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Add foreign key restraints, expand and fix tests, add deletion and forking.
[misc] / ledger.py
index a1b31eb9f9c4d56739340aa8658721b9eb61368d..358cf295c153597f8c91053a7ccc3ad557e18169 100755 (executable)
--- a/ledger.py
+++ b/ledger.py
-from http.server import BaseHTTPRequestHandler, HTTPServer
-import sys
 import os
-import html
+import decimal
+from datetime import datetime, timedelta
 from urllib.parse import parse_qs, urlparse
-hostName = "localhost"
-serverPort = 8082
-
-
-class HandledException(Exception):
-    pass
-
-
-def handled_error_exit(msg):
-    print(f"ERROR: {msg}")
-    sys.exit(1)
-
-
-def apply_booking_to_account_balances(account_sums, account, currency, amount):
-    if not account in account_sums:
-        account_sums[account] = {currency: amount}
-    elif not currency in account_sums[account].keys():
-        account_sums[account][currency] = amount
-    else:
-        account_sums[account][currency] += amount
-
-
-def add_taxes(lines):
-    import decimal
-    bookings, _ = parse_lines(lines.copy())
-    _, account_sums = bookings_to_account_tree(bookings)
-    expenses_so_far = -1 * account_sums['Assets']['€']
-    needed_income_before_krankenkasse = expenses_so_far
-    ESt_this_month = 0
-    left_over = needed_income_before_krankenkasse - ESt_this_month
-    too_low = 0
-    too_high = 2 * needed_income_before_krankenkasse 
-    E0 = 10908
-    E1 = 15999 
-    E2 = 62809 
-    E3 = 277825 
-    while True:
-        zvE = 12 * needed_income_before_krankenkasse
-        if zvE < E0:
-            ESt = decimal.Decimal(0)
-        elif zvE < E1:
-            y = (zvE - E0)/10000
-            ESt = (decimal.Decimal(979.18) * y + 1400) * y
-        elif zvE < E2:
-            y = (zvE - E1)/10000
-            ESt = (decimal.Decimal(192.59) * y + 2397) * y + decimal.Decimal(966.53)
-        elif zvE < E3:
-            ESt = decimal.Decimal(0.42) * (zvE - decimal.Decimal(62809))  + decimal.Decimal(16405.54)
-        else: 
-            ESt = decimal.Decimal(0.45) * (zvE - decimal.Decimal(277825)) + decimal.Decimal(106713.52) 
-        ESt_this_month = ESt / 12
-        left_over = needed_income_before_krankenkasse - ESt_this_month
-        if abs(left_over - expenses_so_far) < 0.1:
-            break
-        elif left_over < expenses_so_far:
-            too_low = needed_income_before_krankenkasse
-        elif left_over > expenses_so_far:
-            too_high = needed_income_before_krankenkasse
-        needed_income_before_krankenkasse = too_low + (too_high - too_low)/2
-    line_income_tax = f'  Reserves:Einkommenssteuer  {ESt_this_month:.2f}€ ; expenses so far: {expenses_so_far:.2f}€; zvE: {zvE:.2f}€; ESt total: {ESt:.2f}€; needed before Krankenkasse: {needed_income_before_krankenkasse:.2f}€'
-    kk_minimum_income = 1096.67 
-    kk_factor = decimal.Decimal(0.189) 
-    kk_minimum_tax = decimal.Decimal(207.27)
-    # kk_minimum_income = 1131.67 
-    # kk_factor = decimal.Decimal(0.191) 
-    # kk_minimum_tax = decimal.Decimal(216.15)
-    # kk_factor = decimal.Decimal(0.197) 
-    # kk_minimum_tax = decimal.Decimal(222.94)
-    kk_add = max(0, kk_factor * needed_income_before_krankenkasse - kk_minimum_tax)
-    line_kk_minimum = f'  Reserves:Month:Krankenkassendefaultbeitrag  {kk_minimum_tax:.2f}€  ; assed minimum income {kk_minimum_income:.2f}€ * {kk_factor:.3f}'
-    line_kk_add = f'  Reserves:Month:Krankenkassenbeitragswachstum {kk_add:.2f}€  ; max(0, {kk_factor:.3f} * {needed_income_before_krankenkasse:.2f}€ - {kk_minimum_tax:.2f}€)'
-    final_minus = expenses_so_far + ESt_this_month + kk_minimum_tax + kk_add 
-    line_finish = f'  Assets  -{final_minus:.2f}€'
-    return [line_income_tax, line_kk_minimum, line_kk_add, line_finish]
-
-
-def bookings_to_account_tree(bookings):
-    account_sums = {}
-    for booking in bookings:
-        for account, changes in booking.account_changes.items():
-            for currency, amount in changes.items():
-                apply_booking_to_account_balances(account_sums, account, currency, amount)
-    account_tree = {}
-    def collect_branches(account_name, path):
-        node = account_tree
-        path_copy = path[:]
-        while len(path_copy) > 0:
-            step = path_copy.pop(0)
-            node = node[step]
-        toks = account_name.split(":", maxsplit=1)
-        parent = toks[0]
-        if parent in node.keys():
-            child = node[parent]
-        else:
-            child = {}
-            node[parent] = child
-        if len(toks) == 2:
-            k, v = collect_branches(toks[1], path + [parent])
-            if k not in child.keys():
-                child[k] = v
-            else:
-                child[k].update(v)
-        return parent, child
-    for account_name in sorted(account_sums.keys()):
-        k, v = collect_branches(account_name, [])
-        if k not in account_tree.keys():
-            account_tree[k] = v
+from jinja2 import Environment as JinjaEnv, FileSystemLoader as JinjaFSLoader 
+from plomlib import PlomDB, PlomException, run_server, PlomHandler 
+from os.path import split as path_split
+
+db_path = '/home/plom/org/ledger2024.dat'
+server_port = 8082
+j2env = JinjaEnv(loader=JinjaFSLoader('ledger_templates'))
+
+class EditableException(PlomException):
+    def __init__(self, booking_index, *args, **kwargs):
+        self.booking_index = booking_index
+        super().__init__(*args, **kwargs)
+    
+
+class LedgerTextLine:
+
+    def __init__(self, text_line):
+        self.text_line = text_line
+        self.comment = '' 
+        split_by_comment = text_line.rstrip().split(sep=';', maxsplit=1)
+        self.non_comment = split_by_comment[0].rstrip()
+        self.empty = len(split_by_comment) == 1 and len(self.non_comment) == 0
+        if self.empty:
+            return
+        if len(split_by_comment) == 2:
+            self.comment = split_by_comment[1].lstrip()
+
+
+class Wealth:
+
+    def __init__(self):
+        self.money_dict = {}
+
+    def __iadd__(self, moneys):
+        money_dict = moneys
+        if type(moneys) == Wealth:
+            moneys = moneys.money_dict
+        for currency, amount in moneys.items():
+            if not currency in self.money_dict.keys():
