/**
 * Browser-side BFF client for chat — the inbox, threads and messages.
 *
 * Mirrors lib/social.ts: `credentials: "include"` so the auth cookie travels,
 * and the {success, data} envelope is unwrapped here so callers see plain data.
 */

const BFF_BASE = process.env.NEXT_PUBLIC_BFF_URL || "http://localhost:8080";

export class ChatError extends Error {
  constructor(
    public status: number,
    message: string,
  ) {
    super(message);
    this.name = "ChatError";
  }
}

type Envelope<T> = {
  success: boolean;
  data?: T;
  error?: { code: number; message: string };
};

async function call<T>(path: string, init?: RequestInit): Promise<T> {
  const res = await fetch(`${BFF_BASE}/api/v1${path}`, {
    credentials: "include",
    headers: { "Content-Type": "application/json", ...(init?.headers ?? {}) },
    ...init,
  });
  if (res.status === 204) return undefined as T;
  const body = (await res.json().catch(() => ({}))) as Envelope<T>;
  if (!res.ok || body.success === false) {
    throw new ChatError(res.status, body.error?.message || res.statusText);
  }
  return (body.data ?? (undefined as unknown as T)) as T;
}

// ─── Types ───────────────────────────────────────────────────────────────

/** Which inbox tab a thread belongs to. `ai` is Kautilya. */
export type ConversationKind = "dm" | "group" | "ai";

/** Roles inside a group, most privileged first. */
export type GroupRole = "owner" | "admin" | "member";

/** Who may post in a group. */
export type SendPolicy = "everyone" | "admins";

export type ChatPeer = {
  id: string;
  handle: string;
  name: string;
  avatar_url?: string | null;
  /** Present on participant lists; absent on a DM's `peer`. */
  role?: GroupRole;
  joined_at?: string | null;
};

export type MessagePreview = {
  seq: number;
  sender_id?: string | null;
  sender_name: string;
  kind: string;
  body: string;
  deleted_at?: string | null;
};

export type InboxItem = {
  id: string;
  kind: ConversationKind;
  title?: string | null;
  avatar_key?: string | null;
  send_policy: SendPolicy;
  last_seq: number;
  last_message_at?: string | null;
  created_at: string;
  unread: number;
  /** Set while muted. Unread still accrues — mute silences alerts only. */
  muted_until?: string | null;
  peer?: ChatPeer | null;
  last_message?: MessagePreview | null;
};

/** A formatting span. Offsets are UTF-16 code units, matching String.slice. */
export type MessageEntity = {
  type: "bold" | "strike" | "code" | "url";
  offset: number;
  length: number;
  url?: string;
};

/** The quoted snippet shown above a reply. */
export type ReplyPreview = {
  id: string;
  seq: number;
  sender_id?: string | null;
  sender_name: string;
  body: string;
  deleted: boolean;
};

export type ChatMessage = {
  id: string;
  conversation_id: string;
  seq: number;
  sender_id?: string | null;
  kind: "text" | "system" | "assistant";
  body: string;
  entities: MessageEntity[];
  client_msg_id?: string | null;
  reply_to_id?: string | null;
  forwarded_from_id?: string | null;
  edited_at?: string | null;
  deleted_at?: string | null;
  created_at: string;
  /** Present when this message replies to another in the same thread. */
  reply_to?: ReplyPreview | null;
  /** Always an array — media, link cards and shared entities. */
  attachments: Attachment[];
  /**
   * Client-only. Set on a message shown optimistically before the server has
   * acknowledged it; never sent by the BFF.
   */
  pending?: boolean;
  /**
   * Client-only. Set when the send failed. The bubble stays put so the text
   * isn't lost and the user can retry — retrying reuses the same
   * `client_msg_id`, which is what makes it safe if the original actually
   * landed.
   */
  failed?: boolean;
};

/** One thread plus who is in it — everything the thread screen needs. */
export type ConversationDetail = {
  id: string;
  kind: ConversationKind;
  title?: string | null;
  avatar_key?: string | null;
  send_policy: SendPolicy;
  /** The caller's own role, so admin controls can be shown without deriving it. */
  my_role: GroupRole;
  last_seq: number;
  last_message_at?: string | null;
  created_at: string;
  peer?: ChatPeer | null;
  participants: ChatPeer[];
  unread: number;
  muted_until?: string | null;
  /** DMs only — a group has no single peer to stand in a relationship with. */
  relationship?: ChatRelationship | null;
};

