import { useCallback, useEffect, useMemo, useRef, useState, type CSSProperties } from "react";
import { useTranslation } from "react-i18next";
import type { Task } from "@fusion/core";
import { getErrorMessage } from "@fusion/core";
import {
  startSubtaskBreakdown,
  retrySubtaskSession,
  connectSubtaskStream,
  createTasksFromBreakdown,
  fetchAiSession,
  fetchTaskWorkflow,
  parseConversationHistory,
  type SubtaskItem,
  type ConversationHistoryEntry,
} from "../api";
import {
  saveSubtaskDescription,
  getSubtaskDescription,
  clearSubtaskDescription,
} from "../hooks/modalPersistence";
import { CheckCircle, Loader2, ListTree, Plus, Trash2, X, GripVertical, ArrowUp, ArrowDown, Minimize2, RefreshCw } from "lucide-react";
import { ConversationHistory } from "./ConversationHistory";
import { useAiSessionSync } from "../hooks/useAiSessionSync";
import { useConfirm } from "../hooks/useConfirm";
import { useMobileKeyboard } from "../hooks/useMobileKeyboard";
import { useMobileScrollLock } from "../hooks/useMobileScrollLock";
import { useViewportMode } from "../hooks/useViewportMode";

const WARNING_ICON = "⚠️";

interface SubtaskBreakdownModalProps {
  isOpen: boolean;
  onClose: () => void;
  initialDescription: string;
  onTasksCreated: (tasks: Task[]) => void;
  parentTaskId?: string;
  projectId?: string;
  /** Active workflow lane selected when the breakdown modal was opened. */
  workflowId?: string | null;
  resumeSessionId?: string;
  onOpenGroupModal?: (groupId: string) => void;
}

type ViewState =
  | { type: "initial" }
  | { type: "generating"; sessionId: string }
  | { type: "editing"; sessionId: string }
  | { type: "error"; sessionId: string; errorMessage: string }
  | { type: "creating"; sessionId: string };

function createEmptySubtask(index: number): SubtaskItem {
  return {
    id: `subtask-${index}`,
    title: "",
    description: "",
    suggestedSize: "M",
    dependsOn: [],
  };
}

function hasDependencyCycle(subtasks: SubtaskItem[]): boolean {
  const graph = new Map(subtasks.map((item) => [item.id, item.dependsOn]));
  const visiting = new Set<string>();
  const visited = new Set<string>();

  const visit = (id: string): boolean => {
    if (visiting.has(id)) return true;
    if (visited.has(id)) return false;
    visiting.add(id);
    for (const dep of graph.get(id) ?? []) {
      if (graph.has(dep) && visit(dep)) return true;
    }
    visiting.delete(id);
    visited.add(id);
    return false;
  };

  return subtasks.some((item) => visit(item.id));
}

export function SubtaskBreakdownModal({ isOpen, onClose, initialDescription, onTasksCreated, parentTaskId, projectId, workflowId, resumeSessionId, onOpenGroupModal }: SubtaskBreakdownModalProps) {
  const { t } = useTranslation("app");
  const viewportMode = useViewportMode();
  useMobileScrollLock(isOpen);
  const { keyboardOverlap, viewportHeight, viewportOffsetTop, keyboardOpen } = useMobileKeyboard({
    enabled: viewportMode === "mobile",
  });
  const keyboardStyle: CSSProperties = keyboardOpen
    ? ({
        "--keyboard-overlap": `${keyboardOverlap}px`,
        "--vv-offset-top": `${viewportOffsetTop}px`,
        ...(viewportHeight !== null ? { "--vv-height": `${viewportHeight}px` } : {}),
      } as CSSProperties)
    : {};
  const [view, setView] = useState<ViewState>({ type: "initial" });
  const [subtasks, setSubtasks] = useState<SubtaskItem[]>([]);
  const [conversationHistory, setConversationHistory] = useState<ConversationHistoryEntry[]>([]);
  const [thinkingOutput, setThinkingOutput] = useState("");
  const [showThinking, setShowThinking] = useState(true);
  const [isReconnecting, setIsReconnecting] = useState(false);
  const [isRetrying, setIsRetrying] = useState(false);
  const [isStartingBreakdown, setIsStartingBreakdown] = useState(false);
  // Local description: synced from prop, can fall back to localStorage
  const [localDescription, setLocalDescription] = useState(initialDescription);
  const [error, setError] = useState<string | null>(null);
  const [dirty, setDirty] = useState(false);
  const [branchMode, setBranchMode] = useState<"project-default" | "auto-new" | "existing" | "custom-new">("project-default");
  const [branchName, setBranchName] = useState("");
  const [baseBranch, setBaseBranch] = useState("");
  const [branchAssignmentMode, setBranchAssignmentMode] = useState<"shared" | "per-task-derived">("shared");
  