+                self.money_dict[currency] = 0
+            self.money_dict[currency] += amount
+        return self
+
+    @property
+    def sink_empty(self):
+        return len(self.as_sink) == 0
+
+    @property
+    def as_sink(self):
+        sink = {} 
+        for currency, amount in self.money_dict.items():
+            if 0 == amount:
+                continue
+            sink[currency] = -amount
+        return sink 
+
+
+class Account:
+
+    def __init__(self, own_name, parent):
+        self.own_name = own_name
+        self.parent = parent
+        if self.parent:
+            self.parent.children += [self]
+        self.own_moneys = Wealth() 
+        self.children = []
+
+    def add_wealth(self, moneys):
+        self.own_moneys += moneys
+
+    @property
+    def full_name(self):
+        if self.parent and len(self.parent.own_name) > 0:
+            return f'{self.parent.full_name}:{self.own_name}'
         else:
-            account_tree[k].update(v)
-    def collect_totals(parent_path, tree_node):
-        for k, v in tree_node.items():
-            child_path = parent_path + ":" + k
-            for currency, amount in collect_totals(child_path, v).items():
-                apply_booking_to_account_balances(account_sums, parent_path, currency, amount)
-        return account_sums[parent_path]
-    for account_name in account_tree.keys():
-        account_sums[account_name] = collect_totals(account_name, account_tree[account_name])
-    return account_tree, account_sums
-
-
-def parse_lines(lines):
-    import datetime
-    import decimal
+            return self.own_name
+
+    @property
+    def full_moneys(self):
+        full_moneys = Wealth() 
+        full_moneys += self.own_moneys
+        for child in self.children:
+            full_moneys += child.full_moneys
+        return full_moneys
+
+
+def parse_lines_to_bookings(lines, ignore_editable_exceptions=False):
+    lines = [LedgerTextLine(line) for line in lines]
+    lines += [LedgerTextLine('')]  # to simulate ending of last booking
+    bookings = []
     inside_booking = False
-    date_string, description = None, None
     booking_lines = []
-    start_line = 0
-    bookings = []
-    comments = []
-    lines += [''] # to ensure a booking-ending last line
+    booking_start_i = 0
+    last_date = '' 
     for i, line in enumerate(lines):
-        prefix = f"line {i}"
-        # we start with the case of an utterly empty line
-        comments += [""]
-        stripped_line = line.rstrip()
-        if stripped_line == '':
+        intro = f'file line {i}'
+        if line.empty: 
             if inside_booking:
-                # assume we finished a booking, finalize, and commit to DB
-                if len(booking_lines) < 2:
-                    raise HandledException(f"{prefix} booking ends to early")
-                booking = Booking(date_string, description, booking_lines, start_line)
+                booking = Booking(lines=booking_lines, starts_at=booking_start_i)
+                if last_date > booking.date and not ignore_editable_exceptions:
+                    raise EditableException(len(bookings), f'{intro}: out-of-order date (follows {last_date})')
+                last_date = booking.date
                 bookings += [booking]
-            # expect new booking to follow so re-zeroall booking data
-            inside_booking = False
-            date_string, description = None, None
-            booking_lines = []
-            continue
-        # if non-empty line, first get comment if any, and commit to DB
-        split_by_comment = stripped_line.split(sep=";", maxsplit=1)
-        if len(split_by_comment) == 2:
-            comments[i] = split_by_comment[1].lstrip()
-        # if pre-comment empty: if inside_booking, this must be a comment-only line so we keep it for later ledger-output to capture those comments; otherwise, no more to process for this line
-        non_comment = split_by_comment[0].rstrip()
-        if non_comment.rstrip() == '':
-             if inside_booking:
-                 booking_lines += ['']
-             continue
-        # if we're starting a booking, parse by first-line pattern
-        if not inside_booking:
-            start_line = i
-            toks = non_comment.split(maxsplit=1)
-            date_string = toks[0]
-            try:
-                datetime.datetime.strptime(date_string, '%Y-%m-%d')
-            except ValueError:
-                raise HandledException(f"{prefix} bad date string: {date_string}")
-            try:
-                description = toks[1]
-            except IndexError:
-                raise HandledException(f"{prefix} bad description: {description}")
+                inside_booking =False
+                booking_lines = []
+        else:
+            if not inside_booking:
+                booking_start_i = i
             inside_booking = True
-            booking_lines += [non_comment]
-            continue
-        # otherwise, read as transfer data
-        toks = non_comment.split()  # ignore specification's allowance of single spaces in names
-        if len(toks) > 3:
-            raise HandledException(f"{prefix} too many booking line tokens: {toks}")
-        amount, currency = None, None
-        account_name = toks[0]
-        if account_name[0] == '[' and account_name[-1] == ']':
-            # ignore specification's differentiation of "virtual" accounts
-            account_name = account_name[1:-1]
-        decimal_chars = ".-0123456789"
-        if len(toks) == 3:
-            i_currency = 1
-            try:
-                amount = decimal.Decimal(toks[1])
-                i_currency = 2
-            except decimal.InvalidOperation:
+            booking_lines += [line]
+    if inside_booking:
+        raise PlomException(f'{intro}: last booking unfinished')
+    return bookings
+
+
+class TransferLine:
+
+    def __init__(self, line=None, account='', amount=None, currency='', comment='', validate=True):
+        self.account = account 
+        self.amount = amount 
+        self.currency = currency 
+        self.comment = comment 
+        if line:
+            if line.empty:
+                raise PlomException('line empty')
