using ClaudeDo.Data;
using ClaudeDo.Data.Models;
using ClaudeDo.Data.Repositories;
using ClaudeDo.Worker.Hub;
using ClaudeDo.Worker.Planning;
using ClaudeDo.Worker.Queue;
using Microsoft.EntityFrameworkCore;
using TaskStatus = ClaudeDo.Data.Models.TaskStatus;

namespace ClaudeDo.Worker.State;

public sealed class TaskStateService : ITaskStateService
{
    private readonly IDbContextFactory<ClaudeDoDbContext> _dbFactory;
    private readonly HubBroadcaster _broadcaster;
    private readonly IQueueWaker _waker;
    private readonly PlanningChainCoordinator _chain;
    private readonly RunCancellationRegistry _runCancels;
    private readonly ILogger<TaskStateService> _logger;

    public TaskStateService(
        IDbContextFactory<ClaudeDoDbContext> dbFactory,
        HubBroadcaster broadcaster,
        IQueueWaker waker,
        PlanningChainCoordinator chain,
        RunCancellationRegistry runCancels,
        ILogger<TaskStateService> logger)
    {
        _dbFactory = dbFactory;
        _broadcaster = broadcaster;
        _waker = waker;
        _chain = chain;
        _runCancels = runCancels;
        _logger = logger;
    }

    public async Task<TransitionResult> EnqueueAsync(string taskId, CancellationToken ct)
    {
        await using var ctx = await _dbFactory.CreateDbContextAsync(ct);

        if (await IsDraftChildAsync(ctx, taskId, ct))
            return new TransitionResult(false, "Draft subtask: finalize the plan before queuing it.");

        if (await IsManualAsync(ctx, taskId, ct))
            return new TransitionResult(false, "Manual task: mark it as a Claude task before queuing it.");

        var affected = await ctx.Tasks
            .Where(t => t.Id == taskId && t.Status != TaskStatus.Running)
            .ExecuteUpdateAsync(s => s.SetProperty(t => t.Status, TaskStatus.Queued), ct);

        if (affected == 0)
            return new TransitionResult(false, "Task not found or already running.");

        _waker.Wake();
        await _broadcaster.TaskUpdated(taskId);
        return new TransitionResult(true, null);
    }

    public async Task<TransitionResult> StartRunningAsync(string taskId, DateTime startedAt, CancellationToken ct)
    {
        await using var ctx = await _dbFactory.CreateDbContextAsync(ct);

        if (await IsDraftChildAsync(ctx, taskId, ct))
            return new TransitionResult(false, "Draft subtask: finalize the plan before running it.");

        if (await IsManualAsync(ctx, taskId, ct))
            return new TransitionResult(false, "Manual task: mark it as a Claude task before running it.");

        var affected = await ctx.Tasks
            .Where(t => t.Id == taskId && t.Status != TaskStatus.Running)
            .ExecuteUpdateAsync(s => s
                .SetProperty(t => t.Status, TaskStatus.Running)
                .SetProperty(t => t.StartedAt, startedAt), ct);

        if (affected == 0)
            return new TransitionResult(false, "Task already running or not found.");

        await _broadcaster.TaskUpdated(taskId);
        return new TransitionResult(true, null);
    }

    public async Task<TransitionResult> CompleteAsync(string taskId, DateTime finishedAt, string? result, CancellationToken ct)
    {
        await using (var ctx = await _dbFactory.CreateDbContextAsync(ct))
        {
            var affected = await ctx.Tasks
                .Where(t => t.Id == taskId && t.Status == TaskStatus.Running)
                .ExecuteUpdateAsync(s => s
                    .SetProperty(t => t.Status, TaskStatus.Done)
                    .SetProperty(t => t.FinishedAt, finishedAt)
                    .SetProperty(t => t.Result, result), ct);

            if (affected == 0)
                return new TransitionResult(false, "Task not running; cannot complete.");
        }

        await OnChildTerminalAsync(taskId, TaskStatus.Done);
        await _broadcaster.TaskUpdated(taskId);
        return new TransitionResult(true, null);
    }

