/**
 * policy.ts — page-scraping helpers for password requirements.
 *
 * Content-side only; no chrome.* API access. Called by both inject.ts
 * (for the inline create form) and index.ts (for the popup's smart
 * GET_SITE_PASSWORD_POLICY request).
 */

import type { PasswordPolicy } from "../shared/types";

const NEGATION_WINDOW = 220;
const MAX_POLICY_TEXT_CHARS = 4_096;
const MAX_POLICY_PART_CHARS = 1_024;
const MAX_DESCRIBED_IDS = 16;
const MAX_HINTS = 32;
const MAX_SCANNED_NODES = 256;

// Characters that plausibly appear in a site's forbidden-character list.
// Restricted to ASCII punctuation a user could actually type. Anything else
// (letters, digits, whitespace) is ignored so descriptive prose like
// "cannot contain the users first name, last name" does not leak the comma.
const FORBIDDEN_CHAR_SET = new Set([
  "`", "~", "<", ">", "\\", "|", "@", "#", "$", "%", "^", "&", "*",
  "(", ")", "[", "]", "{", "}", "+", "=", "?", "!", ";", ":", "/", '"', "'",
]);

export function extractNearbyText(el: HTMLInputElement | null): string {
  if (!el) return "";
  const parts: string[] = [];
  let remaining = MAX_POLICY_TEXT_CHARS;
  const append = (text: string | null | undefined) => {
    const separator = parts.length > 0 ? 1 : 0;
    const length = Math.min(MAX_POLICY_PART_CHARS, remaining - separator);
    if (!text || length <= 0) return;
    parts.push(text.slice(0, length));
    remaining -= Math.min(text.length, length) + separator;
  };
  const boundedText = (root: Element): string => {
    const text: string[] = [];
    let chars = 0;
    let visited = 0;
    const walker = root.ownerDocument.createTreeWalker(root, NodeFilter.SHOW_ALL);
    let current = walker.nextNode();
    while (visited < MAX_SCANNED_NODES && chars < MAX_POLICY_PART_CHARS && current) {
      visited += 1;
      if (current.nodeType === Node.TEXT_NODE && current.nodeValue) {
        const value = current.nodeValue.slice(0, MAX_POLICY_PART_CHARS - chars);
        text.push(value);
        chars += value.length;
      }
      current = walker.nextNode();
    }
    return text.join(" ");
  };

  // aria-describedby may be a space-separated list of IDs
  const describedBy = el.getAttribute("aria-describedby");
  if (describedBy) {
    for (const id of describedBy.trim().split(/\s+/).slice(0, MAX_DESCRIBED_IDS)) {
      const desc = el.ownerDocument.getElementById(id);
      if (desc) append(boundedText(desc));
    }
  }

  // Field-level attributes that sometimes carry requirements
  append(el.title);
  append(el.placeholder);
  const ariaLabel = el.getAttribute("aria-label");
  append(ariaLabel);

  const HINT_SELECTOR =
    "p, span, li, small, label, div, .hint, .requirement, .password-rule, .password-hint, .password-rules, .field-hint, .helper-text, .input-hint";

  let node: Element | null = el;
  for (let i = 0; i < 5; i++) {
    node = node?.parentElement ?? null;
    if (!node) break;
    const walker = node.ownerDocument.createTreeWalker(node, NodeFilter.SHOW_ELEMENT);
    let current = walker.nextNode();
    let visited = 0;
    let hints = 0;
    while (visited < MAX_SCANNED_NODES && hints < MAX_HINTS && current) {
      visited += 1;
      if (current instanceof Element && current.matches(HINT_SELECTOR)) {
        append(boundedText(current));
        hints += 1;
      }
      current = walker.nextNode();
    }
    if (hints > 0) {
      break;
    }
  }

  return parts.join(" ");
}

export function detectPasswordPolicy(doc: Document = document): PasswordPolicy {
  const policy: PasswordPolicy = {};