/** Link preview metadata. Always fetched by the BFF, never composed here. */
export type LinkPreview = {
  url: string;
  title?: string;
  description?: string;
  site_name?: string;
  image_url?: string;
};

export type AttachmentKind =
  | "image"
  | "video"
  | "audio"
  | "file"
  | "link"
  | "entity";

export type Attachment = {
  id: string;
  message_id: string;
  ord: number;
  kind: AttachmentKind;
  mime?: string | null;
  size_bytes?: number | null;
  width?: number | null;
  height?: number | null;
  duration_ms?: number | null;
  blurhash?: string | null;
  file_name?: string | null;
  url?: string | null;
  title?: string | null;
  description?: string | null;
  site_name?: string | null;
  image_url?: string | null;
};

/** How two people in a DM stand with each other. */
export type ChatRelationship = {
  following: boolean;
  followed_by: boolean;
  blocked: boolean;
  blocked_by: boolean;
  /** When the first follow between them was accepted. */
  friends_since?: string | null;
};

export type Receipts = { delivered_seq: number; read_seq: number };

export type MuteDuration = "8h" | "1w" | "always" | "off";

/** Who may START a conversation with you. */
export type WhoCanMessage =
  | "anyone"
  | "friends"
  | "account_age"
  | "same_gender";

export type ChatSettings = {
  read_receipts: boolean;
  who_can_message: WhoCanMessage;
  min_account_age_months: number;
  train_kautilya: boolean;
  /** Whether a gender is set on the profile — same_gender needs one. */
  gender_set: boolean;
};

export type InboxTab = "chats" | "kautilya";

// ─── API ─────────────────────────────────────────────────────────────────

export const chat = {
  inbox: (tab: InboxTab) =>
    call<InboxItem[]>(`/chat/conversations?tab=${tab}`),

  /**
   * Opens (or returns) the DM with a profile. Idempotent, and keyed by handle
   * because that is what a profile page has.
   */
  openDM: (handle: string) =>
    call<{ id: string; kind: ConversationKind }>("/chat/conversations/dm", {
      method: "POST",
      body: JSON.stringify({ handle }),
    }),

  createGroup: (title: string, handles: string[]) =>
    call<{ id: string }>("/chat/conversations/group", {
      method: "POST",
      body: JSON.stringify({ title, member_handles: handles }),
    }),

  detail: (conversationId: string) =>
    call<ConversationDetail>(`/chat/conversations/${conversationId}`),

  messages: (conversationId: string, beforeSeq = 0, limit = 30) =>
    call<ChatMessage[]>(
      `/chat/conversations/${conversationId}/messages?before_seq=${beforeSeq}&limit=${limit}`,
    ),

  send: (
    conversationId: string,
    body: string,
    opts?: {
      clientMsgId?: string;
      replyToId?: string;
      previewUrl?: string;
      attachments?: UploadedAttachment[];
    },
  ) =>
    call<ChatMessage>(`/chat/conversations/${conversationId}/messages`, {
      method: "POST",
      body: JSON.stringify({
        body,
        client_msg_id: opts?.clientMsgId ?? null,
        reply_to_id: opts?.replyToId ?? null,
        // Only the URL: the BFF fetches the card's contents itself.
        preview_url: opts?.previewUrl ?? null,
        attachments: opts?.attachments ?? [],
      }),
    }),

  /**
   * Members are named by handle, not id: search results and follow lists
   * identify people by handle, and it matches /u/{handle}/block elsewhere.
   */
  addMembers: (conversationId: string, handles: string[]) =>
    call<void>(`/chat/conversations/${conversationId}/members`, {
      method: "POST",
      body: JSON.stringify({ member_handles: handles }),
    }),

