using System.Text.Json;

namespace Sdt.Config;

public static class WorkspaceLoader
{
    private const string FileName = "sdt-workspace.json";

    private static readonly JsonSerializerOptions JsonOptions = new()
    {
        PropertyNameCaseInsensitive = true,
        PropertyNamingPolicy = JsonNamingPolicy.CamelCase,
        AllowTrailingCommas = true,
        ReadCommentHandling = JsonCommentHandling.Skip,
    };

    /// <summary>
    /// Walks up from <paramref name="startDir"/> (or CWD) to find sdt-workspace.json.
    /// Returns null if not found.
    /// </summary>
    public static (WorkspaceConfig Config, string WorkspaceRoot)? FindAndLoad(string? startDir = null)
    {
        var dir = new DirectoryInfo(startDir ?? Directory.GetCurrentDirectory());
        while (dir is not null)
        {
            var candidate = Path.Combine(dir.FullName, FileName);
            if (File.Exists(candidate))
            {
                try
                {
                    var json = File.ReadAllText(candidate);
                    var config = JsonSerializer.Deserialize<WorkspaceConfig>(json, JsonOptions)
                        ?? throw new InvalidOperationException($"{FileName} deserialized to null.");
                    return (config, dir.FullName);
                }
                catch (Exception ex)
                {
                    throw new InvalidOperationException(
                        $"Failed to parse {FileName} at {candidate}: {ex.Message}", ex);
                }
            }
            dir = dir.Parent!;
        }
        return null;
    }

    /// <summary>
    /// Resolves the absolute project root for a workspace project entry.
    /// </summary>
    public static string ResolveProjectRoot(string workspaceRoot, WorkspaceProject project)
        => Path.GetFullPath(Path.Combine(workspaceRoot, project.Path));
}