# /home/Autopartes/pos/blueprints/inventory_bp.py
"""Inventory blueprint: CRUD for inventory items + stock operations + reports."""

import json
from datetime import datetime, timedelta
from flask import Blueprint, request, jsonify, g
from middleware import require_auth, has_permission
from tenant_db import get_tenant_conn
from services.inventory_engine import (
    get_stock, get_stock_bulk, record_purchase, record_return,
    record_adjustment, record_transfer, record_initial,
    get_alerts, get_movement_history
)
from services.barcode_generator import generate_barcode
from services.audit import log_action

inventory_bp = Blueprint('inventory', __name__, url_prefix='/pos/api/inventory')


# ─── Item CRUD ──────────────────────────────────

@inventory_bp.route('/items', methods=['GET'])
@require_auth('inventory.view')
def list_items():
    """List inventory items with current stock. Supports search, pagination, filtering.

    The low_stock filter is applied at the SQL level via a LEFT JOIN + HAVING clause,
    so pagination counts remain accurate.
    """
    conn = get_tenant_conn(g.tenant_id)
    cur = conn.cursor()

    page = int(request.args.get('page', 1))
    per_page = min(int(request.args.get('per_page', 50)), 200)
    search = request.args.get('q', '')
    category = request.args.get('category', '')
    brand = request.args.get('brand', '')
    branch_id = request.args.get('branch_id', g.branch_id)
    low_stock = request.args.get('low_stock', '') == 'true'

    where_clauses = ["i.is_active = true"]
    params = []

    if branch_id:
        where_clauses.append("i.branch_id = %s")
        params.append(branch_id)
    if search:
        where_clauses.append("(i.part_number ILIKE %s OR i.name ILIKE %s OR i.barcode ILIKE %s)")
        params.extend([f'%{search}%', f'%{search}%', f'%{search}%'])
    if category:
        where_clauses.append("i.category_id = %s")
        params.append(int(category))
    if brand:
        where_clauses.append("i.brand ILIKE %s")
        params.append(f'%{brand}%')

    where = " AND ".join(where_clauses)

    if low_stock:
        # low_stock filter: JOIN with stock subquery, filter items where stock < min_stock
        # This keeps pagination accurate because the filter is in the SQL WHERE clause.
        count_sql = f"""
            SELECT count(*) FROM inventory i
            LEFT JOIN (
                SELECT inventory_id, COALESCE(SUM(quantity), 0) AS stock
                FROM inventory_operations GROUP BY inventory_id
            ) s ON s.inventory_id = i.id
            WHERE {where} AND i.min_stock IS NOT NULL AND i.min_stock > 0
              AND COALESCE(s.stock, 0) < i.min_stock
        """
        cur.execute(count_sql, params)
        total = cur.fetchone()[0]

        cur.execute(f"""
            SELECT i.id, i.branch_id, i.part_number, i.barcode, i.name, i.description,
                   i.category_id, i.brand, i.unit, i.cost, i.price_1, i.price_2, i.price_3,
                   i.tax_rate, i.min_stock, i.max_stock, i.location, i.image_url, i.catalog_part_id,
                   COALESCE(s.stock, 0) AS stock
            FROM inventory i
            LEFT JOIN (
                SELECT inventory_id, COALESCE(SUM(quantity), 0) AS stock
                FROM inventory_operations GROUP BY inventory_id
            ) s ON s.inventory_id = i.id
            WHERE {where} AND i.min_stock IS NOT NULL AND i.min_stock > 0
              AND COALESCE(s.stock, 0) < i.min_stock
            ORDER BY i.name
            LIMIT %s OFFSET %s
        """, params + [per_page, (page - 1) * per_page])