  // Drag-and-drop state
  const [draggingId, setDraggingId] = useState<string | null>(null);
  const [dragOverId, setDragOverId] = useState<string | null>(null);
  const [dragOverPosition, setDragOverPosition] = useState<'before' | 'after' | null>(null);
  
  const streamRef = useRef<{ close: () => void; isConnected: () => boolean } | null>(null);
  const titleRefs = useRef<Array<HTMLInputElement | null>>([]);
  const autoStartedRef = useRef(false);

  const sessionId = view.type === "generating" || view.type === "editing" || view.type === "creating" || view.type === "error"
    ? view.sessionId
    : null;
  /*
  FNXC:PlanningMultiTab 2026-07-14-00:00:
  No tab lock: the persisted session row is the shared source of truth, so every tab may read
  and interact with this breakdown. The lock overlay, Take Control affordance, ownership
  broadcasts, heartbeat, and the "active in another tab" banner were removed; only
  session-status sync remains.
  */
  const { broadcastUpdate, broadcastCompleted } = useAiSessionSync();

  const isInvalid = useMemo(() => {
    if (subtasks.length === 0) return true;
    if (subtasks.some((subtask) => !subtask.title.trim())) return true;
    if ((branchMode === "existing" || branchMode === "custom-new") && !branchName.trim()) return true;
    return hasDependencyCycle(subtasks);
  }, [branchMode, branchName, subtasks]);

  const showSendToBackgroundButton = view.type === "generating" || view.type === "editing" || view.type === "error";
  const { confirm } = useConfirm();

  const resetState = useCallback(() => {
    // Save to localStorage before cleanup (preserve for re-entry)
    if (localDescription) {
      saveSubtaskDescription(localDescription, projectId);
    }
    streamRef.current?.close();
    streamRef.current = null;
    setView({ type: "initial" });
    setSubtasks([]);
    setConversationHistory([]);
    setThinkingOutput("");
    setShowThinking(true);
    setIsReconnecting(false);
    setIsRetrying(false);
    setIsStartingBreakdown(false);
    setError(null);
    setDirty(false);
    setBranchMode("project-default");
    setBranchName("");
    setBaseBranch("");
    setBranchAssignmentMode("shared");
    autoStartedRef.current = false;
  }, [localDescription, projectId]);

  const keepSessionReachableInBackground = useCallback(() => {
    if (!sessionId) return;

    /**
     * FNXC:SubtaskBreakdown 2026-06-16-21:10:
     * Closing the modal is an exit affordance, not an explicit discard. Preserve running and review-ready subtask sessions in the background-session list so users can resume from BackgroundTasksIndicator instead of losing AI work.
     */
    if (view.type !== "generating" && view.type !== "editing") return;

    const resumableStatus = view.type === "generating" ? "generating" : "awaiting_input";
    broadcastUpdate({
      sessionId,
      status: resumableStatus,
      needsInput: resumableStatus === "awaiting_input",
      type: "subtask",
      title: localDescription.trim() || undefined,
      projectId: projectId ?? null,
    });
  }, [broadcastUpdate, localDescription, projectId, sessionId, view.type]);

  const handleSendToBackground = useCallback(() => {
    keepSessionReachableInBackground();
    streamRef.current?.close();
    streamRef.current = null;
    onClose();
  }, [keepSessionReachableInBackground, onClose]);

  const handleClose = useCallback(async () => {
    const hasUnsavedChanges = dirty || view.type === "editing" || view.type === "creating";
    if (hasUnsavedChanges) {
      const shouldClose = await confirm({
        title: t("subtasks.keepSessionTitle", "Keep subtask session available?"),
        message: t("subtasks.keepSessionMessage", "Close this modal and keep the subtask session available from Background Tasks? Edited fields that have not been saved to the session may be reset when you resume."),
      });
      if (!shouldClose) {
        return;
      }
    }

    keepSessionReachableInBackground();
    streamRef.current?.close();
    streamRef.current = null;
    resetState();
    onClose();
  }, [dirty, keepSessionReachableInBackground, onClose, resetState, view.type, confirm, t]);