+            self.comment = line.comment
+            toks = line.non_comment.split()
+            if (len(toks) not in {1, 3}):
+                if validate:
+                    raise PlomException(f'number of non-comment tokens not 1 or 3')
+                elif len(toks) == 2:
+                    toks += ['']
+                else:
+                    toks = 3*['']
+            self.account = toks[0]
+            if len(toks) != 1:
                 try:
-                    amount = decimal.Decimal(toks[2])
+                    self.amount = decimal.Decimal(toks[1])
                 except decimal.InvalidOperation:
-                    raise HandledException(f"{prefix} no decimal number in: {toks[1:]}")
-            currency = toks[i_currency]
-            if currency[0] in decimal_chars:
-                raise HandledException(f"{prefix} currency starts with int, dot, or minus: {currency}")
-        elif len(toks) == 2:
-            value = toks[1]
-            inside_amount = False
-            inside_currency = False
-            amount_string = ""
-            currency = ""
-            dots_counted = 0
-            for i, c in enumerate(value):
-                if i == 0:
-                    if c in decimal_chars:
-                        inside_amount = True
-                    else:
-                        inside_currency = True
-                if inside_currency:
-                    if c in decimal_chars and len(amount_string) == 0:
-                        inside_currency = False
-                        inside_amount = True
+                    if validate:
+                        raise PlomException(f'invalid token for Decimal: {toks[1]}')
                     else:
-                        currency += c
-                        continue
-                if inside_amount:
-                    if c not in decimal_chars:
-                        if len(currency) > 0:
-                            raise HandledException(f"{prefix} amount has non-decimal chars: {value}")
-                        inside_currency = True
-                        inside_amount = False
-                        currency += c
-                        continue
-                    if c == '-' and len(amount_string) > 1:
-                        raise HandledException(f"{prefix} amount has non-start '-': {value}")
-                    if c == '.':
-                        if dots_counted > 1:
-                            raise HandledException(f"{prefix} amount has multiple dots: {value}")
-                        dots_counted += 1
-                    amount_string += c
-            if len(amount_string) == 0:
-                raise HandledException(f"{prefix} amount missing: {value}")
-            if len(currency) == 0:
-                raise HandledException(f"{prefix} currency missing: {value}")
-            amount = decimal.Decimal(amount_string)
-        booking_lines += [(account_name, amount, currency)]
-    if inside_booking:
-        raise HandledException(f"{prefix} last booking unfinished")
-    return bookings, comments
+                        self.comment = f'unparsed: {toks[1]}; {self.comment}'
+                self.currency = toks[2]
+
+    @property
+    def amount_fmt(self):
+        if self.amount is None:
+            return ''
+        elif self.amount.as_tuple().exponent < -2:
+            return f'{self.amount:.1f}…'
+        else:
+            return f'{self.amount:.2f}'
+
+    @property
+    def for_writing(self):
+        line = f'  {self.account}'
+        if self.amount is not None:
+            line += f'  {self.amount} {self.currency}'
+        if self.comment != '':
+            line += f' ; {self.comment}' 
+        return line
+
+    @property
+    def comment_cols(self):
+        return max(20, len(self.comment))
+
 
 class Booking:
 
-    def __init__(self, date_string, description, booking_lines, start_line):
-        self.date_string = date_string
-        self.description = description
-        self.lines = booking_lines
-        self.start_line = start_line
-        self.validate_booking_lines()
-        self.account_changes = self.parse_booking_lines_to_account_changes()
-
-    def validate_booking_lines(self):
-        prefix = f"booking at line {self.start_line}"
-        sums = {}
-        empty_values = 0
-        for line in self.lines[1:]:
-            if line == '':
-                continue
-            _, amount, currency = line
-            if amount is None:
-                if empty_values > 0:
-                    raise HandledException(f"{prefix} relates more than one empty value of same currency {currency}")
-                empty_values += 1
-                continue
-            if currency not in sums:
-                sums[currency] = 0
-            sums[currency] += amount
-        if empty_values == 0:
-            for k, v in sums.items():
-                if v != 0:
-                    raise HandledException(f"{prefix} does not sum up to zero")
+    def __init__(self, lines=None, starts_at='?', date='', description='', top_comment='', transfer_lines=None, validate=True):
+        self.validate = validate
+        self.starts_at = starts_at 
+        self.intro = f'booking starting at line {self.starts_at}'
+        self.clean()
+        if lines:
+            self.lines = lines 
+            self.parse_lines()
         else:
-            sinkable = False
-            for k, v in sums.items():
-                if v != 0:
-                    sinkable = True
-            if not sinkable:
-                raise HandledException(f"{prefix} has empty value that cannot be filled")
-
-    def parse_booking_lines_to_account_changes(self):
-        account_changes = {}
-        debt = {}
-        sink_account = None
-        for line in self.lines[1:]:
-            if line == '':
+            self.date = date
+            self.description = description
+            self.top_comment = top_comment 
+            self.validate_head()
+            self.transfer_lines = transfer_lines if transfer_lines else []
+            if self.validate and len(self.transfer_lines) < 2:
+                raise PlomException(f'{self.intro}: too few transfer lines')
+            self.calculate_account_changes()