    public async Task<TransitionResult> SubmitForReviewAsync(string taskId, DateTime finishedAt, string? result, CancellationToken ct)
    {
        await using var ctx = await _dbFactory.CreateDbContextAsync(ct);
        var affected = await ctx.Tasks
            .Where(t => t.Id == taskId && t.Status == TaskStatus.Running)
            .ExecuteUpdateAsync(s => s
                .SetProperty(t => t.Status, TaskStatus.WaitingForReview)
                .SetProperty(t => t.FinishedAt, finishedAt)
                .SetProperty(t => t.Result, result), ct);

        if (affected == 0)
            return new TransitionResult(false, "Task not running; cannot submit for review.");

        await _broadcaster.TaskUpdated(taskId);
        return new TransitionResult(true, null);
    }

    // Submit an interactively-worked task (a ConPTY session left its worktree with commits/changes)
    // for review. Unlike SubmitForReviewAsync — which only fires from the headless Running state —
    // this transitions from Idle or Failed, the states an interactive task sits in after the user
    // finishes the session by hand. The caller commits the worktree first so there is a diff to merge.
    public async Task<TransitionResult> SubmitInteractiveForReviewAsync(string taskId, DateTime finishedAt, CancellationToken ct)
    {
        await using var ctx = await _dbFactory.CreateDbContextAsync(ct);
        var affected = await ctx.Tasks
            .Where(t => t.Id == taskId && (t.Status == TaskStatus.Idle || t.Status == TaskStatus.Failed))
            .ExecuteUpdateAsync(s => s
                .SetProperty(t => t.Status, TaskStatus.WaitingForReview)
                .SetProperty(t => t.FinishedAt, finishedAt), ct);

        if (affected == 0)
            return new TransitionResult(false, "Task is not Idle or Failed; cannot submit for review.");

        await _broadcaster.TaskUpdated(taskId);
        return new TransitionResult(true, null);
    }

    public async Task<TransitionResult> SubmitForChildrenAsync(string taskId, DateTime finishedAt, string? result, CancellationToken ct)
    {
        await using var ctx = await _dbFactory.CreateDbContextAsync(ct);
        var affected = await ctx.Tasks
            .Where(t => t.Id == taskId && t.Status == TaskStatus.Running)
            .ExecuteUpdateAsync(s => s
                .SetProperty(t => t.Status, TaskStatus.WaitingForChildren)
                .SetProperty(t => t.FinishedAt, finishedAt)
                .SetProperty(t => t.Result, result), ct);

        if (affected == 0)
            return new TransitionResult(false, "Task not running; cannot submit for children.");

        await _broadcaster.TaskUpdated(taskId);
        return new TransitionResult(true, null);
    }

    public async Task<TransitionResult> ApproveReviewAsync(string taskId, CancellationToken ct)
    {
        var now = DateTime.UtcNow;
        await using (var ctx = await _dbFactory.CreateDbContextAsync(ct))
        {
            var affected = await ctx.Tasks
                .Where(t => t.Id == taskId && t.Status == TaskStatus.WaitingForReview)
                .ExecuteUpdateAsync(s => s
                    .SetProperty(t => t.Status, TaskStatus.Done)
                    .SetProperty(t => t.FinishedAt, now), ct);

            if (affected == 0)
                return new TransitionResult(false, "Task is not waiting for review; cannot approve.");
        }

        await OnChildTerminalAsync(taskId, TaskStatus.Done);
        await _broadcaster.TaskUpdated(taskId);
        return new TransitionResult(true, null);
    }

    public async Task<TransitionResult> RejectToQueueAsync(string taskId, string feedback, CancellationToken ct)
    {
        if (string.IsNullOrWhiteSpace(feedback))
            return new TransitionResult(false, "Feedback is required to reject for re-run.");

        await using var ctx = await _dbFactory.CreateDbContextAsync(ct);
        var affected = await ctx.Tasks
            .Where(t => t.Id == taskId && t.Status == TaskStatus.WaitingForReview)
            .ExecuteUpdateAsync(s => s
                .SetProperty(t => t.Status, TaskStatus.Queued)
                .SetProperty(t => t.ReviewFeedback, feedback)
                .SetProperty(t => t.StartedAt, (DateTime?)null)
                .SetProperty(t => t.FinishedAt, (DateTime?)null), ct);

        if (affected == 0)
            return new TransitionResult(false, "Task is not waiting for review; cannot reject.");

