const { outputProgress, formatElapsedTime, estimateRemaining, calculateRate } = require('../metrics/utils/progress');

async function importPurchaseOrders(prodConnection, localConnection, incrementalUpdate = true) {
  const startTime = Date.now();
  let recordsAdded = 0;
  let recordsUpdated = 0;

  try {
    // Get last sync info
    const [syncInfo] = await localConnection.query(
      "SELECT last_sync_timestamp FROM sync_status WHERE table_name = 'purchase_orders'"
    );
    const lastSyncTime = syncInfo?.[0]?.last_sync_timestamp || '1970-01-01';

    console.log('Purchase Orders: Using last sync time:', lastSyncTime);

    // Insert temporary table creation query for purchase orders
    await localConnection.query(`
      CREATE TABLE IF NOT EXISTS temp_purchase_orders (
        po_id INT UNSIGNED NOT NULL,
        pid INT UNSIGNED NOT NULL,
        vendor VARCHAR(255),
        date DATE,
        expected_date DATE,
        status INT,
        notes TEXT,
        PRIMARY KEY (po_id, pid)
      ) ENGINE=InnoDB DEFAULT CHARSET=utf8;
    `);

    outputProgress({
      operation: `Starting ${incrementalUpdate ? 'incremental' : 'full'} purchase orders import`,
      status: "running",
    });

    // Get column names for the insert
    const [columns] = await localConnection.query(`
      SELECT COLUMN_NAME 
      FROM INFORMATION_SCHEMA.COLUMNS 
      WHERE TABLE_NAME = 'purchase_orders'
      ORDER BY ORDINAL_POSITION
    `);
    const columnNames = columns
      .map((col) => col.COLUMN_NAME)
      .filter((name) => name !== "id");

    // Build incremental conditions
    const incrementalWhereClause = incrementalUpdate
      ? `AND (
          p.date_updated > ? 
          OR p.date_ordered > ?
          OR p.date_estin > ?
          OR r.date_updated > ?
          OR r.date_created > ?
          OR r.date_checked > ?
          OR rp.stamp > ?
          OR rp.received_date > ?
        )`
      : "";
    const incrementalParams = incrementalUpdate
      ? [lastSyncTime, lastSyncTime, lastSyncTime, lastSyncTime, lastSyncTime, lastSyncTime, lastSyncTime, lastSyncTime]
      : [];

    // First get all relevant PO IDs with basic info
    const [[{ total }]] = await prodConnection.query(`
      SELECT COUNT(*) as total
      FROM (
        SELECT DISTINCT pop.po_id, pop.pid
        FROM po p 
        USE INDEX (idx_date_created)
        JOIN po_products pop ON p.po_id = pop.po_id
        JOIN suppliers s ON p.supplier_id = s.supplierid
        WHERE p.date_ordered >= DATE_SUB(CURRENT_DATE, INTERVAL ${incrementalUpdate ? '1' : '5'} YEAR)
          ${incrementalUpdate ? `
            AND (
              p.date_updated > ? 
              OR p.date_ordered > ?
              OR p.date_estin > ?
            )
          ` : ''}
        UNION
        SELECT DISTINCT r.receiving_id as po_id, rp.pid
        FROM receivings_products rp
        USE INDEX (received_date)
        LEFT JOIN receivings r ON r.receiving_id = rp.receiving_id
        WHERE rp.received_date >= DATE_SUB(CURRENT_DATE, INTERVAL ${incrementalUpdate ? '1' : '5'} YEAR)
          ${incrementalUpdate ? `
            AND (
              r.date_created > ?
              OR r.date_checked > ?
              OR rp.stamp > ?
              OR rp.received_date > ?
            )
          ` : ''}
      ) all_items
    `, incrementalUpdate ? [
      lastSyncTime, lastSyncTime, lastSyncTime,  // PO conditions
      lastSyncTime, lastSyncTime, lastSyncTime, lastSyncTime  // Receiving conditions
    ] : []);

    console.log('Purchase Orders: Found changes:', total);

