first-repo/sqlite_ex.c

#include "sqlite_ex.h"

static char date_string[STR_SIZE];
static meas *measurements;
static int meas_count;
static Datetime twnth_day;
static Cost costs;
static char *zErrMsg = NULL;
static sqlite3 *db;

int main(int argc, char **argv) {
  int respCode;
  if ((respCode = sqlite3_open("communal.db", &db))) {
    fprintf(stderr, "Can't open database: %s\n", sqlite3_errmsg(db));
    sqlite3_close(db);
    return 1;
  }

  if (argc == 2 && !strcmp(argv[1], "-t")) {
    sqlite_list_tables(db);
  } else {
    sqlite_exec_query(SELECT_COUNT_MEAS, count_measurements);
    measurements = malloc(sizeof(meas) * meas_count);

    sqlite_exec_query(SELECT_MEASUREMENTS, parse_measurements);
    measurements -= meas_count; // bring it back to the start of array

    sqlite_exec_query(SELECT_TWNTH_DAY, select_twnth_day);

    sqlite3_stmt *st;
    respCode = sqlite3_prepare_v2(db, SELECT_CURRENT_COSTS, -1, &st, NULL);
    if (respCode != SQLITE_OK) {
      fprintf(stderr, "Prepared statement error: %d\n", respCode);
    }
    sqlite3_bind_int(st, 1, measurements[meas_count - 1].cost_id);
    respCode = sqlite3_step(st);
    if (respCode == SQLITE_ROW) {
      int n_cols = sqlite3_column_count(st);
      for (int col_ind = 0; col_ind < n_cols; ++col_ind) {
        const char *col_name = sqlite3_column_name(st, col_ind);
        if (!strcmp(col_name, "gas_cost")) {
          costs.gas_c = sqlite3_column_double(st, col_ind);
        } else if (!strcmp(col_name, "water_cost")) {
          costs.water_c = sqlite3_column_double(st, col_ind);
        } else if (!strcmp(col_name, "electricity_cost")) {
          costs.electricity_c = sqlite3_column_double(st, col_ind);
        } else if (!strcmp(col_name, "other_cost")) {
          costs.housing_c = sqlite3_column_double(st, col_ind);
        }
      }
    }
    respCode = sqlite3_finalize(st);
    if (respCode != SQLITE_OK) {
      fprintf(stderr, "Prepared statement finalization error: %d\n", respCode);
      sqlite3_free(zErrMsg);
    }

    print_measurements();

    for (int i = meas_count - 1; i >= 0; --i) {
      Datetime *dt = measurements[i].datetime;
      if (dates_same(dt, &twnth_day)) {
        if (i == meas_count - 1) {
          printf("No measurements were made since last time!\n");
          goto free;
        }
        double total = communal_difference(&measurements[meas_count - 1],
                                           &measurements[i]);
        strftime(date_string, STR_SIZE, "%x",
                 measurements[meas_count - 1].datetime);
        printf("date of last measurement: %s\n", date_string);
        printf("total: %f\n", total);
      }
    }

  free:
    free_measurements();
  }

  sqlite3_close(db);
  return 0;
}

void sqlite_exec_query(char *query, void *callback) {
  int respCode = sqlite3_exec(db, query, callback, 0, &zErrMsg);
  if (respCode != SQLITE_OK) {
    fprintf(stderr, "SQL error: %s\n", zErrMsg);
    sqlite3_free(zErrMsg);
  }
}

int count_measurements(void *_, int n_cols, char **row_vals, char **cols) {
  meas_count = atoi(row_vals[0]);
  return 0;
}

int parse_measurements(void *_, int n_cols, char **row_vals, char **cols) {
  meas measurement;

  for (int col = 0; col < n_cols; ++col) {
    if (!strcmp(cols[col], "gas")) {
      measurement.gas = atof(row_vals[col]);
    } else if (!strcmp(cols[col], "water")) {
      measurement.water = atof(row_vals[col]);
    } else if (!strcmp(cols[col], "electricity")) {
      measurement.electricity = atof(row_vals[col]);
    } else if (!strcmp(cols[col], "date")) {
      Datetime *dt = malloc(sizeof(Datetime));
      strptime(row_vals[col], "%F", dt);
      measurement.datetime = dt;
    } else if (!strcmp(cols[col], "costs")) {
      measurement.cost_id = atoi(row_vals[col]);
    }
  }
  *measurements++ = measurement;

  return 0;
}

void sqlite_list_tables(sqlite3 *db) {
  char *errMsg = NULL;
  int respCode = sqlite3_exec(db, SELECT_ALL_TABLES, print_tables, 0, &errMsg);
  if (respCode != SQLITE_OK) {
    fprintf(stderr, "SQL error: %s\n", errMsg);
    sqlite3_free(errMsg);
  }
}

int print_tables(void *_, int rows_n, char **rows, char **cols) {
  for (int i = 0; i < rows_n; ++i) {
    printf("%s = %s\n", cols[i], rows[i] ? rows[i] : "NULL");
  }
  printf("\n");
  return 0;
}

int select_twnth_day(void *_, int n_cols, char **row_vals, char **cols) {
  strptime(row_vals[0], "%F", &twnth_day);
  return 0;
}

int dates_same(Datetime *dt1, Datetime *dt2) {
  return dt1->tm_year == dt2->tm_year && dt1->tm_mon == dt2->tm_mon &&
         dt1->tm_mday == dt2->tm_mday;
}

double communal_difference(meas *m_now, meas *m_twnth) {
  double gas_diff = m_now->gas - m_twnth->gas;
  double water_diff = m_now->water - m_twnth->water;
  double electricity_diff = m_now->electricity - m_twnth->electricity;

  return gas_diff * costs.gas_c + water_diff * costs.water_c +
         electricity_diff * costs.electricity_c + costs.housing_c;
}

void print_measurements() {
  for (int i = 0; i < meas_count; ++i) {
    meas m = measurements[i];
    strftime(date_string, STR_SIZE, "%x", m.datetime);
    printf("%-15s%11s\n%-15s%11f\n%-15s%11f\n%-15s%11f\n\n",
           "date:", date_string, "gas:", m.gas, "water:", m.water,
           "electricity:", m.electricity);
  }
}

void free_measurements() {
  for (int i = 0; i < meas_count; ++i)
    free(measurements[i].datetime);
  free(measurements);
}