using System.Text.RegularExpressions;

namespace ItWorx.KnowledgeHub.Domain.Sources;

public enum DataSourceKind { Inventory, Gitea, KnowledgeClient, ManualIntake, LeafWiki, CuratedPackage }

/// <summary>Operator registration and observed evidence; credentials never enter this aggregate.</summary>
public sealed class DataSource
{
    private DataSource() { }
    public Guid Id { get; private set; }
    public Guid WorkspaceId { get; private set; }
    public string SourceKey { get; private set; } = "";
    public string DisplayName { get; private set; } = "";
    public DataSourceKind Kind { get; private set; }
    public bool Enabled { get; private set; } = true;
    public int ExpectedIntervalHours { get; private set; }
    public int Version { get; private set; } = 1;
    public DateTimeOffset CreatedAt { get; private set; }
    public DateTimeOffset? LastAttemptAt { get; private set; }
    public DateTimeOffset? LastSuccessAt { get; private set; }
    public DateTimeOffset? LastFailureAt { get; private set; }
    public DateTimeOffset? DataObservedAt { get; private set; }
    public long? RecordCount { get; private set; }
    public string? LastErrorCode { get; private set; }
    public string? LastCorrelationId { get; private set; }

    public static DataSource Create(Guid workspaceId, string sourceKey, string displayName, DataSourceKind kind, int expectedIntervalHours, DateTimeOffset now)
    {
        if (workspaceId == Guid.Empty || !Enum.IsDefined(kind) || !Regex.IsMatch(sourceKey, "^[a-zA-Z0-9][a-zA-Z0-9_.:-]{0,199}$", RegexOptions.CultureInvariant))
        {
            throw new ArgumentException("Invalid source identity.");
        }
        var source = new DataSource { Id = Guid.NewGuid(), WorkspaceId = workspaceId, SourceKey = sourceKey, Kind = kind, CreatedAt = now, Version = 0 };
        source.Configure(displayName, true, expectedIntervalHours);
        return source;
    }

    public void Configure(string displayName, bool enabled, int expectedIntervalHours)
    {
        if (string.IsNullOrWhiteSpace(displayName) || displayName.Length > 120 || displayName.Any(char.IsControl) || expectedIntervalHours is < 1 or > 8760)
        {
            throw new ArgumentException("Invalid source policy.");
        }
        DisplayName = displayName.Trim();
        Enabled = enabled;
        ExpectedIntervalHours = expectedIntervalHours;
        Version++;
    }

    public void Observe(bool success, long? recordCount, string? errorCode, string? correlationId, DateTimeOffset observedAt, DateTimeOffset? dataObservedAt = null)
    {
        if (recordCount < 0 || (!success && errorCode is not ("authentication" or "connectivity" or "validation" or "unexpected"))
            || (LastAttemptAt is { } previous && observedAt < previous)
            || dataObservedAt > observedAt || correlationId?.Length > 100 || correlationId?.Any(char.IsControl) == true)
        {
            throw new ArgumentException("Invalid source observation.");
        }
        LastAttemptAt = observedAt;
        LastCorrelationId = correlationId;
        if (success)
        {
            LastSuccessAt = observedAt;
            var captured = dataObservedAt ?? observedAt;
            if (DataObservedAt is null || captured >= DataObservedAt)
            {
                DataObservedAt = captured;
                RecordCount = recordCount;
            }
            LastErrorCode = null;
        }
        else
        {
            LastFailureAt = observedAt;
            LastErrorCode = errorCode;
        }
        Version++;
    }

    public string GetState(DateTimeOffset now)
    {
        if (!Enabled) return "Disabled";
        if (LastErrorCode is not null) return "Failed";
        if (DataObservedAt is null || DataObservedAt > now) return "Unknown";
        return now - DataObservedAt.Value > TimeSpan.FromHours(ExpectedIntervalHours) ? "Stale" : "Current";
    }
}