  /** Passing your own handle is how you leave. */
  removeMember: (conversationId: string, handle: string) =>
    call<void>(
      `/chat/conversations/${conversationId}/members/${encodeURIComponent(handle)}`,
      { method: "DELETE" },
    ),

  setMemberRole: (conversationId: string, handle: string, role: GroupRole) =>
    call<void>(
      `/chat/conversations/${conversationId}/members/${encodeURIComponent(handle)}`,
      { method: "PATCH", body: JSON.stringify({ role }) },
    ),

  updateGroup: (
    conversationId: string,
    patch: { title?: string; send_policy?: SendPolicy; avatar_key?: string },
  ) =>
    call<void>(`/chat/conversations/${conversationId}`, {
      method: "PATCH",
      body: JSON.stringify(patch),
    }),

  settings: () => call<ChatSettings>("/chat/settings"),

  /** Partial: anything omitted keeps its current value. */
  updateSettings: (patch: Partial<Omit<ChatSettings, "gender_set">>) =>
    call<ChatSettings>("/chat/settings", {
      method: "PATCH",
      body: JSON.stringify(patch),
    }),

  gallery: (conversationId: string, tab: "media" | "links", before?: string) =>
    call<Attachment[]>(
      `/chat/conversations/${conversationId}/gallery?tab=${tab}` +
        (before ? `&before=${encodeURIComponent(before)}` : ""),
    ),

  starred: (conversationId: string) =>
    call<ChatMessage[]>(`/chat/conversations/${conversationId}/starred`),

  deleteMessage: (
    conversationId: string,
    messageId: string,
    scope: "me" | "everyone",
  ) =>
    call<void>(
      `/chat/conversations/${conversationId}/messages/${messageId}?scope=${scope}`,
      { method: "DELETE" },
    ),

  /** The path names the destination; the body names the message copied in. */
  forward: (toConversationId: string, messageId: string) =>
    call<ChatMessage>(`/chat/conversations/${toConversationId}/forward`, {
      method: "POST",
      body: JSON.stringify({ message_id: messageId }),
    }),

  report: (
    conversationId: string,
    messageId: string,
    category: string,
    reason: string,
  ) =>
    call<void>(
      `/chat/conversations/${conversationId}/messages/${messageId}/report`,
      { method: "POST", body: JSON.stringify({ category, reason }) },
    ),

  setStar: (conversationId: string, messageId: string, starred: boolean) =>
    call<void>(
      `/chat/conversations/${conversationId}/messages/${messageId}/star`,
      { method: starred ? "POST" : "DELETE" },
    ),

  presignGroupAvatar: (conversationId: string, contentType: string) =>
    call<{ upload_url: string; key: string }>(
      `/chat/conversations/${conversationId}/avatar/presign`,
      { method: "POST", body: JSON.stringify({ content_type: contentType }) },
    ),

  presignAttachment: (conversationId: string, contentType: string) =>
    call<{ upload_url: string; key: string }>(
      `/chat/conversations/${conversationId}/attachments/presign`,
      { method: "POST", body: JSON.stringify({ content_type: contentType }) },
    ),

  /** Metadata for a link the user is typing, so they can dismiss the card. */
  linkPreview: (url: string) =>
    call<LinkPreview>("/chat/link-preview", {
      method: "POST",
      body: JSON.stringify({ url }),
    }),

  markRead: (conversationId: string, seq: number) =>
    call<void>(`/chat/conversations/${conversationId}/read`, {
      method: "POST",
      body: JSON.stringify({ seq }),
    }),

  markDelivered: (conversationId: string, seq: number) =>
    call<void>(`/chat/conversations/${conversationId}/delivered`, {
      method: "POST",
      body: JSON.stringify({ seq }),
    }),

  receipts: (conversationId: string) =>
    call<Receipts>(`/chat/conversations/${conversationId}/receipts`),

  setMute: (conversationId: string, duration: MuteDuration) =>
    call<{ muted_until: string | null }>(
      `/chat/conversations/${conversationId}/mute`,
      { method: "POST", body: JSON.stringify({ duration }) },
    ),
};

/** A file already uploaded to the private bucket, ready to attach on send. */
export type UploadedAttachment = {
  key: string;
  mime: string;
  size_bytes?: number;
  width?: number;
  height?: number;
  file_name?: string;
};

/** Natural dimensions of an image file, or nothing if it can't be decoded. */
async function imageSize(
  file: File,
): Promise<{ width: number; height: number } | null> {
  if (!file.type.startsWith("image/")) return null;
  try {
    const bitmap = await createImageBitmap(file);
    const size = { width: bitmap.width, height: bitmap.height };
    bitmap.close();
    return size;
  } catch {
    return null;
  }
}

