"use client";

import {
  createContext,
  useCallback,
  useContext,
  useEffect,
  useId,
  useMemo,
  useRef,
  useState,
  type ReactNode,
} from "react";
import { usePathname } from "next/navigation";
import type {
  AssistantCommandId,
  AssistantMention,
  NumoIntent,
  AssistantPageContext,
} from "@/lib/assistant-types";
import type { PanelDisplayMode } from "@/components/assistant/panel-geometry";
import type { ResourceInput } from "@/lib/types";
import { projectIdFromPath } from "@/lib/project-id-from-path";
import { trackEvent } from "@/lib/analytics";

export interface OpenAssistantOptions {
  /** Project context attached by this opening; never replaces the conversation. */
  projectId?: string | null;
  /**
   * Open ON a persisted conversation instead of the live one. The panel loads
   * it and marks it read — the entry of inbox rows and "view the session"
   * gestures, which have no page to push any more.
   */
  conversationId?: string | null;
  /** Auto-send a one-shot message right after opening. */
  prompt?: string;
  /**
 * What the "@" and "/" of the original composer set in `prompt`.
 * Home opens its own composer, mentions and command included: without
 * these two, the text would arrive at Numo but stripped of what it
 * designates — a mention becomes text again, a command with no effect.
 */
  mentions?: AssistantMention[];
  command?: AssistantCommandId;
  /**
 * Attachments from the original composer, ALREADY uploaded: `ResourceInput`
 * only carries a storage path, not a file. The reception can therefore en
 * join — the wait which goes up for them is played out in its composition, and the opening
 * only carries references.
 */
  attachments?: ResourceInput[];
  /** Pre-fill the composer without sending (one-shot). */
  draft?: string;
  /**
   * What the user is currently looking at (e.g. the issue open in the side
   * panel). Sent with the conversation's messages so Numo can resolve
   * "ce ticket" and edit it directly. Persists for the opened session.
   */
  pageContext?: AssistantPageContext;
  /** Provenance retained when an old caller still uses `open` directly. */
  intent?: Pick<NumoIntent, "source" | "action">;
  /**
   * Display mode the panel should open in. Absent = keep whatever mode the
   * session is already in (the toolbar toggle stays authoritative). The home
   * composer asks for `"expanded"`: a message sent from the dashboard is a
   * work session, not a popover glance.
   */
  displayMode?: PanelDisplayMode;
  /**
   * Put the caret in the composer once the panel is ready, without sending or
   * filling anything: the opener hands the user a context to ask about.
   */
  focusComposer?: boolean;
}

/** Opening-time presentation choices of `openIntent`. */
export interface OpenIntentOptions {
  displayMode?: PanelDisplayMode;
  /** See `OpenAssistantOptions.focusComposer`. */
  focusComposer?: boolean;
}

export interface AssistantPanelContextValue {
  isOpen: boolean;
  /** Options consumed by AssistantPanel on the next open cycle. */
  pendingOptions: OpenAssistantOptions | null;
  /**
   * Page context active for the open session (e.g. the issue being viewed).
   * Set on open, cleared on close — survives `clearPendingOptions` so manual
   * follow-up messages keep carrying it. Set in event handlers, so the panel
   * never has to setState inside an effect.
   */
  activePageContext: AssistantPageContext | null;
  /**
   * Ambient context derived from the page the user is currently on (e.g. the
   * issue whose side panel is open). Unlike `activePageContext`, it exists
   * independently of open/close — it drives the FAB badge (panel closed) and
   * is the default context attached to messages when the panel is opened
   * without an explicit one. Set declaratively via `useAssistantContext`.
   */
  ambientContext: AssistantPageContext | null;
  /**
   * Set/clear the ambient context. `ownerId` scopes ownership so a page
   * unmounting only clears the context if it still owns it — prevents a
   * navigation's unmount/mount race from wiping the next page's context.
   */
  setAmbientContext: (
    ctx: AssistantPageContext | null,
    ownerId: string,
  ) => void;
  /**
 * Does a surface already show Numo's conversation on screen (Home, MIN-930)?
 * Declared by the surface itself (`useSuppressAssistantFab`) rather than
 * deduced from a list of routes. The Numo launchers then stop signalling
 * Numo's activity, as they do while the panel is open: the user is watching
 * it already.
 */
  fabSuppressed: boolean;
  /** `ownerId` counts surfaces: several can be mounted at once. */
  setFabSuppressed: (suppressed: boolean, ownerId: string) => void;
  open: (opts?: OpenAssistantOptions) => void;
  /** The common entry for every voluntary request to Numo. `opts` carries the
      opening-time presentation choices (e.g. the home composer opens
      fullscreen). */
  openIntent: (intent: NumoIntent, opts?: OpenIntentOptions) => void;
  /**
   * The ambient context at call time, read without subscribing: an action
   * (such as "Ask Numo" on a selection) needs it once, when it runs, and must
   * not rerender its toolbar whenever the page publishes a new context.
   */
  readAmbientContext: () => AssistantPageContext | null;
  /**
   * Drop the quoted selection from the open session's context. Called when
   * the user removes its pill, and once the message carrying it is sent.
   */
  clearSelectionContext: () => void;
  close: () => void;
  toggle: () => void;
  /** Called by the panel after consuming pendingOptions. */
  clearPendingOptions: () => void;
  /** Project id derived from the current URL when no override is provided. */
  routeProjectId: string | null;
}