    const [poList] = await prodConnection.query(`
      SELECT DISTINCT 
        COALESCE(p.po_id, r.receiving_id) as po_id,
        COALESCE(
          NULLIF(s1.companyname, ''),
          NULLIF(s2.companyname, ''),
          'Unknown Vendor'
        ) as vendor,
        CASE 
          WHEN p.po_id IS NOT NULL THEN 
            DATE(COALESCE(
              NULLIF(p.date_ordered, '0000-00-00 00:00:00'),
              p.date_created
            ))
          WHEN r.receiving_id IS NOT NULL THEN
            DATE(r.date_created)
        END as date,
        CASE 
          WHEN p.date_estin = '0000-00-00' THEN NULL
          WHEN p.date_estin IS NULL THEN NULL
          WHEN p.date_estin NOT REGEXP '^[0-9]{4}-[0-9]{2}-[0-9]{2}$' THEN NULL
          ELSE p.date_estin
        END as expected_date,
        COALESCE(p.status, 50) as status,
        p.short_note as notes,
        p.notes as long_note
      FROM (
        SELECT po_id FROM po 
        USE INDEX (idx_date_created)
        WHERE date_ordered >= DATE_SUB(CURRENT_DATE, INTERVAL ${incrementalUpdate ? '1' : '5'} YEAR)
          ${incrementalUpdate ? `
            AND (
              date_ordered > ? 
              OR date_updated > ?
              OR date_estin > ?
            )
          ` : ''}
        UNION
        SELECT DISTINCT r.receiving_id as po_id
        FROM receivings r
        JOIN receivings_products rp USE INDEX (received_date) ON r.receiving_id = rp.receiving_id
        WHERE rp.received_date >= DATE_SUB(CURRENT_DATE, INTERVAL ${incrementalUpdate ? '1' : '5'} YEAR)
          ${incrementalUpdate ? `
            AND (
              r.date_created > ?
              OR r.date_checked > ?
              OR rp.stamp > ?
              OR rp.received_date > ?
            )
          ` : ''}
      ) ids
      LEFT JOIN po p ON ids.po_id = p.po_id
      LEFT JOIN suppliers s1 ON p.supplier_id = s1.supplierid
      LEFT JOIN receivings r ON ids.po_id = r.receiving_id
      LEFT JOIN suppliers s2 ON r.supplier_id = s2.supplierid
      ORDER BY po_id
    `, incrementalUpdate ? [
      lastSyncTime, lastSyncTime, lastSyncTime,  // PO conditions
      lastSyncTime, lastSyncTime, lastSyncTime, lastSyncTime  // Receiving conditions
    ] : []);

    console.log('Sample PO dates:', poList.slice(0, 5).map(po => ({
      po_id: po.po_id,
      raw_date_ordered: po.raw_date_ordered,
      raw_date_created: po.raw_date_created,
      raw_date_estin: po.raw_date_estin,
      computed_date: po.date,
      expected_date: po.expected_date
    })));

    const totalItems = total;
    let processed = 0;

    const BATCH_SIZE = 5000;
    const PROGRESS_INTERVAL = 500;
    let lastProgressUpdate = Date.now();

    outputProgress({
      operation: `Starting purchase orders import - Processing ${totalItems} purchase order items`,
      status: "running",
    });

    for (let i = 0; i < poList.length; i += BATCH_SIZE) {
      const batch = poList.slice(i, Math.min(i + BATCH_SIZE, poList.length));
      const poIds = batch.map(po => po.po_id);

      // Get all products for these POs in one query
      const [poProducts] = await prodConnection.query(`
        SELECT 
          pop.po_id,
          pop.pid,
          pr.itemnumber as sku,
          pr.description as name,
          pop.cost_each,
          pop.qty_each as ordered
        FROM po_products pop
        USE INDEX (PRIMARY)
        JOIN products pr ON pop.pid = pr.pid
        WHERE pop.po_id IN (?)
      `, [poIds]);

      // Process PO products in smaller sub-batches to avoid packet size issues
      const SUB_BATCH_SIZE = 5000;
      for (let j = 0; j < poProducts.length; j += SUB_BATCH_SIZE) {
        const productBatch = poProducts.slice(j, j + SUB_BATCH_SIZE);
        const productPids = [...new Set(productBatch.map(p => p.pid))];
        const batchPoIds = [...new Set(productBatch.map(p => p.po_id))];

