using AxCopilot.Models;

namespace AxCopilot.Services;

/// <summary>
/// 드래프트 큐 항목의 실행 전이와 재시도 정책을 담당합니다.
/// ChatWindow가 직접 상태 전이를 조합하지 않도록 별도 서비스로 분리합니다.
/// </summary>
public sealed class DraftQueueProcessorService
{
    public bool CanStartNext(ChatSessionStateService? session, string tab)
        => session?.GetNextQueuedDraft(tab) != null;

    public DraftQueueItem? TryStartNext(ChatSessionStateService? session, string tab, ChatStorageService? storage = null, string? preferredDraftId = null, TaskRunService? taskRuns = null)
    {
        if (session == null)
            return null;

        DraftQueueItem? next = null;

        if (!string.IsNullOrWhiteSpace(preferredDraftId))
        {
            next = session.GetDraftQueueItems(tab)
                .FirstOrDefault(x => string.Equals(x.Id, preferredDraftId, StringComparison.OrdinalIgnoreCase));

            if (next != null &&
                !string.Equals(next.State, "queued", StringComparison.OrdinalIgnoreCase))
            {
                session.ResetDraftToQueued(tab, next.Id, storage);
                next = session.GetDraftQueueItems(tab)
                    .FirstOrDefault(x => string.Equals(x.Id, preferredDraftId, StringComparison.OrdinalIgnoreCase));
            }
        }

        next ??= session.GetNextQueuedDraft(tab);
        if (next == null)
            return null;

        if (!session.MarkDraftRunning(tab, next.Id, storage))
            return null;

        taskRuns?.StartQueueRun(tab, next.Id, next.Text);

        return session.GetDraftQueueItems(tab)
            .FirstOrDefault(x => string.Equals(x.Id, next.Id, StringComparison.OrdinalIgnoreCase))
            ?? next;
    }

    public bool Complete(ChatSessionStateService? session, string tab, string draftId, ChatStorageService? storage = null, TaskRunService? taskRuns = null)
    {
        var completed = session?.MarkDraftCompleted(tab, draftId, storage) ?? false;
        if (completed)
            taskRuns?.CompleteQueueRun(tab, draftId, "대기열 작업 완료", "completed");
        return completed;
    }

    public bool HandleFailure(ChatSessionStateService? session, string tab, string draftId, string? error, bool cancelled = false, int maxAutoRetries = 3, ChatStorageService? storage = null, TaskRunService? taskRuns = null)
    {
        if (session == null)
            return false;

        if (cancelled)
        {
            var reset = session.ResetDraftToQueued(tab, draftId, storage);
            if (reset)
                taskRuns?.CompleteQueueRun(tab, draftId, string.IsNullOrWhiteSpace(error) ? "대기열 작업 중단" : error, "cancelled");
            return reset;
        }

        var handled = session.ScheduleDraftRetry(tab, draftId, error, maxAutoRetries, storage);
        if (handled)
        {
            var item = session.GetDraftQueueItems(tab)
                .FirstOrDefault(x => string.Equals(x.Id, draftId, StringComparison.OrdinalIgnoreCase));
            var blocked = item?.NextRetryAt.HasValue == true;
            taskRuns?.CompleteQueueRun(
                tab,
                draftId,
                string.IsNullOrWhiteSpace(error) ? (blocked ? "재시도 대기" : "대기열 작업 실패") : error,
                blocked ? "blocked" : "failed");
        }

        return handled;
    }

    public int PromoteReadyBlockedItems(ChatSessionStateService? session, string tab, ChatStorageService? storage = null)
    {
        if (session == null)
            return 0;

        var promoted = 0;
        foreach (var item in session.GetDraftQueueItems(tab)
                     .Where(x => string.Equals(x.State, "queued", StringComparison.OrdinalIgnoreCase)
                                 && x.NextRetryAt.HasValue
                                 && x.NextRetryAt.Value <= DateTime.Now)
                     .ToList())
        {
            if (session.ResetDraftToQueued(tab, item.Id, storage))
                promoted++;
        }

        return promoted;
    }

    public int ClearCompleted(ChatSessionStateService? session, string tab, ChatStorageService? storage = null)
        => ClearByState(session, tab, "completed", storage);

    public int ClearFailed(ChatSessionStateService? session, string tab, ChatStorageService? storage = null)
        => ClearByState(session, tab, "failed", storage);

    private static int ClearByState(ChatSessionStateService? session, string tab, string state, ChatStorageService? storage)
    {
        if (session == null)
            return 0;

        var removed = 0;
        foreach (var item in session.GetDraftQueueItems(tab)
                     .Where(x => string.Equals(x.State, state, StringComparison.OrdinalIgnoreCase))
                     .ToList())
        {
            if (session.RemoveDraft(tab, item.Id, storage))
                removed++;
        }

        return removed;
    }
}