import { useCoordinatorWorkspaceEnabled } from "@/hooks/useCoordinatorWorkspaceEnabled";
import { useCallback, useEffect, useLayoutEffect, useRef, useState, type ReactNode } from "react";
import { X } from "lucide-react";
import { usePanel } from "../context/PanelContext";
import { useClassicTaskInterfaceEnabled } from "../hooks/useClassicTaskInterfaceEnabled";
import { useStreamlinedUiEnabled } from "../hooks/useStreamlinedUiEnabled";
import { cn } from "../lib/utils";
import { Button } from "@/components/ui/button";
import { ScrollArea } from "@/components/ui/scroll-area";
import { SidePanelFrame, SidePanelWindowControls } from "@/components/side-panel";
import { useDesignSandbox } from "@/context/DesignSandboxContext";

export function PropertiesPanel({ taskDetailLayout = false }: { taskDetailLayout?: boolean }) {
  const {
    panelContent,
    panelContentMode,
    panelVisible,
    setPanelVisible,
    panelMaximizeRequested,
    clearPanelMaximizeRequest,
  } = usePanel();
  const { enabled: classicTaskInterfaceEnabled } = useClassicTaskInterfaceEnabled();
  const { enabled: streamlinedUiEnabled } = useStreamlinedUiEnabled();
  const designSandbox = useDesignSandbox();
  const { enabled: coordinatorWorkspaceEnabled } = useCoordinatorWorkspaceEnabled();
  const streamlinedTaskDetailLayout = (streamlinedUiEnabled || coordinatorWorkspaceEnabled) && taskDetailLayout;
  // Keep the zero-width host mounted while route data loads. Inserting an
  // already-open pane skips its width transition and snaps the thread sideways.
  const visible = panelVisible && panelContent != null;

  if (classicTaskInterfaceEnabled && !coordinatorWorkspaceEnabled) {
    return (
      <aside
        inert={!visible}
        aria-hidden={!visible}
        className={cn("hidden md:flex border-border bg-card flex-col shrink-0 overflow-hidden h-full", panelContent != null && "properties-panel-docked", visible && "border-l")}
        style={{ width: visible ? 320 : 0, opacity: visible ? 1 : 0 }}
      >
        <div className="w-80 flex-1 flex flex-col min-w-(--sz-320px) min-h-0">
          <div className="flex items-center justify-between px-4 py-2 border-b border-border">
            <span className="text-sm font-medium">Properties</span>
            <Button variant="ghost" size="icon-xs" onClick={() => setPanelVisible(false)}>
              <X className="h-4 w-4" />
            </Button>
          </div>
          <ScrollArea className="flex-1">
            <div className="p-4">{panelContent}</div>
          </ScrollArea>
        </div>
      </aside>
    );
  }

  return (
    <ResizablePropertiesPanel
      key={`${streamlinedTaskDetailLayout ? "task-detail" : "default"}-${designSandbox ? "proposal" : "production"}`}
      panelContent={panelContent}
      panelContentMode={panelContentMode}
      panelVisible={visible}
      setPanelVisible={setPanelVisible}
      taskDetailLayout={streamlinedTaskDetailLayout}
      designSandbox={designSandbox}
      maximizeRequested={panelMaximizeRequested}
      clearMaximizeRequest={clearPanelMaximizeRequest}
    />
  );
}

/* ------------------------------------------------------------------------- *
 * Production chat-style resizable/maximizable variant. Streamlined UI only
 * changes its task-detail dimensions; Classic Task Interface selects the
 * fixed panel above.
 * ------------------------------------------------------------------------- */

/**
 * Portal target in the redesigned pane's header bar: hosted content (the
 * Properties | Plan | Artifacts tab strip, including the single active
 * Properties tab) renders here, left of the window controls. See
 * IssueProperties' flag-ON shell.
 */
export const PROPERTIES_PANE_HEADER_SLOT_ID = "properties-pane-header-slot";
/**
 * Portal target pinned below the pane's scroll area: hosted content (the plan
 * confirmation action bar) renders here so it stays visible while the pane
 * body scrolls.
 */
export const PROPERTIES_PANE_FOOTER_SLOT_ID = "properties-pane-footer-slot";

const WIDTH_STORAGE_KEY = "taskChatRedesign.propertiesPaneWidth";
const TASK_DETAIL_WIDTH_STORAGE_KEY = "taskChatRedesign.taskDetailPropertiesPaneWidth";
const PROPOSAL_WIDTH_STORAGE_KEY = "paperclip.design-proposal.properties-pane-width";
const DEFAULT_PANE_WIDTH = 322;
const TASK_DETAIL_DEFAULT_PANE_WIDTH = 434;
const MIN_PANE_WIDTH = 260;
/** ~236px sidebar + ~420px minimum center column stay usable while resizing. */
const RESERVED_LAYOUT_WIDTH = 656;
/** Content cap while maximized so text doesn't span the full viewport. */
const MAXIMIZED_CONTENT_MAX_WIDTH = 840;
/**
 * Defensive fallback (in milliseconds) for the restore glide in case
 * `transitionend` never fires; slightly longer than the --motion-pane-glide
 * token in index.css.
 */
const RESTORE_FALLBACK_DELAY = 400;