+            self.lines = [LedgerTextLine(l) for l in self.for_writing]
+
+    @classmethod
+    def from_postvars(cls, postvars, starts_at='?', validate=True):
+        date = postvars['date'][0] 
+        description = postvars['description'][0] 
+        top_comment = postvars['top_comment'][0] 
+        transfer_lines = []
+        for i, account in enumerate(postvars['account']):
+            if len(account) == 0:
                 continue
-            account, amount, currency = line
-            if amount is None:
-                sink_account = account
-                continue
-            apply_booking_to_account_balances(account_changes, account, currency, amount)
-            if currency not in debt:
-                debt[currency] = amount
+            amount = None
+            if len(postvars['amount'][i]) > 0:
+                amount = decimal.Decimal(postvars['amount'][i])
+            transfer_lines += [TransferLine(None, account, amount, postvars['currency'][i], postvars['comment'][i])]
+        return cls(None, starts_at, date, description, top_comment, transfer_lines, validate=validate)
+
+    def clean(self):
+        self.transfer_lines = []
+        self.account_changes = {}
+
+    def parse_lines(self):
+        if len(self.lines) < 3 and self.validate:
+            raise PlomException(f'{self.intro}: ends with less than 3 lines:' + str(self.lines))
+        top_line = self.lines[0]
+        if top_line.empty and self.validate:
+            raise PlomException('{self.intro}: headline empty')
+        self.top_comment = top_line.comment
+        toks = top_line.non_comment.split(maxsplit=1)
+        if len(toks) < 2:
+            if self.validate:
+                raise PlomException(f'{self.intro}: headline missing elements: {non_comment}')
+            elif 0 == len(toks):
+                toks = 2*['']
+            else:
+                toks += ['']
+        self.date = toks[0]
+        self.description = toks[1]
+        self.validate_head()
+        for i, line in enumerate(self.lines[1:]):
+            try:
+                self.transfer_lines += [TransferLine(line, validate=self.validate)]
+            except PlomException as e:
+                raise PlomException(f'{self.intro}, transfer line {i}: {e}')
+        self.calculate_account_changes()
+
+    def calculate_account_changes(self):
+        sink_account = None 
+        money_changes = Wealth() 
+        for i, transfer_line in enumerate(self.transfer_lines):
+            intro = f'{self.intro}, transfer line {i}'
+            if transfer_line.amount is None:
+                if sink_account is not None and self.validate:
+                    raise PlomException(f'{intro}: second sink found (only one allowed)')
+                sink_account = transfer_line.account
+            else:
+                if not transfer_line.account in self.account_changes.keys():
+                    self.account_changes[transfer_line.account] = Wealth()
+                money = {transfer_line.currency: transfer_line.amount}
+                self.account_changes[transfer_line.account] += money
+                money_changes += money
+        if sink_account is None and (not money_changes.sink_empty) and self.validate:
+            raise PlomException(f'{intro}: does not balance (undeclared non-empty sink)')
+        if sink_account is not None:
+            if not sink_account in self.account_changes.keys():
+                self.account_changes[sink_account] = Wealth()
+            self.account_changes[sink_account] += money_changes.as_sink
+
+    @property
+    def for_writing(self):
+        lines = [f'{self.date} {self.description}']
+        if self.top_comment is not None and self.top_comment.rstrip() != '':
+            lines[0] += f' ; {self.top_comment}'
+        for line in self.transfer_lines:
+            lines += [line.for_writing]
+        return lines
+
+    @property
+    def comment_cols(self):
+        return max(20, len(self.top_comment))
+
+    def validate_head(self):
+        if not self.validate:
+            return
+        if len(self.date) == 0:
+            raise PlomException(f'{self.intro}: missing date')
+        if len(self.description) == 0:
+            raise PlomException(f'{self.intro}: missing description')
+        try:
+            datetime.strptime(self.date, '%Y-%m-%d')
+        except ValueError:
+            raise PlomException(f'{self.intro}: bad headline date format: {self.date}')
+
+    def fill_sink(self):
+        replacement_lines = []
+        for i, line in enumerate(self.transfer_lines):
+            if line.amount is None:
+                for currency, amount in self.account_changes[line.account].money_dict.items():
+                    replacement_lines += [TransferLine(None, f'{line.account}', amount, currency).for_writing]
+                break
+        lines = self.lines[:i+1] + [LedgerTextLine(l) for l in replacement_lines] + self.lines[i+2:]
+        self.clean()
+        self.lines = lines
+        self.parse_lines()
+
+    def mirror(self):
+        new_transfer_lines = []
+        for transfer_line in self.transfer_lines:
+            uncommented_source = LedgerTextLine(transfer_line.for_writing).non_comment
+            comment = f're: {uncommented_source.lstrip()}'
+            new_account = '?'
+            new_transfer_lines += [TransferLine(None, new_account, -transfer_line.amount, transfer_line.currency, comment)]
+        for transfer_line in new_transfer_lines:
+            self.lines += [LedgerTextLine(transfer_line.for_writing)]
+        self.clean()
+        self.parse_lines()
+
+    def replace(self, replace_from, replace_to):
+        lines = [] 
+        for l in self.for_writing:
+            lines += [l.replace(replace_from, replace_to)]
+        self.lines = [LedgerTextLine(l) for l in lines]
+        self.clean()
+        self.parse_lines()
+
+    def add_taxes(self, db):
+        acc_kk_add = 'Reserves:KrankenkassenBeitragsWachstum'
+        acc_kk_minimum = 'Reserves:Monthly:KrankenkassenDefaultBeitrag'
+        acc_kk = 'Expenses:KrankenKasse'
+        acc_ESt = 'Reserves:EinkommensSteuer'
+        acc_assets = 'Assets'
+        acc_neuanfangspuffer_expenses = 'Reserves:NeuAnfangsPuffer:Ausgaben'