        _waker.Wake();
        await _broadcaster.TaskUpdated(taskId);
        return new TransitionResult(true, null);
    }

    public async Task<TransitionResult> RejectToIdleAsync(string taskId, CancellationToken ct)
    {
        await using var ctx = await _dbFactory.CreateDbContextAsync(ct);
        var affected = await ctx.Tasks
            .Where(t => t.Id == taskId && t.Status == TaskStatus.WaitingForReview)
            .ExecuteUpdateAsync(s => s
                .SetProperty(t => t.Status, TaskStatus.Idle)
                .SetProperty(t => t.ReviewFeedback, (string?)null), ct);

        if (affected == 0)
            return new TransitionResult(false, "Task is not waiting for review; cannot park.");

        await _broadcaster.TaskUpdated(taskId);
        return new TransitionResult(true, null);
    }

    public async Task<TransitionResult> ClearReviewFeedbackAsync(string taskId, CancellationToken ct)
    {
        await using var ctx = await _dbFactory.CreateDbContextAsync(ct);
        var affected = await ctx.Tasks
            .Where(t => t.Id == taskId)
            .ExecuteUpdateAsync(s => s.SetProperty(t => t.ReviewFeedback, (string?)null), ct);

        return affected == 0
            ? new TransitionResult(false, "Task not found.")
            : new TransitionResult(true, null);
    }

    public async Task<TransitionResult> FailAsync(string taskId, DateTime finishedAt, string? error, CancellationToken ct)
    {
        await using (var ctx = await _dbFactory.CreateDbContextAsync(ct))
        {
            // Queued is intentional: OverrideSlotService dispatches RunAsync before calling
            // StartRunningAsync, so a preflight failure (list not found, worktree setup) can
            // reach MarkFailed while the task is still Queued in the DB.
            var affected = await ctx.Tasks
                .Where(t => t.Id == taskId &&
                    (t.Status == TaskStatus.Running || t.Status == TaskStatus.Queued))
                .ExecuteUpdateAsync(s => s
                    .SetProperty(t => t.Status, TaskStatus.Failed)
                    .SetProperty(t => t.FinishedAt, finishedAt)
                    .SetProperty(t => t.Result, error), ct);

            if (affected == 0)
                return new TransitionResult(false, "Task not in a failable state (must be Running or Queued).");
        }

        await OnChildTerminalAsync(taskId, TaskStatus.Failed);
        await _broadcaster.TaskUpdated(taskId);
        return new TransitionResult(true, null);
    }

    // allowFromIdle: only the external update_task_status(Cancelled) path sets this — it lets
    // an Idle task be retired without deleting it. Every other caller (hub CancelReview,
    // PlanningChainCoordinator's chain-walk, batch cancel) relies on Idle staying a no-op here;
    // PlanningChainCoordinator specifically uses "parked back to Idle" as a deliberate opt-out
    // signal, so do not flip this default.
    public async Task<TransitionResult> CancelAsync(
        string taskId, DateTime finishedAt, CancellationToken ct, bool allowFromIdle = false)
    {
        List<string> cancelledChildIds;
        await using (var ctx = await _dbFactory.CreateDbContextAsync(ct))
        {
            var affected = await ctx.Tasks
                .Where(t => t.Id == taskId &&
                    (t.Status == TaskStatus.Running || t.Status == TaskStatus.Queued
                     || t.Status == TaskStatus.WaitingForReview
                     || t.Status == TaskStatus.WaitingForChildren
                     || (allowFromIdle && t.Status == TaskStatus.Idle)))
                .ExecuteUpdateAsync(s => s
                    .SetProperty(t => t.Status, TaskStatus.Cancelled)
                    .SetProperty(t => t.FinishedAt, finishedAt), ct);

            if (affected == 0)
                return new TransitionResult(false, "Task not in cancellable state.");