        items = []
        for r in cur.fetchall():
            items.append({
                'id': r[0], 'branch_id': r[1], 'part_number': r[2], 'barcode': r[3],
                'name': r[4], 'description': r[5], 'category_id': r[6], 'brand': r[7],
                'unit': r[8], 'cost': float(r[9]) if r[9] else 0,
                'price_1': float(r[10]) if r[10] else 0,
                'price_2': float(r[11]) if r[11] else 0,
                'price_3': float(r[12]) if r[12] else 0,
                'tax_rate': float(r[13]) if r[13] else 0.16,
                'min_stock': r[14], 'max_stock': r[15], 'location': r[16],
                'image_url': r[17], 'catalog_part_id': r[18],
                'stock': r[19]
            })
    else:
        # Normal path: count, fetch items, then bulk-lookup stock
        cur.execute(f"SELECT count(*) FROM inventory i WHERE {where}", params)
        total = cur.fetchone()[0]

        cur.execute(f"""
            SELECT i.id, i.branch_id, i.part_number, i.barcode, i.name, i.description,
                   i.category_id, i.brand, i.unit, i.cost, i.price_1, i.price_2, i.price_3,
                   i.tax_rate, i.min_stock, i.max_stock, i.location, i.image_url, i.catalog_part_id
            FROM inventory i
            WHERE {where}
            ORDER BY i.name
            LIMIT %s OFFSET %s
        """, params + [per_page, (page - 1) * per_page])

        items_raw = cur.fetchall()

        # Get stock for all returned items
        inv_ids = [r[0] for r in items_raw]
        stock_map = {}
        if inv_ids:
            cur.execute("""
                SELECT inventory_id, COALESCE(SUM(quantity), 0)
                FROM inventory_operations
                WHERE inventory_id = ANY(%s)
                GROUP BY inventory_id
            """, (inv_ids,))
            stock_map = {r[0]: r[1] for r in cur.fetchall()}

        items = []
        for r in items_raw:
            stock = stock_map.get(r[0], 0)
            items.append({
                'id': r[0], 'branch_id': r[1], 'part_number': r[2], 'barcode': r[3],
                'name': r[4], 'description': r[5], 'category_id': r[6], 'brand': r[7],
                'unit': r[8], 'cost': float(r[9]) if r[9] else 0,
                'price_1': float(r[10]) if r[10] else 0,
                'price_2': float(r[11]) if r[11] else 0,
                'price_3': float(r[12]) if r[12] else 0,
                'tax_rate': float(r[13]) if r[13] else 0.16,
                'min_stock': r[14], 'max_stock': r[15], 'location': r[16],
                'image_url': r[17], 'catalog_part_id': r[18],
                'stock': stock
            })

    cur.close()
    conn.close()

    total_pages = (total + per_page - 1) // per_page
    return jsonify({
        'data': items,
        'pagination': {'page': page, 'per_page': per_page, 'total': total, 'total_pages': total_pages}
    })


@inventory_bp.route('/items/<int:item_id>', methods=['GET'])
@require_auth('inventory.view')
def get_item(item_id):
    """Get a single inventory item with stock and movement history."""
    conn = get_tenant_conn(g.tenant_id)
    cur = conn.cursor()
    cur.execute("""
        SELECT i.*, b.name as branch_name
        FROM inventory i
        LEFT JOIN branches b ON i.branch_id = b.id
        WHERE i.id = %s
    """, (item_id,))
    row = cur.fetchone()
    if not row:
        cur.close(); conn.close()
        return jsonify({'error': 'Item not found'}), 404

    cols = [desc[0] for desc in cur.description]
    item = dict(zip(cols, row))
    # Convert Decimal to float
    for k in ('cost', 'price_1', 'price_2', 'price_3', 'tax_rate'):
        if item.get(k) is not None:
            item[k] = float(item[k])

    item['stock'] = get_stock(conn, item_id, item.get('branch_id'))
    item['history'] = get_movement_history(conn, item_id, limit=20)

    cur.close()
    conn.close()
    return jsonify(item)


