/**
 * useSnapshotSendController
 *
 * Payload-agnostic upload → send controller for sharing a snapshot to a Buzz
 * DM. The caller supplies an encode function and an async destination resolver;
 * the controller guards destination creation plus prepare → encode → upload →
 * send, with fail-closed eligibility checks at both action boundaries.
 *
 * This hook does not know what kind of snapshot the bytes contain.  A future
 * team-snapshot or other payload can reuse it unchanged by passing different
 * bytes and a filename.  Hard-coded semantics for `.agent.*` live only in
 * the export-dialog layer above this hook.
 */

import * as React from "react";
import type { QueryClient } from "@tanstack/react-query";
import { useQueryClient } from "@tanstack/react-query";

import { uploadMediaBytes, type BlobDescriptor } from "@/shared/api/tauri";
import {
  buildOutgoingMessage,
  formatImetaMediaLine,
} from "@/features/messages/lib/imetaMediaMarkdown";
import { channelsQueryKey } from "@/features/channels/hooks";
import { isModerationDm } from "@/features/moderation/lib/moderationDm";
import {
  relaySelfQueryKey,
  useRelaySelfQuery,
} from "@/features/moderation/hooks";
import { getTimeoutSnapshot } from "@/features/moderation/lib/timeoutStore";
import { isTimeoutActive } from "@/features/moderation/lib/timeout";
import { useIdentityQuery } from "@/shared/api/hooks";
import { useSendMessageMutation } from "@/features/messages/hooks";
import type { Channel, Identity } from "@/shared/api/types";

// ── Public types ──────────────────────────────────────────────────────────────

export type SendPhase =
  | "idle"
  | "preparing"
  | "uploading"
  | "sending"
  | "done"
  | "error";

export type SnapshotSendState = {
  phase: SendPhase;
  error: string | null;
};

/**
 * A joined, non-archived, non-forum destination. Moderation DM exclusion is
 * handled separately because it requires the current identity and relay self.
 */
export function isSendableDestination(ch: Channel): boolean {
  return ch.isMember && ch.archivedAt === null && ch.channelType !== "forum";
}

/**
 * Pure factory for a single-concurrency action guard.
 *
 * Returns `{ runGuarded }` where `runGuarded(action)` executes `action()`
 * only when no other call is currently in flight; any concurrent call receives
 * `false` immediately.  The guard is the same mechanism used by
 * `beginSend` in `useSnapshotSendController` — exported so unit tests can
 * exercise the production guard logic directly without requiring a React
 * rendering context.
 *
 * @example
 * ```ts
 * const { runGuarded } = createSendGuard();
 * const [r1, r2] = await Promise.all([
 *   runGuarded(async () => { ...encode/upload/send... }),
 *   runGuarded(async () => { ...encode/upload/send... }),
 * ]);
 * // r1 === true (ran), r2 === false (blocked)
 * ```
 */
export function createSendGuard(): {
  runGuarded: (action: () => Promise<boolean>) => Promise<boolean>;
  get inFlight(): boolean;
} {
  let inFlight = false;
  return {
    runGuarded: async (action) => {
      if (inFlight) return false;
      inFlight = true;
      try {
        return await action();
      } finally {
        inFlight = false;
      }
    },
    get inFlight() {
      return inFlight;
    },
  };
}

/**
 * Read current eligibility for `channelId` directly from live query-cache
 * sources and the timeout external store.  Does NOT read rendered React state
 * or component refs; safe to call inside a `runGuarded` action where render
 * state may be stale.
 *
 * Returns `null` when the channel is eligible; returns a human-readable error
 * string when it is not.
 *
 * Fail-closed on DM classification: a DM destination is blocked unless both
 * identity and relay-self have successfully resolved (`status === "success"`).
 * This covers pending, fetching, absent (never fetched), and errored states.
 * The semantic distinction is preserved: a successfully resolved
 * `relaySelf === null` means the relay advertises no self pubkey — that IS a
 * known result and the generic moderation helper's fail-open behavior applies.
 * Any other state (absent, errored, or in-flight) is unknown and must block.
 */
export function checkSendEligibility(
  queryClient: QueryClient,
  channelId: string,
  nowMs: number = Date.now(),
): string | null {
  // ── Timeout check ─────────────────────────────────────────────────────────
  // Read the module-level snapshot from timeoutStore directly — this is the
  // same value `useTimeoutState` serves but without requiring a render cycle.
  const timeoutState = getTimeoutSnapshot();
  if (timeoutState.active && isTimeoutActive(timeoutState.expiresAtMs, nowMs)) {
    return "You are currently timed out and cannot send messages.";
  }

  // ── Channel-cache check ───────────────────────────────────────────────────
  const channels = queryClient.getQueryData<Channel[]>(channelsQueryKey) ?? [];
  const channel = channels.find((ch) => ch.id === channelId);

  if (!channel) {
    return "The selected destination is no longer available. Please pick another.";
  }
  if (!isSendableDestination(channel)) {
    return "The selected destination is no longer available. Please pick another.";
  }

