const { db } = require('../db');
const { getPlayerFromDB, getRoundHistoryFromDB, savePredictedRatingToDB, savePlayerToDB, getMonthlyHistory, getAllMonthlyHistoriesFromDB, getAllRatingHistoriesFromDB } = require('../models/player');
const { fetchPlayerDataHTTP, parsePlayerData } = require('../scrapers/player-http');
const { calculatePredictedRating, getPreviousPDGAUpdateDate } = require('./rating-calculator');
const logger = require('../logger');

function formatDisplayDate(dateStr) {
  return new Date(dateStr).toLocaleDateString('en-US', {
    day: '2-digit', month: 'short', year: 'numeric'
  });
}

// Derives previous-month rating and the delta to it. Prefers PDGA's reported
// rating_change (canonical), falls back to our own monthly snapshots when
// rating_change is missing — common for players whose latest scrape failed.
function deriveMonthlyDeltas(rating, rawRatingChange, monthlyHistory) {
  if (rating != null && rawRatingChange != null) {
    return { lastMonthRating: rating - rawRatingChange, ratingChange: rawRatingChange };
  }
  if (rating != null && monthlyHistory && monthlyHistory.length >= 1) {
    // The "last month" snapshot depends on whether current_rating is already in
    // history. If equal, current is the most recent entry — last month is the one
    // before it. If not, current is newer than history — the latest entry IS last month.
    const lastIdx = monthlyHistory.length - 1;
    const lastMonth = (monthlyHistory[lastIdx] === rating)
      ? (monthlyHistory.length >= 2 ? monthlyHistory[lastIdx - 1] : null)
      : monthlyHistory[lastIdx];
    if (lastMonth != null) {
      return { lastMonthRating: lastMonth, ratingChange: rating - lastMonth };
    }
  }
  return { lastMonthRating: null, ratingChange: rawRatingChange };
}

async function getPlayerDataFromDB(pdgaNumber, { includeMonthlyHistory = true } = {}) {
  try {
    const cachedPlayer = await getPlayerFromDB(pdgaNumber);
    if (cachedPlayer) {
      logger.debug(`Loading PDGA ${pdgaNumber} from DB (source of truth)`);

      let predictedRating = cachedPlayer.predicted_rating;
      let stdDev = cachedPlayer.std_dev;
      let excludedRoundsCount = cachedPlayer.excluded_rounds_count;
      let cutoffRating = cachedPlayer.cutoff_rating;
      let predictedCalculatedAtRaw = cachedPlayer.predicted_calculated_at;
      if (!predictedRating || predictedRating === 0) {
        predictedRating = await getPredictedRatingFromDB(pdgaNumber);
        const updatedPlayer = await getPlayerFromDB(pdgaNumber);
        stdDev = updatedPlayer?.std_dev;
        excludedRoundsCount = updatedPlayer?.excluded_rounds_count;
        cutoffRating = updatedPlayer?.cutoff_rating;
        predictedCalculatedAtRaw = updatedPlayer?.predicted_calculated_at;
      }

      // Staleness-check: invalidate cached predicted_rating if the PDGA cycle has
      // rolled over since it was calculated. Don't recompute — round_history may be
      // equally stale. UI will show "—" until the next manual refresh.
      const predictedCalculatedAt = predictedCalculatedAtRaw
        ? new Date(predictedCalculatedAtRaw)
        : null;
      const previousUpdate = getPreviousPDGAUpdateDate();
      const hasPredicted = predictedRating !== null && predictedRating !== 0;
      const isStale = hasPredicted && (
        predictedCalculatedAt === null || predictedCalculatedAt < previousUpdate
      );
      if (isStale) {
        logger.debug(`PDGA ${pdgaNumber}: predicted rating stale (calculated ${predictedCalculatedAt?.toISOString() ?? 'unknown'}, cycle rolled ${previousUpdate.toISOString()})`);
        predictedRating = null;
        stdDev = null;
        excludedRoundsCount = null;
        cutoffRating = null;
      }

      const rating = cachedPlayer.current_rating;
      const rawRatingChange = cachedPlayer.rating_change;
      const resolvedPredicted = predictedRating > 0 ? predictedRating : null;
      const resolvedStdDev = stdDev > 0 ? stdDev : null;