  const passwordField = doc.querySelector<HTMLInputElement>(
    'input[autocomplete="new-password"], input[type="password"]'
  );
  const maxLen = passwordField?.maxLength ?? 0;
  if (maxLen > 0) policy.maxLength = maxLen;
  if (passwordField?.pattern) {
    const pat = passwordField.pattern;
    // .{N,M} — range; .{N,} — min only; .{N} — exact
    const rangeMatch = pat.match(/\{(\d+),(\d+)\}/);
    const minOnlyMatch = pat.match(/\{(\d+),\}/);
    const exactMatch = pat.match(/\{(\d+)\}/);
    if (rangeMatch) {
      policy.minLength = Number.parseInt(rangeMatch[1]!, 10);
      policy.maxLength = Number.parseInt(rangeMatch[2]!, 10);
    } else if (minOnlyMatch) {
      policy.minLength = Number.parseInt(minOnlyMatch[1]!, 10);
    } else if (exactMatch) {
      policy.minLength = Number.parseInt(exactMatch[1]!, 10);
      policy.maxLength = Number.parseInt(exactMatch[1]!, 10);
    }
  }

  const text = extractNearbyText(passwordField);

  // "8-20 characters", "8–20 characters", "8 - 20 chars" — most common real-world format
  const dashRangeMatch = text.match(/(\d+)\s*[-–—]\s*(\d+)\s*char/i);
  // "between 8 and 20", "between 8-20"
  const betweenMatch = text.match(/between\D*?(\d+)\D+?(\d+)/i);
  const minMatch = text.match(/(?:at least|minimum|min(?:imum)?|must be (?:at least )?)(?:\D*?)(\d+)/i);
  const maxMatch = text.match(/(?:at most|maximum|max(?:imum)?|up to|cannot exceed|must not exceed|no more than|must be (?:no more than |at most )?)(?:\D*?)(\d+)/i);
  const exactMatch2 = text.match(/(?:exactly|must be)\D*?(\d+)\s*characters?/i);
  // dash range takes priority as the most unambiguous format
  if (dashRangeMatch && !policy.minLength) policy.minLength = Number.parseInt(dashRangeMatch[1]!, 10);
  if (dashRangeMatch && !policy.maxLength) policy.maxLength = Number.parseInt(dashRangeMatch[2]!, 10);
  if (betweenMatch && !policy.minLength) policy.minLength = Number.parseInt(betweenMatch[1]!, 10);
  if (betweenMatch && !policy.maxLength) policy.maxLength = Number.parseInt(betweenMatch[2]!, 10);
  if (minMatch && !policy.minLength) policy.minLength = Number.parseInt(minMatch[1]!, 10);
  if (maxMatch && !policy.maxLength) policy.maxLength = Number.parseInt(maxMatch[1]!, 10);
  if (exactMatch2 && !policy.minLength) policy.minLength = Number.parseInt(exactMatch2[1]!, 10);
  if (exactMatch2 && !policy.maxLength) policy.maxLength = Number.parseInt(exactMatch2[1]!, 10);

  if (/no\s+(?:special|symbol)/i.test(text)) policy.forbidsSymbols = true;
  if (/(?:special|symbol|punctuation)/i.test(text)) policy.requiresSymbols = true;
  if (/(?:uppercase|capital)/i.test(text)) policy.requiresUppercase = true;
  if (/number|digit/i.test(text)) policy.requiresNumbers = true;

  // Forbidden characters — scan a ~220-char window after the first negation
  // keyword and collect single-symbol tokens bounded by whitespace, commas,
  // backticks, or quotes. This tolerates the phrasings actually seen in the
  // wild ("cannot contain ` ~ < > \ characters", backtick-formatted code,
  // comma lists). Descriptive prose ("cannot contain the user's email")
  // does not contribute symbols because the only punctuation it includes
  // (comma, period, apostrophe) is boundary, not content.
  const negation = text.match(
    /(?:cannot|can not|must not|may not|no |without|except|excluding|not allowed|not permitted|invalid|disallowed)[\s\S]*/i
  );
  if (negation) {
    const window = negation[0].slice(0, NEGATION_WINDOW);
    const seen = new Set<string>();
    const tokenRegex = /(?:^|[\s`"',.([])([!-/:-@[-`{-~])(?=[\s`"',.)\]]|$)/g;
    let m: RegExpExecArray | null;
    // biome-ignore lint/suspicious/noAssignInExpressions: standard RegExp.exec loop idiom
    while ((m = tokenRegex.exec(window)) !== null) {
      const ch = m[1]!;
      if (FORBIDDEN_CHAR_SET.has(ch)) seen.add(ch);
    }
    if (seen.size > 0) policy.forbiddenChars = [...seen].join("");
  }

  return policy;
}