function readProposalPaneWidth(fallback: number): number {
  if (typeof window === "undefined") return fallback;
  const tokenWidth = Number.parseFloat(getComputedStyle(document.documentElement).getPropertyValue("--design-page-aside-width"));
  return Number.isFinite(tokenWidth) && tokenWidth > 0 ? tokenWidth : fallback;
}

function clampPaneWidth(width: number): number {
  const max =
    typeof window === "undefined"
      ? Number.POSITIVE_INFINITY
      : Math.max(MIN_PANE_WIDTH, window.innerWidth - RESERVED_LAYOUT_WIDTH);
  return Math.min(Math.max(Math.round(width), MIN_PANE_WIDTH), max);
}

function readStoredPaneWidth(storageKey: string, defaultWidth: number): number {
  if (typeof window === "undefined") return defaultWidth;
  try {
    const raw = window.localStorage.getItem(storageKey);
    const parsed = raw === null ? Number.NaN : Number(raw);
    return Number.isFinite(parsed) ? parsed : defaultWidth;
  } catch {
    return defaultWidth;
  }
}

function persistPaneWidth(storageKey: string, width: number) {
  if (typeof window === "undefined") return;
  try {
    window.localStorage.setItem(storageKey, String(width));
  } catch {
    // Ignore storage failures.
  }
}

function clearStoredPaneWidth(storageKey: string) {
  if (typeof window === "undefined") return;
  try {
    window.localStorage.removeItem(storageKey);
  } catch {
    // Ignore storage failures.
  }
}

function prefersReducedMotion(): boolean {
  if (typeof window === "undefined" || typeof window.matchMedia !== "function") return false;
  return window.matchMedia("(prefers-reduced-motion: reduce)").matches;
}

/** Fixed-position geometry while the panel is maximized (or gliding). */
interface FixedPane {
  top: number;
  /** Animated by the .tc-pane-glide transition. */
  left: number;
  /** Distance from the viewport's right edge to the panel's right edge. */
  rightInset: number;
  /** Glide target: the layout row's left edge (flush with the sidebar). */
  parentLeft: number;
}

interface ResizablePropertiesPanelProps {
  panelContent: ReactNode | null;
  panelContentMode: "padded" | "prose" | "full-bleed";
  panelVisible: boolean;
  setPanelVisible: (visible: boolean) => void;
  taskDetailLayout: boolean;
  designSandbox: boolean;
  /** Pending `viewer=full` deep-link request (LOOA-2181); cleared once consumed. */
  maximizeRequested: boolean;
  clearMaximizeRequest: () => void;
}

function ResizablePropertiesPanel({
  panelContent,
  panelContentMode,
  panelVisible,
  setPanelVisible,
  taskDetailLayout,
  designSandbox,
  maximizeRequested,
  clearMaximizeRequest,
}: ResizablePropertiesPanelProps) {
  const productionPaneWidth = taskDetailLayout
    ? TASK_DETAIL_DEFAULT_PANE_WIDTH
    : DEFAULT_PANE_WIDTH;
  const defaultPaneWidth = designSandbox ? readProposalPaneWidth(productionPaneWidth) : productionPaneWidth;
  const widthStorageKey = designSandbox
    ? `${PROPOSAL_WIDTH_STORAGE_KEY}.${taskDetailLayout ? "task-detail" : "default"}`
    : taskDetailLayout
    ? TASK_DETAIL_WIDTH_STORAGE_KEY
    : WIDTH_STORAGE_KEY;
  const [width, setWidth] = useState(() =>
    clampPaneWidth(readStoredPaneWidth(widthStorageKey, defaultPaneWidth)),
  );
  const [dragging, setDragging] = useState(false);
  const [maximized, setMaximized] = useState(false);
  const [fixedPane, setFixedPane] = useState<FixedPane | null>(null);

  // The host can outlive a viewport change while its content is loading.
  // Clamp before revealing it, without overwriting the user's saved width.
  useLayoutEffect(() => {
    if (panelVisible) setWidth(clampPaneWidth);
  }, [panelVisible]);

  const asideRef = useRef<HTMLElement | null>(null);
  const widthRef = useRef(width);
  widthRef.current = width;
  const dragStateRef = useRef<{ pointerId: number; startX: number; startWidth: number } | null>(
    null,
  );
  const previousBodyUserSelectRef = useRef("");
  const restoreTimerRef = useRef<number | null>(null);

  const clearRestoreTimer = useCallback(() => {
    if (restoreTimerRef.current !== null) {
      window.clearTimeout(restoreTimerRef.current);
      restoreTimerRef.current = null;
    }
  }, []);

  const finishRestore = useCallback(() => {
    clearRestoreTimer();
    setFixedPane(null);
  }, [clearRestoreTimer]);

