import { lookup } from "node:dns/promises";
import {
  buildHostnameAllowlistPolicyFromSuffixAllowlist,
  isHttpsUrlAllowedByHostnameSuffixAllowlist,
  isPrivateIpAddress,
  normalizeHostnameSuffixAllowlist,
} from "../../runtime-api.js";
import type { SsrFPolicy } from "../../runtime-api.js";
import type { MSTeamsAttachmentLike } from "./types.js";

type InlineImageCandidate =
  | {
      kind: "data";
      data: Buffer;
      contentType?: string;
      placeholder: string;
    }
  | {
      kind: "url";
      url: string;
      contentType?: string;
      fileHint?: string;
      placeholder: string;
    };

export const IMAGE_EXT_RE = /\.(avif|bmp|gif|heic|heif|jpe?g|png|tiff?|webp)$/i;

export const IMG_SRC_RE = /<img[^>]+src=["']([^"']+)["'][^>]*>/gi;
export const ATTACHMENT_TAG_RE = /<attachment[^>]+id=["']([^"']+)["'][^>]*>/gi;

export const DEFAULT_MEDIA_HOST_ALLOWLIST = [
  "graph.microsoft.com",
  "graph.microsoft.us",
  "graph.microsoft.de",
  "graph.microsoft.cn",
  "sharepoint.com",
  "sharepoint.us",
  "sharepoint.de",
  "sharepoint.cn",
  "sharepoint-df.com",
  "1drv.ms",
  "onedrive.com",
  "teams.microsoft.com",
  "teams.cdn.office.net",
  "statics.teams.cdn.office.net",
  "office.com",
  "office.net",
  // Azure Media Services / Skype CDN for clipboard-pasted images
  "asm.skype.com",
  "ams.skype.com",
  "media.ams.skype.com",
  // Bot Framework attachment URLs
  "trafficmanager.net",
  "blob.core.windows.net",
  "azureedge.net",
  "microsoft.com",
] as const;

export const DEFAULT_MEDIA_AUTH_HOST_ALLOWLIST = [
  "api.botframework.com",
  "botframework.com",
  "graph.microsoft.com",
  "graph.microsoft.us",
  "graph.microsoft.de",
  "graph.microsoft.cn",
] as const;

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

export function isRecord(value: unknown): value is Record<string, unknown> {
  return Boolean(value) && typeof value === "object" && !Array.isArray(value);
}

export function resolveRequestUrl(input: RequestInfo | URL): string {
  if (typeof input === "string") {
    return input;
  }
  if (input instanceof URL) {
    return input.toString();
  }
  if (typeof input === "object" && input && "url" in input && typeof input.url === "string") {
    return input.url;
  }
  return String(input);
}

export function normalizeContentType(value: unknown): string | undefined {
  if (typeof value !== "string") {
    return undefined;
  }
  const trimmed = value.trim();
  return trimmed ? trimmed : undefined;
}

export function inferPlaceholder(params: {
  contentType?: string;
  fileName?: string;
  fileType?: string;
}): string {
  const mime = params.contentType?.toLowerCase() ?? "";
  const name = params.fileName?.toLowerCase() ?? "";
  const fileType = params.fileType?.toLowerCase() ?? "";

  const looksLikeImage =
    mime.startsWith("image/") || IMAGE_EXT_RE.test(name) || IMAGE_EXT_RE.test(`x.${fileType}`);

  return looksLikeImage ? "<media:image>" : "<media:document>";
}

export function isLikelyImageAttachment(att: MSTeamsAttachmentLike): boolean {
  const contentType = normalizeContentType(att.contentType) ?? "";
  const name = typeof att.name === "string" ? att.name : "";
  if (contentType.startsWith("image/")) {
    return true;
  }
  if (IMAGE_EXT_RE.test(name)) {
    return true;
  }

  if (
    contentType === "application/vnd.microsoft.teams.file.download.info" &&
    isRecord(att.content)
  ) {
    const fileType = typeof att.content.fileType === "string" ? att.content.fileType : "";
    if (fileType && IMAGE_EXT_RE.test(`x.${fileType}`)) {
      return true;
    }
    const fileName = typeof att.content.fileName === "string" ? att.content.fileName : "";
    if (fileName && IMAGE_EXT_RE.test(fileName)) {
      return true;
    }
  }

  return false;
}

/**
 * Returns true if the attachment can be downloaded (any file type).
 * Used when downloading all files, not just images.
 */
export function isDownloadableAttachment(att: MSTeamsAttachmentLike): boolean {
  const contentType = normalizeContentType(att.contentType) ?? "";

  // Teams file download info always has a downloadUrl
  if (
    contentType === "application/vnd.microsoft.teams.file.download.info" &&
    isRecord(att.content) &&
    typeof att.content.downloadUrl === "string"
  ) {
    return true;
  }