        // Get receivings for this batch with employee names
        const [receivings] = await prodConnection.query(`
          SELECT 
            r.po_id,
            rp.pid,
            rp.receiving_id,
            rp.qty_each,
            rp.cost_each,
            COALESCE(rp.received_date, r.date_created) as received_date,
            rp.received_by,
            CONCAT(e.firstname, ' ', e.lastname) as received_by_name,
            CASE 
              WHEN r.po_id IS NULL THEN 2  -- No PO
              WHEN r.po_id IN (?) THEN 0   -- Original PO
              ELSE 1                       -- Different PO
            END as is_alt_po
          FROM receivings_products rp
          USE INDEX (received_date)
          LEFT JOIN receivings r ON r.receiving_id = rp.receiving_id
          LEFT JOIN employees e ON rp.received_by = e.employeeid
          WHERE rp.pid IN (?)
            AND rp.received_date >= DATE_SUB(CURRENT_DATE, INTERVAL 5 YEAR)
          ORDER BY r.po_id, rp.pid, rp.received_date
        `, [batchPoIds, productPids]);

        // Create maps for this sub-batch
        const poProductMap = new Map();
        productBatch.forEach(product => {
          const key = `${product.po_id}-${product.pid}`;
          poProductMap.set(key, product);
        });

        const receivingMap = new Map();
        const altReceivingMap = new Map();
        const noPOReceivingMap = new Map();
        
        receivings.forEach(receiving => {
          const key = `${receiving.po_id}-${receiving.pid}`;
          if (receiving.is_alt_po === 2) {
            // No PO
            if (!noPOReceivingMap.has(receiving.pid)) {
              noPOReceivingMap.set(receiving.pid, []);
            }
            noPOReceivingMap.get(receiving.pid).push(receiving);
          } else if (receiving.is_alt_po === 1) {
            // Different PO
            if (!altReceivingMap.has(receiving.pid)) {
              altReceivingMap.set(receiving.pid, []);
            }
            altReceivingMap.get(receiving.pid).push(receiving);
          } else {
            // Original PO
            if (!receivingMap.has(key)) {
              receivingMap.set(key, []);
            }
            receivingMap.get(key).push(receiving);
          }
        });

        // Verify PIDs exist
        const [existingPids] = await localConnection.query(
          'SELECT pid FROM products WHERE pid IN (?)',
          [productPids]
        );
        const validPids = new Set(existingPids.map(p => p.pid));

        // First check which PO lines already exist and get their current values
        const poLines = Array.from(poProductMap.values())
          .filter(p => validPids.has(p.pid))
          .map(p => [p.po_id, p.pid]);

        const [existingPOs] = await localConnection.query(
          `SELECT ${columnNames.join(',')} FROM purchase_orders WHERE (po_id, pid) IN (${poLines.map(() => "(?,?)").join(",")})`,
          poLines.flat()
        );
        const existingPOMap = new Map(
          existingPOs.map(po => [`${po.po_id}-${po.pid}`, po])
        );

        // Split into inserts and updates
        const insertsAndUpdates = { inserts: [], updates: [] };
        let batchProcessed = 0;

        for (const po of batch) {
          const poProducts = Array.from(poProductMap.values())
            .filter(p => p.po_id === po.po_id && validPids.has(p.pid));

          for (const product of poProducts) {
            const key = `${po.po_id}-${product.pid}`;
            const receivingHistory = receivingMap.get(key) || [];
            const altReceivingHistory = altReceivingMap.get(product.pid) || [];
            const noPOReceivingHistory = noPOReceivingMap.get(product.pid) || [];
            
            // Combine all receivings and sort by date
            const allReceivings = [
              ...receivingHistory.map(r => ({ ...r, type: 'original' })),
              ...altReceivingHistory.map(r => ({ ...r, type: 'alternate' })),
              ...noPOReceivingHistory.map(r => ({ ...r, type: 'no_po' }))
            ].sort((a, b) => new Date(a.received_date || '9999-12-31') - new Date(b.received_date || '9999-12-31'));