@inventory_bp.route('/items', methods=['POST'])
@require_auth('inventory.create')
def create_item():
    """Create a new inventory item. Optionally set initial stock."""
    data = request.get_json() or {}
    required = ['part_number', 'name']
    for f in required:
        if not data.get(f):
            return jsonify({'error': f'{f} required'}), 400

    branch_id = data.get('branch_id', g.branch_id)
    if not branch_id:
        return jsonify({'error': 'branch_id required'}), 400

    conn = get_tenant_conn(g.tenant_id)
    cur = conn.cursor()

    # Generate barcode if not provided
    barcode = data.get('barcode')
    if not barcode:
        # Look up tenant db_name
        from tenant_db import get_master_conn
        mconn = get_master_conn()
        mcur = mconn.cursor()
        mcur.execute("SELECT db_name FROM tenants WHERE id = %s", (g.tenant_id,))
        db_name = mcur.fetchone()[0]
        mcur.close(); mconn.close()
        barcode = generate_barcode(conn, db_name)

    try:
        cur.execute("""
            INSERT INTO inventory
                (branch_id, part_number, barcode, name, description, category_id, brand,
                 vehicle_compatibility, unit, cost, price_1, price_2, price_3, tax_rate,
                 min_stock, max_stock, location, image_url, catalog_part_id)
            VALUES (%s,%s,%s,%s,%s,%s,%s,%s,%s,%s,%s,%s,%s,%s,%s,%s,%s,%s,%s)
            RETURNING id
        """, (
            branch_id, data['part_number'], barcode, data['name'],
            data.get('description'), data.get('category_id'), data.get('brand'),
            json.dumps(data.get('vehicle_compatibility')) if data.get('vehicle_compatibility') else None,
            data.get('unit', 'PZA'), data.get('cost', 0),
            data.get('price_1', 0), data.get('price_2', 0), data.get('price_3', 0),
            data.get('tax_rate', 0.16),
            data.get('min_stock', 0), data.get('max_stock', 0),
            data.get('location'), data.get('image_url'), data.get('catalog_part_id')
        ))
        item_id = cur.fetchone()[0]

        # Record initial stock if provided
        initial_stock = data.get('initial_stock', 0)
        if initial_stock > 0:
            record_initial(conn, item_id, branch_id, initial_stock, data.get('cost'))

        log_action(conn, 'INVENTORY_CREATE', 'inventory', item_id,
                   new_value={'part_number': data['part_number'], 'name': data['name'], 'initial_stock': initial_stock})

        conn.commit()
        cur.close(); conn.close()
        return jsonify({'id': item_id, 'barcode': barcode, 'message': 'Item created'}), 201

    except Exception as e:
        conn.rollback()
        cur.close(); conn.close()
        if 'idx_inventory_branch_part' in str(e):
            return jsonify({'error': 'Part number already exists in this branch'}), 409
        return jsonify({'error': str(e)}), 500


@inventory_bp.route('/items/<int:item_id>', methods=['PUT'])
@require_auth('inventory.edit')
def update_item(item_id):
    """Update inventory item fields (not stock — use operations for that)."""
    data = request.get_json() or {}
    conn = get_tenant_conn(g.tenant_id)
    cur = conn.cursor()

    # Get current values for audit
    cur.execute("SELECT * FROM inventory WHERE id = %s", (item_id,))
    old = cur.fetchone()
    if not old:
        cur.close(); conn.close()
        return jsonify({'error': 'Item not found'}), 404

    old_cols = [desc[0] for desc in cur.description]
    old_dict = dict(zip(old_cols, old))

    # Price change requires special permission
    price_fields = {'price_1', 'price_2', 'price_3', 'cost'}
    changing_prices = price_fields & set(data.keys())
    if changing_prices and not has_permission('config.edit_prices'):
        return jsonify({'error': 'Permission config.edit_prices required to change prices'}), 403