+        months_passed = datetime.strptime(self.date, '%Y-%m-%d').month - 1
+        past_kk_expenses = 0
+        past_kk_add = 0
+        past_neuanfangspuffer_expenses = 0
+        for b in db.bookings:
+            if b.date == self.date:
+                break
+            if acc_neuanfangspuffer_expenses in b.account_changes.keys():
+                past_neuanfangspuffer_expenses -= b.account_changes[acc_neuanfangspuffer_expenses].money_dict['€']
+            if acc_kk_add in b.account_changes.keys():
+                past_kk_add += b.account_changes[acc_kk_add].money_dict['€']
+            if acc_kk_minimum in b.account_changes.keys():
+                past_kk_expenses += b.account_changes[acc_kk_minimum].money_dict['€']
+
+        needed_netto = -self.account_changes['Assets'].money_dict['€']
+        past_taxed_needs_before_kk = past_neuanfangspuffer_expenses - past_kk_expenses
+        ESt_this_month = 0
+        E0 = decimal.Decimal(11604)
+        E1 = decimal.Decimal(17006)
+        E2 = decimal.Decimal(66761)
+        E3 = decimal.Decimal(277826)
+        taxed_income_before_kk = needed_netto
+        too_low = 0
+        too_high = 2 * needed_netto 
+        while True:
+            estimate_for_remaining_year = (12 - months_passed) * taxed_income_before_kk 
+            zvE = past_taxed_needs_before_kk + estimate_for_remaining_year
+            if zvE < E0:
+                ESt_year = decimal.Decimal(0)
+            elif zvE < E1:
+                y = (zvE - E0)/10000
+                ESt_year = (decimal.Decimal(922.98) * y + 1400) * y
+            elif zvE < E2:
+                y = (zvE - E1)/10000
+                ESt_year = (decimal.Decimal(181.19) * y + 2397) * y + decimal.Decimal(1025.38)
+            elif zvE < E3:
+                ESt_year = decimal.Decimal(0.42) * zvE - 10602.13 
             else:
-                debt[currency] += amount
-        if sink_account:
-            for currency, amount in debt.items():
-                apply_booking_to_account_balances(account_changes, sink_account, currency, -amount)
-        return account_changes
+                ESt_year = decimal.Decimal(0.45) * zvE - 18936.88 
+            ESt_this_month = ESt_year / 12
+            taxed_income_minus_ESt = taxed_income_before_kk - ESt_this_month
+            if abs(taxed_income_minus_ESt - needed_netto) < 0.001:
+                break
+            elif taxed_income_minus_ESt < needed_netto:
+                too_low = taxed_income_before_kk 
+            elif taxed_income_minus_ESt > needed_netto:
+                too_high = taxed_income_before_kk 
+            taxed_income_before_kk = too_low + (too_high - too_low)/2
+        ESt_this_month = ESt_this_month.quantize(decimal.Decimal('0.00'))
+        comment = f'estimated zvE: {past_taxed_needs_before_kk}€ + {estimate_for_remaining_year:.2f}€ = {zvE:.2f}€ → year ESt: {ESt_year:.2f} → needed taxed income before Krankenkasse: {taxed_income_before_kk:.2f}€'
+        self.transfer_lines += [TransferLine(None, acc_ESt, ESt_this_month, '€', comment)]
+
+        kk_factor = decimal.Decimal(1.197)
+        kk_minimum_income = 1178.33 
+        kk_minimum_tax = decimal.Decimal(232.13).quantize(decimal.Decimal('0.00'))
+        if self.date < '2024-02-01':
+            kk_minimum_income = 1131.67
+            kk_minimum_tax = decimal.Decimal(222.94).quantize(decimal.Decimal('0.00'))
+        comment = f'assumed minimum income of {kk_minimum_income:.2f}€ * {kk_factor:.3f}'
+        self.transfer_lines += [TransferLine(None, acc_kk_minimum, kk_minimum_tax, '€', comment)]
+        kk_add = taxed_income_before_kk * kk_factor - taxed_income_before_kk - kk_minimum_tax
+        kk_add = decimal.Decimal(kk_add).quantize(decimal.Decimal('0.00'))
+        if past_kk_add + kk_add < 0:   # *if* kk_add would actually kill all earlier kk_add …
+            kk_add = - past_kk_add     # … shrink it so it won't push the kk_add total below 0
+            comment = f'local negative as large as possible without moving {acc_kk_add} below zero'
+        else:
+            comment = f'({taxed_income_before_kk:.2f}€ * {kk_factor:.3f}) - {taxed_income_before_kk:.2f} - {kk_minimum_tax}'
+        self.transfer_lines += [TransferLine(None, acc_kk_add, kk_add, '€', comment)]
 
+        diff_through_taxes_and_kk = ESt_this_month + kk_minimum_tax + kk_add 
+        comment = f'{ESt_this_month} + {kk_minimum_tax} + {kk_add}'
+        self.transfer_lines += [TransferLine(None, acc_assets, -diff_through_taxes_and_kk, '€', comment)]
+        final_loss = diff_through_taxes_and_kk + needed_netto
+        comment = f'{needed_netto} + {diff_through_taxes_and_kk}'
+        self.transfer_lines += [TransferLine(None, acc_assets, final_loss, '€', comment)]
+        self.transfer_lines += [TransferLine(None, acc_neuanfangspuffer_expenses, -final_loss, '€')]
 
 
-class Database:
+class LedgerDB(PlomDB):
 
-    def __init__(self):
-        db_name = "_ledger"
-        self.db_file = db_name + ".json"
-        self.lock_file = db_name+ ".lock"
+    def __init__(self, prefix, ignore_editable_exceptions=False):
+        self.prefix = prefix 
         self.bookings = []
         self.comments = []
-        self.real_lines = []
-        if os.path.exists(self.db_file):
-            with open(self.db_file, "r") as f:
-                self.real_lines += f.readlines()
-        ret = parse_lines(self.real_lines)
-        self.bookings += ret[0]
-        self.comments += ret[1]
-
-    def get_lines(self, start, end):
-        return self.real_lines[start:end]
-
-    def replace(self, start, end, lines):
-        import shutil
-        if os.path.exists(self.lock_file):
-            raise HandledException('Sorry, lock file!')
-        if os.path.exists(self.db_file):
-            shutil.copy(self.db_file, self.db_file + ".bak")
-        f = open(self.lock_file, 'w+')
-        f.close()
-        text = ''.join(self.real_lines[:start]) + '\n'.join(lines) + ''.join(self.real_lines[end:])
-        with open(self.db_file, 'w') as f:
-            f.write(text);
-        os.remove(self.lock_file)
-
-    def append(self, lines):
-        import shutil
-        if os.path.exists(self.lock_file):
-            raise HandledException('Sorry, lock file!')
