# -*- coding: utf-8 -*-
from . import Blueprint, flash, db, \
        current_user, login_required, \
        assert_authorisation, templated, redirect, request, url_for, today

from flask import Markup

from ..model import Category, SingleExpense, CatExpense, MonthExpense
from .. import forms as F

import datetime
from sqlalchemy import func
from functools import partial

assert_authorisation = partial(assert_authorisation, SingleExpense.get)
mod = Blueprint('expenses', __name__)

#
# Form
#
class ExpenseForm(F.Form):
    date = F.DateField(u'Datum', F.req,
            format="%d.%m.%Y",
            default=lambda: today())

    expense = F.DecimalField(u'Betrag', F.req,
            description=u'EUR',
            places=2)

    description = F.StringField(u'Beschreibung')

    category = F.QuerySelectField(u'Kategorie',
            get_label='name')

    def __init__(self, obj = None, description_req = True):
        super(ExpenseForm, self).__init__(obj = obj)
        self.category.query = Category.of(current_user).order_by(Category.name)

        if description_req:
            self.description.validators.extend(F.req)

#
# Utilities
#
def calc_month_exp(year, month):
    """Returns the `MonthExpense` for the given month."""
    ssum = func.sum(SingleExpense.expense)
    query = SingleExpense.of_month(current_user, month, year)

    result = query.group_by(SingleExpense.category_id).\
             values(SingleExpense.category_id, ssum)

    exps = [CatExpense(Category.get(c), s, query.filter(SingleExpense.category_id == c)) for c,s in result]

    return MonthExpense(current_user, datetime.date(year, month, 1), exps)


def pie_data(exp):
    """Generates the dictionary needed to show the pie diagram.
    The resulting dict is category → sum of expenses.
    """
    expenses = {}
    for c in exp.catexps:
        expenses[c.cat.name] = float(c.sum)

    for c in Category.of(current_user).order_by(Category.name).all():
        yield (c.name, expenses.get(c.name, 0.0))


def calc_month_and_pie(year, month):
    exp = calc_month_exp(year,month)
    pie = pie_data(exp)
    return (exp, dict(pie))


def entry_flash(msg, exp):
    """When changing/adding an entry, a message is shown."""
    url = url_for('.edit', id = exp.id)
    link = u"<a href=\"%s\">%s</a>" % (url, exp.description)
    flash(Markup(msg % link))

#
# Template additions
#
@mod.app_template_filter()
def prev_date(exp):
    if exp.date.month == 1:
        return exp.date.replace(year = exp.date.year - 1, month = 12)
    else:
        return exp.date.replace(month = exp.date.month - 1)


@mod.app_template_filter()
def next_date(exp):
    if exp.date.month == 12:
        return exp.date.replace(year = exp.date.year + 1, month = 1)
    else:
        return exp.date.replace(month = exp.date.month + 1)


@mod.app_template_test('last_date')
def is_last(exp):
    return exp.date >= today().replace(day = 1)

#
# Views
#
@mod.route('/')
@login_required
@templated
def show():
    """Show this and the last month."""
    d = today()

    first, pfirst = calc_month_and_pie(d.year, d.month)
    if d.month == 1:
        second, psecond = calc_month_and_pie(d.year - 1, 12)
    else:
        second, psecond = calc_month_and_pie(d.year, d.month - 1)

    return { 'exps' : [first, second], 'pies': [pfirst, psecond] }


@mod.route('/<int(fixed_digits=4):year>/<int(fixed_digits=2):month>')
@login_required
@templated('.show')
def show_date(year, month):
    """Show the expenses of the specified month."""
    c,p = calc_month_and_pie(year, month)
    return { 'exps' : [c], 'pies' : [p] }

# shortcut to allow calling the above route, when year/month is a string
mod.add_url_rule('/<path:p>', endpoint = 'show_date_str', build_only = True)


@mod.route('/edit/<int:id>', methods=('GET', 'POST'))
@login_required
@assert_authorisation('id')
@templated
def edit(id):
    """Edit a single expense, given by `id`."""
    exp = SingleExpense.get(id)
    form = ExpenseForm(exp)

    if form.is_submitted():
        if 'deleteB' in request.form:
            db.session.delete(exp)

        elif form.flash_validate(): # change
            form.populate_obj(exp)

        else:
            return { 'form': form }

        db.session.commit()
        entry_flash(u"Eintrag %s geändert.", exp)
        return redirect('index')

    return { 'form': form }


@mod.route('/add', methods=('GET', 'POST'))
@login_required
@templated
def add():
    """Add a new expense."""
    form = ExpenseForm(description_req=False)

    if form.validate_on_submit():
        if not form.description.data.strip():
            form.description.data = form.category.data.name

        exp = SingleExpense()

        form.populate_obj(exp)
        exp.user = current_user

        db.session.add(exp)
        db.session.commit()

        entry_flash(u"Neuer Eintrag %s hinzugefügt.", exp)

        return redirect('.add')

    return { 'form': form }