  const connectToSubtaskStream = useCallback(
    (activeSessionId: string) => {
      streamRef.current?.close();
      streamRef.current = connectSubtaskStream(activeSessionId, projectId, {
        onThinking: (data) => {
          setThinkingOutput((prev) => prev + data);
          broadcastUpdate({
            sessionId: activeSessionId,
            status: "generating",
            needsInput: false,
            type: "subtask",
            title: localDescription.trim() || undefined,
            projectId: projectId ?? null,
          });
        },
        onSubtasks: (items) => {
          setIsReconnecting(false);
          setIsRetrying(false);
          clearSubtaskDescription(projectId);
          setSubtasks(items);
          setView({ type: "editing", sessionId: activeSessionId });
          setDirty(false);

          broadcastUpdate({
            sessionId: activeSessionId,
            status: "awaiting_input",
            needsInput: true,
            type: "subtask",
            title: localDescription.trim() || undefined,
            projectId: projectId ?? null,
          });
        },
        onError: (message) => {
          const errorMessage = message || t("subtasks.errorSessionFailed", "Session failed while contacting the AI.");
          setIsReconnecting(false);
          setIsRetrying(false);
          setError(null);
          setView({ type: "error", sessionId: activeSessionId, errorMessage });

          broadcastUpdate({
            sessionId: activeSessionId,
            status: "error",
            needsInput: false,
            type: "subtask",
            title: localDescription.trim() || undefined,
            projectId: projectId ?? null,
          });
          broadcastCompleted({ sessionId: activeSessionId, status: "error" });
        },
        onComplete: () => {
          broadcastCompleted({ sessionId: activeSessionId, status: "complete" });
        },
        onConnectionStateChange: (state) => {
          setIsReconnecting(state === "reconnecting");
        },
      });
    },
    [
      broadcastCompleted,
      broadcastUpdate,
      localDescription,
      projectId,
    ],
  );

  const beginBreakdown = useCallback(async () => {
    if (!localDescription.trim()) return;
    setError(null);
    setConversationHistory([]);
    setThinkingOutput("");
    setIsReconnecting(false);
    setIsStartingBreakdown(true);

    try {
      const { sessionId } = await startSubtaskBreakdown(localDescription.trim(), projectId);
      setView({ type: "generating", sessionId });
      broadcastUpdate({
        sessionId,
        status: "generating",
        needsInput: false,
          type: "subtask",
        title: localDescription.trim() || undefined,
        projectId: projectId ?? null,
      });
      connectToSubtaskStream(sessionId);
    } catch (err) {
      setError(getErrorMessage(err) || t("subtasks.errorStartBreakdown", "Failed to start subtask breakdown"));
      setView({ type: "initial" });
    } finally {
      setIsStartingBreakdown(false);
    }
  }, [broadcastUpdate, connectToSubtaskStream, localDescription, projectId, t]);

  useEffect(() => {
    if (!isOpen) {
      resetState();
      return;
    }

    if (isOpen && initialDescription && !autoStartedRef.current) {
      setLocalDescription(initialDescription);
      autoStartedRef.current = true;
      void beginBreakdown();
    } else if (isOpen && !initialDescription && !autoStartedRef.current) {
      // Check localStorage for persisted description when no prop provided
      const persisted = getSubtaskDescription(projectId);
      if (persisted) {
        setLocalDescription(persisted);
      }
    }
  }, [isOpen, initialDescription, beginBreakdown, resetState]);

  useEffect(() => {
    if (!isOpen || !resumeSessionId || view.type !== "initial") return;

    void (async () => {
      try {
        const session = await fetchAiSession(resumeSessionId);
        if (!session) return;

        const parsedHistory = parseConversationHistory(session.conversationHistory);
        setConversationHistory(parsedHistory);

        if (session.status === "generating" || session.status === "awaiting_input") {
          setThinkingOutput(session.thinkingOutput ?? "");
          setView({ type: "generating", sessionId: resumeSessionId });
          connectToSubtaskStream(resumeSessionId);
        } else if (session.status === "complete" && session.result) {
          clearSubtaskDescription(projectId);
          const items = JSON.parse(session.result) as SubtaskItem[];
          setSubtasks(items);
          setView({ type: "editing", sessionId: resumeSessionId });
        } else if (session.status === "error") {
          setError(null);
          setView({
            type: "error",
            sessionId: resumeSessionId,
            errorMessage: session.error ?? t("subtasks.errorSessionEncountered", "Session encountered an error"),
          });
        }
      } catch (err) {
        setError(getErrorMessage(err) || t("subtasks.errorResumeSession", "Failed to resume session"));
      }
    })();
  }, [connectToSubtaskStream, isOpen, resumeSessionId, view.type, projectId]);

