/*
  linked-list symbol table
*/
#include <stdio.h>
#include <stdlib.h>
#include <string.h>

#include "ss.h"
#include "parse.h"

const char *symbol_format = "%g";

void install_symbol_format( const char *fmt)
{
  symbol_format = fmt;
}

/*** head and tail of the symbol table ***/

static Symbol *chead = NULL, *head = NULL, *tail = NULL;

/* chead -> constants -> ... (head) -> variables -> ... */

/*** internal functions: new_name, new_symbol  ***/

/* create unique names for unnamed "" symbols */

static char *new_name( void)
{
  static int n = 0;
  static char buf[32];

  ++n;
  sprintf( buf, "$%d", n);
  return estrdup( buf);
}
   
/* allocate new symbol, exit if malloc fails */

static Symbol *new_symbol( const char *name, int constant, double val)
{
  Symbol *e = malloc( sizeof( Symbol) );

  if( e == NULL)
  {
    yyerror( "new_symbol: malloc failed");
    exit(1);
  }

  e->name = *name ? name : new_name();
  e->constant = constant;
  e->val = val;
  e->state = constant ? EVALUATED : UNEVALUATED;
  e->depend = NULL;
  e->n = NULL;
  e->next = NULL;

  return e;
}

/* install constant in symbol table */

void install_constant( const char *name, double val)
{
  Symbol *e = new_symbol( name, 1, val);

  if( chead == NULL)
  {
    chead = tail = e;
  }
  else
  {
    tail->next = e;
    tail = e;
  }
}

/* try to find name in symbol table */

Symbol *find_symbol( const char *name)
{
  Symbol *e;

  for( e = chead; e; e = e->next)
    if( strcmp( e->name, name) == 0)
      return e;

  return NULL;
}

/* lookup name in symbol table, install if not found */

Symbol *lookup_symbol( const char *name)
{
  Symbol *e;

  if( *name && (e = find_symbol( name)) )
    return e;

  e = new_symbol( name, 0, 0.0);

  /* chead and tail are not NULL since constants were installed at startup */

  tail->next = e;
  tail = e;

  if( head == NULL)
    head = tail;

  return e;
}

/* install formula in symbol table */

void install_symbol( Symbol *e, Node *n)
{
  if( e->constant)
  {
    fprintf( out, "warning: can not change constant %s = ", e->name);
    fprintf( out, symbol_format, e->val);
    fprintf( out, "\n");
    return;
  }

  if( e->n) fprintf( out, "warning: overwriting symbol %s\n", e->name);

  if( n->type == NUMBER)
  {
    e->val = n->u.val;
    e->state = EVALUATED;
    e->n = NULL;
  }
  else
  {
    e->n = n;

    if( n->type == STRING)
    {
      e->state = EVALUATED;
    }
    else
    {
      install_tree( n, &cell_00, 1);
      e->state = UNEVALUATED;
    }
  }
}

/* evaluate the symbol table - called only from ss_eval() */

int eval_symbols( void)
{
  Symbol *e;
  double oldval;
  int changed = 0;

  for( e = head; e; e = e->next)
  {
    if( debug)
    {
      fprintf( out, "eval_symbols: %s, state = %d", e->name, e->state);
      if( e->depend) fprintf( out, " - depends on %s", e->depend->name);
      else if( !e->n || e->n->type == STRING) fprintf( out, " - constant");
      putc( '\n', out);
    }

    if( depend)
    {
      eval_symbol(e); // sets e->val if necessary
    }
    else if( e->n)
    {
      oldval = e->val;
      e->val = eval_tree( e->n, &cell_00);
      if( oldval != e->val)
        changed = 1;
    }
  }

  return changed;
}

/* set non-constant symbol states to UNEVALUATED */

void reset_symbols( void)
{
  Symbol *e;

  for( e = head; e; e = e->next)
    if( e->depend || (e->n != NULL && e->n->type != STRING))
      e->state = UNEVALUATED;
}

/* print one symbol */

static void print_symbol( const Symbol *e)
{
  fprintf( out, "  %s", e->name);

  if( e->n)
  {
    int t = func[e->n->type]->type;

    if( *e->name && (!t || !(t & SS_ASGN)) )
      fprintf( out, " = ");

    print_tree( e->n, &cell_00, 0);
  }

  fprintf( out, " = ");
  fprintf( out, symbol_format, e->val);
  fprintf( out, "\n");
}

/* print the symbol table list, except for constants */

void print_symbols( void)
{
  Symbol *e;

  for( e = head; e; e = e->next)
    print_symbol( e);
}

/* print the symbol table list constants */

void print_constants( void)
{
  Symbol *e;

  fprintf( out, "Constants:\n");

  for( e = chead; e != head ; e = e->next)
  {
    fprintf( out, "  %s = ", e->name);
    fprintf( out, symbol_format, e->val);
    fprintf( out, "\n");
  }
}

/* print the symbol table list states */

void print_symbol_states( void)
{
  Symbol *e;

  fprintf( out, "States:\n");

  for( e = chead; e; e = e->next)
  {
    if( e->depend)
      fprintf( out, "  %d (%s) %s\n", e->state, e->depend->name, e->name);
    else
      fprintf( out, "  %d %s\n", e->state, e->name);
  }
}