using System.Text.RegularExpressions;

namespace NozCli.Core.Client;

public static class NoteLinkHelper
{
    /// Inserts a wikilink to <paramref name="targetSlug"/> into <paramref name="markdown"/>.
    /// Appends to an existing section matching <paramref name="sectionHeader"/>,
    /// or creates that section at the end of the note if absent.
    public static string AddLink(string markdown, string targetSlug, string sectionHeader = "Siehe auch")
    {
        var link = $"- [[{targetSlug}]]";

        // Find the section heading (## Siehe auch, ## See also, etc.)
        var sectionMatch = Regex.Match(
            markdown,
            $@"(?m)^##\s+{Regex.Escape(sectionHeader)}\s*$",
            RegexOptions.IgnoreCase);

        if (sectionMatch.Success)
        {
            // Already has this link?
            if (markdown.Contains($"[[{targetSlug}]]", StringComparison.Ordinal))
                return markdown;

            // Insert at the end of this section's content (before next ## heading or EOF)
            var afterSection = markdown.IndexOf('\n', sectionMatch.Index + sectionMatch.Length);
            if (afterSection < 0) afterSection = markdown.Length;

            var nextHeading = Regex.Match(
                markdown[afterSection..],
                @"(?m)^##\s",
                RegexOptions.IgnoreCase);

            var insertAt = nextHeading.Success
                ? afterSection + nextHeading.Index
                : markdown.Length;

            var before = markdown[..insertAt].TrimEnd();
            var after  = markdown[insertAt..];

            return before + "\n" + link + "\n" + (after.Length > 0 ? "\n" + after.TrimStart() : "");
        }

        // No section found — create one at the end
        return markdown.TrimEnd() + $"\n\n## {sectionHeader}\n\n{link}\n";
    }

    /// Replaces template placeholders with actual values.
    public static string ApplyPlaceholders(
        string template, string title, string topic, string lang, string status)
    {
        return template
            .Replace("{{title}}",  title,                         StringComparison.Ordinal)
            .Replace("{{topic}}",  topic,                         StringComparison.Ordinal)
            .Replace("{{lang}}",   lang,                          StringComparison.Ordinal)
            .Replace("{{status}}", status,                        StringComparison.Ordinal)
            .Replace("{{date}}",   DateTime.UtcNow.ToString("yyyy-MM-dd"), StringComparison.Ordinal);
    }
}