  // ── Moderation-DM check (fail-closed) ────────────────────────────────────
  if (channel.channelType === "dm") {
    const identityState = queryClient.getQueryState<Identity>(["identity"]);
    const relaySelfState = queryClient.getQueryState<string | null>(
      relaySelfQueryKey,
    );

    // Fail-closed: block the DM unless both identity AND relay-self have
    // successfully resolved.  Absent state (undefined — never fetched or
    // cache evicted), pending/fetching, and errored states are all unknown
    // and must block to prevent misclassification.
    //
    // The only exception is a successfully resolved `relaySelf === null`:
    // that means the relay advertises no self pubkey (a valid, known answer),
    // and we pass it to isModerationDm, which fails open by its own contract.
    if (identityState?.status !== "success") {
      return "The selected destination is no longer available. Please pick another.";
    }
    if (relaySelfState?.status !== "success") {
      return "The selected destination is no longer available. Please pick another.";
    }

    const identity = queryClient.getQueryData<Identity>(["identity"]);
    const relaySelf = queryClient.getQueryData<string | null>(
      relaySelfQueryKey,
    );

    if (isModerationDm(channel, identity?.pubkey, relaySelf ?? undefined)) {
      return "The selected destination is no longer available. Please pick another.";
    }
  }

  return null;
}

/**
 * The core send pipeline: prepare → [eligibility] → encode → [eligibility] →
 * upload → send.  Extracted as a standalone async function so unit tests can
 * import and exercise it directly with injected dependencies — the production
 * hook calls it inside `runGuarded`.
 *
 * Dependencies are injected rather than closed-over from React scope so the
 * function is pure-async and fully testable without a rendering context.
 */
export async function runSendPipeline(deps: {
  encodeFn: () => Promise<{ fileBytes: number[]; fileName: string }>;
  uploadFn: (bytes: number[], filename: string) => Promise<BlobDescriptor>;
  sendFn: (args: {
    channelId: string;
    content: string;
    mediaTags: string[][];
  }) => Promise<unknown>;
  setStateFn: (state: SnapshotSendState) => void;
  buildMessageFn: (descriptor: BlobDescriptor) => {
    content: string;
    mediaTags: string[][] | null | undefined;
  };
  checkEligibilityFn: () => string | null;
  channelId: string;
}): Promise<boolean> {
  const {
    encodeFn,
    uploadFn,
    sendFn,
    setStateFn,
    buildMessageFn,
    checkEligibilityFn,
    channelId,
  } = deps;

  // ── Eligibility checkpoint 1: before encode ───────────────────────────────
  // Reads live sources directly — timeout store, channel cache, identity cache,
  // relay-self cache.  Not a render snapshot.
  const reason1 = checkEligibilityFn();
  if (reason1 !== null) {
    setStateFn({ phase: "error", error: reason1 });
    return false;
  }

  // ── Prepare (encode) ─────────────────────────────────────────────────────
  setStateFn({ phase: "preparing", error: null });

  let fileBytes: number[];
  let fileName: string;
  try {
    const encoded = await encodeFn();
    fileBytes = encoded.fileBytes;
    fileName = encoded.fileName;
  } catch (err) {
    setStateFn({
      phase: "error",
      error:
        err instanceof Error
          ? `Encode failed: ${err.message}`
          : "Encode failed.",
    });
    return false;
  }

  // ── Eligibility checkpoint 2: after encode, before upload ─────────────────
  // State can change while encode is awaited (channel archived, membership
  // lost, timeout received, relay-self resolves to classify DM).
  const reason2 = checkEligibilityFn();
  if (reason2 !== null) {
    setStateFn({ phase: "error", error: reason2 });
    return false;
  }

  // ── Upload ────────────────────────────────────────────────────────────────
  setStateFn({ phase: "uploading", error: null });

  let descriptor: BlobDescriptor;
  try {
    descriptor = await uploadFn(fileBytes, fileName);
  } catch (err) {
    setStateFn({
      phase: "error",
      error:
        err instanceof Error
          ? `Upload failed: ${err.message}`
          : "Upload failed.",
    });
    return false;
  }

  // Preserve the original filename so `buildImetaTags` emits a `filename`
  // field and the recipient's FileCard renders the correct label. Snapshot
  // sends never emit `thumb`: NIP-92 requires it to be this upload's local
  // thumbnail sidecar, which an agent avatar is not.
  const { thumb: _thumb, ...descriptorWithoutThumb } = descriptor;
  const descriptorWithFilename: BlobDescriptor = {
    ...descriptorWithoutThumb,
    filename: fileName,
  };

  // ── Build message content + NIP-92 imeta tags ─────────────────────────────
  const { content, mediaTags } = buildMessageFn(descriptorWithFilename);