  // Any attachment with a contentUrl can be downloaded
  if (typeof att.contentUrl === "string" && att.contentUrl.trim()) {
    return true;
  }

  return false;
}

function isHtmlAttachment(att: MSTeamsAttachmentLike): boolean {
  const contentType = normalizeContentType(att.contentType) ?? "";
  return contentType.startsWith("text/html");
}

export function extractHtmlFromAttachment(att: MSTeamsAttachmentLike): string | undefined {
  if (!isHtmlAttachment(att)) {
    return undefined;
  }
  if (typeof att.content === "string") {
    return att.content;
  }
  if (!isRecord(att.content)) {
    return undefined;
  }
  const text =
    typeof att.content.text === "string"
      ? att.content.text
      : typeof att.content.body === "string"
        ? att.content.body
        : typeof att.content.content === "string"
          ? att.content.content
          : undefined;
  return text;
}

function decodeDataImage(src: string): InlineImageCandidate | null {
  const match = /^data:(image\/[a-z0-9.+-]+)?(;base64)?,(.*)$/i.exec(src);
  if (!match) {
    return null;
  }
  const contentType = match[1]?.toLowerCase();
  const isBase64 = Boolean(match[2]);
  if (!isBase64) {
    return null;
  }
  const payload = match[3] ?? "";
  if (!payload) {
    return null;
  }
  try {
    const data = Buffer.from(payload, "base64");
    return { kind: "data", data, contentType, placeholder: "<media:image>" };
  } catch {
    return null;
  }
}

function fileHintFromUrl(src: string): string | undefined {
  try {
    const url = new URL(src);
    const name = url.pathname.split("/").pop();
    return name || undefined;
  } catch {
    return undefined;
  }
}

export function extractInlineImageCandidates(
  attachments: MSTeamsAttachmentLike[],
): InlineImageCandidate[] {
  const out: InlineImageCandidate[] = [];
  for (const att of attachments) {
    const html = extractHtmlFromAttachment(att);
    if (!html) {
      continue;
    }
    IMG_SRC_RE.lastIndex = 0;
    let match: RegExpExecArray | null = IMG_SRC_RE.exec(html);
    while (match) {
      const src = match[1]?.trim();
      if (src && !src.startsWith("cid:")) {
        if (src.startsWith("data:")) {
          const decoded = decodeDataImage(src);
          if (decoded) {
            out.push(decoded);
          }
        } else {
          out.push({
            kind: "url",
            url: src,
            fileHint: fileHintFromUrl(src),
            placeholder: "<media:image>",
          });
        }
      }
      match = IMG_SRC_RE.exec(html);
    }
  }
  return out;
}

export function safeHostForUrl(url: string): string {
  try {
    return new URL(url).hostname.toLowerCase();
  } catch {
    return "invalid-url";
  }
}

export function resolveAllowedHosts(input?: string[]): string[] {
  return normalizeHostnameSuffixAllowlist(input, DEFAULT_MEDIA_HOST_ALLOWLIST);
}

export function resolveAuthAllowedHosts(input?: string[]): string[] {
  return normalizeHostnameSuffixAllowlist(input, DEFAULT_MEDIA_AUTH_HOST_ALLOWLIST);
}

export type MSTeamsAttachmentFetchPolicy = {
  allowHosts: string[];
  authAllowHosts: string[];
};

export function resolveAttachmentFetchPolicy(params?: {
  allowHosts?: string[];
  authAllowHosts?: string[];
}): MSTeamsAttachmentFetchPolicy {
  return {
    allowHosts: resolveAllowedHosts(params?.allowHosts),
    authAllowHosts: resolveAuthAllowedHosts(params?.authAllowHosts),
  };
}

export function isUrlAllowed(url: string, allowlist: string[]): boolean {
  return isHttpsUrlAllowedByHostnameSuffixAllowlist(url, allowlist);
}

export function applyAuthorizationHeaderForUrl(params: {
  headers: Headers;
  url: string;
  authAllowHosts: string[];
  bearerToken?: string;
}): void {
  if (!params.bearerToken) {
    params.headers.delete("Authorization");
    return;
  }
  if (isUrlAllowed(params.url, params.authAllowHosts)) {
    params.headers.set("Authorization", `Bearer ${params.bearerToken}`);
    return;
  }
  params.headers.delete("Authorization");
}

export function resolveMediaSsrfPolicy(allowHosts: string[]): SsrFPolicy | undefined {
  return buildHostnameAllowlistPolicyFromSuffixAllowlist(allowHosts);
}

/**
 * Returns true if the given IPv4 or IPv6 address is in a private, loopback,
 * or link-local range that must never be reached from media downloads.
 *
 * Delegates to the SDK's `isPrivateIpAddress` which handles IPv4-mapped IPv6,
 * expanded notation, NAT64, 6to4, Teredo, octal IPv4, and fails closed on
 * parse errors.
 */
export const isPrivateOrReservedIP: (ip: string) => boolean = isPrivateIpAddress;