            // Cascade to this task's own non-terminal children (one level — children are
            // leaves in the current model) so a Queued/Running child doesn't keep going
            // against a parent that's already gone, orphaning its worktree commit.
            cancelledChildIds = await ctx.Tasks
                .Where(t => t.ParentTaskId == taskId
                    && t.Status != TaskStatus.Done
                    && t.Status != TaskStatus.Failed
                    && t.Status != TaskStatus.Cancelled)
                .Select(t => t.Id)
                .ToListAsync(ct);

            if (cancelledChildIds.Count > 0)
                await ctx.Tasks
                    .Where(t => cancelledChildIds.Contains(t.Id))
                    .ExecuteUpdateAsync(s => s
                        .SetProperty(t => t.Status, TaskStatus.Cancelled)
                        .SetProperty(t => t.FinishedAt, finishedAt)
                        .SetProperty(t => t.BlockedByTaskId, (string?)null), ct);
        }

        // Also stop the actual Claude processes: the DB flip above doesn't reach a run
        // already executing in a queue/override slot — without this it would keep going
        // and only fail its final (now-invalid) transition.
        _runCancels.TryCancel(taskId);
        foreach (var childId in cancelledChildIds)
            _runCancels.TryCancel(childId);

        await OnChildTerminalAsync(taskId, TaskStatus.Cancelled);
        await _broadcaster.TaskUpdated(taskId);
        foreach (var childId in cancelledChildIds)
            await _broadcaster.TaskUpdated(childId);
        return new TransitionResult(true, null);
    }

    public async Task<TransitionResult> ResetToIdleAsync(string taskId, CancellationToken ct)
    {
        await using var ctx = await _dbFactory.CreateDbContextAsync(ct);
        var affected = await ctx.Tasks
            .Where(t => t.Id == taskId && t.Status != TaskStatus.Running)
            .ExecuteUpdateAsync(s => s
                .SetProperty(t => t.Status, TaskStatus.Idle)
                .SetProperty(t => t.StartedAt, (DateTime?)null)
                .SetProperty(t => t.FinishedAt, (DateTime?)null)
                .SetProperty(t => t.Result, (string?)null), ct);

        if (affected == 0)
            return new TransitionResult(false, "Task is running; cannot reset.");

        await _broadcaster.TaskUpdated(taskId);
        return new TransitionResult(true, null);
    }

    // Unconditional status write — bypasses transition rules. Used by the UI's
    // "set status freely" affordance; intentionally no guards (caller may strand
    // the runner if used while a task is executing). It also bypasses chain/parent
    // advancement — forcing a chain child or a WaitingForChildren parent's child to a
    // terminal status here does not unblock its successor or re-check the parent.
    public async Task<TransitionResult> ForceSetStatusAsync(string taskId, TaskStatus status, CancellationToken ct)
    {
        await using var ctx = await _dbFactory.CreateDbContextAsync(ct);
        var affected = status == TaskStatus.Done
            ? await ctx.Tasks
                .Where(t => t.Id == taskId)
                .ExecuteUpdateAsync(s => s
                    .SetProperty(t => t.Status, status)
                    .SetProperty(t => t.FinishedAt, DateTime.UtcNow), ct)
            : await ctx.Tasks
                .Where(t => t.Id == taskId)
                .ExecuteUpdateAsync(s => s.SetProperty(t => t.Status, status), ct);

        if (affected == 0)
            return new TransitionResult(false, "Task not found.");

        if (status == TaskStatus.Queued) _waker.Wake();
        await _broadcaster.TaskUpdated(taskId);
        return new TransitionResult(true, null);
    }

    public async Task<TransitionResult> StartPlanningAsync(string parentId, CancellationToken ct)
    {
        await using var ctx = await _dbFactory.CreateDbContextAsync(ct);
        var affected = await ctx.Tasks
            .Where(t => t.Id == parentId
                        && t.Status == TaskStatus.Idle
                        && t.PlanningPhase == PlanningPhase.None)
            .ExecuteUpdateAsync(s => s
                .SetProperty(t => t.PlanningPhase, PlanningPhase.Active), ct);

        if (affected == 0)
            return new TransitionResult(false, "Task not in plannable state.");

