cashbook_investment/book.py

# -*- coding: utf-8 -*-
# This file is part of the cashbook-module from m-ds for Tryton.
# The COPYRIGHT file at the top level of this repository contains the
# full copyright notices and license terms.

from trytond.model import fields, SymbolMixin, Index
from trytond.pool import PoolMeta, Pool
from trytond.pyson import Eval, Or, Len, Bool, If
from trytond.modules.cashbook.book import STATES2, DEPENDS2
from trytond.transaction import Transaction
from trytond.report import Report
from trytond.config import config
from decimal import Decimal
from datetime import timedelta
from sql import Literal
from sql.functions import CurrentDate
from sql.aggregate import Sum
from sql.conditionals import Case, Coalesce
from trytond.modules.cashbook.model import sub_ids_hierarchical,\
    CACHEKEY_CURRENCY, AnyInArray
from .asset import CACHEKEY_ASSETRATE


# enable/disable caching of cachekey for 'currency.rate'
if config.get(
        'cashbook', 'cache_currency',
        default='yes').lower() in ['yes', '1', 'true']:
    ENA_CURRKEY = True
else:
    ENA_CURRKEY = False

# enable/disable caching of cachekey for 'currency.rate'
if config.get(
        'cashbook', 'cache_asset',
        default='yes').lower() in ['yes', '1', 'true']:
    ENA_ASSETKEY = True
else:
    ENA_ASSETKEY = False


class Book(SymbolMixin, metaclass=PoolMeta):
    __name__ = 'cashbook.book'

    asset = fields.Many2One(
        string='Asset',
        model_name='investment.asset', ondelete='RESTRICT',
        states={
            'required': Eval('feature', '') == 'asset',
            'invisible': Eval('feature', '') != 'asset',
            'readonly': Or(
                    STATES2['readonly'],
                    Len(Eval('lines')) > 0)},
        depends=DEPENDS2+['feature', 'lines'])
    quantity_digits = fields.Integer(
        string='Digits', help='Quantity Digits',
        domain=[
                ('quantity_digits', '>=', 0),
                ('quantity_digits', '<=', 6)],
        states={
            'required': Eval('feature', '') == 'asset',
            'invisible': Eval('feature', '') != 'asset',
            'readonly': Or(
                    STATES2['readonly'],
                    Len(Eval('lines')) > 0)},
        depends=DEPENDS2+['feature', 'lines'])
    asset_uomcat = fields.Function(fields.Many2One(
        string='UOM Category', readonly=True,
        model_name='product.uom.category',
        states={'invisible': True}), 'on_change_with_asset_uomcat')
    quantity_uom = fields.Many2One(
        string='UOM',
        model_name='product.uom', ondelete='RESTRICT',
        domain=[('category.id', '=', Eval('asset_uomcat', -1))],
        states={
            'required': Eval('feature', '') == 'asset',
            'invisible': Eval('feature', '') != 'asset',
            'readonly': Or(
                STATES2['readonly'],
                Len(Eval('lines')) > 0)},
        depends=DEPENDS2+['feature', 'lines', 'asset_uomcat'])
    symbol = fields.Function(fields.Char(
        string='Symbol', readonly=True), 'on_change_with_symbol')
    asset_symbol = fields.Function(fields.Many2One(
        string='Symbol', readonly=True, model_name='cashbook.book'),
        'on_change_with_asset_symbol')
    quantity = fields.Function(fields.Numeric(
        string='Quantity', help='Quantity of assets until to date',
        readonly=True, digits=(16, Eval('quantity_digits', 4)),
        states={'invisible': Eval('feature', '') != 'asset'},
        depends=['quantity_digits', 'feature']), 'get_asset_quantity')
    quantity_all = fields.Function(fields.Numeric(
        string='Total Quantity', help='Total quantity of all assets',
        readonly=True, digits=(16, Eval('quantity_digits', 4)),
        states={'invisible': Eval('feature', '') != 'asset'},
        depends=['quantity_digits', 'feature']), 'get_asset_quantity')
    current_value = fields.Function(fields.Numeric(
        string='Value',
        help='Valuation of the investment based on the current ' +
        'stock market price.',
        readonly=True, digits=(16, Eval('currency_digits', 2)),
        states={'invisible': ~Eval('show_performance', False)},
        depends=['currency_digits', 'show_performance']),
        'get_asset_quantity')
    current_value_ref = fields.Function(fields.Numeric(
        string='Value (Ref.)',
        help='Valuation of the investment based on the current stock' +
        ' exchange price, converted into the company currency.',
        readonly=True, digits=(16, Eval('currency_digits', 2)),
        states={
            'invisible': Or(
                ~Eval('show_performance', False),
                ~Bool(Eval('company_currency', -1)))},
        depends=['currency_digits', 'show_performance', 'company_currency']),
        'get_asset_quantity')