  useEffect(() => {
    return () => {
      streamRef.current?.close();
    };
  }, []);

  useEffect(() => {
    if (!isOpen) return;
    const handleKeyDown = (event: KeyboardEvent) => {
      if (event.key === "Escape") {
        event.preventDefault();
        void handleClose();
      }
    };
    document.addEventListener("keydown", handleKeyDown);
    return () => document.removeEventListener("keydown", handleKeyDown);
  }, [isOpen, handleClose]);

  const updateSubtask = useCallback((id: string, patch: Partial<SubtaskItem>) => {
    setSubtasks((current) => current.map((item) => item.id === id ? { ...item, ...patch } : item));
    setDirty(true);
  }, []);

  const addSubtask = useCallback(() => {
    setSubtasks((current) => [...current, createEmptySubtask(current.length + 1)]);
    setDirty(true);
  }, []);

  const removeSubtask = useCallback((id: string) => {
    setSubtasks((current) => current
      .filter((item) => item.id !== id)
      .map((item) => ({ ...item, dependsOn: item.dependsOn.filter((dep) => dep !== id) })));
    setDirty(true);
  }, []);

  // Drag-and-drop handlers
  const handleDragStart = useCallback((subtaskId: string) => (e: React.DragEvent) => {
    setDraggingId(subtaskId);
    e.dataTransfer.setData('text/plain', subtaskId);
    e.dataTransfer.effectAllowed = 'move';
  }, []);

  const handleDragEnd = useCallback(() => {
    setDraggingId(null);
    setDragOverId(null);
    setDragOverPosition(null);
  }, []);

  const handleDragOver = useCallback((targetId: string) => (e: React.DragEvent) => {
    e.preventDefault();
    if (targetId === draggingId) return;
    
    const rect = (e.currentTarget as HTMLElement).getBoundingClientRect();
    const midY = rect.top + rect.height / 2;
    const position: 'before' | 'after' = e.clientY < midY ? 'before' : 'after';
    
    setDragOverId(targetId);
    setDragOverPosition(position);
  }, [draggingId]);

  const handleDrop = useCallback((targetId: string) => (e: React.DragEvent) => {
    e.preventDefault();
    const draggedId = e.dataTransfer.getData('text/plain');
    
    if (!draggedId || draggedId === targetId) {
      setDraggingId(null);
      setDragOverId(null);
      setDragOverPosition(null);
      return;
    }

    setSubtasks((current) => {
      const fromIndex = current.findIndex((s) => s.id === draggedId);
      const toIndex = current.findIndex((s) => s.id === targetId);
      
      if (fromIndex === -1 || toIndex === -1) return current;
      
      const newSubtasks = [...current];
      const [moved] = newSubtasks.splice(fromIndex, 1);
      
      let insertIndex = toIndex;
      if (dragOverPosition === 'after' && fromIndex < toIndex) insertIndex--;
      if (dragOverPosition === 'after') insertIndex++;
      
      newSubtasks.splice(insertIndex, 0, moved);
      return newSubtasks;
    });
    
    setDirty(true);
    setDraggingId(null);
    setDragOverId(null);
    setDragOverPosition(null);
  }, [dragOverPosition]);

  const handleDragLeave = useCallback((e: React.DragEvent) => {
    const rect = (e.currentTarget as HTMLElement).getBoundingClientRect();
    const x = e.clientX;
    const y = e.clientY;
    
    // Only clear if leaving the element entirely, not just moving between children
    if (x < rect.left || x > rect.right || y < rect.top || y > rect.bottom) {
      setDragOverId(null);
      setDragOverPosition(null);
    }
  }, []);

  // Keyboard reordering handlers
  const moveSubtask = useCallback((fromIndex: number, toIndex: number) => {
    if (toIndex < 0 || toIndex >= subtasks.length) return;
    
    setSubtasks((current) => {
      const newSubtasks = [...current];
      const [moved] = newSubtasks.splice(fromIndex, 1);
      newSubtasks.splice(toIndex, 0, moved);
      return newSubtasks;
    });
    setDirty(true);
  }, [subtasks.length]);

  const moveFocusToNext = useCallback((index: number) => {
    titleRefs.current[index + 1]?.focus();
  }, []);

