using System.IO;
using System.Reflection;

namespace Explorer.App;

public static class DocumentationLoader
{
    public const string EmbeddedName = "Explorer.Documentation.md";
    public const string FileName = "Documentation.md";

    public static LoadedDocumentation Load()
    {
        foreach (var path in CandidatePaths())
        {
            try
            {
                if (File.Exists(path))
                {
                    return new LoadedDocumentation(File.ReadAllText(path), path);
                }
            }
            catch (IOException)
            {
                // try the next candidate
            }
        }

        var assembly = typeof(DocumentationLoader).Assembly;
        using var stream = assembly.GetManifestResourceStream(EmbeddedName);
        if (stream is null)
        {
            return new LoadedDocumentation(
                "# Documentation\n\nThe user guide file was not found. Add `docs/Documentation.md` to the project.",
                null);
        }

        using var reader = new StreamReader(stream);
        return new LoadedDocumentation(reader.ReadToEnd(), null);
    }

    public static IEnumerable<string> CandidatePaths()
    {
        var baseDir = AppContext.BaseDirectory;
        yield return Path.Combine(baseDir, FileName);
        yield return Path.Combine(baseDir, "docs", FileName);
        var dir = new DirectoryInfo(baseDir);
        for (var n = 0; n < 8 && dir is not null; n++, dir = dir.Parent)
        {
            yield return Path.Combine(dir.FullName, "docs", FileName);
            yield return Path.Combine(dir.FullName, FileName);
        }
    }
}

public sealed record LoadedDocumentation(string Markdown, string? SourcePath);