import type { Task, TaskDetail, Column as ColumnType, TaskCreateInput } from "@fusion/core";
import { COLUMNS } from "@fusion/core";
import { compareTaskPriority, sortTasksByPriorityThenAgeAndId } from "../../../core/src/task-priority";
import { Column } from "./Column";
import type { ToastType } from "../hooks/useToast";
import { useState, useMemo, useEffect, useCallback, useRef } from "react";
import { useBatchBadgeFetch } from "../hooks/useBatchBadgeFetch";
import { fetchWorkflowSteps, type ModelInfo } from "../api";

interface BoardProps {
  tasks: Task[];
  projectId?: string;
  maxConcurrent: number;
  onMoveTask: (id: string, column: ColumnType) => Promise<Task>;
  onPauseTask?: (id: string) => Promise<Task>;
  onOpenDetail: (task: Task | TaskDetail) => void;
  addToast: (message: string, type?: ToastType) => void;
  onQuickCreate?: (input: TaskCreateInput) => Promise<Task | void>;
  onNewTask: () => void;
  autoMerge: boolean;
  onToggleAutoMerge: () => void;
  globalPaused?: boolean;
  onUpdateTask?: (
    id: string,
    updates: { title?: string; description?: string; dependencies?: string[] }
  ) => Promise<Task>;
  onRetryTask?: (id: string) => Promise<Task>;
  onArchiveTask?: (id: string) => Promise<Task>;
  onUnarchiveTask?: (id: string) => Promise<Task>;
  onDeleteTask?: (id: string) => Promise<Task>;
  onArchiveAllDone?: () => Promise<Task[]>;
  /** Lazy-load archived tasks. Called the first time the user expands the archived column. */
  onLoadArchivedTasks?: () => Promise<void>;
  searchQuery?: string;
  availableModels?: ModelInfo[];
  /**
   * Called when the user clicks the "Plan" button in the inline create card.
   */
  onPlanningMode?: (initialPlan: string) => void;
  /**
   * Called when the user clicks the "Subtask" button in the inline create card.
   */
  onSubtaskBreakdown?: (description: string) => void;
  onOpenDetailWithTab?: (task: Task | TaskDetail, initialTab: "changes") => void;
  favoriteProviders?: string[];
  favoriteModels?: string[];
  onToggleFavorite?: (provider: string) => void;
  onToggleModelFavorite?: (modelId: string) => void;
  /** Project-level stuck task timeout in milliseconds (undefined = disabled) */
  taskStuckTimeoutMs?: number;
  /** Called when user clicks a mission badge on a task card */
  onOpenMission?: (missionId: string) => void;
  /** Timestamp (ms) when task data was last confirmed fresh from the server. Used for freshness-aware stuck detection. */
  lastFetchTimeMs?: number;
}

function compareTaskIdNumeric(a: string, b: string): number {
  const aNum = Number.parseInt(a.slice(a.lastIndexOf("-") + 1), 10);
  const bNum = Number.parseInt(b.slice(b.lastIndexOf("-") + 1), 10);

  if (Number.isFinite(aNum) && Number.isFinite(bNum) && aNum !== bNum) {
    return aNum - bNum;
  }

  return a.localeCompare(b);
}

function getDoneSortTimestamp(task: Task): number {
  const timestamp = task.columnMovedAt ?? task.updatedAt ?? task.createdAt;
  const parsed = Date.parse(timestamp);
  return Number.isFinite(parsed) ? parsed : 0;
}

function sortTasksForColumn(tasks: Task[], column: ColumnType): Task[] {
  if (column === "todo") {
    // Match scheduler pickup order: priority DESC, createdAt ASC, id ASC.
    return sortTasksByPriorityThenAgeAndId(tasks);
  }

  return [...tasks].sort((a, b) => {
    if (column === "done") {
      const timestampCmp = getDoneSortTimestamp(b) - getDoneSortTimestamp(a);
      if (timestampCmp !== 0) {
        return timestampCmp;
      }