  const handleCreateTasks = useCallback(async () => {
    if (!sessionId || isInvalid) return;
    setError(null);
    setView({ type: "creating", sessionId });
    try {
      let effectiveWorkflowId = workflowId;
      if (parentTaskId) {
        try {
          effectiveWorkflowId = (await fetchTaskWorkflow(parentTaskId, projectId)).workflowId;
        } catch {
          effectiveWorkflowId = workflowId;
        }
      }
      const result = await createTasksFromBreakdown(sessionId, subtasks, parentTaskId, projectId, {
        branchSelection: {
          mode: branchMode,
          ...(branchMode === "existing" || branchMode === "custom-new" ? { branchName } : {}),
          ...(baseBranch.trim() ? { baseBranch: baseBranch.trim() } : {}),
        },
        branchAssignment: { mode: branchAssignmentMode },
        /*
        FNXC:WorkflowSelection 2026-06-20-16:48:
        Subtask Breakdown children inherit the parent task's workflow when available, otherwise they keep the workflow lane that opened this modal.
        */
        ...(effectiveWorkflowId !== undefined ? { workflowId: effectiveWorkflowId } : {}),
      });
      onTasksCreated(result.tasks);
      resetState();
      onClose();
    } catch (err) {
      setError(getErrorMessage(err) || t("subtasks.errorCreateTasks", "Failed to create tasks"));
      setView({ type: "editing", sessionId });
    }
  }, [baseBranch, branchAssignmentMode, branchMode, branchName, isInvalid, onClose, onTasksCreated, parentTaskId, projectId, resetState, sessionId, subtasks, workflowId]);

  const handleRetry = useCallback(async () => {
    if (view.type !== "error") {
      return;
    }

    const retrySessionId = view.sessionId;
    setError(null);
    setIsRetrying(true);
    setThinkingOutput("");
    setView({ type: "generating", sessionId: retrySessionId });
    connectToSubtaskStream(retrySessionId);

    try {
      await retrySubtaskSession(retrySessionId, projectId);
    } catch (err) {
      let retryError: unknown = err;
      const retryErrorMessage = getErrorMessage(err) || "";

      if (retryErrorMessage.includes("not in an error state")) {
        try {
          const session = await fetchAiSession(retrySessionId);
          if (!session) {
            throw new Error(t("subtasks.errorRefreshSession", "Failed to refresh subtask session."));
          }

          setConversationHistory(parseConversationHistory(session.conversationHistory));

          if (session.status === "generating" || session.status === "awaiting_input") {
            setThinkingOutput(session.thinkingOutput ?? "");
            setView({ type: "generating", sessionId: session.id });
            if (!streamRef.current?.isConnected()) {
              connectToSubtaskStream(session.id);
            }
          } else if (session.status === "complete") {
            if (!session.result) {
              throw new Error(t("subtasks.errorSessionNoResult", "Subtask session is complete but has no result."));
            }
            clearSubtaskDescription(projectId);
            const items = JSON.parse(session.result) as SubtaskItem[];
            setSubtasks(items);
            setView({ type: "editing", sessionId: session.id });
            setDirty(false);
          } else if (session.status === "error") {
            setView({
              type: "error",
              sessionId: session.id,
              errorMessage: session.error ?? t("subtasks.errorRetryFailed", "Retry failed. Please try again."),
            });
          }

          setIsReconnecting(false);
          return;
        } catch (sessionRefreshError) {
          retryError = sessionRefreshError;
        }
      }

      streamRef.current?.close();
      streamRef.current = null;
      setView({
        type: "error",
        sessionId: retrySessionId,
        errorMessage: getErrorMessage(retryError) || t("subtasks.errorRetryFailed", "Retry failed. Please try again."),
      });
      setIsReconnecting(false);
    } finally {
      setIsRetrying(false);
    }
  }, [connectToSubtaskStream, projectId, view]);

  if (!isOpen) return null;

  return (
    <div className="modal-overlay open" onClick={(event) => event.target === event.currentTarget && void handleClose()} role="dialog" aria-modal="true">
      <div className="modal modal-lg planning-modal" style={keyboardStyle}>
        <div className="modal-header">
          <div className="detail-title-row">
            <ListTree size={20} className="icon-triage" />
            <h3>{t("subtasks.modalTitle", "Subtask Breakdown")}</h3>
          </div>
          <div className="modal-header-actions">
            {showSendToBackgroundButton && (
              <button
                className="modal-send-to-background"
                onClick={handleSendToBackground}
                title={t("subtasks.sendToBackgroundTitle", "Send to background")}
                aria-label={t("subtasks.sendToBackgroundAriaLabel", "Send to background")}
              >
                <Minimize2 size={16} />
              </button>
            )}
            <button className="modal-close" onClick={() => void handleClose()} aria-label={t("common.close", "Close")}>
              <X size={20} />
            </button>
          </div>
        </div>