    # Build dynamic update
    allowed = ['part_number', 'barcode', 'name', 'description', 'category_id', 'brand',
               'vehicle_compatibility', 'unit', 'cost', 'price_1', 'price_2', 'price_3',
               'tax_rate', 'min_stock', 'max_stock', 'location', 'image_url', 'catalog_part_id', 'is_active']
    sets = []
    vals = []
    for field in allowed:
        if field in data:
            val = data[field]
            if field == 'vehicle_compatibility' and isinstance(val, (dict, list)):
                val = json.dumps(val)
            sets.append(f"{field} = %s")
            vals.append(val)

    if not sets:
        cur.close(); conn.close()
        return jsonify({'error': 'No fields to update'}), 400

    vals.append(item_id)
    cur.execute(f"UPDATE inventory SET {', '.join(sets)} WHERE id = %s", vals)

    if changing_prices:
        log_action(conn, 'PRICE_CHANGE', 'inventory', item_id,
                   old_value={k: float(old_dict[k]) if old_dict[k] else 0 for k in changing_prices},
                   new_value={k: data[k] for k in changing_prices})

    conn.commit()
    cur.close(); conn.close()
    return jsonify({'message': 'Item updated'})


# ─── Stock Operations ──────────────────────────

@inventory_bp.route('/purchase', methods=['POST'])
@require_auth('inventory.create')
def api_purchase():
    """Record a purchase entry (stock in)."""
    data = request.get_json() or {}
    required = ['inventory_id', 'quantity', 'unit_cost']
    for f in required:
        if not data.get(f) and data.get(f) != 0:
            return jsonify({'error': f'{f} required'}), 400

    conn = get_tenant_conn(g.tenant_id)
    branch_id = data.get('branch_id', g.branch_id)
    op_id = record_purchase(
        conn, data['inventory_id'], branch_id,
        data['quantity'], data['unit_cost'],
        supplier_invoice=data.get('supplier_invoice'),
        notes=data.get('notes')
    )
    conn.commit()
    conn.close()
    return jsonify({'operation_id': op_id, 'message': 'Purchase recorded'})


@inventory_bp.route('/adjustment', methods=['POST'])
@require_auth('inventory.adjust')
def api_adjustment():
    """Record a manual stock adjustment."""
    data = request.get_json() or {}
    if not data.get('inventory_id') or data.get('quantity') is None or not data.get('reason'):
        return jsonify({'error': 'inventory_id, quantity, and reason required'}), 400

    conn = get_tenant_conn(g.tenant_id)
    try:
        branch_id = data.get('branch_id', g.branch_id)
        op_id = record_adjustment(conn, data['inventory_id'], branch_id, data['quantity'], data['reason'])
        conn.commit()
        conn.close()
        return jsonify({'operation_id': op_id, 'message': 'Adjustment recorded'})
    except ValueError as e:
        conn.close()
        return jsonify({'error': str(e)}), 400


@inventory_bp.route('/transfer', methods=['POST'])
@require_auth('inventory.transfer')
def api_transfer():
    """Transfer stock between branches."""
    data = request.get_json() or {}
    required = ['inventory_id', 'from_branch_id', 'to_branch_id', 'quantity']
    for f in required:
        if not data.get(f):
            return jsonify({'error': f'{f} required'}), 400

    conn = get_tenant_conn(g.tenant_id)
    out_id, in_id = record_transfer(
        conn, data['inventory_id'], data['from_branch_id'],
        data['to_branch_id'], data['quantity'], data.get('notes')
    )
    conn.commit()
    conn.close()
    return jsonify({'out_operation_id': out_id, 'in_operation_id': in_id, 'message': 'Transfer recorded'})


@inventory_bp.route('/return', methods=['POST'])
@require_auth('inventory.create')
def api_return():
    """Record a customer return."""
    data = request.get_json() or {}
    if not data.get('inventory_id') or not data.get('quantity'):
        return jsonify({'error': 'inventory_id and quantity required'}), 400

    conn = get_tenant_conn(g.tenant_id)
    branch_id = data.get('branch_id', g.branch_id)
    op_id = record_return(conn, data['inventory_id'], branch_id,
                          data['quantity'], data.get('sale_id'), data.get('notes'))
    conn.commit()
    conn.close()
    return jsonify({'operation_id': op_id, 'message': 'Return recorded'})


# ─── Physical Count (two-phase: start → approve) ──────────

@inventory_bp.route('/physical-count/start', methods=['POST'])
@require_auth('inventory.view')
def physical_count_start():
    """Start a physical count. Creates a draft that compares expected vs counted
    WITHOUT making any adjustments. Returns a draft ID and comparison results.