        await _broadcaster.TaskUpdated(parentId);
        return new TransitionResult(true, null);
    }

    public async Task<TransitionResult> FinalizePlanningAsync(string parentId, CancellationToken ct)
    {
        await using var ctx = await _dbFactory.CreateDbContextAsync(ct);
        var hasChildren = await ctx.Tasks.AnyAsync(t => t.ParentTaskId == parentId, ct);
        var newStatus = hasChildren ? TaskStatus.WaitingForChildren : TaskStatus.WaitingForReview;

        var affected = await ctx.Tasks
            .Where(t => t.Id == parentId && t.PlanningPhase == PlanningPhase.Active)
            .ExecuteUpdateAsync(s => s
                .SetProperty(t => t.PlanningPhase, PlanningPhase.Finalized)
                .SetProperty(t => t.PlanningFinalizedAt, DateTime.UtcNow)
                .SetProperty(t => t.PlanningSessionToken, (string?)null)
                .SetProperty(t => t.Status, newStatus), ct);

        if (affected == 0)
            return new TransitionResult(false, "No active planning session.");

        await _broadcaster.TaskUpdated(parentId);
        return new TransitionResult(true, null);
    }

    public async Task<TransitionResult> BlockOnAsync(string taskId, string predecessorTaskId, CancellationToken ct)
    {
        await using var ctx = await _dbFactory.CreateDbContextAsync(ct);
        var affected = await ctx.Tasks
            .Where(t => t.Id == taskId)
            .ExecuteUpdateAsync(s => s.SetProperty(t => t.BlockedByTaskId, predecessorTaskId), ct);

        if (affected == 0)
            return new TransitionResult(false, "Task not found.");

        await _broadcaster.TaskUpdated(taskId);
        return new TransitionResult(true, null);
    }

    public async Task<TransitionResult> UnblockAsync(string taskId, CancellationToken ct)
    {
        await using var ctx = await _dbFactory.CreateDbContextAsync(ct);
        var affected = await ctx.Tasks
            .Where(t => t.Id == taskId)
            .ExecuteUpdateAsync(s => s.SetProperty(t => t.BlockedByTaskId, (string?)null), ct);

        if (affected == 0)
            return new TransitionResult(false, "Task not found.");

        _waker.Wake();
        await _broadcaster.TaskUpdated(taskId);
        return new TransitionResult(true, null);
    }

    public async Task<int> RecoverStaleRunningAsync(string reason, CancellationToken ct)
    {
        var resultText = "[stale] " + reason;
        var now = DateTime.UtcNow;
        List<string> recoveredIds;
        int affected;
        await using (var ctx = await _dbFactory.CreateDbContextAsync(ct))
        {
            recoveredIds = await ctx.Tasks
                .Where(t => t.Status == TaskStatus.Running)
                .Select(t => t.Id)
                .ToListAsync(ct);

            affected = await ctx.Tasks
                .Where(t => t.Status == TaskStatus.Running)
                .ExecuteUpdateAsync(s => s
                    .SetProperty(t => t.Status, TaskStatus.Failed)
                    .SetProperty(t => t.FinishedAt, now)
                    .SetProperty(t => t.Result, resultText), ct);
        }

        // A recovered task may have been a planning/improvement chain child or the last
        // non-terminal child of a WaitingForChildren parent. The bulk flip above skips the
        // usual terminal-transition side effects, so without this a crash mid-run would
        // leave the chain successor blocked forever and the parent wedged in
        // WaitingForChildren with nothing left to re-check it.
        foreach (var taskId in recoveredIds)
            await OnChildTerminalAsync(taskId, TaskStatus.Failed);

        return affected;
    }

    // A subtask is "draft" only while its planning parent has an open (Active) session.
    // Improvement children whose parent has PlanningPhase.None are not drafts and may be
    // queued freely. Standalone tasks (no parent) are never draft.
    // Server-side backstop for the manual flag: the UI hides the hand-off affordances, but the
    // MCP surface and hub can still be driven directly.
    private static Task<bool> IsManualAsync(ClaudeDoDbContext ctx, string taskId, CancellationToken ct)
        => ctx.Tasks.AsNoTracking().AnyAsync(t => t.Id == taskId && t.IsManual, ct);