const AssistantPanelContext = createContext<AssistantPanelContextValue | null>(
  null,
);

export type AssistantPanelActions = Pick<
  AssistantPanelContextValue,
  "setAmbientContext" | "setFabSuppressed" | "open" | "openIntent" |
  "close" | "toggle" | "clearPendingOptions" | "readAmbientContext" |
  "clearSelectionContext"
>;

const AssistantPanelActionsContext = createContext<AssistantPanelActions | null>(null);

export function AssistantPanelProvider({ children }: { children: ReactNode }) {
  const pathname = usePathname();
  const routeProjectId = useMemo(
    () => projectIdFromPath(pathname ?? ""),
    [pathname],
  );

  const [isOpen, setIsOpen] = useState(false);
  const [pendingOptions, setPendingOptions] =
    useState<OpenAssistantOptions | null>(null);
  const [activePageContext, setActivePageContext] =
    useState<AssistantPageContext | null>(null);
  useEffect(() => {
    setActivePageContext(null);
  }, [pathname]);
  const [ambientContext, setAmbientContextState] =
    useState<AssistantPageContext | null>(null);
  // Which mounted surface owns the current ambient context. Only the owner may
  // clear it, so navigating A→B (B mounts before A's cleanup runs) never wipes
  // B's freshly-set context.
  const ambientOwnerRef = useRef<string | null>(null);
  // Mirrors `ambientContext` for `readAmbientContext`, so the actions object
  // stays stable while the page republishes its context.
  const ambientContextRef = useRef<AssistantPageContext | null>(null);
  useEffect(() => {
    ambientContextRef.current = ambientContext;
  }, [ambientContext]);
  const readAmbientContext = useCallback(() => ambientContextRef.current, []);

  const setAmbientContext = useCallback(
    (ctx: AssistantPageContext | null, ownerId: string) => {
      if (ctx) {
        ambientOwnerRef.current = ownerId;
        setAmbientContextState(ctx);
      } else if (ambientOwnerRef.current === ownerId) {
        ambientOwnerRef.current = null;
        setAmbientContextState(null);
      }
    },
    [],
  );

  /**
 * Surfaces that hide the FAB, by id. A SET and not a boolean:
 * two can overlap (one agent conversation in full page, one
 * another in a modal on top), and the first to unmount would make
 * the FAB while the second still covers it.
 */
  const [fabOwners, setFabOwners] = useState<ReadonlySet<string>>(
    () => new Set(),
  );
  const setFabSuppressed = useCallback((suppressed: boolean, ownerId: string) => {
    setFabOwners((prev) => {
      if (suppressed === prev.has(ownerId)) return prev;
      const next = new Set(prev);
      if (suppressed) next.add(ownerId);
      else next.delete(ownerId);
      return next;
    });
  }, []);

  const open = useCallback((opts?: OpenAssistantOptions) => {
    // `prompt` = ouverture programmatique (home, action de ticket) ; sans lui
    // it's a direct click on the panel.
    trackEvent("assistant_opened", {
      source: opts?.prompt ? "home" : opts?.pageContext ? "issue" : "fab",
      has_page_context: !!opts?.pageContext,
      autosend: !!opts?.prompt,
    });
    setPendingOptions(opts ?? null);
    setActivePageContext(opts?.pageContext ?? (opts?.projectId ? { projectId: opts.projectId } : null));
    setIsOpen(true);
  }, []);

  const openIntent = useCallback(
    (intent: NumoIntent, opts?: OpenIntentOptions) => {
      open({
        projectId: intent.projectId,
        prompt: intent.prompt,
        pageContext: intent.pageContext,
        mentions: intent.mentions,
        command: intent.command,
        attachments: intent.attachments,
        intent: { source: intent.source, action: intent.action },
        displayMode: opts?.displayMode,
        ...(opts?.focusComposer ? { focusComposer: true } : {}),
      });
    },
    [open],
  );

  const close = useCallback(() => {
    trackEvent("assistant_closed", {});
    setIsOpen(false);
    setActivePageContext(null);
  }, []);

  const toggle = useCallback(() => {
    setIsOpen((prev) => {
      if (prev) {
        trackEvent("assistant_closed", {});
        setActivePageContext(null);
        return false;
      }
      trackEvent("assistant_opened", { source: "shortcut", has_page_context: false, autosend: false });
      // Toggle-open clears any stale pending options/context from a previous open.
      setPendingOptions(null);
      setActivePageContext(null);
      return true;
    });
  }, []);

