from __future__ import division
import datetime
import math
import numpy as np
import pandas as pd

from pyisda.legs import ContingentLeg, FeeLeg
from quantlib.settings import Settings
from quantlib.time.api import Date, Actual365Fixed
from termcolor import colored
from pandas.tseries.offsets import BDay
from dates import prev_immdate
from db import dbconn
from psycopg2 import DataError
from pyisda.curve import SpreadCurve
from .utils import previous_twentieth
from scipy.optimize import brentq
from yieldcurve import YC, ql_to_jp, roll_yc, rate_helpers

serenitasdb  = dbconn('serenitasdb')

def g(index, spread, exercise_date, forward_yc = None):
    """computes the strike clean price using the expected forward yield curve """
    if forward_yc is None:
        forward_yc = index._yc
    step_in_date = exercise_date + datetime.timedelta(days=1)
    exercise_date_settle = (pd.Timestamp(exercise_date) + 3* BDay()).date()
    sc = SpreadCurve(exercise_date, forward_yc, index.start_date,
                     step_in_date, exercise_date_settle,
                     [index.end_date], np.array([spread * 1e-4]),
                     index.recovery)
    a = index._fee_leg.pv(exercise_date, step_in_date, exercise_date_settle,
                          forward_yc, sc, True)
    return (spread - index.fixed_rate) * a *1e-4

class Index(object):
    """ minimal class to represent a credit index """
    def __init__(self, start_date, end_date, recovery, fixed_rate,
                 notional = 10e6):
        """
        start_date : :class:`datetime.date`
            index start_date (Could be issue date, or last imm date)
        end_date : :class:`datetime.date`
            index last date
        recovery :
            recovery rate (between 0 and 1)
        fixed_rate :
            fixed coupon (in bps)
        """
        self.fixed_rate = fixed_rate
        self.notional = notional
        self._start_date = start_date
        self._end_date = end_date
        self.recovery = recovery

        self._fee_leg = FeeLeg(self._start_date, end_date, True, 1, 1)
        self._default_leg = ContingentLeg(self._start_date, end_date, 1)
        self._trade_date = None
        self._yc = None
        self._sc = None
        self._risky_annuity = None
        self._spread = None
        self._price = None
        self.name = None

    @property
    def start_date(self):
        return self._start_date

    @property
    def end_date(self):
        return self._end_date

    @start_date.setter
    def start_date(self, d):
        self._fee_leg = FeeLeg(d, self.end_date, True, 1, 1)
        self._default_leg = ContingentLeg(d, self.end_date, 1)
        self._start_date = d

    @end_date.setter
    def end_date(self, d):
        self._fee_leg = FeeLeg(self.start_date, d, True, 1, 1)
        self._default_leg = ContingentLeg(self.start_date, d, 1)
        self._end_date = d

    @property
    def spread(self):
        if self._spread is not None:
            return self._spread * 1e4
        else:
            return None

    def _update(self):
        self._sc = SpreadCurve(self.trade_date, self._yc, self.start_date,
                               self._step_in_date, self._value_date,
                               [self.end_date], np.array([self._spread]),
                               self.recovery)
        self._risky_annuity = self._fee_leg.pv(self.trade_date, self._step_in_date,
                                               self._value_date, self._yc,
                                               self._sc, False)
        self._dl_pv = self._default_leg.pv(
            self.trade_date, self._step_in_date, self._value_date,
            self._yc, self._sc, self.recovery)
        self._pv = self._dl_pv - self._risky_annuity * self.fixed_rate * 1e-4
        self._clean_pv = self._pv + self._accrued * self.fixed_rate * 1e-4
        self._price = 100 * (1 - self._clean_pv)

    @spread.setter
    def spread(self, s):
        """ s: spread in bps """
        if self.spread is None or s != self.spread:
            self._spread = s * 1e-4
            self._update()

    @property
    def flat_hazard(self):
        sc_data = self._sc.inspect()['data']
        ## conversion to continuous compounding
        return math.log(1 + sc_data[0][1])

    @property
    def pv(self):
        return self.notional * self._pv

    @property
    def accrued(self):
        return - self.notional * self._accrued * self.fixed_rate * 1e-4

