#include <stdio.h>
#include <string.h>
#include <stdlib.h>
#include <assert.h>
#include "symboltable.h"

#define MAX_KEY 256
#define SIZE 109

#define MAX_STACK 256
static char* undo_stack[MAX_STACK];
static int undo_sp = 0;

void undo_stack_push(char* s) {
  undo_stack[undo_sp++] = s;
}

char* undo_stack_pop() {
  char *s = undo_stack[--undo_sp];
  return s;
}

extern void yyerror(char* err);

void yyerror(char* err) {
  fprintf(stderr, "%s\n", err);
}

typedef struct _bucket {
  char key[MAX_KEY];
  struct _bucket* next;
  void* binding;
} bucket;

static bucket* table[SIZE];

unsigned hash(char* s) {
  unsigned h = 0;
  char* t;
  for (t = s; *t; t++)
    h = h * 65599 + *t;
  return h;
}

bucket* add_bucket(char* key, void* binding, bucket* next) {
  bucket* b = malloc(sizeof(bucket));
  if (b == NULL) yyerror("Alloc error\n");
  strcpy(b->key, key);
  b->binding = binding;
  b->next = next;
  return b;
}

void insert(char* key, void* binding) {
  undo_stack_push(strdup(key));
  unsigned i = hash(key) % SIZE;
  table[i] = add_bucket(key, binding, table[i]);
}

void* lookup(char* key) {
  unsigned i = hash(key) % SIZE;
  bucket* b;
  for (b = table[i]; b; b = b->next)
    if (strcmp(b->key, key) == 0)
      return b->binding;
  return NULL;
}

void delete(char* key) {
  unsigned i = hash(key) % SIZE;
  bucket* head = table[i];
  assert(strcmp(head->key, key) == 0);
  table[i] = head->next;
  free(head->binding);
  free(head);
}

void begin_scope() {
  undo_stack_push(NULL);
}

void end_scope() {
  while(1) {
    char *s = undo_stack_pop();
    if (s == NULL) break;
    delete(s);
    free(s);
  }
}

void* make_binding(int x) {
  int* b = (int*)malloc(sizeof(int));
  *b = x;
  return (void*)b;
}

int main() {
  begin_scope();
  insert("x", make_binding(1));
  insert("y", make_binding(2));
  insert("z", make_binding(3));
  printf("x: %d\n", *(int*)lookup("x"));
  printf("y: %d\n", *(int*)lookup("y"));
  printf("z: %d\n", *(int*)lookup("z"));
  begin_scope();
  insert("y", make_binding(5));
  insert("w", make_binding(4));
  printf("x: %d\n", *(int*)lookup("x"));
  printf("y: %d\n", *(int*)lookup("y"));
  printf("z: %d\n", *(int*)lookup("z"));
  printf("w: %d\n", *(int*)lookup("w"));
  end_scope();
  printf("x: %d\n", *(int*)lookup("x"));
  printf("y: %d\n", *(int*)lookup("y"));
  printf("z: %d\n", *(int*)lookup("z"));
  end_scope();
  return 0;
}