        <div className="planning-modal-body">
          {error && <div className="form-error planning-error">{error}</div>}
          {isReconnecting && <div className="form-hint text-muted">{t("subtasks.reconnecting", "Reconnecting…")}</div>}

          {view.type === "initial" && (
            <div className="planning-loading" data-testid="subtask-progress-state">
              <div className="planning-view-scroll">
                {/*
                 * FNXC:SubtaskBreakdown 2026-06-16-00:00:
                 * Subtask generation must show live progress as soon as a run is requested, before the session id or streamed thinking exists, so users do not see a dead static preparation state.
                 */}
                <Loader2 size={40} className="spin icon-todo" aria-hidden="true" />
                <p>{isStartingBreakdown ? t("subtasks.startingBreakdown", "Starting subtask breakdown...") : t("subtasks.preparingBreakdown", "Preparing to break this task into subtasks.")}</p>
                <p className="text-muted">{t("subtasks.progressHint", "Fusion will keep working while the AI prepares subtasks.")}</p>
                <pre className="planning-thinking-output">{localDescription}</pre>
              </div>
            </div>
          )}

          {view.type === "generating" && (
            <div className="planning-loading" data-testid="subtask-progress-state">
              {conversationHistory.length > 0 && (
                <>
                  <ConversationHistory entries={conversationHistory} defaultShowThinking={true} />
                  <div className="conversation-separator" />
                </>
              )}
              <Loader2 size={40} className="spin icon-todo" aria-hidden="true" />
              <p>{isReconnecting ? t("subtasks.reconnecting", "Reconnecting…") : t("subtasks.generatingSubtasks", "AI is generating subtasks...")}</p>
              <p className="text-muted">{t("subtasks.progressHint", "Fusion will keep working while the AI prepares subtasks.")}</p>
              <div className="planning-thinking-container">
                <button className="planning-thinking-toggle" onClick={() => setShowThinking(!showThinking)} type="button">
                  {showThinking ? t("subtasks.hideThinking", "Hide thinking") : t("subtasks.showThinking", "Show thinking")}
                </button>
                {showThinking && (
                  <div className="planning-thinking-output">
                    {thinkingOutput ? <pre>{thinkingOutput}</pre> : <p className="text-muted">{t("subtasks.waitingForThinking", "Waiting for AI progress updates...")}</p>}
                  </div>
                )}
              </div>
            </div>
          )}

          {view.type === "error" && (
            <div className="planning-summary">
              <div className="planning-view-scroll planning-summary-scroll">
                {conversationHistory.length > 0 && (
                  <>
                    <ConversationHistory entries={conversationHistory} defaultShowThinking={true} />
                    <div className="conversation-separator" />
                  </>
                )}
                <div
                  className="ai-error-panel"
                  role="alert"
                >
                  <div className="ai-error-icon">{WARNING_ICON}</div>
                  <div className="ai-error-message">{view.errorMessage}</div>
                  <div className="ai-error-actions">
                    <button className="btn btn-primary" onClick={() => void handleRetry()} disabled={isRetrying}>
                      {isRetrying ? <Loader2 size={14} className="spin" /> : <RefreshCw size={14} />}
                      <span className="icon-ml-6">{isRetrying ? t("subtasks.retrying", "Retrying...") : t("subtasks.retry", "Retry")}</span>
                    </button>
                    <button className="btn" onClick={() => void handleClose()} disabled={isRetrying}>{t("common.cancel", "Cancel")}</button>
                  </div>
                </div>
              </div>
            </div>
          )}

          {(view.type === "editing" || view.type === "creating") && (
            <div className="planning-summary">
              <div className="planning-view-scroll planning-summary-scroll">
                {conversationHistory.length > 0 && (
                  <>
                    <ConversationHistory entries={conversationHistory} />
                    <div className="conversation-separator" />
                  </>
                )}

                <div className="planning-summary-header">
                  <CheckCircle size={24} className="icon-success" />
                  <h4>{t("subtasks.reviewSubtasksHeading", "Review your subtasks")}</h4>
                  <p className="text-muted">{t("subtasks.reviewSubtasksHint", "Edit titles, descriptions, sizes, and dependencies before creating all tasks at once.")}</p>
                </div>