  // Hiding the panel keeps today's collapse-to-0 behavior; if it was
  // maximized (or mid-glide), just unmaximize instantly first.
  useEffect(() => {
    if (!panelVisible) {
      setMaximized(false);
      finishRestore();
    }
  }, [panelVisible, finishRestore]);

  useEffect(
    () => () => {
      if (restoreTimerRef.current !== null) window.clearTimeout(restoreTimerRef.current);
      if (dragStateRef.current !== null) {
        document.body.style.userSelect = previousBodyUserSelectRef.current;
      }
    },
    [],
  );

  const endDrag = useCallback((persist: boolean) => {
    if (dragStateRef.current === null) return;
    dragStateRef.current = null;
    setDragging(false);
    document.body.style.userSelect = previousBodyUserSelectRef.current;
    if (persist) persistPaneWidth(widthStorageKey, widthRef.current);
  }, [widthStorageKey]);

  const handleGripPointerDown = useCallback((event: React.PointerEvent<HTMLDivElement>) => {
    // Primary button only (touch/pen report button 0 or -1 for down events).
    if (event.pointerType === "mouse" && event.button !== 0) return;
    event.preventDefault();
    event.currentTarget.setPointerCapture(event.pointerId);
    dragStateRef.current = {
      pointerId: event.pointerId,
      startX: event.clientX,
      startWidth: widthRef.current,
    };
    previousBodyUserSelectRef.current = document.body.style.userSelect;
    document.body.style.userSelect = "none";
    setDragging(true);
  }, []);

  const handleGripPointerMove = useCallback((event: React.PointerEvent<HTMLDivElement>) => {
    const drag = dragStateRef.current;
    if (drag === null || drag.pointerId !== event.pointerId) return;
    // The grip sits on the panel's LEFT border: moving left widens the panel.
    setWidth(clampPaneWidth(drag.startWidth + (drag.startX - event.clientX)));
  }, []);

  const handleGripPointerUp = useCallback(
    (event: React.PointerEvent<HTMLDivElement>) => {
      const drag = dragStateRef.current;
      if (drag === null || drag.pointerId !== event.pointerId) return;
      endDrag(true);
    },
    [endDrag],
  );

  const handleGripLostPointerCapture = useCallback(() => {
    endDrag(true);
  }, [endDrag]);

  const handleGripDoubleClick = useCallback(() => {
    setWidth(designSandbox ? clampPaneWidth(readProposalPaneWidth(productionPaneWidth)) : defaultPaneWidth);
    clearStoredPaneWidth(widthStorageKey);
  }, [defaultPaneWidth, designSandbox, productionPaneWidth, widthStorageKey]);

  const handleMaximize = useCallback(() => {
    const aside = asideRef.current;
    const row = aside?.parentElement;
    if (!aside || !row) return;
    clearRestoreTimer();
    setMaximized(true);
    const rowRect = row.getBoundingClientRect();
    setFixedPane((pane) => {
      // Re-maximizing mid-restore: keep the current geometry, glide back left.
      if (pane) return { ...pane, left: pane.parentLeft };
      const rect = aside.getBoundingClientRect();
      const seeded: FixedPane = {
        top: rect.top,
        left: rect.left,
        rightInset: Math.max(0, window.innerWidth - rect.right),
        parentLeft: rowRect.left,
      };
      if (prefersReducedMotion()) return { ...seeded, left: seeded.parentLeft };
      // Seed at the current left, then glide to the row's left edge once the
      // fixed position has been committed (double rAF).
      window.requestAnimationFrame(() => {
        window.requestAnimationFrame(() => {
          setFixedPane((current) => (current ? { ...current, left: current.parentLeft } : current));
        });
      });
      return seeded;
    });
  }, [clearRestoreTimer]);

  const handleRestore = useCallback(() => {
    const row = asideRef.current?.parentElement;
    setMaximized(false);
    if (prefersReducedMotion()) {
      finishRestore();
      return;
    }
    setFixedPane((pane) => {
      if (!pane) return pane;
      const rowRight = row
        ? row.getBoundingClientRect().right
        : window.innerWidth - pane.rightInset;
      return { ...pane, left: rowRight - widthRef.current };
    });
    clearRestoreTimer();
    restoreTimerRef.current = window.setTimeout(finishRestore, RESTORE_FALLBACK_DELAY);
  }, [clearRestoreTimer, finishRestore]);