            // Split receivings into original PO and others
            const originalPOReceivings = allReceivings.filter(r => r.type === 'original');
            const otherReceivings = allReceivings.filter(r => r.type !== 'original');

            // Track FIFO fulfillment
            let remainingToFulfill = product.ordered;
            const fulfillmentTracking = [];
            let totalReceived = 0;
            let actualCost = null; // Will store the cost of the first receiving that fulfills this PO
            let firstFulfillmentReceiving = null;
            let lastFulfillmentReceiving = null;

            for (const receiving of allReceivings) {
              const qtyToApply = Math.min(remainingToFulfill, receiving.qty_each);
              if (qtyToApply > 0) {
                // If this is the first receiving being applied, use its cost
                if (actualCost === null) {
                  actualCost = receiving.cost_each;
                  firstFulfillmentReceiving = receiving;
                }
                lastFulfillmentReceiving = receiving;
                fulfillmentTracking.push({
                  receiving_id: receiving.receiving_id,
                  qty_applied: qtyToApply,
                  qty_total: receiving.qty_each,
                  cost: receiving.cost_each,
                  date: receiving.received_date,
                  received_by: receiving.received_by,
                  received_by_name: receiving.received_by_name || 'Unknown',
                  type: receiving.type,
                  remaining_qty: receiving.qty_each - qtyToApply
                });
                remainingToFulfill -= qtyToApply;
              } else {
                // Track excess receivings
                fulfillmentTracking.push({
                  receiving_id: receiving.receiving_id,
                  qty_applied: 0,
                  qty_total: receiving.qty_each,
                  cost: receiving.cost_each,
                  date: receiving.received_date,
                  received_by: receiving.received_by,
                  received_by_name: receiving.received_by_name || 'Unknown',
                  type: receiving.type,
                  is_excess: true
                });
              }
              totalReceived += receiving.qty_each;
            }

            const receiving_status = !totalReceived ? 1 : // created
                                   remainingToFulfill > 0 ? 30 : // partial
                                   40; // full

            function formatDate(dateStr) {
              if (!dateStr) return null;
              if (dateStr === '0000-00-00' || dateStr === '0000-00-00 00:00:00') return null;
              if (typeof dateStr === 'string' && !dateStr.match(/^\d{4}-\d{2}-\d{2}/)) return null;
              try {
                const date = new Date(dateStr);
                if (isNaN(date.getTime())) return null;
                if (date.getFullYear() < 1900 || date.getFullYear() > 2100) return null;
                return date.toISOString().split('T')[0];
              } catch (e) {
                return null;
              }
            }

            const rowValues = columnNames.map(col => {
              switch (col) {
                case 'po_id': return po.po_id;
                case 'vendor': return po.vendor;
                case 'date': return formatDate(po.date);
                case 'expected_date': return formatDate(po.expected_date);
                case 'pid': return product.pid;
                case 'sku': return product.sku;
                case 'name': return product.name;
                case 'cost_price': return actualCost || product.cost_each;
                case 'po_cost_price': return product.cost_each;
                case 'status': return po.status;
                case 'notes': return po.notes;
                case 'long_note': return po.long_note;
                case 'ordered': return product.ordered;
                case 'received': return totalReceived;
                case 'unfulfilled': return remainingToFulfill;
                case 'excess_received': return Math.max(0, totalReceived - product.ordered);
                case 'received_date': return formatDate(firstFulfillmentReceiving?.received_date);
                case 'last_received_date': return formatDate(lastFulfillmentReceiving?.received_date);
                case 'received_by': return firstFulfillmentReceiving?.received_by_name || null;
                case 'receiving_status': return receiving_status;
                case 'receiving_history': return JSON.stringify({
                  fulfillment: fulfillmentTracking,
                  ordered_qty: product.ordered,
                  total_received: totalReceived,
                  remaining_unfulfilled: remainingToFulfill,
                  excess_received: Math.max(0, totalReceived - product.ordered),
                  po_cost: product.cost_each,
                  actual_cost: actualCost || product.cost_each
                });
                default: return null;
              }
            });

