#include "truth_table.h"

int intpow(int b, int e) {
  int acc = 1;
  for (int i = 0; i < e; i++) {
    acc *= b;
  }
  return acc;
}

struct expr_input_iter expr_input_iter_init(struct truth_table *tt) {
  return (struct expr_input_iter){
    .src = tt,
    .acc = 0,
    .count = 0,
  };
}

int32_t expr_input_iter_next(struct expr_input_iter *self) {
  uint32_t bak = self->acc;
  if (self->count > self->src->lines_count-1) return -1;
  for (int i = self->src->letters_count - 1; i >= 0; i--) {
    uint8_t idx = self->src->letters[i] - 'a';
    self->acc ^= 1 << idx;
    if (self->acc & (1 << idx)) break;
  }
  self->count++;
  return bak;
}

struct truth_table *truth_table_create(node *root, uint32_t letters_bitfield) {
  struct truth_table *tt = calloc(1, sizeof(struct truth_table));
  char letters[27] = {0};
  char letters_needle = 0;
  for (char i = 0; i <= ('z'-'a'); i++) {
    if (letters_bitfield & (1 << i)) {
      letters[letters_needle] = 'a'+i;
      letters_needle++;
    }
  }
  tt->letters = malloc(letters_needle * sizeof(char));
  strncpy(tt->letters, letters, letters_needle);
  tt->letters_count = letters_needle;
  tt->lines_count = intpow(2,tt->letters_count);
  tt->lines = malloc(tt->lines_count * sizeof(uint32_t));

  struct expr_input_iter inp_iter = expr_input_iter_init(tt);
  for (int i = 0; i < tt->lines_count; i++) {
    int32_t input = expr_input_iter_next(&inp_iter);
    uint8_t output = eval_tree(root, input);
    tt->lines[i] = input | (output << 26);
  }

  return tt;
}

void truth_table_destroy(struct truth_table *tt) {
  free(tt->lines);
  free(tt->letters);
  free(tt);
}

void truth_table_fprint(FILE *stream, struct truth_table *tt) {
  fprintf(stream, "\t%s | S\n\t", tt->letters);
  for (int i = 0; i < (tt->letters_count + 4); i++) putc('-', stream);
  putc('\n', stream);
  for (int i = 0; i < tt->lines_count; i++) {
    putc('\t', stream);
    uint32_t line = tt->lines[i];
    for (int j = 0; j < tt->letters_count; j++) {
      int actual_idx = tt->letters[j] - 'a';
      putc((line & (1 << actual_idx))? '1' : '0', stream);
    }
    fprintf(stream, " | %c\n", (line & (1 << 26))? '1' : '0');
  }
}