    # performance
    diff_amount = fields.Function(fields.Numeric(
        string='Difference',
        help='Difference between acquisition value and current value',
        readonly=True, digits=(16, Eval('currency_digits', 2)),
        states={'invisible': ~Eval('show_performance', False)},
        depends=['currency_digits', 'show_performance']),
        'get_asset_quantity')
    diff_percent = fields.Function(fields.Numeric(
        string='Percent',
        help='percentage performance since acquisition',
        readonly=True, digits=(16, Eval('currency_digits', 2)),
        states={'invisible': ~Eval('show_performance', False)},
        depends=['currency_digits', 'show_performance']),
        'get_asset_quantity')
    show_performance = fields.Function(fields.Boolean(
        string='Performance', readonly=True), 'on_change_with_show_performance')
    current_rate = fields.Function(fields.Numeric(
        string='Rate',
        help='Rate per unit of investment based on current stock ' +
        'exchange price.',
        readonly=True, digits=(16, Eval('currency_digits', 2)),
        states={'invisible': Eval('feature', '') != 'asset'},
        depends=['currency_digits', 'feature']), 'get_asset_quantity')
    purchase_amount = fields.Function(fields.Numeric(
        string='Purchase Amount',
        help='Total purchase amount, from shares and fees.',
        readonly=True, digits=(16, Eval('currency_digits', 2)),
        states={'invisible': Eval('feature', '') != 'asset'},
        depends=['currency_digits', 'feature']), 'get_asset_quantity')

    # yield
    yield_dividend_total = fields.Function(fields.Numeric(
        string='Dividend', help='Total dividends received',
        readonly=True, digits=(16, Eval('currency_digits', 2)),
        states={'invisible': Eval('feature', '') != 'asset'},
        depends=['currency_digits', 'feature']), 'get_yield_data')
    yield_dividend_12m = fields.Function(fields.Numeric(
        string='Dividend 1y',
        help='Dividends received in the last twelve months',
        readonly=True, digits=(16, Eval('currency_digits', 2)),
        states={'invisible': Eval('feature', '') != 'asset'},
        depends=['currency_digits', 'feature']), 'get_yield_data')
    yield_fee_total = fields.Function(fields.Numeric(
        string='Trade Fee', help='Total trade fees payed',
        readonly=True, digits=(16, Eval('currency_digits', 2)),
        states={'invisible': Eval('feature', '') != 'asset'},
        depends=['currency_digits', 'feature']), 'get_yield_data')
    yield_fee_12m = fields.Function(fields.Numeric(
        string='Trade Fee 1y',
        help='Trade fees payed in the last twelve month',
        readonly=True, digits=(16, Eval('currency_digits', 2)),
        states={'invisible': Eval('feature', '') != 'asset'},
        depends=['currency_digits', 'feature']), 'get_yield_data')
    yield_sales = fields.Function(fields.Numeric(
        string='Sales', help='Total profit or loss on sale of shares.',
        readonly=True, digits=(16, Eval('currency_digits', 2)),
        states={'invisible': Eval('feature', '') != 'asset'},
        depends=['currency_digits', 'feature']), 'get_yield_data')
    yield_sales_12m = fields.Function(fields.Numeric(
        string='Sales 1y',
        help='Total profit or loss on sale of shares in the last twelve month.',
        readonly=True, digits=(16, Eval('currency_digits', 2)),
        states={'invisible': Eval('feature', '') != 'asset'},
        depends=['currency_digits', 'feature']), 'get_yield_data')
    yield_balance = fields.Function(fields.Numeric(
        string='Total Yield',
        help='Total income: price gain + dividends + sales gains - fees',
        readonly=True, digits=(16, Eval('currency_digits', 2)),
        states={'invisible': Eval('feature', '') != 'asset'},
        depends=['currency_digits', 'feature']), 'on_change_with_yield_balance')