            if (existingPOMap.has(key)) {
              const existing = existingPOMap.get(key);
              // Check if any values are different
              const hasChanges = columnNames.some(col => {
                const newVal = rowValues[columnNames.indexOf(col)];
                const oldVal = existing[col] ?? null;
                // Special handling for numbers to avoid type coercion issues
                if (typeof newVal === 'number' && typeof oldVal === 'number') {
                  return Math.abs(newVal - oldVal) > 0.00001; // Allow for tiny floating point differences
                }
                // Special handling for receiving_history - parse and compare
                if (col === 'receiving_history') {
                  const newHistory = JSON.parse(newVal || '{}');
                  const oldHistory = JSON.parse(oldVal || '{}');
                  return JSON.stringify(newHistory) !== JSON.stringify(oldHistory);
                }
                return newVal !== oldVal;
              });

              if (hasChanges) {
                insertsAndUpdates.updates.push({
                  po_id: po.po_id,
                  pid: product.pid,
                  values: rowValues
                });
              }
            } else {
              insertsAndUpdates.inserts.push({
                po_id: po.po_id,
                pid: product.pid,
                values: rowValues
              });
            }
            batchProcessed++;
          }
        }

        // Handle inserts
        if (insertsAndUpdates.inserts.length > 0) {
          const insertPlaceholders = insertsAndUpdates.inserts
            .map(() => `(${Array(columnNames.length).fill("?").join(",")})`)
            .join(",");

          const insertResult = await localConnection.query(`
            INSERT INTO purchase_orders (${columnNames.join(",")})
            VALUES ${insertPlaceholders}
          `, insertsAndUpdates.inserts.map(i => i.values).flat());

          recordsAdded += insertResult[0].affectedRows;
        }

        // Handle updates - now we know these actually have changes
        if (insertsAndUpdates.updates.length > 0) {
          const updatePlaceholders = insertsAndUpdates.updates
            .map(() => `(${Array(columnNames.length).fill("?").join(",")})`)
            .join(",");

          const updateResult = await localConnection.query(`
            INSERT INTO purchase_orders (${columnNames.join(",")})
            VALUES ${updatePlaceholders}
            ON DUPLICATE KEY UPDATE ${columnNames
              .filter((col) => col !== "po_id" && col !== "pid")
              .map((col) => `${col} = VALUES(${col})`)
              .join(",")};
          `, insertsAndUpdates.updates.map(u => u.values).flat());

          recordsUpdated += updateResult[0].affectedRows / 2;  // Each update counts as 2 in affectedRows
        }

        processed += batchProcessed;
        
        // Update progress based on time interval
        const now = Date.now();
        if (now - lastProgressUpdate >= PROGRESS_INTERVAL || processed === totalItems) {
          outputProgress({
            status: "running",
            operation: "Purchase orders import",
            current: processed,
            total: totalItems,
            elapsed: formatElapsedTime((Date.now() - startTime) / 1000),
            remaining: estimateRemaining(startTime, processed, totalItems),
            rate: calculateRate(startTime, processed)
          });
          lastProgressUpdate = now;
        }
      }
    }

    // Only update sync status if we get here (no errors thrown)
    await localConnection.query(`
      INSERT INTO sync_status (table_name, last_sync_timestamp)
      VALUES ('purchase_orders', NOW())
      ON DUPLICATE KEY UPDATE 
        last_sync_timestamp = NOW(),
        last_sync_id = LAST_INSERT_ID(last_sync_id)
    `);

    return {
      status: "complete",
      totalImported: totalItems,
      recordsAdded: recordsAdded || 0,
      recordsUpdated: recordsUpdated || 0,
      incrementalUpdate,
      lastSyncTime
    };

  } catch (error) {
    outputProgress({
      operation: `${incrementalUpdate ? 'Incremental' : 'Full'} purchase orders import failed`,
      status: "error",
      error: error.message,
    });
    throw error;
  }
}

module.exports = importPurchaseOrders;