/**
 * Resolve a hostname via DNS and reject private/reserved IPs.
 * Throws if the resolved IP is private or resolution fails.
 */
export async function resolveAndValidateIP(
  hostname: string,
  resolveFn?: (hostname: string) => Promise<{ address: string }>,
): Promise<string> {
  const resolve = resolveFn ?? lookup;
  let resolved: { address: string };
  try {
    resolved = await resolve(hostname);
  } catch {
    throw new Error(`DNS resolution failed for "${hostname}"`);
  }
  if (isPrivateOrReservedIP(resolved.address)) {
    throw new Error(`Hostname "${hostname}" resolves to private/reserved IP (${resolved.address})`);
  }
  return resolved.address;
}

/** Maximum number of redirects to follow in safeFetch. */
const MAX_SAFE_REDIRECTS = 5;

/**
 * Fetch a URL with redirect: "manual", validating each redirect target
 * against the hostname allowlist and optional DNS-resolved IP (anti-SSRF).
 *
 * This prevents:
 * - Auto-following redirects to non-allowlisted hosts
 * - DNS rebinding attacks when a lookup function is provided
 */
export async function safeFetch(params: {
  url: string;
  allowHosts: string[];
  /**
   * Optional allowlist for forwarding Authorization across redirects.
   * When set, Authorization is stripped before following redirects to hosts
   * outside this list.
   */
  authorizationAllowHosts?: string[];
  fetchFn?: typeof fetch;
  requestInit?: RequestInit;
  resolveFn?: (hostname: string) => Promise<{ address: string }>;
}): Promise<Response> {
  const fetchFn = params.fetchFn ?? fetch;
  const resolveFn = params.resolveFn;
  const hasDispatcher = Boolean(
    params.requestInit &&
    typeof params.requestInit === "object" &&
    "dispatcher" in (params.requestInit as Record<string, unknown>),
  );
  const currentHeaders = new Headers(params.requestInit?.headers);
  let currentUrl = params.url;

  if (!isUrlAllowed(currentUrl, params.allowHosts)) {
    throw new Error(`Initial download URL blocked: ${currentUrl}`);
  }

  if (resolveFn) {
    try {
      const initialHost = new URL(currentUrl).hostname;
      await resolveAndValidateIP(initialHost, resolveFn);
    } catch {
      throw new Error(`Initial download URL blocked: ${currentUrl}`);
    }
  }

  for (let i = 0; i <= MAX_SAFE_REDIRECTS; i++) {
    const res = await fetchFn(currentUrl, {
      ...params.requestInit,
      headers: currentHeaders,
      redirect: "manual",
    });

    if (![301, 302, 303, 307, 308].includes(res.status)) {
      return res;
    }

    const location = res.headers.get("location");
    if (!location) {
      return res;
    }

    let redirectUrl: string;
    try {
      redirectUrl = new URL(location, currentUrl).toString();
    } catch {
      throw new Error(`Invalid redirect URL: ${location}`);
    }

    // Validate redirect target against hostname allowlist
    if (!isUrlAllowed(redirectUrl, params.allowHosts)) {
      throw new Error(`Media redirect target blocked by allowlist: ${redirectUrl}`);
    }

    // Prevent credential bleed: only keep Authorization on redirect hops that
    // are explicitly auth-allowlisted.
    if (
      currentHeaders.has("authorization") &&
      params.authorizationAllowHosts &&
      !isUrlAllowed(redirectUrl, params.authorizationAllowHosts)
    ) {
      currentHeaders.delete("authorization");
    }

    // When a pinned dispatcher is already injected by an upstream guard
    // (for example fetchWithSsrFGuard), let that guard own redirect handling
    // after this allowlist validation step.
    if (hasDispatcher) {
      return res;
    }

    // Validate redirect target's resolved IP
    if (resolveFn) {
      const redirectHost = new URL(redirectUrl).hostname;
      await resolveAndValidateIP(redirectHost, resolveFn);
    }

    currentUrl = redirectUrl;
  }

  throw new Error(`Too many redirects (>${MAX_SAFE_REDIRECTS})`);
}

export async function safeFetchWithPolicy(params: {
  url: string;
  policy: MSTeamsAttachmentFetchPolicy;
  fetchFn?: typeof fetch;
  requestInit?: RequestInit;
  resolveFn?: (hostname: string) => Promise<{ address: string }>;
}): Promise<Response> {
  return await safeFetch({
    url: params.url,
    allowHosts: params.policy.allowHosts,
    authorizationAllowHosts: params.policy.authAllowHosts,
    fetchFn: params.fetchFn,
    requestInit: params.requestInit,
    resolveFn: params.resolveFn,
  });
}