src/engine/steps/viewer-similarity.ts

import type { Page, Frame } from 'playwright';
import { logger } from '../../utils/logger';
import { readScopeDeepText } from '../selectors';

type Scope = Page | Frame;

// ---------------------------------------------------------------------------
// Parsing helpers
// ---------------------------------------------------------------------------

/**
 * Extract a similarity percentage from text.
 *
 * Handles multiple formats found across Turnitin UI versions:
 *  - "45% Overall Similarity"
 *  - "Similarity: 45%"
 *  - "Overall Similarity 45 %"
 *  - Plain "45" or "45%" (when extracted directly from a score element)
 */
function parseSimilarityPercent(text: string): number | null {
  const normalized = String(text || '').replace(/\s+/g, ' ').trim();

  // Pattern 1: "45% Overall Similarity"
  const labelled = normalized.match(
    /(\d{1,3})\s*%\s*Overall Similarity/i,
  );
  // Pattern 2: "Similarity: 45%"  or  "Overall Similarity: 45%"
  const generic = normalized.match(
    /(?:Overall\s+)?Similarity[:\s]+(\d{1,3})\s*%/i,
  );
  // Pattern 3: "Overall Similarity 45 %" (label before value)
  const reversed = normalized.match(
    /Overall Similarity\s+(\d{1,3})\s*%/i,
  );
  // Pattern 4: Plain number from a score element — "45" or "45%"
  const plain = normalized.match(/^(\d{1,3})\s*%?$/);

  const value = Number(
    labelled?.[1] ?? generic?.[1] ?? reversed?.[1] ?? plain?.[1] ?? NaN,
  );
  if (!Number.isFinite(value)) return null;
  return Math.max(0, Math.min(100, value));
}

// ---------------------------------------------------------------------------
// CSS selectors for the similarity score in the report viewer
// ---------------------------------------------------------------------------

const SCORE_SELECTORS = [
  // Primary — Turnitin viewer overview score
  '.tii-SimilarityHeader__heading-content .tii-OverviewScore__Value',
  '.tii-OverviewScore__Value',
  'span.tii-OverviewScore__Value',
  // Heading area with live region
  'h1[aria-live="polite"] span',
  'h1[aria-live="polite"]',
  // Alternative UI variants
  '.tii-SimilarityReportPanelHeader__OverviewScore span',
  '.similarity-score',
  '.overall-similarity-score',
  '[data-testid="similarity-score"]',
  // Badge-style display
  'span[part="tii-grn-badge-label"]',
];

// ---------------------------------------------------------------------------
// Public API
// ---------------------------------------------------------------------------

/**
 * Read the current overall similarity score from the Turnitin report viewer.
 *
 * Handles:
 *  - Multiple CSS selector strategies for different Turnitin UI versions
 *  - Shadow DOM deep text fallback
 *  - Automatic retry with short wait to handle post-filter score updates
 *
 * This is used both as a fallback for assignment pages that still show
 * similarity as pending, and as the authoritative read after filter
 * application (where the displayed score may differ from the pre-filter value).
 */
export async function readViewerSimilarityPercent(
  page: Scope,
): Promise<number | null> {
  // Allow up to 3 attempts with a short stabilization wait between each.
  // After filters are applied the score element may take a moment to update.
  const MAX_READ_ATTEMPTS = 3;

  for (let attempt = 1; attempt <= MAX_READ_ATTEMPTS; attempt++) {
    // Small wait for DOM to stabilize (especially after filter application)
    if (attempt > 1) {
      await page.waitForTimeout(2000);
    }

    // --- Strategy 1: CSS selector scan ---
    for (const selector of SCORE_SELECTORS) {
      const element = page.locator(selector).first();

      const rawText = await element
        .textContent({ timeout: 2000 })
        .catch(() => null);

      if (rawText !== null && rawText.trim() !== '') {
        // Try parsing as-is first (may already contain "Overall Similarity")
        let parsed = parseSimilarityPercent(rawText.trim());
        // Fallback: append context so the labelled regex can match plain numbers
        if (parsed === null) {
          parsed = parseSimilarityPercent(`${rawText.trim()} Overall Similarity`);
        }

        if (parsed !== null) {
          logger.info('Read similarity score from viewer selector', {
            selector,
            rawText: rawText.trim(),
            similarityPercent: parsed,
            attempt,
          });
          return parsed;
        }
      }
    }

    // --- Strategy 2: Deep text scan (traverses shadow DOM) ---
    const deepText = await readScopeDeepText(page);
    if (deepText) {
      const parsed = parseSimilarityPercent(deepText);
      if (parsed !== null) {
        logger.info('Read similarity score from viewer deep text', {
          similarityPercent: parsed,
          attempt,
        });
        return parsed;
      }
    }

    if (attempt < MAX_READ_ATTEMPTS) {
      logger.debug(`Similarity score not found on attempt ${attempt}/${MAX_READ_ATTEMPTS}; retrying`);
    }
  }

  logger.warn('Could not read similarity score from viewer after all attempts');
  return null;
}