    @classmethod
    def __setup__(cls):
        super(Book, cls).__setup__()
        t = cls.__table__()
        cls._sql_indexes.update({
            Index(
                t,
                (t.asset, Index.Equality())),
            Index(
                t,
                (t.quantity_uom, Index.Equality())),
            })

    @classmethod
    def view_attributes(cls):
        return super(Book, cls).view_attributes() + [
            ('/tree', 'visual',
                If(Eval('show_performance', False),
                    If(Eval('diff_percent', 0) < 0, 'danger',
                        If(Eval('diff_percent', 0) > 0,
                            'success', '')), '')),
            ]

    def get_rec_name(self, name):
        """ add quantities - if its a asset-cashbook
        """
        recname = super(Book, self).get_rec_name(name)
        if self.feature == 'asset':
            recname += ' | %(quantity)s %(uom_symbol)s' % {
                'quantity': Report.format_number(
                    self.quantity or 0.0, None,
                    digits=self.quantity_digits),
                'uom_symbol': getattr(self.quantity_uom, 'symbol', '-'),
                }
        return recname

    @fields.depends('asset', 'quantity_uom')
    def on_change_asset(self):
        """ get uom from asset
        """
        if self.asset:
            self.quantity_uom = self.asset.uom.id

    @classmethod
    def default_quantity_digits(cls):
        """ default: 4
        """
        return 4

    @fields.depends('yield_sales', 'yield_dividend_total', 'diff_amount')
    def on_change_with_yield_balance(self, name=None):
        """ calculate yield total
            fee is already contained in 'diff_amount'
        """
        sum_lst = [
            self.diff_amount, self.yield_dividend_total, self.yield_sales]
        sum2 = sum([x for x in sum_lst if x is not None])
        return sum2

    @classmethod
    def get_yield_data_sql(cls, date_from=None, date_to=None):
        """ collect yield data
        """
        pool = Pool()
        Line = pool.get('cashbook.line')
        Currency = pool.get('currency.currency')
        (tab_line1, tab_line_yield) = Line.get_yield_data_sql()
        (tab_line2, tab_line_gainloss) = Line.get_gainloss_data_sql()
        tab_book = cls.__table__()
        tab_line = Line.__table__()
        tab_cur = Currency.__table__()

        where = Literal(True)
        if date_from:
            where &= tab_line.date >= date_from
        if date_to:
            where &= tab_line.date <= date_to

        query = tab_book.join(
                tab_line,
                condition=tab_line.cashbook == tab_book.id,
            ).join(
                tab_cur,
                condition=tab_cur.id == tab_book.currency,
            ).join(
                tab_line_yield,
                condition=tab_line_yield.id == tab_line.id,
            ).join(
                tab_line_gainloss,
                condition=tab_line_gainloss.id == tab_line.id,
            ).select(
                tab_book.id,
                Sum(tab_line_yield.fee).as_('fee'),
                Sum(tab_line_yield.dividend).as_('dividend'),
                Sum(tab_line_gainloss.gainloss).as_('gainloss'),
                tab_cur.digits.as_('currency_digits'),
                group_by=[tab_book.id, tab_cur.digits],
                where=where)
        return (tab_book, query)

    @classmethod
    def get_yield_data(cls, cashbooks, names):
        """ collect yield data
        """
        pool = Pool()
        IrDate = pool.get('ir.date')
        MemCache = pool.get('cashbook.memcache')
        cursor = Transaction().connection.cursor()
        context = Transaction().context
        result = {
            x: {y.id: Decimal('0.0') for y in cashbooks}
            for x in [
                'yield_fee_total', 'yield_dividend_total',
                'yield_sales', 'yield_fee_12m', 'yield_dividend_12m',
                'yield_sales_12m']}

        def quantize_val(value, digits):
            """ quantize...
            """
            return (
                    value or Decimal('0.0')
                ).quantize(Decimal(str(1/10 ** digits)))

        query_date = context.get('date', IrDate.today())
        cache_keys = {
                x.id: MemCache.get_key_by_record(
                    name='get_yield_data',
                    record=x,
                    query=[{
                            'model': 'cashbook.line',
                            'query': [('cashbook.parent', 'child_of', [x.id])],
                        }, {
                            'model': 'currency.currency.rate',
                            'query': [('currency.id', '=', x.currency.id)],
                            'cachekey' if ENA_CURRKEY else 'disabled':
                                CACHEKEY_CURRENCY % x.currency.id,
                        }, {
                            'model': 'investment.rate',
                            'query': [('asset.id', '=', x.asset.id)],
                            'cachekey' if ENA_ASSETKEY else 'disabled':
                                CACHEKEY_ASSETRATE % x.asset.id,
                        } if x.asset is not None else {}],
                    addkeys=[query_date.isoformat()])
                for x in cashbooks
            }

