/**
 * This file is part of the Fun programming language.
 * https://fun-lang.xyz/
 *
 * Copyright 2025 Johannes Findeisen <you@hanez.org>
 * Licensed under the terms of the Apache-2.0 license.
 * https://opensource.org/license/apache-2-0
 */

/**
 * @file iter.c
 * @brief Iterator-style helpers exposed as built-ins (enumerate, zip).
 */

#include "value.h"
#include <stdlib.h>

/**
 * @brief Build an array of [index, value] pairs from an input array.
 *
 * For an input array [v0, v1, ...], returns [[0, v0], [1, v1], ...].
 * Non-array inputs are treated as empty arrays by array_length/array_get_copy.
 *
 * Ownership: The returned Value owns its internal array; caller must free it
 * with free_value().
 *
 * @param arr Input array Value.
 * @return An array Value of length equal to the input's length.
 */
Value bi_enumerate(const Value *arr) {
  int n = array_length(arr);
  if (n <= 0) return make_array_from_values(NULL, 0);
  Value *pairs = (Value *)malloc(sizeof(Value) * n);
  if (!pairs) return make_array_from_values(NULL, 0);
  for (int i = 0; i < n; ++i) {
    Value elem;
    array_get_copy(arr, i, &elem);
    Value kv_vals[2];
    kv_vals[0] = make_int(i);
    kv_vals[1] = elem;
    Value kv = make_array_from_values(kv_vals, 2);
    free_value(kv_vals[0]);
    free_value(kv_vals[1]);
    pairs[i] = kv;
  }
  Value out = make_array_from_values(pairs, n);
  for (int i = 0; i < n; ++i)
    free_value(pairs[i]);
  free(pairs);
  return out;
}

/**
 * @brief Zip two arrays into an array of pairs up to the shorter length.
 *
 * For inputs a=[a0,a1,...], b=[b0,b1,...], returns [[a0,b0],[a1,b1], ...]
 * with length min(len(a), len(b)).
 *
 * Ownership: The returned Value owns its internal array; caller must free it
 * with free_value().
 *
 * @param a First input array Value.
 * @param b Second input array Value.
 * @return Array of pairs as a Value.
 */
Value bi_zip(const Value *a, const Value *b) {
  int na = array_length(a);
  int nb = array_length(b);
  int n = na < nb ? na : nb;
  if (n <= 0) return make_array_from_values(NULL, 0);
  Value *pairs = (Value *)malloc(sizeof(Value) * n);
  if (!pairs) return make_array_from_values(NULL, 0);
  for (int i = 0; i < n; ++i) {
    Value av, bv;
    array_get_copy(a, i, &av);
    array_get_copy(b, i, &bv);
    Value kv_vals[2];
    kv_vals[0] = av;
    kv_vals[1] = bv;
    Value kv = make_array_from_values(kv_vals, 2);
    free_value(kv_vals[0]);
    free_value(kv_vals[1]);
    pairs[i] = kv;
  }
  Value out = make_array_from_values(pairs, n);
  for (int i = 0; i < n; ++i)
    free_value(pairs[i]);
  free(pairs);
  return out;
}