using System.Collections.Generic;
using System.Linq;
using System.Text.RegularExpressions;

using MfGames.Gallium;
using MfGames.Nitride.Contents;
using MfGames.Nitride.Slugs;

namespace MfGames.Nitride.Markdown;

/// <summary>
/// An operation that turns list items that starts with a link into a single
/// link for the entire list item, even if there are additional links in the
/// list.
/// </summary>
public class MakeSingleLinkListItems : IOperation
{
    private readonly ISlugConverter slugs;

    public MakeSingleLinkListItems(ISlugConverter slugs)
    {
        this.slugs = slugs;
    }

    /// <inheritdoc />
    public IEnumerable<Entity> Run(IEnumerable<Entity> input)
    {
        return input
            .SelectManyEntity<IsMarkdown>(
                x => x
                    .Select(this.MakeSingleLinkLists));
    }

    /// <summary>
    /// This turns all links that start with a link into a single link while
    /// removing all trailing links within the line. This is to simplify the
    /// rendering of the link on page.
    /// </summary>
    private Entity MakeSingleLinkLists(Entity entity)
    {
        string content = entity.GetText()!;

        string output = Regex.Replace(
            content,
            @"- \[\[(?<label>[^\]]+?)\]\](?<post>[^\n]+)\n",
            match =>
            {
                string wiki = match.Groups["label"].ToString();
                string path = string.Format(
                    "/{0}/",
                    this.slugs.ToSlug(wiki.Split('|').First()));
                string label = wiki.Split('|').Last();
                string after = match.Groups["post"].ToString();
                string post = this.RemoveLinks(after);
                string value = $"- [{label}{post}]({path})\n";

                return value;
            });

        output = Regex.Replace(
            output,
            @"- \[(?<label>[^\]]+?)\]\((?<path>[^\)]+?)\)(?<post>[^\n]+)\n",
            match =>
            {
                string label = match.Groups["label"].ToString();
                string path = match.Groups["path"].ToString();
                string after = match.Groups["post"].ToString();
                string post = this.RemoveLinks(after);
                string value = $"- [{label}{post}]({path})\n";

                return value;
            });

        return entity.SetTextContent(output);
    }

    /// <summary>
    /// Removes a normal link and replaces it with the text.
    /// </summary>
    private string RemoveLinks(string input)
    {
        string output = Regex.Replace(
            input,
            @"\[\[(?<label>[^\]]+)\]\]",
            match =>
            {
                string link1 = match.Groups["label"].ToString();
                string path1 = string.Format(
                    "/{0}/",
                    this.slugs.ToSlug(link1.Split('|').First()));
                string label1 = link1.Split('|').Last();

                return label1;
            });

        output = Regex.Replace(
            output,
            @"\[(?<label>[^\]]+)\]\([^)]+\)",
            match => match.Groups["label"].ToString());

        return output;
    }
}