    @property
    def days_accrued(self):
        return int(self._accrued * 360)

    @property
    def clean_pv(self):
        return self.notional * self._clean_pv

    @property
    def price(self):
        return self._price

    @price.setter
    def price(self, val):
        if self._price is None or math.fabs(val-self._price) > 1e-6:
            def handle(x, self, val):
                self._spread = x
                self._update()
                return val - self.price
            eta = 1.2
            a = self.fixed_rate*1e-4 * 0.5
            b = a * eta
            while True:
                if handle(b, self, val) > 0:
                    break
                b *= eta
            self._spread = brentq(handle, a, b, args = (self, val))
            self._update()

    @property
    def DV01(self):
        old_pv = self.pv
        self.spread += 1
        dv01 = self.pv - old_pv
        self.spread -= 1
        return dv01

    @property
    def IRDV01(self):
        old_pv = self.pv
        old_yc = self._yc
        # for rh in self._helpers:
        #     rh.quote += 1e-4
        # self._yc = ql_to_jp(self._ql_yc)
        helpers = rate_helpers(self.currency)
        for rh in helpers:
            rh.quote += 1e-4
        ql_yc = YC(helpers)
        self._yc = ql_to_jp(ql_yc)
        self._update() ## to force recomputation
        new_pv = self.pv
        # for r in self._helpers:
        #     r.quote -= 1e-4
        self._yc = old_yc
        self._update()
        return new_pv - old_pv

    @property
    def rec_risk(self):
        old_pv = self.pv
        old_recovery = self.recovery
        self.recovery = old_recovery - 0.01
        self._update()
        pv_minus = self.pv
        self.recovery = old_recovery + 0.01
        self._update()
        pv_plus = self.pv
        self.recovery = old_recovery
        self._update()
        return (pv_plus - pv_minus)/2

    @property
    def jump_to_default(self):
        return self.notional * (1 - self.recovery) - self.clean_pv

    @property
    def risky_annuity(self):
        return self._risky_annuity - self._accrued

    @property
    def trade_date(self):
        if self._trade_date is None:
            raise AttributeError('Please set trade_date first')
        else:
            return self._trade_date

    @trade_date.setter
    def trade_date(self, d):
        settings = Settings()
        settings.evaluation_date = Date.from_datetime(d)
        self.start_date = previous_twentieth(d)
        # self._helpers = rate_helpers(self.currency)
        # self._ql_yc = YC(self._helpers)
        # self._yc = ql_to_jp(self._ql_yc)
        ql_yc = YC(currency = self.currency)
        self._yc = ql_to_jp(ql_yc)
        self._trade_date = d
        self._step_in_date = self.trade_date + datetime.timedelta(days=1)
        self._accrued = self._fee_leg.accrued(self._step_in_date)
        self._value_date = (pd.Timestamp(self._trade_date) + 3* BDay()).date()
        if self._spread is not None:
            self._update()

    @classmethod
    def from_name(cls, index, series, tenor, trade_date = datetime.date.today(),
                  notional = 10e6):
        try:
            with serenitasdb.cursor() as c:
                c.execute("SELECT maturity, coupon FROM index_maturity " \
                          "WHERE index=%s AND series=%s AND tenor = %s",
                          (index.upper(), series, tenor))
                maturity, coupon = next(c)
        except DataError as e:
            raise
        else:
            recovery = 0.4 if index.lower() == "ig" else 0.3
            instance = cls(trade_date, maturity, recovery, coupon)
            instance.name = "MARKIT CDX.NA.{}.{} {:%m/%y} ".format(
                index.upper(),
                series,
                maturity)
            if index.upper() in ["IG", "HY"]:
                instance.currency = "USD"
            else:
                instance.currency = "EUR"
            instance.notional = notional
            instance.trade_date = trade_date
            return instance