        # read from cache
        (todo_cashbook, result) = MemCache.read_from_cache(
            cashbooks, cache_keys, names, result)
        if len(todo_cashbook) == 0:
            return result

        # results for 'total'
        records_total = []
        records_12m = []
        if len(todo_cashbook) > 0:
            (tab_book1, query_total) = cls.get_yield_data_sql()
            query_total.where &= tab_book1.id.in_([x.id for x in todo_cashbook])
            cursor.execute(*query_total)
            records_total = cursor.fetchall()

            # results for 12 months
            (tab_book2, query_12m) = cls.get_yield_data_sql(
                    date_to=query_date,
                    date_from=query_date - timedelta(days=365),
                )
            query_12m.where &= tab_book2.id.in_([x.id for x in todo_cashbook])
            cursor.execute(*query_12m)
            records_12m = cursor.fetchall()

        for record in records_total:
            result['yield_fee_total'][record[0]] = quantize_val(
                record[1], record[4])
            result['yield_dividend_total'][record[0]] = quantize_val(
                record[2], record[4])
            result['yield_sales'][record[0]] = quantize_val(
                record[3], record[4])

        for record in records_12m:
            result['yield_fee_12m'][record[0]] = quantize_val(
                record[1], record[4])
            result['yield_dividend_12m'][record[0]] = quantize_val(
                record[2], record[4])
            result['yield_sales_12m'][record[0]] = quantize_val(
                record[3], record[4])

        # store to cache
        MemCache.store_result(cashbooks, cache_keys, result, todo_cashbook)
        return {x: result[x] for x in names}

    @classmethod
    def get_asset_quantity_sql(cls):
        """ get table of asset and its value, rate, ...
        """
        pool = Pool()
        CBook = pool.get('cashbook.book')
        BookType = pool.get('cashbook.type')
        Line = pool.get('cashbook.line')
        Asset = pool.get('investment.asset')
        Currency = pool.get('currency.currency')
        tab_book = CBook.__table__()
        tab_type = BookType.__table__()
        tab_line = Line.__table__()
        tab_cur = Currency.__table__()
        tab_asset = Asset.__table__()
        (tab_rate, tab2) = Asset.get_rate_data_sql()
        (tab_balance, tab2) = CBook.get_balance_of_cashbook_sql()
        (tab_line_yield, query_yield) = Line.get_yield_data_sql()
        context = Transaction().context

        query_date = context.get('qdate', CurrentDate())
        query = tab_book.join(
                tab_line,
                condition=(tab_book.id == tab_line.cashbook),
            ).join(
                tab_type,
                condition=tab_book.btype == tab_type.id,
            ).join(
                tab_cur,
                condition=tab_book.currency == tab_cur.id,
            ).join(
                tab_asset,
                condition=tab_book.asset == tab_asset.id,
            ).join(
                query_yield,
                condition=query_yield.id == tab_line.id,
            ).join(
                tab_balance,
                condition=tab_book.id == tab_balance.cashbook,
                type_='LEFT OUTER',
            ).join(
                tab_rate,
                condition=tab_book.asset == tab_rate.id,
                type_='LEFT OUTER',
            ).select(
                tab_book.id,    # 0
                Coalesce(Sum(Case(
                    (tab_line.date <= query_date,
                        tab_line.quantity_credit - tab_line.quantity_debit),
                    else_=Decimal('0.0'),
                )), Decimal('0.0')).as_('quantity'),    # 1
                Sum(
                    tab_line.quantity_credit -
                    tab_line.quantity_debit).as_('quantity_all'),   # 2
                Coalesce(tab_rate.rate, Decimal('0.0')).as_('rate'),    # 3
                tab_book.currency,  # 4
                tab_cur.digits.as_('currency_digits'),     # 5
                tab_asset.uom,          # 6
                tab_book.quantity_uom,  # 7
                tab_asset.currency.as_('asset_currency'),   # 8
                (
                    Sum(query_yield.fee) + tab_balance.balance
                ).as_('purchase_amount'),   # 9
                group_by=[
                    tab_book.id, tab_rate.rate,
                    tab_book.currency, tab_cur.digits, tab_asset.uom,
                    tab_book.quantity_uom, tab_asset.currency,
                    tab_balance.balance],
                where=(tab_type.feature == 'asset'))
        return (query, tab_book)