    Body: { items: [{inventory_id, counted_quantity}, ...], branch_id, notes }
    """
    data = request.get_json() or {}
    items = data.get('items', [])
    branch_id = data.get('branch_id', g.branch_id)
    notes = data.get('notes', 'Toma fisica')

    if not items:
        return jsonify({'error': 'items array required'}), 400

    conn = get_tenant_conn(g.tenant_id)
    cur = conn.cursor()

    # Create a draft physical count record
    cur.execute("""
        INSERT INTO physical_counts (branch_id, status, notes, employee_id, created_at)
        VALUES (%s, 'draft', %s, %s, NOW())
        RETURNING id
    """, (branch_id, notes, getattr(g, 'employee_id', None)))
    count_id = cur.fetchone()[0]

    results = []
    for item in items:
        inv_id = item.get('inventory_id')
        counted = item.get('counted_quantity', 0)
        expected = get_stock(conn, inv_id, branch_id)
        diff = counted - expected

        # Store each line in the draft
        cur.execute("""
            INSERT INTO physical_count_lines
                (physical_count_id, inventory_id, expected_quantity, counted_quantity, difference)
            VALUES (%s, %s, %s, %s, %s)
        """, (count_id, inv_id, expected, counted, diff))

        results.append({
            'inventory_id': inv_id,
            'expected': expected,
            'counted': counted,
            'difference': diff,
            'needs_adjustment': diff != 0
        })

    conn.commit()
    cur.close()
    conn.close()

    adjustments_needed = sum(1 for r in results if r['needs_adjustment'])
    return jsonify({
        'count_id': count_id,
        'status': 'draft',
        'message': f'Draft created. {adjustments_needed} items need adjustment.',
        'results': results
    })


@inventory_bp.route('/physical-count/approve', methods=['POST'])
@require_auth('inventory.adjust')
def physical_count_approve():
    """Approve a draft physical count and create ADJUST operations for all differences.

    Body: { count_id: int }
    Requires inventory.adjust permission.
    """
    data = request.get_json() or {}
    count_id = data.get('count_id')
    if not count_id:
        return jsonify({'error': 'count_id required'}), 400

    conn = get_tenant_conn(g.tenant_id)
    cur = conn.cursor()

    # Verify draft exists and is still draft
    cur.execute("SELECT branch_id, status, notes FROM physical_counts WHERE id = %s", (count_id,))
    row = cur.fetchone()
    if not row:
        cur.close(); conn.close()
        return jsonify({'error': 'Physical count not found'}), 404
    branch_id, status, notes = row
    if status != 'draft':
        cur.close(); conn.close()
        return jsonify({'error': f'Count already {status} — cannot approve again'}), 409

    # Get all lines with differences
    cur.execute("""
        SELECT inventory_id, expected_quantity, counted_quantity, difference
        FROM physical_count_lines
        WHERE physical_count_id = %s AND difference != 0
    """, (count_id,))
    lines = cur.fetchall()

    results = []
    for inv_id, expected, counted, diff in lines:
        record_adjustment(
            conn, inv_id, branch_id, diff,
            f"{notes}: contado={counted}, esperado={expected}, diferencia={diff}"
        )
        results.append({
            'inventory_id': inv_id,
            'expected': expected,
            'counted': counted,
            'difference': diff,
            'adjusted': True
        })