-        if os.path.exists(self.db_file):
-            shutil.copy(self.db_file, self.db_file + ".bak")
-        f = open(self.lock_file, 'w+')
-        f.close()
-        with open(self.db_file, 'a') as f:
-            f.write('\n' + '\n'.join(lines) + '\n');
-        os.remove(self.lock_file)
-
-
-class MyServer(BaseHTTPRequestHandler):
-    header = """<html>
-<meta charset="UTF-8">
-<style>
-body { color: #000000; }
-table { margin-bottom: 2em; }
-th, td { text-align: left }
-.money { font-family: monospace; text-align: right; }
-.comment { font-style: italic; color: #777777; }
-.full_line_comment { display: block; white-space: nowrap; width: 0; }
-</style>
-<body>
-<a href="/ledger">ledger</a>
-<a href="/balance">balance</a>
-<a href="/add_free">add free</a>
-<a href="/add_structured">add structured</a>
-<hr />
-"""
-    footer = "</body>\n<html>"
+        self.text_lines = []
+        super().__init__(db_path)
+        self.bookings = parse_lines_to_bookings(self.text_lines, ignore_editable_exceptions)
+
+    def read_db_file(self, f):
+        self.text_lines += f.readlines()
+
+    def insert_booking_at_date(self, booking):
+        place_at = 0
+        if len(self.bookings) > 0:
+            for i, iterated_booking in enumerate(self.bookings):
+                if booking.date < iterated_booking.date:
+                    break
+                elif booking.date == iterated_booking.date:
+                    place_at = i
+                    break
+                else:
+                    place_at = i + 1
+        self.bookings.insert(place_at, booking)
+
+    def ledger_as_html(self):
+        for index, booking in enumerate(self.bookings):
+            booking.can_up = index > 0 and self.bookings[index - 1].date == booking.date
+            booking.can_down = index < len(self.bookings) - 1 and self.bookings[index + 1].date == booking.date
+        return j2env.get_template('ledger.html').render(bookings=self.bookings)
+
+    def balance_as_html(self, until_after=None):
+        bookings = self.bookings[:(until_after if until_after is None else int(until_after)+1)]
+        account_trunk = Account('', None)
+        accounts = {account_trunk.full_name: account_trunk}
+        for booking in bookings:
+            for full_account_name, moneys in booking.account_changes.items():
+                toks = full_account_name.split(':')
+                path = [] 
+                for tok in toks:
+                    parent_name = ':'.join(path) 
+                    path += [tok] 
+                    account_name = ':'.join(path)
+                    if not account_name in accounts.keys():
+                        accounts[account_name] = Account(own_name=tok, parent=accounts[parent_name])
+                accounts[full_account_name].add_wealth(moneys)
+        class Node:
+            def __init__(self, indent, name, moneys):
+                self.indent = indent
+                self.name = name
+                self.moneys = moneys.money_dict
+        nodes = []
+        def walk_tree(nodes, indent, account):
+            nodes += [Node(indent, account.own_name, account.full_moneys)]
+            for child in account.children:
+                walk_tree(nodes, indent+1, child)
+        for acc in account_trunk.children:
+            walk_tree(nodes, 0, acc)
+        return j2env.get_template('balance.html').render(nodes=nodes)
+
+    def edit(self, index, sent=None, error_msg=None, edit_mode='table', copy=False):
+        accounts = set() 
+        if sent or -1 == index:
+            content = sent if sent else ([] if 'textarea'==edit_mode else None)
+        else:
+            content = self.bookings[index]
+        date_today = str(datetime.now())[:10]
+        if copy:
+            content.date = date_today 
+            index = -1
+        elif -1 == index and (content is None or [] == content):
+            content = Booking(date=date_today, validate=False)
+        if 'textarea' == edit_mode and content:
+            content = content.for_writing
+        else:
+            for booking in self.bookings:
+                for transfer_line in booking.transfer_lines:
+                    accounts.add(transfer_line.account)
+        return j2env.get_template('edit.html').render(
+                content=content,
+                index=index,
+                error_msg=error_msg,
+                edit_mode=edit_mode,
+                accounts=accounts,
+                adding=-1 == index)
+
+    def move_up(self, index):
+        return self.move(index, -1) 
+
+    def move_down(self, index):
+        return self.move(index, +1) 
+
+    def move(self, index, direction):
+        to_move = self.bookings[index]
+        swap_index = index + 1*(direction)
+        to_swap = self.bookings[swap_index]
+        self.bookings[index] = to_swap 
+        self.bookings[index + 1*(direction)] = to_move 
+        return swap_index
+
+    def write_db(self):
+        lines = []
+        for i, booking in enumerate(self.bookings):
+            if i > 0:
+                lines += ['']
+            lines += booking.for_writing
+        self.write_text_to_db('\n'.join(lines) + '\n')
+
+
+class LedgerHandler(PlomHandler):
+    
+    def app_init(self, handler):
+        default_path = '/ledger'
+        handler.add_route('GET', default_path, self.forward_gets) 
+        handler.add_route('POST', default_path, self.forward_posts)
+        return 'ledger', default_path 
 
     def do_POST(self):
-        db = Database()
+        self.try_do(self.forward_posts)
+
+    def forward_posts(self):
+        prefix = self.apps['ledger'] if hasattr(self, 'apps') else '' 
         length = int(self.headers['content-length'])
         postvars = parse_qs(self.rfile.read(length).decode(), keep_blank_values=1)
+        db = LedgerDB(prefix, ignore_editable_exceptions=True)
+        index = 0
         parsed_url = urlparse(self.path)
-        if '/add_structured' == parsed_url.path:
-            date = postvars['date'][0]
-            description = postvars['description'][0]
-            start_comment = postvars['line_0_comment'][0]
-            lines = [f'{date} {description} ; {start_comment}']
-            i = 1
-            while f'line_{i}_comment' in postvars.keys():
-                account = postvars[f'line_{i}_account'][0]
-                amount = postvars[f'line_{i}_amount'][0]
-                currency = postvars[f'line_{i}_currency'][0]
-                comment = postvars[f'line_{i}_comment'][0]
-                i += 1
-                new_main = f'{account} {amount} {currency}'
-                if '' == new_main.rstrip() == comment.rstrip():  # don't write empty lines
-                    continue
-                new_line = new_main
-                if comment.rstrip() != '':
-                    new_line += f' ; {comment}'
-                lines += [new_line]
-            if 'add_income_tax' in postvars.keys():
-                lines += add_taxes(lines)
-        elif '/add_free' == parsed_url.path:
-            lines = postvars['booking'][0].splitlines()
-        start = int(postvars['start'][0])
-        end = int(postvars['end'][0])
-        try:
-            _, _ = parse_lines(lines)
-            if start == end == 0:
-                db.append(lines)
+        site = path_split(parsed_url.path)[1]
+        for string in {'update', 'add', 'check', 'mirror', 'fill_sink', 'textarea', 'table', 'move_up', 'move_down', 'add_taxes', 'replace'}:
+            if string in postvars.keys():
+                submit_button = string
+                break
+        if 'ledger' == site and submit_button in {'move_up', 'move_down'}:
+            mover = getattr(db, submit_button)
+            index = mover(int(postvars[submit_button][0]))
+        elif 'edit' == site:
+            index = int(postvars['index'][0])
+            edit_mode = postvars['edit_mode'][0]
+            validate = submit_button in {'update', 'add', 'copy', 'check'}
+            starts_at = '?' if index == -1 else db.bookings[index].starts_at
+            delete = False
+            if 'textarea' == edit_mode:
+                lines = [LedgerTextLine(line) for line in postvars['booking'][0].rstrip().split('\n')]
+                if len(lines) == 1 and lines[0].text_line == 'delete':
+                    delete = True
+                else:
+                    booking = Booking(lines, starts_at, validate=validate)
             else:
-                db.replace(start, end, lines)
-            self.send_response(301)
-            redir_url = '/'
-            if 'add_income_tax' in postvars.keys():
-                redir_url = f'/add_structured?start={start}&end={start+len(lines)-1}'
-            self.send_header('Location', redir_url)
-            self.end_headers()
-        except HandledException as e:
-            self.send_response(400)
-            self.end_headers()
-            page = f'{self.header}ERROR: {e}{self.footer}'
-            self.wfile.write(bytes(page, "utf-8"))
+                booking = Booking.from_postvars(postvars, starts_at, validate)
+            if submit_button in {'update', 'add'}:
+                if submit_button == 'update':
+                    if 'textarea' == edit_mode and delete:
+                       del db.bookings[index]
+                    # if not creating new Booking, and date unchanged, keep it in place 
+                    elif booking.date == db.bookings[index].date:
+                       db.bookings[index] = booking 
+                    else:
+                       del db.bookings[index]
+                       db.insert_booking_at_date(booking)
+                else: 
+                    db.insert_booking_at_date(booking)
+            else:  # non-DB-writing calls
+                error_msg = None
+                if 'check' == submit_button:
+                    error_msg = 'All looks fine!'
