using System.Text;

namespace Nuuru.Server.Services.BBCode
{
    /// <summary>
    /// Serializes a BBCode AST back to raw BBCode text.
    /// </summary>
    public static class BbSerializer
    {
        public static string Serialize(List<BbNode> nodes)
        {
            var sb = new StringBuilder();
            foreach (var node in nodes)
                SerializeNode(node, sb);
            return sb.ToString();
        }

        /// <summary>
        /// Extract plain text from AST nodes (no tags, no HTML).
        /// </summary>
        public static string ExtractText(List<BbNode> nodes)
        {
            var sb = new StringBuilder();
            foreach (var node in nodes)
                ExtractTextNode(node, sb);
            return sb.ToString();
        }

        private static void SerializeNode(BbNode node, StringBuilder sb)
        {
            switch (node)
            {
                case TextNode t:
                    sb.Append(t.Content);
                    break;

                case NewlineNode:
                    sb.Append('\n');
                    break;

                case EmoteNode em:
                    sb.Append(':').Append(em.Name).Append(':');
                    break;

                case ThumbNode t:
                    sb.Append("[thumb]").Append(t.PostId).Append("[/thumb]");
                    break;

                case MentionNode m:
                    sb.Append("[mention userguid=").Append(m.UserId).Append(']')
                      .Append(m.UserName).Append("[/mention]");
                    break;

                case AttachmentNode a:
                    sb.Append("[attachment");
                    if (a.IsThumbnail)
                        sb.Append("=thumb");
                    else
                    {
                        if (a.Width.HasValue) sb.Append(" width=").Append(a.Width);
                        if (a.Height.HasValue) sb.Append(" height=").Append(a.Height);
                    }
                    sb.Append(']').Append(a.AttachmentId).Append("[/attachment]");
                    break;

                case UrlNode u:
                    sb.Append("[url=").Append(u.Href).Append(']');
                    foreach (var child in u.Children)
                        SerializeNode(child, sb);
                    sb.Append("[/url]");
                    break;

                case QuoteNode q:
                    SerializeQuote(q, sb);
                    break;

                case ElementNode e:
                    SerializeElement(e, sb);
                    break;
            }
        }

        private static void SerializeQuote(QuoteNode q, StringBuilder sb)
        {
            sb.Append("[quote");
            if (!string.IsNullOrEmpty(q.SourceType) && !string.IsNullOrEmpty(q.SourceId))
            {
                var idAttr = q.SourceType == "forum" ? "postId" : "commentId";
                sb.Append(' ').Append(idAttr).Append('=').Append(q.SourceId);
                if (!string.IsNullOrEmpty(q.AuthorName))
                    sb.Append(" author=").Append(q.AuthorName);
                if (!string.IsNullOrEmpty(q.ProvidedHash))
                    sb.Append(" hash=").Append(q.ProvidedHash);
            }
            else if (!string.IsNullOrEmpty(q.AuthorName))
            {
                sb.Append('=').Append(q.AuthorName);
            }
            sb.Append(']');
            foreach (var child in q.Children)
                SerializeNode(child, sb);
            sb.Append("[/quote]");
        }

        private static void SerializeElement(ElementNode e, StringBuilder sb)
        {
            var tag = e.Tag;

            // Greentext/orangetext lines use >text / <text syntax
            if (e is { Tag: "greentext", Attribute: "line" })
            {
                sb.Append('>');
                foreach (var child in e.Children)
                    SerializeNode(child, sb);
                return;
            }
            if (e is { Tag: "orangetext", Attribute: "line" })
            {
                sb.Append('<');
                foreach (var child in e.Children)
                    SerializeNode(child, sb);
                return;
            }

            // List items: [*] with no closing tag
            if (tag == "*")
            {
                sb.Append("[*]");
                foreach (var child in e.Children)
                    SerializeNode(child, sb);
                return;
            }

            // Inline mark shortcuts
            var shortcut = GetInlineShortcut(tag, e.Attribute);
            if (shortcut != null)
            {
                sb.Append(shortcut.Value.open);
                foreach (var child in e.Children)
                    SerializeNode(child, sb);
                sb.Append(shortcut.Value.close);
                return;
            }

            // General [tag] or [tag=attr] ... [/tag]
            sb.Append('[').Append(tag);
            if (e.Attribute != null)
                sb.Append('=').Append(e.Attribute);
            sb.Append(']');
            foreach (var child in e.Children)
                SerializeNode(child, sb);
            sb.Append("[/").Append(tag).Append(']');
        }

        private static (string open, string close)? GetInlineShortcut(string tag, string? _)
        {
            return tag.ToLowerInvariant() switch
            {
                "redtext" => ("==", "=="),
                "bluetext" => ("--", "--"),
                "glowtext" => ("%%", "%%"),
                "redglow" => ("!!", "!!"),
                "yellowglow" => ("::", "::"),
                "rainbow" => ("~-~", "~-~"),
                _ => null
            };
        }

        private static void ExtractTextNode(BbNode node, StringBuilder sb)
        {
            switch (node)
            {
                case TextNode t:
                    sb.Append(t.Content);
                    break;
                case NewlineNode:
                    sb.Append('\n');
                    break;
                case ElementNode e:
                    foreach (var child in e.Children)
                        ExtractTextNode(child, sb);
                    break;
                case QuoteNode q:
                    foreach (var child in q.Children)
                        ExtractTextNode(child, sb);
                    break;
                case UrlNode u:
                    foreach (var child in u.Children)
                        ExtractTextNode(child, sb);
                    break;
                case MentionNode m:
                    sb.Append('@').Append(m.UserName);
                    break;
                case EmoteNode em:
                    sb.Append(':').Append(em.Name).Append(':');
                    break;
            }
        }
    }
}