nexus/backend/Domain/Entities.cs

namespace Nexus.Api.Domain;

public enum OperationalStatus
{
    Online,
    Degraded,
    Offline,
    Unknown
}

/// <summary>
/// Strongly-typed task lifecycle states.
/// String values (e.g. "In progress") are preserved for API compatibility
/// via <see cref="TaskStateHelper"/>; the WorkTask entity continues to store
/// state as a string in the database.
/// </summary>
public enum TaskState
{
    Backlog,
    InProgress,
    Blocked,
    Done
}

public static class TaskStateHelper
{
    private static readonly Dictionary<TaskState, string> StateToString = new()
    {
        [TaskState.Backlog] = "Backlog",
        [TaskState.InProgress] = "In progress",
        [TaskState.Blocked] = "Blocked",
        [TaskState.Done] = "Done"
    };

    private static readonly Dictionary<string, TaskState> StringToState = new(StringComparer.OrdinalIgnoreCase)
    {
        ["Backlog"] = TaskState.Backlog,
        ["In progress"] = TaskState.InProgress,
        ["Blocked"] = TaskState.Blocked,
        ["Done"] = TaskState.Done
    };

    /// <summary>Valid task-state string values for API validation.</summary>
    public static readonly string[] AllStates = ["Backlog", "In progress", "Blocked", "Done"];

    /// <summary>Convert a TaskState enum to its API string representation.</summary>
    public static string ToStateString(this TaskState state) => StateToString[state];

    /// <summary>Parse a string to TaskState; defaults to Backlog for unrecognized input.</summary>
    public static TaskState ToTaskState(this string state) =>
        StringToState.TryGetValue(state, out var result) ? result : TaskState.Backlog;

    /// <summary>Returns true if the string is a recognized task state (case-insensitive).</summary>
    public static bool IsValidState(string? state) =>
        !string.IsNullOrWhiteSpace(state) && StringToState.ContainsKey(state);

    public static bool IsInProgressOrBlocked(string? state) =>
        string.Equals(state, "In progress", StringComparison.OrdinalIgnoreCase)
        || string.Equals(state, "Blocked", StringComparison.OrdinalIgnoreCase);

    public static bool IsDoneOrBacklog(string? state) =>
        string.Equals(state, "Done", StringComparison.OrdinalIgnoreCase)
        || string.Equals(state, "Backlog", StringComparison.OrdinalIgnoreCase);
}

public sealed class Project
{
    public Guid Id { get; init; } = Guid.NewGuid();
    public required string Name { get; set; }
    public string Description { get; set; } = string.Empty;
    public int Progress { get; set; }
    public OperationalStatus Status { get; set; } = OperationalStatus.Unknown;
    public DateTimeOffset UpdatedAt { get; set; } = DateTimeOffset.UtcNow;
}

public sealed class WorkTask
{
    public Guid Id { get; init; } = Guid.NewGuid();
    public required string Title { get; set; }
    public string State { get; set; } = "Backlog";
    public string Priority { get; set; } = "Normal";
    public Guid? ProjectId { get; set; }
    public DateTimeOffset UpdatedAt { get; set; } = DateTimeOffset.UtcNow;
}

public sealed class ActivityEvent
{
    public long Id { get; init; }
    public required string Type { get; set; }
    public required string Message { get; set; }
    public DateTimeOffset CreatedAt { get; set; } = DateTimeOffset.UtcNow;
}