    @classmethod
    def get_asset_quantity(cls, cashbooks, names):
        """ get quantities
            field: quantity, quantity_all, current_value,
                current_value_ref, diff_amount, diff_percent,
                current_rate, purchase_amount
        """
        pool = Pool()
        CBook = pool.get('cashbook.book')
        Uom = pool.get('product.uom')
        Currency = pool.get('currency.currency')
        IrDate = pool.get('ir.date')
        MemCache = pool.get('cashbook.memcache')
        cursor = Transaction().connection.cursor()
        context = Transaction().context
        (query, tab_book) = cls.get_asset_quantity_sql()

        company_currency = CBook.default_currency()
        result = {
            x: {y.id: None for y in cashbooks}
            for x in [
                'quantity', 'quantity_all', 'current_value',
                'current_value_ref', 'diff_amount', 'diff_percent',
                'current_rate', 'purchase_amount', 'purchase_amount_ref',
                'digits']
            }

        cache_keys = {
            x.id: MemCache.get_key_by_record(
                name='get_asset_quantity',
                record=x,
                query=[{
                    'model': 'cashbook.line',
                    'query': [('cashbook.parent', 'child_of', [x.id])],
                    }, {
                    'model': 'currency.currency.rate',
                    'query': [('currency.id', '=', x.currency.id)],
                    'cachekey' if ENA_CURRKEY else 'disabled':
                        CACHEKEY_CURRENCY % x.currency.id,
                    }, {
                    'model': 'investment.rate',
                    'query': [('asset.id', '=', x.asset.id)],
                    'cachekey' if ENA_ASSETKEY else 'disabled':
                        CACHEKEY_ASSETRATE % x.asset.id,
                    } if x.asset is not None else {}],
                addkeys=[
                        str(company_currency),
                        str(context.get('qdate', IrDate.today()).toordinal()),
                    ])
            for x in cashbooks
            }

        # read from cache
        (todo_cashbook, result) = MemCache.read_from_cache(
            cashbooks, cache_keys, names, result)
        if len(todo_cashbook) == 0:
            return result

        def values_from_record(rdata):
            """ compute values for record
            """
            # uom-factor
            if rdata[6] == rdata[7]:
                uom_factor = Decimal('1.0')
            else:
                uom_factor = Decimal(
                    Uom.compute_qty(
                        Uom(rdata[6]), 1.0,
                        Uom(rdata[7]), round=False))

            current_value = Currency.compute(
                    rdata[8],
                    rdata[3] * rdata[1] / uom_factor,
                    rdata[4])
            return (record[0], {
                'quantity': rdata[1],
                'quantity_all': rdata[2],
                'current_value': current_value,
                'current_value_ref': Currency.compute(
                        rdata[8],
                        rdata[3] * rdata[1] / uom_factor,
                        company_currency
                        if company_currency is not None else rdata[8]),
                'diff_amount': current_value - rdata[9],
                'diff_percent': (
                        Decimal('100.0') * current_value /
                        rdata[9] - Decimal('100.0')
                    ).quantize(Decimal(str(1/10**rdata[5])))
                if rdata[9] != Decimal('0.0') else None,
                'current_rate': (
                        current_value / rdata[1]
                    ).quantize(Decimal(str(1/10**rdata[5])))
                if rdata[1] != Decimal('0.0') else None,
                'purchase_amount': record[9].quantize(
                    Decimal(str(1/10**rdata[5]))),
                'purchase_amount_ref': Currency.compute(
                        rdata[4],
                        record[9],
                        company_currency
                        if company_currency is not None else rdata[4]),
                })

        ids_assetbooks = [x.id for x in cashbooks if x.btype is not None]
        ids_nonebtypes = [x.id for x in cashbooks if x.btype is None]

        # get values of asset-cashbooks in 'cashbooks' of type=asset
        if len(ids_assetbooks) > 0:
            query.where &= tab_book.id.in_(ids_assetbooks)
            cursor.execute(*query)
            records = cursor.fetchall()

            for record in records:
                (book_id, values) = values_from_record(record)

                for name in values.keys():
                    result[name][book_id] = values[name]