  const clearPendingOptions = useCallback(() => {
    setPendingOptions(null);
  }, []);

  const clearSelectionContext = useCallback(() => {
    setActivePageContext((prev) => {
      if (!prev?.selection) return prev;
      const rest: AssistantPageContext = { ...prev };
      delete rest.selection;
      return Object.values(rest).some((value) => value !== undefined) ? rest : null;
    });
  }, []);

  const actions = useMemo<AssistantPanelActions>(() => ({
    setAmbientContext,
    setFabSuppressed,
    open,
    openIntent,
    close,
    toggle,
    clearPendingOptions,
    readAmbientContext,
    clearSelectionContext,
  }), [setAmbientContext, setFabSuppressed, open, openIntent, close, toggle, clearPendingOptions, readAmbientContext, clearSelectionContext]);

  const value = useMemo<AssistantPanelContextValue>(
    () => ({
      isOpen,
      pendingOptions,
      activePageContext,
      ambientContext,
      setAmbientContext,
      fabSuppressed: fabOwners.size > 0,
      setFabSuppressed,
      open,
      openIntent,
      close,
      toggle,
      clearPendingOptions,
      readAmbientContext,
      clearSelectionContext,
      routeProjectId,
    }),
    [
      isOpen,
      pendingOptions,
      activePageContext,
      ambientContext,
      setAmbientContext,
      fabOwners,
      setFabSuppressed,
      open,
      openIntent,
      close,
      toggle,
      clearPendingOptions,
      readAmbientContext,
      clearSelectionContext,
      routeProjectId,
    ],
  );

  return (
    <AssistantPanelActionsContext.Provider value={actions}>
      <AssistantPanelContext.Provider value={value}>
        {children}
      </AssistantPanelContext.Provider>
    </AssistantPanelActionsContext.Provider>
  );
}

/** Card and menu actions do not subscribe to the current issue or conversation. */
export function useAssistantPanelActions(): AssistantPanelActions {
  const actions = useContext(AssistantPanelActionsContext);
  if (!actions) {
    throw new Error("useAssistantPanelActions must be used within an AssistantPanelProvider");
  }
  return actions;
}

/**
 * The panel actions, or `null` outside an `AssistantPanelProvider`: public
 * surfaces (`app/f/**`, `app/p/**`) mount the shared editor without Numo.
 */
export function useOptionalAssistantPanelActions(): AssistantPanelActions | null {
  return useContext(AssistantPanelActionsContext);
}

export function useAssistantPanel(): AssistantPanelContextValue {
  const ctx = useContext(AssistantPanelContext);
  if (!ctx) {
    throw new Error(
      "useAssistantPanel must be used within an AssistantPanelProvider",
    );
  }
  return ctx;
}

/**
 * Declaratively register the assistant's ambient context for the lifetime of a
 * component. Pass the context the current surface represents (e.g. the issue
 * open in the side panel), or `null` when there is none. The context is
 * published while mounted and cleared on unmount; it powers the FAB badge and
 * the chip above the composer, and rides on messages when the panel is opened
 * without an explicit context. Safe to call once per page/surface.
 */
export function useAssistantContext(
  context: AssistantPageContext | null,
): void {
  const { setAmbientContext } = useAssistantPanelActions();
  const ownerId = useId();
  // Serialize to a stable key so the effect re-publishes only on a real change
  // (the caller passes a fresh object each render). The object is rebuilt from
  // the key inside the effect — no ref reads during render.
  const contextKey = context ? JSON.stringify(context) : null;

  useEffect(() => {
    const next = contextKey
      ? (JSON.parse(contextKey) as AssistantPageContext)
      : null;
    setAmbientContext(next, ownerId);
    return () => setAmbientContext(null, ownerId);
  }, [contextKey, ownerId, setAmbientContext]);
}

/**
 * Hides Numo's FAB as long as this component is mounted and `active`.
 *
 * To be called from the surface that already has a composer, for one of two reasons that make the button float too much:
 *
 * - he COVERS it — a composer pinned at the bottom of the screen, where the FAB falls
 * often right on its send button (agent conversations);
 * - he REPEATS it — the welcome, whose composer is in the center of the screen and already does
 * what the FAB offers. There, the deletion is conditional: the FAB
 * returns as soon as it has something else to offer, namely a conversation with
 * reopen (see `useResumableConversation`).
 *
 * It's the surface that knows, not the road — the Agents page shows a
 * conversation under its Conversations tab and a simple list under its
 * Routines tab, at the same URL.
 */
export function useSuppressAssistantFab(active = true): void {
  const { setFabSuppressed } = useAssistantPanelActions();
  const ownerId = useId();

  useEffect(() => {
    setFabSuppressed(active, ownerId);
    return () => setFabSuppressed(false, ownerId);
  }, [active, ownerId, setFabSuppressed]);
}