const { db } = require('../db');
const { parseDate } = require('../services/rating-calculator');

function getPlayerFromDB(pdgaNumber) {
  return new Promise((resolve, reject) => {
    db.get(
      'SELECT * FROM players WHERE pdga_number = ?',
      [pdgaNumber],
      (err, row) => {
        if (err) reject(err);
        else resolve(row);
      }
    );
  });
}

function savePlayerToDB(playerData) {
  return new Promise((resolve, reject) => {
    db.run(
      `INSERT OR REPLACE INTO players (pdga_number, name, current_rating, rating_change, last_updated)
       VALUES (?, ?, ?, ?, datetime('now'))`,
      [playerData.pdgaNumber, playerData.name, playerData.rating, playerData.ratingChange],
      function(err) {
        if (err) reject(err);
        else resolve(this.lastID);
      }
    );
  });
}

function getRatingHistoryFromDB(pdgaNumber) {
  return new Promise((resolve, reject) => {
    db.get('SELECT id FROM players WHERE pdga_number = ?', [pdgaNumber], (err, player) => {
      if (err) return reject(err);
      if (!player) return resolve(null);

      db.all(
        'SELECT * FROM rating_history WHERE player_id = ? ORDER BY date ASC',
        [player.id],
        (err, rows) => {
          if (err) reject(err);
          else resolve(rows);
        }
      );
    });
  });
}

function saveRatingHistoryToDB(pdgaNumber, ratingHistory) {
  return new Promise((resolve, reject) => {
    db.get('SELECT id FROM players WHERE pdga_number = ?', [pdgaNumber], (err, player) => {
      if (err) return reject(err);
      if (!player) return reject(new Error('Player not found'));

      db.run('DELETE FROM rating_history WHERE player_id = ?', [player.id], (err) => {
        if (err) return reject(err);

        if (ratingHistory.length === 0) {
          return resolve();
        }

        let completed = 0;
        const total = ratingHistory.length;

        ratingHistory.forEach(entry => {
          const parsedDate = parseDate(entry.date);

          db.run(
            'INSERT INTO rating_history (player_id, date, rating) VALUES (?, ?, ?)',
            [player.id, parsedDate.toISOString().split('T')[0], entry.rating],
            (err) => {
              if (err) return reject(err);

              completed++;
              if (completed === total) {
                resolve();
              }
            }
          );
        });
      });
    });
  });
}

function getRoundHistoryFromDB(pdgaNumber) {
  return new Promise((resolve, reject) => {
    db.get('SELECT id FROM players WHERE pdga_number = ?', [pdgaNumber], (err, player) => {
      if (err) return reject(err);
      if (!player) return resolve([]);

      db.all(
        'SELECT * FROM round_history WHERE player_id = ? ORDER BY date DESC',
        [player.id],
        (err, rows) => {
          if (err) reject(err);
          else resolve(rows);
        }
      );
    });
  });
}

function getLastRoundUpdateDate(pdgaNumber) {
  return new Promise((resolve, reject) => {
    db.get(
      'SELECT last_round_update FROM players WHERE pdga_number = ?',
      [pdgaNumber],
      (err, row) => {
        if (err) reject(err);
        else resolve(row ? row.last_round_update : null);
      }
    );
  });
}

function updateLastRoundUpdateDate(pdgaNumber) {
  return new Promise((resolve, reject) => {
    db.run(
      'UPDATE players SET last_round_update = CURRENT_TIMESTAMP WHERE pdga_number = ?',
      [pdgaNumber],
      function(err) {
        if (err) reject(err);
        else resolve();
      }
    );
  });
}

function saveRoundHistoryToDB(pdgaNumber, roundData, isIncremental = false) {
  return new Promise((resolve, reject) => {
    db.get('SELECT id FROM players WHERE pdga_number = ?', [pdgaNumber], (err, player) => {
      if (err) return reject(err);
      if (!player) return reject(new Error('Player not found'));

      const processRounds = () => {
        if (roundData.length === 0) {
          db.run('UPDATE players SET last_round_update = datetime("now") WHERE pdga_number = ?', [pdgaNumber], (err) => {
            if (err) reject(err);
            else resolve();
          });
          return;
        }