      // Skip in bulk-fetch paths where caller supplies history via getAllMonthlyHistoriesFromDB
      const monthlyHistory = includeMonthlyHistory
        ? await getMonthlyHistory(cachedPlayer.pdga_number)
        : [];

      const { lastMonthRating, ratingChange } = deriveMonthlyDeltas(rating, rawRatingChange, monthlyHistory);

      return {
        pdgaNumber: cachedPlayer.pdga_number,
        name: cachedPlayer.name,
        rating,
        ratingChange,
        predictedRating: resolvedPredicted,
        stdDev: resolvedStdDev,
        excludedRoundsCount: (excludedRoundsCount != null && excludedRoundsCount >= 0) ? excludedRoundsCount : null,
        cutoffRating: (cutoffRating != null && cutoffRating > 0) ? cutoffRating : null,
        lastMonthRating,
        // gap between next predicted update and current rating (null when either is missing)
        deltaPredicted: (resolvedPredicted != null && rating != null) ? resolvedPredicted - rating : null,
        monthlyHistory
      };
    }
    return null;
  } catch (err) {
    logger.error(`Database error for PDGA ${pdgaNumber}:`, err.message);
    return null;
  }
}

async function scrapePDGARating(pdgaNumber, retries = 3) {
  logger.info(`Refreshing PDGA ${pdgaNumber} from PDGA website`);
  
  for (let attempt = 1; attempt <= retries; attempt++) {
    try {
      logger.info(`Attempt ${attempt}/${retries} for PDGA ${pdgaNumber} (using HTTP)`);
      
      const html = await fetchPlayerDataHTTP(pdgaNumber);
      const result = parsePlayerData(html, pdgaNumber);
      
      try {
        await savePlayerToDB(result);
        logger.info(`Saved PDGA ${pdgaNumber} to database`);
      } catch (dbErr) {
        logger.error(`Failed to save PDGA ${pdgaNumber} to database:`, dbErr.message);
      }
      
      logger.info(`Successfully scraped PDGA ${pdgaNumber} on attempt ${attempt}`);
      return result;
      
    } catch (error) {
      logger.error(`Attempt ${attempt}/${retries} failed for PDGA ${pdgaNumber}:`, error.message);
      
      if (attempt === retries) {
        return {
          pdgaNumber,
          name: 'Error',
          rating: 0,
          ratingChange: null,
          predictedRating: null
        };
      }
      
      let retryDelay = 2000 * attempt;
      
      if (error.rateLimitInfo) {
        const retryAfter = error.rateLimitInfo.headers['retry-after'];
        if (retryAfter) {
          retryDelay = Math.max(retryDelay, (parseInt(retryAfter) + 1) * 1000);
          logger.warn(`Using Retry-After header: waiting ${retryDelay/1000}s`);
        }
      }
      
      if (error.code === 'ECONNRESET') {
        retryDelay = Math.max(retryDelay, 10000);
        logger.warn(`Connection reset detected: waiting ${retryDelay/1000}s`);
      }
      
      await new Promise(resolve => setTimeout(resolve, retryDelay));
    }
  }
}

async function getPredictedRatingFromDB(pdgaNumber) {
  try {
    const roundHistory = await getRoundHistoryFromDB(pdgaNumber);
    if (roundHistory.length > 0) {
      logger.debug(`Using ${roundHistory.length} cached rounds for PDGA ${pdgaNumber} prediction`);

      const roundRatings = roundHistory.map(round => ({
        rating: round.rating,
        date: new Date(round.date),
        competition: round.competition_name || 'Unknown'
      }));

      const result = calculatePredictedRating(roundRatings);

      await savePredictedRatingToDB(pdgaNumber, result.rating, result.stdDev, result.excludedRoundsCount, result.cutoffRating);

      return result.rating;
    }
    return 0;
  } catch (err) {
    logger.error(`Error getting predicted rating from DB for ${pdgaNumber}:`, err.message);
    return 0;
  }
}

async function getAllRatingsFromDB(progressCallback = null) {
  try {
    const allPlayers = await new Promise((resolve, reject) => {
      db.all(
        'SELECT pdga_number, name, current_rating, rating_change FROM players ORDER BY pdga_number',
        [],
        (err, rows) => {
          if (err) reject(err);
          else resolve(rows || []);
        }
      );
    });

    logger.info(`Loading ${allPlayers.length} players from database...`);

    // Fetch all monthly histories in one query so the per-player loop doesn't add N extra queries
    const monthlyHistoryMap = await getAllMonthlyHistoriesFromDB(12);
    const ratingHistoryMap = await getAllRatingHistoriesFromDB();

    const ratings = [];
    const total = allPlayers.length;

    for (let i = 0; i < allPlayers.length; i++) {
      const player = allPlayers[i];
      const pdgaNumber = player.pdga_number;

      if (progressCallback) {
        progressCallback({
          current: i + 1,
          total,
          pdgaNumber,
          status: 'loading'
        });
      }

      try {
        const playerData = await getPlayerDataFromDB(pdgaNumber, { includeMonthlyHistory: false });