    # Mark count as approved
    cur.execute("""
        UPDATE physical_counts SET status = 'approved', approved_at = NOW(),
               approved_by = %s WHERE id = %s
    """, (getattr(g, 'employee_id', None), count_id))

    conn.commit()
    cur.close()
    conn.close()

    return jsonify({
        'count_id': count_id,
        'status': 'approved',
        'message': f'Physical count approved. {len(results)} adjustments created.',
        'results': results
    })


# ─── Alerts and History ────────────────────────

@inventory_bp.route('/alerts', methods=['GET'])
@require_auth('inventory.view')
def api_alerts():
    """Get stock alerts (zero, low, over)."""
    conn = get_tenant_conn(g.tenant_id)
    branch_id = request.args.get('branch_id', g.branch_id)
    alerts = get_alerts(conn, branch_id)
    conn.close()
    return jsonify({'data': alerts, 'count': len(alerts)})


@inventory_bp.route('/items/<int:item_id>/history', methods=['GET'])
@require_auth('inventory.view')
def api_history(item_id):
    """Get movement history for an item."""
    conn = get_tenant_conn(g.tenant_id)
    limit = min(int(request.args.get('limit', 50)), 200)
    history = get_movement_history(conn, item_id, limit)
    conn.close()
    return jsonify({'data': history})


# ─── Inventory Reports ────────────────────────

@inventory_bp.route('/reports/valuation', methods=['GET'])
@require_auth('inventory.view')
def report_valuation():
    """Inventory valuation report: stock x cost per item, with totals.

    Returns each active item with its current stock and cost, plus the
    line-level value (stock * cost) and a grand total across all items.
    """
    conn = get_tenant_conn(g.tenant_id)
    cur = conn.cursor()
    branch_id = request.args.get('branch_id', g.branch_id)

    where = "i.is_active = true"
    params = []
    if branch_id:
        where += " AND i.branch_id = %s"
        params.append(branch_id)

    cur.execute(f"""
        SELECT i.id, i.part_number, i.name, i.brand, i.cost, i.branch_id,
               COALESCE(s.stock, 0) AS stock,
               COALESCE(s.stock, 0) * COALESCE(i.cost, 0) AS value
        FROM inventory i
        LEFT JOIN (
            SELECT inventory_id, SUM(quantity) AS stock
            FROM inventory_operations GROUP BY inventory_id
        ) s ON s.inventory_id = i.id
        WHERE {where}
        ORDER BY value DESC
    """, params)

    items = []
    grand_total = 0
    for r in cur.fetchall():
        val = float(r[7])
        grand_total += val
        items.append({
            'id': r[0], 'part_number': r[1], 'name': r[2], 'brand': r[3],
            'cost': float(r[4]) if r[4] else 0, 'branch_id': r[5],
            'stock': r[6], 'value': round(val, 2)
        })

    cur.close(); conn.close()
    return jsonify({'data': items, 'grand_total': round(grand_total, 2), 'item_count': len(items)})


@inventory_bp.route('/reports/abc', methods=['GET'])
@require_auth('inventory.view')
def report_abc():
    """ABC classification by sales volume (last 90 days).

    A = top 80% of sales volume, B = next 15%, C = remaining 5%.
    """
    conn = get_tenant_conn(g.tenant_id)
    cur = conn.cursor()
    branch_id = request.args.get('branch_id', g.branch_id)
    days = int(request.args.get('days', 90))

    where_branch = ""
    params = [datetime.utcnow() - timedelta(days=days)]
    if branch_id:
        where_branch = "AND io.branch_id = %s"
        params.append(branch_id)

    cur.execute(f"""
        SELECT i.id, i.part_number, i.name, i.brand,
               COALESCE(ABS(SUM(io.quantity)), 0) AS sales_volume
        FROM inventory i
        LEFT JOIN inventory_operations io
            ON io.inventory_id = i.id
            AND io.operation_type = 'SALE'
            AND io.created_at >= %s
            {where_branch}
        WHERE i.is_active = true
        GROUP BY i.id, i.part_number, i.name, i.brand
        ORDER BY sales_volume DESC
    """, params)

