/**
 * Custom JS injector — run user-provided JavaScript in the context of each crawled page.
 *
 * Use cases:
 * - Extract custom data points not captured by standard extractors
 * - Set localStorage/sessionStorage values before crawl
 * - Override fetch() to intercept API calls
 * - Simulate user events (keydown, focus, etc.)
 * - Bypass specific anti-bot checks
 *
 * Security: scripts run in the page context (sandboxed by Chromium's renderer).
 * They cannot access the Node.js process or file system.
 * ZeTa validates scripts are strings before injection.
 */

import type { Page } from 'playwright';

export interface JsInjectionOpts {
  /** Script to run on every page BEFORE navigation (via page.addInitScript) */
  initScript?: string;
  /** Script to run on every page AFTER navigation completes (via page.evaluate) */
  postLoadScript?: string;
  /** Key-value pairs to set in localStorage before page load */
  localStorage?: Record<string, string>;
  /** Key-value pairs to set in sessionStorage before page load */
  sessionStorage?: Record<string, string>;
  /** Cookie key-value pairs to add before page load */
  cookies?: Array<{ name: string; value: string; domain?: string; path?: string }>;
}

export interface JsInjectionResult {
  initScriptApplied: boolean;
  postLoadResult: unknown;
  storageSet: boolean;
  cookiesSet: number;
  error?: string;
}

export async function injectCustomJs(page: Page, opts: JsInjectionOpts): Promise<JsInjectionResult> {
  const result: JsInjectionResult = {
    initScriptApplied: false,
    postLoadResult: null,
    storageSet: false,
    cookiesSet: 0,
  };

  // Set cookies via Playwright context
  if (opts.cookies?.length) {
    try {
      await page.context().addCookies(
        opts.cookies.map(c => ({ name: c.name, value: c.value, domain: c.domain ?? '', path: c.path ?? '/', url: page.url() || undefined }))
      );
      result.cookiesSet = opts.cookies.length;
    } catch (e: any) {
      result.error = `Cookie injection failed: ${e.message}`;
    }
  }

  // Init script (runs before page load on every navigation)
  if (opts.initScript || opts.localStorage || opts.sessionStorage) {
    const storageSetup = [
      opts.localStorage ? `Object.entries(${JSON.stringify(opts.localStorage)}).forEach(([k,v])=>localStorage.setItem(k,v));` : '',
      opts.sessionStorage ? `Object.entries(${JSON.stringify(opts.sessionStorage)}).forEach(([k,v])=>sessionStorage.setItem(k,v));` : '',
    ].filter(Boolean).join('\n');

    const combinedInit = [storageSetup, opts.initScript ?? ''].filter(Boolean).join('\n');
    try {
      await page.addInitScript(combinedInit);
      result.initScriptApplied = true;
      result.storageSet = !!(opts.localStorage || opts.sessionStorage);
    } catch (e: any) {
      result.error = `Init script failed: ${e.message}`;
    }
  }

  // Post-load script (runs after navigation)
  if (opts.postLoadScript) {
    try {
      result.postLoadResult = await page.evaluate(opts.postLoadScript);
    } catch (e: any) {
      result.error = `Post-load script failed: ${e.message}`;
    }
  }

  return result;
}

/** Safe string validator — ensures script is a string, not an object/function reference */
export function validateScript(script: unknown): string {
  if (typeof script !== 'string') throw new Error('Script must be a string');
  if (script.length > 50_000) throw new Error('Script too large (>50KB)');
  return script;
}