    private static async Task<bool> IsDraftChildAsync(ClaudeDoDbContext ctx, string taskId, CancellationToken ct)
    {
        var parentId = await ctx.Tasks.AsNoTracking()
            .Where(t => t.Id == taskId)
            .Select(t => t.ParentTaskId)
            .FirstOrDefaultAsync(ct);
        if (parentId is null) return false;

        return await ctx.Tasks.AsNoTracking()
            .AnyAsync(p => p.Id == parentId && p.PlanningPhase == PlanningPhase.Active, ct);
    }

    private async Task OnChildTerminalAsync(string taskId, TaskStatus finalStatus)
    {
        // Terminal child writes are best-effort and use CancellationToken.None so the
        // task lifecycle is never left partially completed because a caller cancelled.
        string? parentId;
        await using (var ctx = await _dbFactory.CreateDbContextAsync(CancellationToken.None))
        {
            parentId = await ctx.Tasks
                .AsNoTracking()
                .Where(t => t.Id == taskId)
                .Select(t => t.ParentTaskId)
                .FirstOrDefaultAsync(CancellationToken.None);
        }
        if (parentId is null) return;

        try
        {
            await _chain.OnChildFinishedAsync(taskId, finalStatus, CancellationToken.None);
        }
        catch (Exception ex)
        {
            _logger.LogWarning(ex, "PlanningChain advance failed for {TaskId}", taskId);
        }

        await TryAdvanceParentAsync(parentId);
    }

    // Any parent (planning or improvement) sitting in WaitingForChildren surfaces for review
    // once every child is terminal (Done/Failed/Cancelled). A failed or cancelled child does
    // not wedge the parent — it is flagged on the result. Also called directly after a child
    // is deleted, since no terminal transition fires in that case.
    public async Task TryAdvanceParentAsync(string parentId)
    {
        try
        {
            await AdvanceParentIfAllChildrenTerminalAsync(parentId);
        }
        catch (Exception ex)
        {
            _logger.LogWarning(ex, "TryAdvanceParent failed for {ParentId}", parentId);
        }
    }

    private async Task AdvanceParentIfAllChildrenTerminalAsync(string parentId)
    {
        string? parentResult;
        List<TaskStatus> childStatuses;
        await using (var ctx = await _dbFactory.CreateDbContextAsync(CancellationToken.None))
        {
            var parent = await ctx.Tasks.AsNoTracking()
                .FirstOrDefaultAsync(t => t.Id == parentId, CancellationToken.None);
            if (parent is null || parent.Status != TaskStatus.WaitingForChildren) return;
            parentResult = parent.Result;
            childStatuses = await ctx.Tasks
                .Where(t => t.ParentTaskId == parentId)
                .Select(t => t.Status)
                .ToListAsync(CancellationToken.None);
        }
        if (childStatuses.Count == 0) return;

        bool allTerminal = childStatuses.All(s =>
            s == TaskStatus.Done || s == TaskStatus.Failed || s == TaskStatus.Cancelled);
        if (!allTerminal) return;

        int failed = childStatuses.Count(s => s == TaskStatus.Failed);
        int cancelled = childStatuses.Count(s => s == TaskStatus.Cancelled);
        var newResult = parentResult;
        if (failed + cancelled > 0)
        {
            var note = $"⚠ Children: {failed} failed, {cancelled} cancelled.";
            newResult = string.IsNullOrWhiteSpace(parentResult) ? note : $"{parentResult}\n\n{note}";
        }

        await using var writeCtx = await _dbFactory.CreateDbContextAsync(CancellationToken.None);
        await writeCtx.Tasks
            .Where(t => t.Id == parentId && t.Status == TaskStatus.WaitingForChildren)
            .ExecuteUpdateAsync(s => s
                .SetProperty(t => t.Status, TaskStatus.WaitingForReview)
                .SetProperty(t => t.Result, newResult), CancellationToken.None);
        await _broadcaster.TaskUpdated(parentId);
    }
}