                <div className="planning-summary-form">
                  <div className="task-detail-section">
                    <div className="form-group">
                      <label>{t("subtasks.branchStrategyLabel", "Branch strategy")}</label>
                      <select value={branchMode} onChange={(event) => setBranchMode(event.target.value as typeof branchMode)} disabled={view.type === "creating"}>
                        <option value="project-default">{t("subtasks.branchModeProjectDefault", "Use project/default branch")}</option>
                        <option value="auto-new">{t("subtasks.branchModeAutoNew", "Create auto-named branch per task")}</option>
                        <option value="existing">{t("subtasks.branchModeExisting", "Use existing branch")}</option>
                        <option value="custom-new">{t("subtasks.branchModeCustomNew", "Create custom new branch")}</option>
                      </select>
                    </div>
                    {(branchMode === "existing" || branchMode === "custom-new") && (
                      <div className="form-group">
                        <label>{t("subtasks.branchNameLabel", "Branch name")}</label>
                        <input value={branchName} onChange={(event) => setBranchName(event.target.value)} disabled={view.type === "creating"} />
                      </div>
                    )}
                    <div className="form-group">
                      <label>{t("subtasks.baseBranchLabel", "Merge target / base branch (optional)")}</label>
                      <input value={baseBranch} onChange={(event) => setBaseBranch(event.target.value)} disabled={view.type === "creating"} placeholder={t("subtasks.baseBranchPlaceholder", "main")} />
                    </div>
                    <div className="form-group">
                      <label>{t("subtasks.planningBranchModeLabel", "Planning branch mode")}</label>
                      <select value={branchAssignmentMode} onChange={(event) => setBranchAssignmentMode(event.target.value as typeof branchAssignmentMode)} disabled={view.type === "creating"}>
                        <option value="shared">{t("subtasks.branchAssignmentShared", "Shared merge target — subtasks run on their own branches")}</option>
                        <option value="per-task-derived">{t("subtasks.branchAssignmentPerTask", "Per-task branches derived from planning branch")}</option>
                      </select>
                      {branchAssignmentMode === "shared" && branchName.trim() && (
                        <p className="text-muted">
                          {t("subtasks.groupedOnSharedBranch", "Grouped on shared branch")} <strong>{branchName.trim()}</strong>
                          {onOpenGroupModal && (
                            <button
                              type="button"
                              className="btn btn-sm"
                              onClick={() => onOpenGroupModal(`BG-${branchName.trim()}`)}
                            >
                              {t("subtasks.openGroupModal", "Open group modal")}
                            </button>
                          )}
                        </p>
                      )}
                    </div>
                  </div>
                  {subtasks.map((subtask, index) => {
                    const isDragging = draggingId === subtask.id;
                    const isDragOver = dragOverId === subtask.id;
                    const dragClasses = [
                      'task-detail-section',
                      'subtask-item',
                      isDragging ? 'subtask-item-dragging' : '',
                      isDragOver ? 'subtask-item-drop-target' : '',
                      isDragOver && dragOverPosition === 'before' ? 'subtask-item-drop-before' : '',
                      isDragOver && dragOverPosition === 'after' ? 'subtask-item-drop-after' : '',
                    ].filter(Boolean).join(' ');

                    return (
                      <div
                        key={subtask.id}
                        className={dragClasses}
                        data-testid={`subtask-item-${index}`}
                        draggable={view.type !== "creating"}
                        onDragStart={handleDragStart(subtask.id)}
                        onDragEnd={handleDragEnd}
                        onDragOver={handleDragOver(subtask.id)}
                        onDrop={handleDrop(subtask.id)}
                        onDragLeave={handleDragLeave}
                      >
                        <div className="detail-title-row subtask-item-header subtask-item-header--between">
                          <div className="subtask-drag-handle" title={t("subtasks.dragToReorder", "Drag to reorder")}>
                            <GripVertical size={16} />
                            <strong>{subtask.id}</strong>
                          </div>
                          <div className="subtask-item-actions">
                            <button
                              type="button"
                              className="btn btn-icon btn-sm"
                              onClick={() => moveSubtask(index, index - 1)}
                              disabled={view.type === "creating" || index === 0}
                              title={t("subtasks.moveUp", "Move up")}
                              aria-label={t("subtasks.moveSubtaskUpAriaLabel", "Move subtask up")}
                            >
                              <ArrowUp />
                            </button>
                            <button
                              type="button"
                              className="btn btn-icon btn-sm"
                              onClick={() => moveSubtask(index, index + 1)}
                              disabled={view.type === "creating" || index === subtasks.length - 1}
                              title={t("subtasks.moveDown", "Move down")}
                              aria-label={t("subtasks.moveSubtaskDownAriaLabel", "Move subtask down")}
                            >
                              <ArrowDown />
                            </button>
                            <button type="button" className="btn btn-sm" onClick={() => removeSubtask(subtask.id)} disabled={view.type === "creating"}>
                              <Trash2 size={14} /> {t("subtasks.remove", "Remove")}
                            </button>
                          </div>
                        </div>