        if (playerData) {
          playerData.monthlyHistory = monthlyHistoryMap.get(pdgaNumber) ?? [];
          const rawHistory = ratingHistoryMap.get(pdgaNumber) ?? [];
          playerData.ratingHistory = rawHistory.map(row => ({
            date: row.date,
            rating: row.rating,
            displayDate: formatDisplayDate(row.date)
          }));
          // Re-derive now that history is attached — bulk path skipped includeMonthlyHistory
          const derived = deriveMonthlyDeltas(playerData.rating, player.rating_change, playerData.monthlyHistory);
          playerData.lastMonthRating = derived.lastMonthRating;
          playerData.ratingChange = derived.ratingChange;
          ratings.push(playerData);
        }

        if (progressCallback) {
          progressCallback({
            current: i + 1,
            total,
            pdgaNumber,
            status: 'completed',
            name: playerData ? playerData.name : player.name
          });
        }
      } catch (error) {
        logger.error(`Failed to load PDGA ${pdgaNumber} from database:`, error.message);
        const errorRating = player.current_rating;
        const errorRatingChange = player.rating_change;
        const errorData = {
          pdgaNumber: parseInt(pdgaNumber),
          name: player.name || 'Database Error',
          rating: errorRating,
          ratingChange: errorRatingChange,
          predictedRating: null,
          stdDev: null,
          excludedRoundsCount: null,
          cutoffRating: null,
          lastMonthRating: (errorRating != null && errorRatingChange != null) ? errorRating - errorRatingChange : null,
          deltaPredicted: null,
          monthlyHistory: [],
          ratingHistory: []
        };
        ratings.push(errorData);

        if (progressCallback) {
          progressCallback({
            current: i + 1,
            total,
            pdgaNumber,
            status: 'error',
            name: player.name || 'Database Error'
          });
        }
      }
    }

    return ratings.sort((a, b) => (b.rating || 0) - (a.rating || 0));
  } catch (error) {
    logger.error('Error loading players from database:', error);
    return [];
  }
}

async function refreshAllPlayersInDB(progressCallback = null) {
  try {
    const allPlayers = await new Promise((resolve, reject) => {
      db.all(
        'SELECT pdga_number, name FROM players ORDER BY pdga_number',
        [],
        (err, rows) => {
          if (err) reject(err);
          else resolve(rows || []);
        }
      );
    });

    logger.info(`Refreshing ${allPlayers.length} players from database...`);

    const ratings = [];
    const total = allPlayers.length;

    for (let i = 0; i < allPlayers.length; i++) {
      const player = allPlayers[i];
      const pdgaNumber = player.pdga_number;

      logger.info(`Refreshing PDGA ${pdgaNumber}... (${i + 1}/${total})`);

      if (progressCallback) {
        progressCallback({
          current: i + 1,
          total,
          pdgaNumber,
          status: 'loading'
        });
      }

      try {
        const playerData = await scrapePDGARating(pdgaNumber);
        ratings.push(playerData);

        if (progressCallback) {
          progressCallback({
            current: i + 1,
            total,
            pdgaNumber,
            status: 'completed',
            name: playerData.name
          });
        }

        await new Promise(resolve => setTimeout(resolve, 2000));
      } catch (error) {
        logger.error(`Failed to refresh PDGA ${pdgaNumber}:`, error.message);
        const errorData = {
          pdgaNumber: parseInt(pdgaNumber),
          name: player.name || 'Error',
          rating: 0,
          ratingChange: null,
          predictedRating: null
        };
        ratings.push(errorData);

        if (progressCallback) {
          progressCallback({
            current: i + 1,
            total,
            pdgaNumber,
            status: 'error',
            name: player.name || 'Error'
          });
        }
      }
    }

    return ratings.sort((a, b) => (b.rating || 0) - (a.rating || 0));
  } catch (error) {
    logger.error('Error refreshing all players:', error);
    return [];
  }
}

/**
 * Aggregates KPI summary stats from an already-fetched player array.
 * All fields are derived from the player list — no extra DB queries.
 */
function computeKpis(players) {
  const active = players.filter(p => p.rating != null && p.rating > 0);
  const avg = active.length > 0
    ? Math.round(active.reduce((sum, p) => sum + p.rating, 0) / active.length)
    : null;

  return {
    tracked: players.length,
    active: active.length,
    avg,
    climbing: players.filter(p => p.ratingChange != null && p.ratingChange > 0).length,
    slipping: players.filter(p => p.ratingChange != null && p.ratingChange < 0).length
  };
}

module.exports = {
  getPlayerDataFromDB,
  scrapePDGARating,
  getPredictedRatingFromDB,
  getAllRatingsFromDB,
  refreshAllPlayersInDB,
  computeKpis,
  formatDisplayDate
};