  // Deep-link maximize (LOOA-2181): the request may predate this mount (the
  // hash routes before the panel content commits), so it lives in context and
  // is consumed here once the panel is actually visible and laid out —
  // handleMaximize measures live geometry, which needs a committed DOM.
  useEffect(() => {
    if (!maximizeRequested || !panelVisible) return;
    clearMaximizeRequest();
    if (!maximized) handleMaximize();
  }, [maximizeRequested, panelVisible, maximized, handleMaximize, clearMaximizeRequest]);

  const handleTransitionEnd = useCallback(
    (event: React.TransitionEvent<HTMLElement>) => {
      if (event.target !== asideRef.current || event.propertyName !== "left") return;
      // Only the restore glide needs to unfix on arrival.
      if (!maximized) finishRestore();
    },
    [maximized, finishRestore],
  );

  // Route cleanup removes content before the maximize reset effect runs.
  // Release fixed geometry immediately so an empty pane cannot cover the next page.
  const isFixed = panelContent != null && fixedPane !== null;

  return (
    <>
      {isFixed ? (
        // Holds the panel's slot in the layout flex row while the panel is
        // position:fixed, so the main column never reflows.
        <div
          aria-hidden
          className="hidden md:block shrink-0"
          style={{ width: panelVisible ? width : 0 }}
        />
      ) : null}
      <aside
        ref={asideRef}
        inert={!panelVisible}
        aria-hidden={!panelVisible}
        className={cn(
          "hidden md:flex bg-card flex-col",
          isFixed
            ? "tc-pane-glide fixed z-40 overflow-hidden"
            : cn(
                "relative h-full shrink-0",
                panelVisible ? "overflow-visible" : "overflow-hidden",
                // The width/opacity transition would fight pointer-driven
                // resizing, so it is suspended while dragging.
                !dragging && panelContent != null && "properties-panel-docked",
              ),
        )}
        style={
          isFixed
            ? {
                top: fixedPane.top,
                bottom: 0,
                left: fixedPane.left,
                right: fixedPane.rightInset,
              }
            : { width: panelVisible ? width : 0, opacity: panelVisible ? 1 : 0 }
        }
        onTransitionEnd={handleTransitionEnd}
      >
        {!isFixed && panelVisible ? (
          <div
            role="separator"
            aria-orientation="vertical"
            aria-label="Resize panel"
            data-dragging={dragging ? "" : undefined}
            className="pane-resize-handle group absolute inset-y-0 z-10 max-w-full cursor-col-resize touch-none"
            style={{ left: -4, width: 8 }}
            onPointerDown={handleGripPointerDown}
            onPointerMove={handleGripPointerMove}
            onPointerUp={handleGripPointerUp}
            onPointerCancel={handleGripPointerUp}
            onLostPointerCapture={handleGripLostPointerCapture}
            onDoubleClick={handleGripDoubleClick}
          >
            <div
              className={cn(
                "mx-auto h-full w-0.5 transition-colors",
                dragging ? "bg-ring" : "bg-transparent group-hover:bg-ring",
              )}
            />
          </div>
        ) : null}
        <div className="flex min-h-0 flex-1 overflow-hidden">
          <div
            className={cn("flex shrink-0 flex-col min-h-0", !maximized && "border-l border-border", isFixed && "w-full")}
            style={isFixed ? undefined : { width, minWidth: width }}
          >
            <SidePanelFrame
              presentation="docked"
              maximized={maximized}
              contentMode="full-bleed"
              headerSize={taskDetailLayout ? "task-detail" : "default"}
              className="flex-1 border-l-0"
              header={(
                <div
                  id={PROPERTIES_PANE_HEADER_SLOT_ID}
                  className="flex min-w-0 flex-1 items-center self-stretch"
                />
              )}
              trailingControls={(
                <SidePanelWindowControls
                  maximized={maximized}
                  closeControl={taskDetailLayout ? "close" : "toggle"}
                  onMaximizedChange={(next) => {
                    if (next) handleMaximize();
                    else handleRestore();
                  }}
                  onToggle={() => setPanelVisible(false)}
                />
              )}
              footer={<div id={PROPERTIES_PANE_FOOTER_SLOT_ID} />}
            >
              {panelContentMode === "full-bleed" ? panelContent : (
                <ScrollArea className="h-full">
                  <div
                    className={cn("p-4", maximized && "mx-auto w-full px-9")}
                    style={maximized ? { maxWidth: MAXIMIZED_CONTENT_MAX_WIDTH } : undefined}
                  >
                    {panelContent}
                  </div>
                </ScrollArea>
              )}
            </SidePanelFrame>
          </div>
        </div>
      </aside>
    </>
  );
}