  // ── Send ──────────────────────────────────────────────────────────────────
  setStateFn({ phase: "sending", error: null });

  try {
    await sendFn({
      channelId,
      content,
      mediaTags: mediaTags ?? [],
    });
  } catch (err) {
    setStateFn({
      phase: "error",
      error:
        err instanceof Error ? `Send failed: ${err.message}` : "Send failed.",
    });
    return false;
  }

  setStateFn({ phase: "done", error: null });
  return true;
}

/**
 * Compose the single-concurrency guard with destination resolution and the
 * send pipeline.
 *
 * This is the exact production composition that `beginSend` uses: a second
 * concurrent call to `runGuardedSend` with the same guard receives `false`
 * immediately — destination creation and encode never start for the blocked
 * call.
 *
 * Exported so unit tests can import and call this exact function twice
 * concurrently with injected counters, proving one encode/upload/send and one
 * blocked result.  A test that stays green after encode is moved outside the
 * guard is not a production-composition test; this function is.
 */
export function runGuardedSend(
  guard: ReturnType<typeof createSendGuard>,
  resolveChannelId: () => Promise<string>,
  buildPipelineDeps: (
    channelId: string,
  ) => Parameters<typeof runSendPipeline>[0],
  setStateFn: (state: SnapshotSendState) => void,
): Promise<boolean> {
  return guard.runGuarded(async () => {
    // Mark the action pending before opening the DM so the active UI disables
    // immediately. The in-memory guard still protects same-tick invocations
    // that arrive before React commits that state.
    setStateFn({ phase: "preparing", error: null });

    let channelId: string;
    try {
      channelId = await resolveChannelId();
    } catch (error) {
      setStateFn({
        phase: "error",
        error:
          error instanceof Error
            ? `Couldn’t open the conversation: ${error.message}`
            : "Couldn’t open the conversation.",
      });
      return false;
    }

    return runSendPipeline(buildPipelineDeps(channelId));
  });
}

export type UseSnapshotSendControllerResult = {
  /** Whether identity and relay-self are resolved for safe DM classification. */
  isDmSafetyReady: boolean;
  /** Relay moderation identity to exclude from the people picker. */
  relaySelfPubkey: string | null;
  state: SnapshotSendState;
  /**
   * Execute destination creation plus prepare → encode → upload → send behind
   * one concurrency guard. A second call while the first is in flight returns
   * false before opening another DM or encoding another snapshot.
   *
   * Eligibility is checked at two internal checkpoints by reading directly
   * from the React Query cache and the timeout external store — not from
   * rendered React state or component refs.  This closes both the
   * pre-flight/guard-entry race and the during-encode state-change race.
   *
   * The caller MUST have already obtained explicit destination-scoped
   * confirmation for memory-bearing payloads before calling this.  Returns
   * false and sets error state if blocked, ineligible, or if any step fails.
   * Never throws.
   *
   */
  beginSend: (
    encodeFn: () => Promise<{ fileBytes: number[]; fileName: string }>,
    resolveChannelId: () => Promise<string>,
    attachmentLabel?: string,
  ) => Promise<boolean | null>;
  reset: () => void;
};

// ── Hook ──────────────────────────────────────────────────────────────────────

export function useSnapshotSendController(
  enableDmSafety: boolean,
): UseSnapshotSendControllerResult {
  const identityQuery = useIdentityQuery();
  const queryClient = useQueryClient();
  // The people picker can create the first DM in a workspace, so relay-self
  // readiness cannot depend on an already-cached DM candidate.
  const relaySelfQuery = useRelaySelfQuery(enableDmSafety);

  const [state, setState] = React.useState<SnapshotSendState>({
    phase: "idle",
    error: null,
  });

  // Single-concurrency guard covering the full encode → upload → send action.
  // Stored in a ref so it survives re-renders without triggering effects.
  const guardRef = React.useRef(createSendGuard());

  // Pass null channel here — we supply the captured channelId per-send instead.
  const sendMutation = useSendMessageMutation(null, identityQuery.data);

  async function beginSend(
    encodeFn: () => Promise<{ fileBytes: number[]; fileName: string }>,
    resolveChannelId: () => Promise<string>,
    attachmentLabel?: string,
  ): Promise<boolean | null> {
    // A duplicate action is intentionally ignored; distinguish it from a
    // failed send so the caller does not show a false failure toast.
    if (guardRef.current.inFlight) return null;

    return runGuardedSend(
      guardRef.current,
      resolveChannelId,
      (channelId) => ({
        encodeFn,
        channelId,
        // Eligibility is checked from live query-cache and timeout sources,
        // not render-captured state.
        checkEligibilityFn: () => checkSendEligibility(queryClient, channelId),
        uploadFn: (bytes, filename) => uploadMediaBytes(bytes, filename),
        sendFn: (args) => sendMutation.mutateAsync(args),
        setStateFn: setState,
        buildMessageFn: (descriptor) => {
          const message = buildOutgoingMessage("", [descriptor]);
          return attachmentLabel?.trim()
            ? {
                ...message,
                content: formatImetaMediaLine(descriptor, {
                  label: attachmentLabel,
                }),
              }
            : message;
        },
      }),
      setState,
    );
  }

  const reset = React.useCallback(() => {
    if (!guardRef.current.inFlight) {
      setState({ phase: "idle", error: null });
    }
  }, []);

  return {
    isDmSafetyReady:
      !enableDmSafety ||
      (identityQuery.status === "success" &&
        relaySelfQuery.status === "success"),
    relaySelfPubkey: relaySelfQuery.data ?? null,
    state,
    beginSend,
    reset,
  };
}