using HtmlAgilityPack;
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Text.RegularExpressions;
using System.Threading.Tasks;

namespace Beam.Dynamic {
    public static partial class HtmlNodeExtensions {
        public static HtmlNode? ThenByClasses(this HtmlNode node, params string[] classes) {
            return node.DescendCollectionTree(ThenByClass, classes);
        }

        public static HtmlNode? ThenByClass(this HtmlNode node, string @class, int count = 1) {
            return node.ThenByFunc((x) => x.ChildNodes.FirstOrDefault((x) => x.HasClass(@class)), count);
        }

        public static HtmlNode? ThenByName(this HtmlNode node, string name, int count = 1) {
            return node.ThenByFunc((x) => x.ChildNodes.FirstOrDefault((x) => x.Name == name), count);
        }

        public static HtmlNode? ThenByNames(this HtmlNode node, params string[] name) {
            return node.DescendCollectionTree(ThenByName, name);
        }

        public static HtmlNode? DescendCollectionTree<T>(this HtmlNode node, Func<HtmlNode, T, int, HtmlNode?> func, params T[] values) {
            return node.DescendCollectionTree((a, b) => func(a, b, 1), values);
        }

        public static HtmlNode? DescendCollectionTree<T>(this HtmlNode node, Func<HtmlNode, T, HtmlNode?> func, params T[] values) {
            HtmlNode? result = node;
            foreach (var value in values) {
                if (result is null)
                    return result;
                result = func(result, value);
            }

            return result;
        }

        public static HtmlNode? ThenByFunc(this HtmlNode node, Func<HtmlNode, HtmlNode?> func, int count = 1) {
            var ret = func(node);
            if (count <= 1)
                return ret;
            return ret?.ThenByFunc(func, count - 1);
        }

        public static string[]? SplitInnerText(this HtmlNode? node, string separators)
            => node?.InnerText.Split(separators, StringSplitOptions.RemoveEmptyEntries);

        public static bool TextNodesOnly(HtmlNode n) => TextNodesOnlyRegex().Match(n.Name).Success;

        public static string InnerLineSeparatedText(this HtmlNode? node, Func<HtmlNode, bool>? filter = null) {
            if (node?.ChildNodes is null || node?.ChildNodes.Count == 0)
                return "";
            return node?.ChildNodes
            .Where(filter ?? ((x) => true))
            .DefaultIfEmpty()
            .Select((x) => x?.InnerText)
            .Where((x) => !string.IsNullOrWhiteSpace(x))
            .DefaultIfEmpty()
            .Aggregate((x, y) => $"{x}\n{y}")
            ?? "";
        }

        [GeneratedRegex("p|h\\d")]
        private static partial Regex TextNodesOnlyRegex();
    }
}