using System.Collections;

namespace GSS2.Core.Extensions;

public static class EnumerableExtensions
{
    public static IEnumerable<(int i, T value)> Enumerate<T>(this IEnumerable<T> values) => values.Select((value, i) => (i, value));

    public static string ToString<TKey, TValue>(this IDictionary<TKey, TValue> values, string separator, int indent) => string.Join(separator, values.Select(v => $"{new string(' ', indent)} {v.Key}: {v.Value}"));
    public static string ToString(this IDictionary values, string separator, int indent)
    {
        var strs = new List<string?>();
        var enumerator = values.GetEnumerator();
        while (enumerator.MoveNext())
            strs.Add($"{enumerator.Key}: {enumerator.Value}");
        return string.Join(separator, strs.Select(s => $"{new string(' ', indent)}{s}"));
    }

    public static string ToString<TValue>(this IEnumerable<TValue> values, string separator, int indent) => (values as IEnumerable).ToString(separator, indent);
    public static string ToString(this IEnumerable values, string separator, int indent)
    {
        var strs = new List<string?>();
        var enumerator = values.GetEnumerator();
        while (enumerator.MoveNext())
            strs.Add(enumerator.Current.ToString());
        return string.Join(separator, strs.Select(s => $"{new string(' ', indent)}{s}"));
    }

    public static bool All(this IEnumerable<bool> values) => values.All(v => v);
    public static bool Any(this IEnumerable<bool> values) => values.Any(v => v);

    public static void AddRange<TValue, TKey>(this IDictionary<TValue, TKey> values, IEnumerable<KeyValuePair<TValue, TKey>> collection)
    {
        foreach (var kv in collection)
            values.Add(kv);
    }

    public static double Variance(this IEnumerable<double> values)
    {
        if (values.Count() == 1)
            return 0;

        double mean = values.Average();
        double variance = 0.0;
        foreach (int value in values)
            variance += Math.Pow(value - mean, 2.0);
        return variance / values.Count();
    }
}