/*
 * SPDX-FileCopyrightText: 2025 William Bell
 *
 * SPDX-License-Identifier: GPL-3.0-or-later
 */

#include "number.h"
#include "../../memory.h"
#include <ctype.h>
#include <gmp.h>
#include <gmp.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>

int parse_exponent(const char *exp_str, long *exp_val) {
  char *endptr;
  long val = strtol(exp_str, &endptr, 10);
  if (*endptr != '\0') {
    // exponent contains invalid chars or decimal point → reject
    return -1;
  }
  *exp_val = val;
  return 0;
}

int mpq_set_decimal_str_exp(mpq_t r, const char *str, size_t len) {
  // Skip leading whitespace
  while (isspace(*str))
    str++;

  // Handle sign
  int negative = 0;
  if (*str == '-') {
    negative = 1;
    str++;
  } else if (*str == '+') {
    str++;
  }

  // Copy input to a buffer for manipulation
  char *buf = malloc(len + 1);
  if (!buf)
    return -1;
  memcpy(buf, str, len);
  buf[len] = '\0';

  // Find 'e' or 'E'
  char *e_ptr = strchr(buf, 'e');
  if (!e_ptr)
    e_ptr = strchr(buf, 'E');

  char *exp_str = NULL;
  if (e_ptr) {
    *e_ptr = '\0';
    exp_str = e_ptr + 1;
  }

  // Validate decimal part (digits and one dot)
  int dot_count = 0;
  for (char *p = buf; *p; p++) {
    if (*p == '.') {
      if (++dot_count > 1) {
        free(buf);
        return -1;
      }
      continue;
    }
    if (!isdigit((unsigned char)*p)) {
      free(buf);
      return -1;
    }
  }

  // Extract integer and fractional parts
  char *dot = strchr(buf, '.');
  size_t int_len = dot ? (size_t)(dot - buf) : strlen(buf);
  size_t frac_len = dot ? strlen(dot + 1) : 0;

  // Validate exponent if present
  int exp_negative = 0;
  long exp_val = 0;
  if (exp_str) {
    // Skip leading spaces in exponent (not in regex but safe)
    while (isspace(*exp_str))
      exp_str++;

    if (*exp_str == '-') {
      exp_negative = 1;
      exp_str++;
    } else if (*exp_str == '+') {
      exp_str++;
    }

    if (!isdigit((unsigned char)*exp_str)) {
      free(buf);
      return -1;
    }

    char *endptr;
    exp_val = strtol(exp_str, &endptr, 10);
    if (*endptr != '\0') {
      free(buf);
      return -1;
    }

    if (endptr - exp_str > 11) {
      free(buf);
      return -1;
    }
    if (exp_negative)
      exp_val = -exp_val;
  }

  // Build numerator string (integer part + fractional part)
  size_t num_len = int_len + frac_len;
  if (num_len == 0) {
    free(buf);
    return -1;
  }

  char *num_str = malloc(num_len + 1);
  if (!num_str) {
    free(buf);
    return -1;
  }

  if (int_len > 0)
    memcpy(num_str, buf, int_len);
  if (frac_len > 0)
    memcpy(num_str + int_len, dot + 1, frac_len);
  num_str[num_len] = '\0';

  // Calculate denominator exponent considering exponent part
  long denom_exp = frac_len - exp_val;

  mpz_t numerator, denominator;
  mpz_init(numerator);
  mpz_init(denominator);

  if (mpz_set_str(numerator, num_str, 10) != 0) {
    free(num_str);
    free(buf);
    mpz_clear(numerator);
    mpz_clear(denominator);
    return -1;
  }
  free(num_str);
  free(buf);

  if (denom_exp >= 0) {
    mpz_ui_pow_ui(denominator, 10, (unsigned long)denom_exp);
  } else {
    mpz_set_ui(denominator, 1);

    mpz_t temp;
    mpz_init(temp);
    mpz_ui_pow_ui(temp, 10, (unsigned long)(-denom_exp));
    mpz_mul(numerator, numerator, temp);
    mpz_clear(temp);
  }

  mpq_set_num(r, numerator);
  mpq_set_den(r, denominator);
  mpq_canonicalize(r);

  if (negative)
    mpq_neg(r, r);

  mpz_clear(numerator);
  mpz_clear(denominator);

  return 0;
}

ParsedValueReturn parse_number(Token *token, char *path) {
  ParsedValue *parsedValue = checked_malloc(sizeof(ParsedValue));
  parsedValue->type = AST_NUMBER;
  mpq_t *r_ptr = malloc(sizeof(mpq_t));
  mpq_init(*r_ptr);
  int err = mpq_set_decimal_str_exp(*r_ptr, token->value, token->length);
  if (err) {
    free_parsed(parsedValue);
    free(parsedValue);
    return (ParsedValueReturn){create_err(token->line, token->column,
                                          token->length, path, "Parsing Error",
                                          "Unable to parse number"),
                               NULL};
  }
  parsedValue->data = r_ptr;
  return (ParsedValueReturn){no_err, parsedValue};
}