        const stmt = db.prepare('INSERT OR REPLACE INTO round_history (player_id, date, competition_name, rating) VALUES (?, ?, ?, ?)');

        for (const round of roundData) {
          stmt.run([player.id, round.date.toISOString().split('T')[0], round.competition || 'Unknown', round.rating]);
        }

        stmt.finalize((err) => {
          if (err) {
            reject(err);
          } else {
            db.run('UPDATE players SET last_round_update = datetime("now") WHERE pdga_number = ?', [pdgaNumber], (updateErr) => {
              if (updateErr) reject(updateErr);
              else resolve();
            });
          }
        });
      };

      if (!isIncremental) {
        db.run('DELETE FROM round_history WHERE player_id = ?', [player.id], (err) => {
          if (err) return reject(err);
          processRounds();
        });
      } else {
        processRounds();
      }
    });
  });
}

function savePredictedRatingToDB(pdgaNumber, predictedRating, stdDev = null) {
  return new Promise((resolve, reject) => {
    db.run(
      'UPDATE players SET predicted_rating = ?, std_dev = ? WHERE pdga_number = ?',
      [predictedRating, stdDev, pdgaNumber],
      function(err) {
        if (err) reject(err);
        else resolve();
      }
    );
  });
}

/**
 * Returns monthly rating snapshots for one player (latest entry per calendar month),
 * ordered oldest → newest. At most `months` entries; [] if none.
 */
function getMonthlyHistory(pdgaNumber, months = 12) {
  return new Promise((resolve, reject) => {
    db.get('SELECT id FROM players WHERE pdga_number = ?', [pdgaNumber], (err, player) => {
      if (err) return reject(err);
      if (!player) return resolve([]);

      db.all(
        `SELECT rating
         FROM rating_history
         WHERE player_id = ?
           AND date IN (
             SELECT MAX(date)
             FROM rating_history
             WHERE player_id = ?
             GROUP BY strftime('%Y-%m', date)
           )
         ORDER BY date DESC
         LIMIT ?`,
        [player.id, player.id, months],
        (err, rows) => {
          if (err) return reject(err);
          resolve(rows.map(r => r.rating).reverse());
        }
      );
    });
  });
}

/**
 * Fetches the last `months` monthly rating snapshots for ALL players in one query.
 * Returns a Map<pdgaNumber, number[]> (oldest → newest per player).
 * Use this in bulk-fetch paths to avoid N+1 queries.
 */
function getAllMonthlyHistoriesFromDB(months = 12) {
  return new Promise((resolve, reject) => {
    db.all(
      `SELECT p.pdga_number, rh.date, rh.rating
       FROM rating_history rh
       JOIN players p ON rh.player_id = p.id
       INNER JOIN (
         SELECT player_id, MAX(date) AS max_date
         FROM rating_history
         GROUP BY player_id, strftime('%Y-%m', date)
       ) latest ON rh.player_id = latest.player_id AND rh.date = latest.max_date
       ORDER BY p.pdga_number, rh.date ASC`,
      [],
      (err, rows) => {
        if (err) return reject(err);

        const map = new Map();
        for (const row of rows) {
          if (!map.has(row.pdga_number)) map.set(row.pdga_number, []);
          map.get(row.pdga_number).push(row.rating);
        }
        // Trim each player's history to the requested window
        for (const [key, arr] of map) {
          if (arr.length > months) map.set(key, arr.slice(-months));
        }
        resolve(map);
      }
    );
  });
}

function getLastRefresh() {
  return new Promise((resolve, reject) => {
    db.get(
      'SELECT MAX(last_updated) AS lastRefresh FROM players',
      [],
      (err, row) => {
        if (err) reject(err);
        else resolve(row ? row.lastRefresh : null);
      }
    );
  });
}

module.exports = {
  getPlayerFromDB,
  savePlayerToDB,
  getRatingHistoryFromDB,
  saveRatingHistoryToDB,
  getRoundHistoryFromDB,
  getLastRoundUpdateDate,
  updateLastRoundUpdateDate,
  saveRoundHistoryToDB,
  savePredictedRatingToDB,
  getLastRefresh,
  getMonthlyHistory,
  getAllMonthlyHistoriesFromDB
};