/**
 * Uploads a file straight to the private bucket and returns what `send` needs.
 *
 * The bytes never touch the BFF — it only signs the URL — which is the same
 * path avatars and post images already take. Dimensions travel with the
 * attachment so the bubble can reserve the right space before the image
 * loads, instead of reflowing the thread when it arrives.
 */
export async function uploadAttachment(
  conversationId: string,
  file: File,
): Promise<UploadedAttachment> {
  const size = await imageSize(file);
  const { upload_url, key } = await chat.presignAttachment(
    conversationId,
    file.type,
  );

  const res = await fetch(upload_url, {
    method: "PUT",
    body: file,
    headers: { "Content-Type": file.type },
  });
  if (!res.ok) {
    throw new ChatError(res.status, "Upload failed");
  }

  return {
    key,
    mime: file.type,
    size_bytes: file.size,
    width: size?.width,
    height: size?.height,
    file_name: file.name,
  };
}

/**
 * Stable URL for a group's photo. Like message attachments it redirects to a
 * short-lived signed URL after re-checking membership, so the object itself
 * stays private. `v` busts the browser cache when the photo changes.
 */
export function groupAvatarUrl(
  conversationId: string,
  avatarKey?: string | null,
): string | undefined {
  if (!avatarKey) return undefined;
  return `${BFF_BASE}/api/v1/chat/conversations/${conversationId}/avatar?v=${encodeURIComponent(
    avatarKey.slice(-12),
  )}`;
}

/**
 * Uploads a new group photo and returns its key for `updateGroup`. Compressed
 * first, which also strips EXIF.
 */
export async function uploadGroupAvatar(
  conversationId: string,
  file: File,
): Promise<string> {
  const { upload_url, key } = await chat.presignGroupAvatar(
    conversationId,
    file.type,
  );
  const res = await fetch(upload_url, {
    method: "PUT",
    body: file,
    headers: { "Content-Type": file.type },
  });
  if (!res.ok) throw new ChatError(res.status, "Upload failed");
  return key;
}

/** MIME types the BFF accepts as chat attachments. */
export const ACCEPTED_ATTACHMENTS = "image/*,video/*,audio/*,application/pdf";

/**
 * Stable URL for a chat attachment. The BFF re-checks membership and redirects
 * to a short-lived signed URL, so this can be cached in markup safely while the
 * underlying object stays private.
 */
export function attachmentUrl(attachmentId: string): string {
  return `${BFF_BASE}/api/v1/chat/attachments/${attachmentId}`;
}

/** First http(s) URL in a string, or null. Mirrors the server's matcher. */
export function firstUrl(text: string): string | null {
  const m = text.match(/(?:https?:\/\/|www\.)[^\s<>()[\]{}"']+/i);
  if (!m) return null;
  const raw = m[0].replace(/[.,;:!?'"]+$/, "");
  return raw.includes("://") ? raw : `https://${raw}`;
}

/** Whether a role may administer a group. */
export function isGroupAdmin(role?: GroupRole | null): boolean {
  return role === "owner" || role === "admin";
}

/** True while `muted_until` is in the future. */
export function isMuted(item: Pick<InboxItem, "muted_until">): boolean {
  return !!item.muted_until && new Date(item.muted_until).getTime() > Date.now();
}

/** Display name for a thread: the peer for a DM, the title otherwise. */
export function conversationTitle(
  item: Pick<InboxItem, "kind" | "peer" | "title">,
): string {
  if (item.kind === "ai") return "Kautilya";
  if (item.kind === "dm") return item.peer?.name || "Unknown";
  return item.title || "Group";
}

/**
 * How to describe a DM's follow state in one line. Deliberately explicit about
 * one-way follows rather than collapsing everything into "friends".
 */
export function followSummary(
  rel: ChatRelationship | null | undefined,
  peerName: string,
): string {
  if (!rel) return "";
  if (rel.following && rel.followed_by) return "You follow each other";
  if (rel.following) return `You follow ${peerName}`;
  if (rel.followed_by) return `${peerName} follows you`;
  return "You don't follow each other";
}

/** Resolves a sender id to a display name using a thread's participants. */
export function senderName(
  senderId: string | null | undefined,
  participants: ChatPeer[],
  selfId: string,
): string {
  if (!senderId) return "Kautilya";
  if (senderId === selfId) return "You";
  return participants.find((p) => p.id === senderId)?.name ?? "Unknown";
}