      // Deterministic tie-breaker when completion timestamps match.
      return compareTaskIdNumeric(a.id, b.id);
    }

    // In the in-review column, merging tasks stay pinned above non-merging tasks.
    if (column === "in-review") {
      const aIsMerging = a.status === "merging" || a.status === "merging-pr" || a.status === "merging-fix";
      const bIsMerging = b.status === "merging" || b.status === "merging-pr" || b.status === "merging-fix";
      if (aIsMerging !== bIsMerging) {
        return aIsMerging ? -1 : 1;
      }
    }

    // Primary sort for non-done/non-todo columns: priority descending.
    const priorityCmp = compareTaskPriority(a.priority, b.priority);
    if (priorityCmp !== 0) {
      return priorityCmp;
    }

    // Secondary sort: numeric task ID ascending (lower number first).
    return compareTaskIdNumeric(a.id, b.id);
  });
}

function areTaskArraysEqual(previous: Task[], next: Task[]): boolean {
  if (previous.length !== next.length) return false;
  return previous.every((task, index) => task === next[index]);
}

const EMPTY_WORKFLOW_STEP_NAME_LOOKUP: ReadonlyMap<string, string> = new Map();

function areWorkflowNameLookupsEqual(previous: ReadonlyMap<string, string>, next: ReadonlyMap<string, string>): boolean {
  if (previous.size !== next.size) return false;
  for (const [key, value] of previous) {
    if (next.get(key) !== value) return false;
  }
  return true;
}

export function Board({ tasks, projectId, maxConcurrent, onMoveTask, onPauseTask, onOpenDetail, addToast, onQuickCreate, onNewTask, autoMerge, onToggleAutoMerge, globalPaused, onUpdateTask, onRetryTask, onArchiveTask, onUnarchiveTask, onDeleteTask, onArchiveAllDone, onLoadArchivedTasks, searchQuery = "", availableModels, onPlanningMode, onSubtaskBreakdown, onOpenDetailWithTab, favoriteProviders, favoriteModels, onToggleFavorite, onToggleModelFavorite, taskStuckTimeoutMs, onOpenMission, lastFetchTimeMs }: BoardProps) {
  const [archivedCollapsed, setArchivedCollapsed] = useState(true);
  const archivedLoadedRef = useRef(false);
  const { fetchBatch } = useBatchBadgeFetch(projectId);
  const debounceTimeoutRef = useRef<ReturnType<typeof setTimeout> | null>(null);
  const [workflowStepNameLookup, setWorkflowStepNameLookup] = useState<ReadonlyMap<string, string>>(EMPTY_WORKFLOW_STEP_NAME_LOOKUP);
  // Normalized search-active signal: trimmed and non-empty
  const isSearchActive = searchQuery.trim() !== "";
  const tasksByColumnCacheRef = useRef<Record<ColumnType, Task[]>>({
    triage: [],
    todo: [],
    "in-progress": [],
    "in-review": [],
    done: [],
    archived: [],
  });

  const handleToggleArchivedCollapse = useCallback(() => {
    setArchivedCollapsed((current) => {
      const next = !current;
      if (!next && !archivedLoadedRef.current && onLoadArchivedTasks) {
        archivedLoadedRef.current = true;
        void onLoadArchivedTasks();
      }
      return next;
    });
  }, [onLoadArchivedTasks]);

  // Tasks are already server-filtered when searchQuery is active (via useTasks hook).
  // Client-side filtering is removed - tasks prop is used directly.
  // Keep per-column array identities stable for unchanged columns so React.memo(Column)
  // can skip sibling rerenders during unrelated task updates.
  const tasksByColumn = useMemo(() => {
    const nextGrouped = Object.fromEntries(
      COLUMNS.map((column) => [column, [] as Task[]]),
    ) as Record<ColumnType, Task[]>;

    for (const task of tasks) {
      nextGrouped[task.column].push(task);
    }

    const previousGrouped = tasksByColumnCacheRef.current;
    const stableGrouped = {} as Record<ColumnType, Task[]>;