+                elif submit_button in {'mirror', 'fill_sink', 'add_taxes'}:
+                    if 'add_taxes' == submit_button:
+                        booking.add_taxes(db)
+                    else:
+                        getattr(booking, submit_button)()
+                elif 'replace' == submit_button:
+                    booking.replace(postvars['replace_from'][0], postvars['replace_to'][0])
+                elif submit_button in {'textarea', 'table'}:
+                    edit_mode = submit_button
+                page = db.edit(index, booking, error_msg=error_msg, edit_mode=edit_mode)
+                self.send_HTML(page)
+                return
+        db.write_db() 
+        index = index if index >= 0 else len(db.bookings) - 1
+        self.redirect(f'ledger#{index}')
 
     def do_GET(self):
-        self.send_response(200)
-        self.send_header("Content-type", "text/html")
-        self.end_headers()
-        db = Database()
+        self.try_do(self.forward_gets)
+
+    def forward_gets(self):
+        prefix = self.apps['ledger'] if hasattr(self, 'apps') else '' 
+        try:
+            db = LedgerDB(prefix=prefix)
+        except EditableException as e:
+            # We catch the EditableException for further editing, and then
+            # re-run the DB initiation without it blocking DB creation.
+            db = LedgerDB(prefix=prefix, ignore_editable_exceptions=True)
+            page = db.edit(index=e.booking_index, error_msg=f'ERROR: {e}')
+            self.send_HTML(page)
+            return
         parsed_url = urlparse(self.path)
-        page = self.header + ''
+        site = path_split(parsed_url.path)[1]
         params = parse_qs(parsed_url.query)
-        start = int(params.get('start', ['0'])[0])
-        end = int(params.get('end', ['0'])[0])
-        bonus_lines = int(params.get('bonus_lines', ['0'])[0])
-        if parsed_url.path == '/balance':
-            page += self.balance_as_html(db)
-        elif parsed_url.path == '/add_free':
-            page += self.add_free(db, start, end)
-        elif parsed_url.path == '/add_structured':
-            page += self.add_structured(db, start, end)
-        elif parsed_url.path == '/copy_free':
-            page += self.add_free(db, start, end, copy=True)
-        elif parsed_url.path == '/copy_structured':
-            page += self.add_structured(db, start, end, copy=True)
+        if site == 'balance':
+            stop = params.get('until_after', [None])[0]
+            page = db.balance_as_html(stop)
+        elif site == 'edit':
+            index = params.get('i', [-1])[0]
+            copy = params.get('copy', [0])[0]
+            page = db.edit(int(index), copy=bool(copy))
         else:
-            page += self.ledger_as_html(db)
-        page += self.footer
-        self.wfile.write(bytes(page, "utf-8"))
+            page = db.ledger_as_html()
+        self.send_HTML(page)
 
-    def balance_as_html(self, db):
-        lines = []
-        account_tree, account_sums = bookings_to_account_tree(db.bookings)
-        def print_subtree(lines, indent, node, subtree, path):
-            line = f"{indent}{node}"
-            n_tabs = 5 - (len(line) // 8)
-            line += n_tabs * "\t"
-            if "€" in account_sums[path + node].keys():
-                amount = account_sums[path + node]["€"]
-                line += f"{amount:9.2f} €\t"
-            else:
-                line += f"\t\t"
-            for currency, amount in account_sums[path + node].items():
-                if currency != '€' and amount > 0:
-                    line += f"{amount:5.2f} {currency}\t"
-            lines += [line]
-            indent += "  "
-            for k, v in sorted(subtree.items()):
-                print_subtree(lines, indent, k, v, path + node + ":")
-        for k, v in sorted(account_tree.items()):
-            print_subtree(lines, "", k, v, "")
-        content = "\n".join(lines)
-        return f"<pre>{content}</pre>"
-
-    # def ledger_as_html(self, db):
-    #     lines = []
-    #     line_sep = '<br />'
-    #     for comment in db.comments:
-    #         line = f' ; {comment}' if comment != '' else ''
-    #         lines += [line + line_sep]
-    #     for booking in db.bookings:
-    #         i = booking.start_line
-    #         suffix = lines[i]
-    #         lines[i] = f'<p>{booking.date_string} {booking.description}{suffix}'
-    #         for booking_line in booking.lines[1:]:
-    #             i += 1
-    #             if booking_line == '':
-    #                 continue
-    #             suffix = f' {lines[i]}' if len(lines[i]) > 0 else ''
-    #             value = f' {booking_line[1]} {booking_line[2]}' if booking_line[1] else ''
-    #             lines[i] = f'{booking_line[0]}{value}{suffix}'
-    #         lines[i] = lines[i][:-len(line_sep)] + f"""</p>
-# edit :
-# <a h ref="/add_structured?start={booking.start_line}&end={i+1}">structured</a>
-# / <a  href="/add_free?start={booking.start_line}&end={i+1}">free</a>
-# | co py:
-# <a h ref="/copy_structured?start={booking.start_line}&end={i+1}">structured</a>
-# / <a  href="/copy_free?start={booking.start_line}&end={i+1}">free</a>
-# <br  />"""
-#          return '\n'.join(lines)
-
-    def ledger_as_html(self, db):
-        lines = []
-        for comment in db.comments:
-            lines += [f'<span class="comment">{comment}</span>' if comment != '' else '']