                      <div className="form-group">
                        <label>{t("subtasks.titleLabel", "Title")}</label>
                        <input
                          ref={(element) => { titleRefs.current[index] = element; }}
                          value={subtask.title}
                          onChange={(event) => updateSubtask(subtask.id, { title: event.target.value })}
                          onKeyDown={(event) => {
                            if (event.key === "Enter") {
                              event.preventDefault();
                              moveFocusToNext(index);
                            }
                          }}
                          disabled={view.type === "creating"}
                        />
                      </div>

                      <div className="form-group">
                        <label>{t("subtasks.descriptionLabel", "Description")}</label>
                        <textarea
                          rows={8}
                          value={subtask.description}
                          onChange={(event) => updateSubtask(subtask.id, { description: event.target.value })}
                          disabled={view.type === "creating"}
                        />
                      </div>

                      <div className="form-group">
                        <label>{t("subtasks.sizeLabel", "Size")}</label>
                        <select
                          className="planning-size-select"
                          value={subtask.suggestedSize}
                          onChange={(event) => updateSubtask(subtask.id, { suggestedSize: event.target.value as "S" | "M" | "L" })}
                          disabled={view.type === "creating"}
                        >
                          <option value="S">S</option>
                          <option value="M">M</option>
                          <option value="L">L</option>
                        </select>
                      </div>

                      <div className="form-group">
                        <label>{t("subtasks.dependenciesLabel", "Dependencies")}</label>
                        <div className="planning-deps-list">
                          {/* Only show subtasks that come BEFORE this one in the list (prevents cycles) */}
                          {subtasks.slice(0, index).filter((item) => item.id !== subtask.id).map((candidate) => {
                            const selected = subtask.dependsOn.includes(candidate.id);
                            return (
                              <label key={candidate.id} className={`planning-dep-chip ${selected ? "selected" : ""}`}>
                                <input
                                  type="checkbox"
                                  checked={selected}
                                  onChange={() => {
                                    const nextDeps = selected
                                      ? subtask.dependsOn.filter((dep) => dep !== candidate.id)
                                      : [...subtask.dependsOn, candidate.id];
                                    updateSubtask(subtask.id, { dependsOn: nextDeps });
                                  }}
                                  disabled={view.type === "creating"}
                                />
                                <span className="planning-dep-id">{candidate.id}</span>
                                <span className="planning-dep-title">{candidate.title || t("subtasks.untitled", "Untitled")}</span>
                              </label>
                            );
                          })}
                          {index === 0 && (
                            <div className="text-muted">{t("subtasks.noDepsFirstSubtask", "First subtask cannot have dependencies.")}</div>
                          )}
                          {index > 0 && subtasks.slice(0, index).filter((item) => item.id !== subtask.id).length === 0 && (
                            <div className="text-muted">{t("subtasks.noPreviousSubtasks", "No previous subtasks available.")}</div>
                          )}
                        </div>
                      </div>
                    </div>
                  );
                  })}

                  <button type="button" className="btn" onClick={addSubtask} disabled={view.type === "creating"}>
                    <Plus size={16} className="icon-mr-6" /> {t("subtasks.addSubtask", "Add subtask")}
                  </button>

                  {hasDependencyCycle(subtasks) && (
                    <div className="form-error planning-error">{t("subtasks.dependencyCycleError", "Dependencies contain a cycle. Remove circular references before creating tasks.")}</div>
                  )}
                </div>
              </div>

              <div className="planning-actions planning-summary-actions">
                <button className="btn" onClick={() => void handleClose()} disabled={view.type === "creating"}>
                  {t("common.cancel", "Cancel")}
                </button>
                <button className="btn btn-primary" onClick={() => void handleCreateTasks()} disabled={view.type === "creating" || isInvalid}>
                  {view.type === "creating" ? (
                    <>
                      <Loader2 size={16} className="spin icon-mr-6" />
                      {t("subtasks.creating", "Creating...")}
                    </>
                  ) : (
                    <>{t("subtasks.createTasks", "Create Tasks")}</>
                  )}
                </button>
              </div>
            </div>
          )}

        </div>
      </div>
    </div>
  );
}

export type { SubtaskBreakdownModalProps };