    for (const column of COLUMNS) {
      const sortedTasks = sortTasksForColumn(nextGrouped[column], column);
      stableGrouped[column] = areTaskArraysEqual(previousGrouped[column], sortedTasks)
        ? previousGrouped[column]
        : sortedTasks;
    }

    tasksByColumnCacheRef.current = stableGrouped;
    return stableGrouped;
  }, [tasks]);

  useEffect(() => {
    let cancelled = false;

    fetchWorkflowSteps(projectId)
      .then((steps) => {
        if (cancelled) return;

        const nextLookup = new Map(steps.map((step) => [step.id, step.name] as const));
        setWorkflowStepNameLookup((previous) => (
          areWorkflowNameLookupsEqual(previous, nextLookup) ? previous : nextLookup
        ));
      })
      .catch(() => {
        if (cancelled) return;
        setWorkflowStepNameLookup((previous) => (previous.size === 0 ? previous : EMPTY_WORKFLOW_STEP_NAME_LOOKUP));
      });

    return () => {
      cancelled = true;
    };
  }, [projectId]);

  // Collect task IDs with GitHub badge info for batch fetching
  const taskIdsWithBadges = useMemo(() => {
    return tasks
      .filter((t) => t.prInfo || t.issueInfo)
      .map((t) => t.id);
  }, [tasks]);

  // Batch fetch badge statuses on mount and when visible tasks change
  useEffect(() => {
    if (taskIdsWithBadges.length === 0) return;

    // Debounce the batch fetch to handle rapid changes
    if (debounceTimeoutRef.current) {
      clearTimeout(debounceTimeoutRef.current);
    }

    debounceTimeoutRef.current = setTimeout(() => {
      // Fetch in chunks of 50 to respect the API limit
      const chunks: string[][] = [];
      for (let i = 0; i < taskIdsWithBadges.length; i += 50) {
        chunks.push(taskIdsWithBadges.slice(i, i + 50));
      }

      // Fire all chunks concurrently - the hook handles deduplication
      chunks.forEach((chunk) => {
        void fetchBatch(chunk);
      });
    }, 500);

    return () => {
      if (debounceTimeoutRef.current) {
        clearTimeout(debounceTimeoutRef.current);
      }
    };
  }, [taskIdsWithBadges, fetchBatch]);

  return (
    <>
      <main className="board" id="board">
        {COLUMNS.map((col) => (
          <Column
            key={col}
            column={col}
            tasks={tasksByColumn[col]}
            projectId={projectId}
            maxConcurrent={maxConcurrent}
            onMoveTask={onMoveTask}
            onPauseTask={onPauseTask}
            onOpenDetail={onOpenDetail}
            addToast={addToast}
            globalPaused={globalPaused}
            onUpdateTask={onUpdateTask}
            onRetryTask={onRetryTask}
            onArchiveTask={onArchiveTask}
            onUnarchiveTask={onUnarchiveTask}
            onDeleteTask={onDeleteTask}
            allTasks={tasks}
            availableModels={availableModels}
            onOpenDetailWithTab={onOpenDetailWithTab}
            favoriteProviders={favoriteProviders}
            favoriteModels={favoriteModels}
            onToggleFavorite={onToggleFavorite}
            onToggleModelFavorite={onToggleModelFavorite}
            isSearchActive={isSearchActive}
            taskStuckTimeoutMs={taskStuckTimeoutMs}
            onOpenMission={onOpenMission}
            lastFetchTimeMs={lastFetchTimeMs}
            workflowStepNameLookup={workflowStepNameLookup}
            {...(col === "triage" ? { onQuickCreate, onNewTask, onPlanningMode, onSubtaskBreakdown } : {})}
            {...(col === "in-review" ? { autoMerge, onToggleAutoMerge } : {})}
            {...(col === "done" ? { onArchiveAllDone } : {})}
            {...(col === "archived" ? { collapsed: archivedCollapsed, onToggleCollapse: handleToggleArchivedCollapse } : {})}
          />
        ))}
      </main>
    </>
  );
}