-        for booking in db.bookings:
-            i = booking.start_line
-            booking_end = booking.start_line + len(booking.lines)
-            lines[i] = f"""{booking.date_string} {booking.description} {lines[i]}
-[edit: <a href="/add_structured?start={booking.start_line}&end={booking_end}">structured</a> 
-/ <a href="/add_free?start={booking.start_line}&end={booking_end}">free</a> 
-| copy:<a href="/copy_structured?start={booking.start_line}&end={booking_end}">structured</a>
-/ <a href="/copy_free?start={booking.start_line}&end={booking_end}">free</a>]
-<table>"""
-            for booking_line in booking.lines[1:]:
-                i += 1
-                if booking_line == '':
-                    lines[i] = f'<tr><td><div class="full_line_comment">{lines[i]}</div></td></tr>'
-                    continue
-                comment = f' {lines[i]}' if len(lines[i]) > 0 else ''
-                money = ''
-                if booking_line[1]:
-                    money = f'{booking_line[1]} {booking_line[2]}'
-                account = booking_line[0] 
-                lines[i] = f'<tr><td>{booking_line[0]}</td><td class="money">{money}</td><td>{comment}</td></tr>'
-            lines[i] = lines[i] + "\n" + '</table>'
-        return '\n'.join(lines)
-
-    def header_add_form(self, action):
-        return f"<form method=\"POST\" action=\"/{action}\">\n"
-
-    def footer_add_form(self, start, end, copy):
-        if copy:
-            start = end = 0
-        return f"""
-<input type="hidden" name="start" value={start} />
-<input type="hidden" name="end" value={end} />
-<input type="submit" name="default">
-</form>"""
-
-    def add_free(self, db, start=0, end=0, copy=False):
-        content = html.escape(''.join(db.get_lines(start, end)))
-        return f'{self.header_add_form("add_free")}<textarea name="booking" rows="8" cols="80">{content}</textarea>{self.footer_add_form(start, end, copy)}'
-
-    def add_structured(self, db, start=0, end=0, bonus_lines=10, copy=False):
-        import datetime
-        lines = db.get_lines(start, end)
-        bookings, comments = parse_lines(lines)
-        if len(bookings) > 1:
-            raise HandledException('can only edit single Booking')
-        last_line = 0
-        def inpu(name, val="", datalist="", input_type='text'):
-            val = val if val is not None else ""
-            safe_val = html.escape(str(val))
-            datalist_string = '' if datalist == '' else f'list="{datalist}"'
-            return f'<input type="{input_type}" name="{name}" value="{safe_val}" {datalist_string}/>'
-        input_lines = inpu('add_income_tax', 'add income tax', '', 'submit') + '<br />'
-        today = str(datetime.datetime.now())[:10]
-        if len(bookings) == 0:
-            input_lines += f'{inpu("date", today)} {inpu("description", "", "descriptions")} ; {inpu("line_0_comment")}<br />'
-            last_line = 1
-        else:
-            booking = bookings[0]
-            last_line = len(comments)
-            date_string = today if copy else booking.date_string
-            input_lines += f'{inpu("date", date_string)} {inpu("description", booking.description, "descriptions")} ; {inpu("line_0_comment", comments[0])}<br />'
-            for i in range(1, len(comments)):
-                account = amount = currency = ''
-                if i < len(booking.lines) and booking.lines[i] != '':
-                    account = booking.lines[i][0]
-                    amount = booking.lines[i][1]
-                    currency = booking.lines[i][2]
-                input_lines += f'{inpu(f"line_{i}_account", account, "accounts")} {inpu(f"line_{i}_amount", amount)} {inpu(f"line_{i}_currency", currency, "currencies")} ; {inpu(f"line_{i}_comment", comments[i])}<br />'
-        for j in range(bonus_lines):
-            i = j + last_line
-            input_lines += f'{inpu(f"line_{i}_account", "", "accounts")} {inpu(f"line_{i}_amount", "", "amounts")} {inpu(f"line_{i}_currency", "", "currencies")} ; {inpu(f"line_{i}_comment")}<br />'
-        datalist_sets = {'descriptions': set(), 'accounts': set(), 'currencies': set()}
-        for b in db.bookings:
-            datalist_sets['descriptions'].add(b.description)
-            for account, moneys in b.account_changes.items():
-                datalist_sets['accounts'].add(account)
-                for currency in moneys.keys():
-                    datalist_sets['currencies'].add(currency)
-        def build_datalist(name):
-            datalist = f'<datalist id="{name}">' + "\n"
-            for item in datalist_sets[name]:
-                safe_item = html.escape(item)
-                datalist += f'<option value="{safe_item}">{safe_item}</option>' + "\n"
-            return f"{datalist}</datalist>\n"
-        datalists = build_datalist('descriptions')
-        datalists += build_datalist('accounts')
-        datalists += build_datalist('currencies')
-        return f'{self.header_add_form("add_structured")}{input_lines}{datalists}{self.footer_add_form(start, end, copy)}'
-
-
-if __name__ == "__main__":    
-    webServer = HTTPServer((hostName, serverPort), MyServer)
-    print(f"Server started http://{hostName}:{serverPort}")
-    try:
-        webServer.serve_forever()
-    except KeyboardInterrupt:
-        pass
-    webServer.server_close()
-    print("Server stopped.")
+
+
+if __name__ == "__main__":  
+    run_server(server_port, LedgerHandler)