const GRAPH = "https://graph.microsoft.com/v1.0";

function escapeODataString(s: string): string {
  return s.replace(/'/g, "''");
}

export interface GraphMessage {
  id: string;
  subject?: string;
}

export interface GraphMailFolder {
  id: string;
  displayName: string;
}

async function graphJson<T>(token: string, pathOrUrl: string, init?: RequestInit): Promise<T> {
  const url = pathOrUrl.startsWith("https://") ? pathOrUrl : `${GRAPH}${pathOrUrl}`;
  const res = await fetch(url, {
    ...init,
    headers: {
      Authorization: `Bearer ${token}`,
      ...(init?.headers ?? {}),
    },
  });
  if (!res.ok) {
    const text = await res.text();
    throw new Error(`Graph ${res.status}: ${text || res.statusText}`);
  }
  return res.json() as Promise<T>;
}

export async function listInboxChildFolders(token: string): Promise<GraphMailFolder[]> {
  const out: GraphMailFolder[] = [];
  let next: string | null =
    "/me/mailFolders/inbox/childFolders?$select=id,displayName&$top=999";

  while (next) {
    const page = await graphJson<{ value: GraphMailFolder[]; "@odata.nextLink"?: string }>(
      token,
      next,
    );
    out.push(...page.value);
    next = page["@odata.nextLink"] ?? null;
  }
  return out;
}

export async function findChildFolderByName(
  token: string,
  displayName: string,
): Promise<GraphMailFolder | undefined> {
  const folders = await listInboxChildFolders(token);
  return folders.find((f) => f.displayName === displayName);
}

export async function createInboxChildFolder(
  token: string,
  displayName: string,
): Promise<GraphMailFolder> {
  return graphJson<GraphMailFolder>(token, "/me/mailFolders/inbox/childFolders", {
    method: "POST",
    headers: { "Content-Type": "application/json" },
    body: JSON.stringify({ displayName }),
  });
}

export async function findOrCreateInboxChildFolder(
  token: string,
  displayName: string,
): Promise<GraphMailFolder> {
  const existing = await findChildFolderByName(token, displayName);
  if (existing) {
    return existing;
  }
  return createInboxChildFolder(token, displayName);
}

async function listMessagesMatchingFilter(
  token: string,
  filter: string,
): Promise<GraphMessage[]> {
  const out: GraphMessage[] = [];
  let next: string | null =
    `/me/messages?$filter=${encodeURIComponent(filter)}&$select=id,subject&$top=999`;

  while (next) {
    const page = await graphJson<{ value: GraphMessage[]; "@odata.nextLink"?: string }>(
      token,
      next,
    );
    out.push(...page.value);
    next = page["@odata.nextLink"] ?? null;
  }
  return out;
}

/**
 * Finds messages whose subject or preview contains "TrackingID#<id>".
 * Falls back to subject-only filter if the tenant rejects bodyPreview in $filter.
 */
export async function findMessagesWithTrackingId(
  token: string,
  trackingId: string,
): Promise<GraphMessage[]> {
  const needle = `TrackingID#${trackingId}`;
  const q = escapeODataString(needle);
  const combined = `(contains(subject,'${q}') or contains(bodyPreview,'${q}'))`;
  const subjectOnly = `contains(subject,'${q}')`;
  try {
    return await listMessagesMatchingFilter(token, combined);
  } catch {
    return listMessagesMatchingFilter(token, subjectOnly);
  }
}

export async function moveMessageToFolder(
  token: string,
  messageId: string,
  destinationFolderId: string,
): Promise<void> {
  await graphJson<unknown>(token, `/me/messages/${encodeURIComponent(messageId)}/move`, {
    method: "POST",
    headers: { "Content-Type": "application/json" },
    body: JSON.stringify({ destinationId: destinationFolderId }),
  });
}