    def __repr__(self):
        if self.days_accrued > 1:
            accrued_str = "Accrued ({} Days)".format(self.days_accrued)
        else:
            accrued_str = "Accrued ({} Day)".format(self.days_accrued)
        s = ["{:<20}\t{:>15}".format("CDS Index", colored(self.name, attrs = ['bold'])),
             "",
             "{:<20}\t{:>15}".format("Trade Date", ('{:%m/%d/%y}'.
                                                    format(self.trade_date))),
             "{:<20}\t{:>15.2f}\t\t{:<20}\t{:>10,.2f}".format("Trd Sprd (bp)",
                                                              self.spread,
                                                              "Coupon (bp)",
                                                              self.fixed_rate),
             "{:<20}\t{:>15.2f}\t\t{:<20}\t{:>10}".format("1st Accr Start",
                                                          self.spread,
                                                          "Payment Freq",
                                                          "Quarterly"),
             "{:<20}\t{:>15}\t\t{:<20}\t{:>10.2f}".format("Maturity Date",
                                                          ('{:%m/%d/%y}'.
                                                           format(self.end_date)),
                                                          "Rec Rate",
                                                          self.recovery),
             "{:<20}\t{:>15}\t\t{:<20}\t{:>10}".format("Bus Day Adj",
                                                       "Following",
                                                       "Day Count",
                                                       "ACT/360"),
             "",
             colored("Calculator", attrs = ['bold']),
             "{:<20}\t{:>15}".format("Valuation Date", ('{:%m/%d/%y}'.
                                                        format(self.trade_date))),
             "{:<20}\t{:>15}".format("Cash Settled On", ('{:%m/%d/%y}'.
                                                         format(self._value_date))),
             "",
             "{:<20}\t{:>15.8f}\t\t{:<20}\t{:>10,.2f}".format("Price",
                                                              self.price,
                                                              "Spread DV01",
                                                              self.DV01),
             "{:<20}\t{:>15,.0f}\t\t{:<20}\t{:>10,.2f}".format("Principal",
                                                               self.clean_pv,
                                                               "IR DV01",
                                                               self.IRDV01),
             "{:<20}\t{:>15,.0f}\t\t{:<20}\t{:>10,.2f}".format(accrued_str,
                                                               self.accrued,
                                                               "Rec Risk (1%)",
                                                               self.rec_risk),
             "{:<20}\t{:>15,.0f}\t\t{:<20}\t{:>10,.0f}".format("Cash Amount",
                                                               self.pv,
                                                               "Def Exposure",
                                                               self.jump_to_default)
        ]
        return "\n".join(s)


class ForwardIndex(object):
    def __init__(self, index, forward_date, ref_is_price = False):
        self.index = index
        self.forward_date = forward_date
        self.exercise_date_settle = (pd.Timestamp(forward_date) + 3* BDay()).date()
        self.df = index._yc.discount_factor(self.exercise_date_settle)
        self._ref_is_price = ref_is_price
        self._update()

    @property
    def forward_annuity(self):
        return self._forward_annuity

    @property
    def forward_pv(self):
        return self._forward_pv

    @property
    def forward_spread(self):
        return self._forward_spread * 1e4

    @property
    def ref(self):
        if ref_is_price:
            return self.index.price
        else:
            return self.index.spread

    @ref.setter
    def ref(self, val):
        if self._ref_is_price:
            if self.index.price is None or \
               math.fabs(self.index.price - val) > 1e-6:
                self.index.price = val
                self._update()
        else:
            if self.index.spread is None or val != self.index.spread:
                self.index.spread = val
                self._update()

    def _update(self):
        if self.index._sc is not None:
            step_in_date = self.forward_date + datetime.timedelta(days=1)
            a = self.index._fee_leg.pv(self.index.trade_date, step_in_date,
                                       self.index.trade_date, self.index._yc, self.index._sc, False)
            Delta = self.index._fee_leg.accrued(step_in_date)
            q = self.index._sc.survival_probability(self.forward_date)
            self._forward_annuity = a - Delta * self.df * q
            self._forward_pv = self._forward_annuity * (self.index.spread - self.index.fixed_rate) * 1e-4
            fep = (1 - self.index.recovery) * (1 - q)
            self._forward_pv =  self._forward_pv / self.df + fep
            self._forward_spread = self.index._spread + fep * self.df / self._forward_annuity
        else:
            self._forward_annuity, self._forward_pv, self._forward_spread = None, None, None