        # add aggregated values of cashbooks without type
        aggr_names = [
            'current_value', 'current_value_ref',
            'diff_amount', 'diff_percent']
        queried_names = list(set(aggr_names).intersection(set(names)))

        if (len(queried_names) > 0) and (len(ids_nonebtypes) > 0):
            # query all subordered asset-cashbooks to get values for
            # cashbooks without type

            (tab_quantity, tab_book) = cls.get_asset_quantity_sql()
            tab_subids = sub_ids_hierarchical('cashbook.book')
            query = tab_book.join(
                    tab_subids,
                    condition=tab_book.id == tab_subids.parent,
                ).join(
                    tab_quantity,
                    condition=tab_quantity.id == AnyInArray(tab_subids.subids),
                ).select(
                    tab_book.id,
                    Sum(tab_quantity.quantity),                 # 1
                    Sum(tab_quantity.quantity_all),             # 2
                    tab_quantity.rate,                          # 3
                    tab_quantity.currency,                      # 4
                    tab_quantity.currency_digits,               # 5
                    tab_quantity.uom,                           # 6
                    tab_quantity.quantity_uom,                  # 7
                    tab_quantity.asset_currency,                # 8
                    Sum(tab_quantity.purchase_amount),          # 9
                    tab_book.currency.as_('currency_book'),     # 10
                    where=tab_book.id.in_(ids_nonebtypes),
                    group_by=[
                        tab_book.id, tab_quantity.rate,
                        tab_quantity.currency, tab_quantity.currency_digits,
                        tab_quantity.uom, tab_quantity.quantity_uom,
                        tab_quantity.asset_currency, tab_book.currency])
            cursor.execute(*query)
            records = cursor.fetchall()

            for record in records:
                (book_id, values) = values_from_record(record)

                for name in [
                        'current_value', 'diff_amount',
                        'current_value_ref', 'purchase_amount_ref']:
                    if result[name][book_id] is None:
                        result[name][book_id] = Decimal('0.0')

                    value = Decimal('0.0')
                    if name == 'current_value':
                        value = Currency.compute(
                            company_currency
                            if company_currency is not None else record[4],
                            values['current_value_ref'],
                            record[10])
                    elif name == 'diff_amount':
                        value = Currency.compute(
                            company_currency
                            if company_currency is not None else record[4],
                            values['current_value_ref'] -
                            values['purchase_amount_ref'],
                            record[10])
                    elif name in ['current_value_ref', 'purchase_amount_ref']:
                        value = values[name]
                        result['digits'][book_id] = record[5]
                    result[name][book_id] += value

            # diff_percent
            for id_book in ids_nonebtypes:
                c_val = result['current_value_ref'][id_book]
                p_amount = result['purchase_amount_ref'][id_book]
                digits = result['digits'][id_book]

                if (p_amount == Decimal('0.0')) or \
                        (p_amount is None) or (c_val is None):
                    continue

                result['diff_percent'][id_book] = (
                        Decimal('100.0') * c_val / p_amount - Decimal('100.0')
                    ).quantize(Decimal(str(1/10 ** digits)))
                result['digits'][id_book] = None

        # store to cache
        MemCache.store_result(cashbooks, cache_keys, result, todo_cashbook)
        return {x: result[x] for x in names}

    @fields.depends('id')
    def on_change_with_show_performance(self, name=None):
        """ return True if current or subordered cashbooks
            are of type=asset
        """
        Book2 = Pool().get('cashbook.book')

        if Book2.search_count([
                ('btype.feature', '=', 'asset'),
                ('parent', 'child_of', [self.id])]) > 0:
            return True
        return False

    @fields.depends('id')
    def on_change_with_asset_symbol(self, name=None):
        """ get current cashbook to enable usage of 'symbol'
            in the form
        """
        return self.id

    @fields.depends('quantity_uom', 'currency')
    def on_change_with_symbol(self, name=None):
        """ get symbol for asset
        """
        return '%(currency)s/%(unit)s' % {
            'currency': getattr(self.currency, 'symbol', '-'),
            'unit': getattr(self.quantity_uom, 'symbol', '-')}

    @fields.depends('asset', '_parent_asset.uom')
    def on_change_with_asset_uomcat(self, name=None):
        """ get uom-category of asset
        """
        if self.asset:
            return self.asset.uom.category.id

# end Book