that the match is at the end of the node
      if(mode==SP_FUNCTION_MODE){
	if(match<str_clean.length-1){
	  fprintf(stderr,"syntax error: functions must occupy an entire node (e.g. <%%exp<...>>), got %s\n",char_array_to_str_noinit(&str));
	  exit(-1);
	}
	else{
	  // set label
	  str_to_char_array(buffer,&label);
	  tree_set_label(label,symbol_tree);
	  free_Char_Array(label);
	}
      }
      break;

    // function
    case '%':
      if(j>0){
	fprintf(stderr,"syntax error: functions must occupy an entire node (e.g. <%%exp<...>>), got %s\n",char_array_to_str_noinit(&str));
	exit(-1);
      }
      mode=SP_FUNCTION_MODE;
      break;

    // product
    case '*':
      if(gotanode==0){
	fprintf(stderr,"syntax error: '*' is not preceded by a node in %s\n",char_array_to_str_noinit(&str));
	exit(-1);
      }
      if(j>=str_clean.length-1){
	fprintf(stderr,"syntax error: '*' cannot be at the end of an expression, got %s\n",char_array_to_str_noinit(&str));
	exit(-1);
      }
      // set label
      init_Char_Array(&label,1);
      char_array_append('*',&label);
      tree_set_label(label,symbol_tree);
      free_Char_Array(label);
      // next child
      char_array_substring(str_clean,j+1,str_clean.length-1,&nodestr);
      // parse subexpression
      char_array_to_symbol_tree(nodestr, &child);
      free_Char_Array(nodestr);
      // append next child
      tree_append_child_noinit(child, symbol_tree);

      // make it stop
      j=str_clean.length-1;
      break;

    // sum
    case '+':
      if(gotanode==0){
	fprintf(stderr,"syntax error: '+' is not preceded by a node in %s\n",char_array_to_str_noinit(&str));
	exit(-1);
      }
      if(j>=str_clean.length-1){
	fprintf(stderr,"syntax error: '+' cannot be at the end of an expression, got %s\n",char_array_to_str_noinit(&str));
	exit(-1);
      }
      // set label
      init_Char_Array(&label,1);
      char_array_append('+',&label);
      tree_set_label(label,symbol_tree);
      free_Char_Array(label);
      // next child
      char_array_substring(str_clean,j+1,str_clean.length-1,&nodestr);
      // parse subexpression
      char_array_to_symbol_tree(nodestr, &child);
      free_Char_Array(nodestr);
      // append next child
      tree_append_child_noinit(child, symbol_tree);

      // make it stop
      j=str_clean.length-1;
      break;

    default:
      if(mode!=SP_NULL_MODE){
	// write to buffer
	buffer_ptr=str_addchar(buffer_ptr,str_clean.str[j]);
      }
      break;
    }
  }

  free_Char_Array(str_clean);
  free(buffer);
  return(0);
}
// from char*
int str_to_symbol_tree(char* str, Tree* symbol_tree){
  Char_Array char_array;
  str_to_char_array(str,&char_array);
  char_array_to_symbol_tree(char_array,symbol_tree);
  free_Char_Array(char_array);
  return(0);
}


// find matching '<' and '>'
int matching_bracket(Char_Array str, int start){
  int bracket_count=0;
  int i;
  for(i=start;i<str.length;i++){
    if(str.str[i]=='<'){
      bracket_count++;
    }
    else if(str.str[i]=='>'){
      bracket_count--;
      if(bracket_count==0){
	return(i);
      }
    }
  }
  // if the function has not returned, then no matching bracket
  return(-1);
}


// resolve a symbol tree to its corresponding polynomial
int resolve_symbol_tree(Tree symbol_tree, Fields_Table fields, Variables variables, Polynomial* output){
  Polynomial poly;
  Tree variable_tree;

  // trivial tree
  if(symbol_tree.length==0){
    // variable
    if(symbol_tree.root_label.length>0 && symbol_tree.root_label.str[0]=='$'){
      variables_find_var(symbol_tree.root_label, variables, &variable_tree);
      resolve_symbol_tree(variable_tree, fields, variables, output);
      free_Tree(variable_tree);
    }
    //polynomial
    else{
      Char_Array_to_Polynomial(symbol_tree.root_label, output);
    }
  }

  // exp
  else if (char_array_cmp_str(symbol_tree.root_label,"exp")==1){
    if(symbol_tree.length!=1){
      fprintf(stderr,"syntax error: exp must have 1 argument\n");
      exit(-1);
    }
    resolve_symbol_tree(symbol_tree.children[0], fields, variables, &poly);
    polynomial_exponential(poly, output, fields);
    free_Polynomial(poly);
  }

  // log
  else if (char_array_cmp_str(symbol_tree.root_label,"log_1")==1){
    if(symbol_tree.length!=1){
      fprintf(stderr,"syntax error: log_1 must have 1 argument\n");
      exit(-1);
    }
    resolve_symbol_tree(symbol_tree.children[0], fields, variables, &poly);
    polynomial_logarithm(poly, output, fields);
    free_Polynomial(poly);
  }

  // product
  else if (char_array_cmp_str(symbol_tree.root_label,"*")==1){
    if(symbol_tree.length!=2){
      fprintf(stderr,"syntax error: '*' must have 2 arguments\n");
      exit(-1);
    }
    resolve_symbol_tree(symbol_tree.children[0], fields, variables, output);
    resolve_symbol_tree(symbol_tree.children[1], fields, variables, &poly);
    polynomial_prod_chain(poly, output, fields);
    free_Polynomial(poly);
  }

  // sum
  else if (char_array_cmp_str(symbol_tree.root_label,"+")==1){
    if(symbol_tree.length!=2){
      fprintf(stderr,"syntax error: '+' must have 2 arguments\n");
      exit(-1);
    }
    resolve_symbol_tree(symbol_tree.children[0], fields, variables, output);
    resolve_symbol_tree(symbol_tree.children[1], fields, variables, &poly);
    polynomial_add_chain_noinit(poly, output, fields);
  }

  else{
    fprintf(stderr,"syntax error: unrecognized operation '%s'\n",char_array_to_str_noinit(&(symbol_tree.root_label)));
    exit(-1);
  }

  return(0);
}