    rows = cur.fetchall()
    total_volume = sum(r[4] for r in rows)

    items = []
    cumulative = 0
    for r in rows:
        vol = r[4]
        cumulative += vol
        pct = (cumulative / total_volume * 100) if total_volume > 0 else 0
        if pct <= 80:
            cls = 'A'
        elif pct <= 95:
            cls = 'B'
        else:
            cls = 'C'
        items.append({
            'id': r[0], 'part_number': r[1], 'name': r[2], 'brand': r[3],
            'sales_volume': vol, 'cumulative_pct': round(pct, 1), 'classification': cls
        })

    cur.close(); conn.close()
    a_count = sum(1 for i in items if i['classification'] == 'A')
    b_count = sum(1 for i in items if i['classification'] == 'B')
    c_count = sum(1 for i in items if i['classification'] == 'C')
    return jsonify({
        'data': items,
        'summary': {'A': a_count, 'B': b_count, 'C': c_count, 'total_volume': total_volume, 'days': days}
    })


@inventory_bp.route('/reports/no-movement', methods=['GET'])
@require_auth('inventory.view')
def report_no_movement():
    """Products with no inventory operations in the last N days (default 60)."""
    conn = get_tenant_conn(g.tenant_id)
    cur = conn.cursor()
    days = int(request.args.get('days', 60))
    branch_id = request.args.get('branch_id', g.branch_id)
    cutoff = datetime.utcnow() - timedelta(days=days)

    where_branch = ""
    params_main = []
    if branch_id:
        where_branch = "AND i.branch_id = %s"
        params_main.append(branch_id)

    cur.execute(f"""
        SELECT i.id, i.part_number, i.name, i.brand, i.cost,
               COALESCE(s.stock, 0) AS stock,
               last_op.last_date
        FROM inventory i
        LEFT JOIN (
            SELECT inventory_id, SUM(quantity) AS stock
            FROM inventory_operations GROUP BY inventory_id
        ) s ON s.inventory_id = i.id
        LEFT JOIN (
            SELECT inventory_id, MAX(created_at) AS last_date
            FROM inventory_operations GROUP BY inventory_id
        ) last_op ON last_op.inventory_id = i.id
        WHERE i.is_active = true {where_branch}
          AND (last_op.last_date IS NULL OR last_op.last_date < %s)
        ORDER BY last_op.last_date ASC NULLS FIRST
    """, params_main + [cutoff])

    items = []
    for r in cur.fetchall():
        items.append({
            'id': r[0], 'part_number': r[1], 'name': r[2], 'brand': r[3],
            'cost': float(r[4]) if r[4] else 0, 'stock': r[5],
            'last_movement': str(r[6]) if r[6] else None
        })

    cur.close(); conn.close()
    return jsonify({'data': items, 'days_threshold': days, 'count': len(items)})


@inventory_bp.route('/reports/low-stock', methods=['GET'])
@require_auth('inventory.view')
def report_low_stock():
    """Items below their min_stock threshold."""
    conn = get_tenant_conn(g.tenant_id)
    cur = conn.cursor()
    branch_id = request.args.get('branch_id', g.branch_id)

    where_branch = ""
    params = []
    if branch_id:
        where_branch = "AND i.branch_id = %s"
        params.append(branch_id)

    cur.execute(f"""
        SELECT i.id, i.part_number, i.name, i.brand, i.min_stock,
               COALESCE(s.stock, 0) AS stock,
               i.min_stock - COALESCE(s.stock, 0) AS deficit
        FROM inventory i
        LEFT JOIN (
            SELECT inventory_id, SUM(quantity) AS stock
            FROM inventory_operations GROUP BY inventory_id
        ) s ON s.inventory_id = i.id
        WHERE i.is_active = true {where_branch}
          AND i.min_stock IS NOT NULL AND i.min_stock > 0
          AND COALESCE(s.stock, 0) < i.min_stock
        ORDER BY deficit DESC
    """, params)

    items = []
    for r in cur.fetchall():
        items.append({
            'id': r[0], 'part_number': r[1], 'name': r[2], 'brand': r[3],
            'min_stock': r[4], 'stock': r[5], 'deficit': r[6]
        })

    cur.close(); conn.close()
    return jsonify({'data': items, 'count': len(items)})


@inventory_bp.route('/reports/branch-comparison', methods=['GET'])
@require_auth('inventory.view')
def report_branch_comparison():
    """Stock comparison across all branches for each item."""
    conn = get_tenant_conn(g.tenant_id)
    cur = conn.cursor()

    cur.execute("""
        SELECT i.id, i.part_number, i.name, i.brand, i.branch_id,
               b.name AS branch_name,
               COALESCE(s.stock, 0) AS stock
        FROM inventory i
        LEFT JOIN branches b ON i.branch_id = b.id
        LEFT JOIN (
            SELECT inventory_id, SUM(quantity) AS stock
            FROM inventory_operations GROUP BY inventory_id
        ) s ON s.inventory_id = i.id
        WHERE i.is_active = true
        ORDER BY i.part_number, b.name
    """)

    # Group by part_number for comparison
    by_part = {}
    for r in cur.fetchall():
        pn = r[1]
        if pn not in by_part:
            by_part[pn] = {'part_number': pn, 'name': r[2], 'brand': r[3], 'branches': []}
        by_part[pn]['branches'].append({
            'inventory_id': r[0], 'branch_id': r[4],
            'branch_name': r[5], 'stock': r[6]
        })

    cur.close(); conn.close()
    items = list(by_part.values())
    return jsonify({'data': items, 'count': len(items)})


# ─── Categories and Brands ─────────────────────

@inventory_bp.route('/categories', methods=['GET'])
@require_auth('inventory.view')
def list_categories():
    """Get distinct categories from inventory."""
    conn = get_tenant_conn(g.tenant_id)
    cur = conn.cursor()
    cur.execute("""
        SELECT DISTINCT category_id FROM inventory
        WHERE is_active = true AND category_id IS NOT NULL
        ORDER BY category_id
    """)
    categories = [r[0] for r in cur.fetchall()]
    cur.close(); conn.close()
    return jsonify({'data': categories})


@inventory_bp.route('/brands', methods=['GET'])
@require_auth('inventory.view')
def list_brands():
    """Get distinct part manufacturer brands from inventory.

    NOTE: These are PART manufacturers (Bosch, NGK, Monroe), not vehicle brands.
    Vehicle compatibility is stored in the vehicle_compatibility JSON field and
    searched via the vehicle_brand parameter on the catalog search endpoint.
    """
    conn = get_tenant_conn(g.tenant_id)
    cur = conn.cursor()
    cur.execute("""
        SELECT DISTINCT brand FROM inventory
        WHERE is_active = true AND brand IS NOT NULL AND brand != ''
        ORDER BY brand
    """)
    brands = [r[0] for r in cur.fetchall()]
    cur.close(); conn.close()
    return jsonify({'data': brands})


# ─── Barcode ───────────────────────────────────

@inventory_bp.route('/generate-barcode', methods=['POST'])
@require_auth('inventory.create')
def api_generate_barcode():
    """Generate a new internal barcode."""
    conn = get_tenant_conn(g.tenant_id)
    from tenant_db import get_master_conn
    mconn = get_master_conn()
    mcur = mconn.cursor()
    mcur.execute("SELECT db_name FROM tenants WHERE id = %s", (g.tenant_id,))
    db_name = mcur.fetchone()[0]
    mcur.close(); mconn.close()

    barcode = generate_barcode(conn, db_name)
    conn.close()
    return jsonify({'barcode': barcode})