"""
Widget for multi-model constraints.
"""
import os

# numpy methods required for the validator! Don't remove.
# pylint: disable=unused-import,unused-wildcard-import,redefined-builtin
from numpy import *

from PyQt5 import QtCore
from PyQt5 import QtGui
from PyQt5 import QtWidgets
import webbrowser

import sas.qtgui.Utilities.GuiUtils as GuiUtils
ALLOWED_OPERATORS = ['=','<','>','>=','<=']

# Local UI
from sas.qtgui.Perspectives.Fitting.UI.ComplexConstraintUI import Ui_ComplexConstraintUI

class ComplexConstraint(QtWidgets.QDialog, Ui_ComplexConstraintUI):
    def __init__(self, parent=None, tabs=None):
        super(ComplexConstraint, self).__init__()

        self.setupUi(self)
        self.setModal(True)

        # Useful globals
        self.tabs = tabs
        self.params = None
        self.tab_names = None
        self.operator = '='

        self.setupData()
        self.setupWidgets()
        self.setupSignals()
        self.setupTooltip()

        self.setFixedSize(self.minimumSizeHint())

        # Default focus is on OK
        self.cmdOK.setFocus()

    def setupData(self):
        """
        Digs into self.tabs and pulls out relevant info
        """
        self.tab_names = [tab.kernel_module.name for tab in self.tabs]
        self.params = [tab.getParamNames() for tab in self.tabs]

    def setupSignals(self):
        """
        Signals from various elements
        """
        self.cmdOK.clicked.connect(self.accept)
        self.cmdHelp.clicked.connect(self.onHelp)
        self.cmdRevert.clicked.connect(self.onRevert)
        self.txtConstraint.editingFinished.connect(self.validateFormula)

        self.cbParam1.currentIndexChanged.connect(self.onParamIndexChange)
        self.cbParam2.currentIndexChanged.connect(self.onParamIndexChange)
        self.cbOperator.currentIndexChanged.connect(self.onOperatorChange)

    def setupWidgets(self):
        """
        Setup widgets based on current parameters
        """
        self.txtName1.setText(self.tab_names[0])
        self.txtName2.setText(self.tab_names[1])

        # Show only parameters not already constrained
        self.cbParam1.clear()
        items = [param for i,param in enumerate(self.params[0]) if not self.tabs[0].rowHasConstraint(i)]
        self.cbParam1.addItems(items)
        self.cbParam2.clear()
        items = [param for i,param in enumerate(self.params[1]) if not self.tabs[1].rowHasConstraint(i)]
        self.cbParam2.addItems(items)

        self.txtParam.setText(self.tab_names[0] + ":" + self.cbParam1.currentText())

        self.cbOperator.clear()
        self.cbOperator.addItems(ALLOWED_OPERATORS)
        self.txtOperator.setText(self.cbOperator.currentText())

        self.txtConstraint.setText(self.tab_names[1]+"."+self.cbParam2.currentText())

    def setupTooltip(self):
        """
        Tooltip for txtConstraint
        """
        p1 = self.tab_names[0] + ":" + self.cbParam1.currentText()
        p2 = self.tab_names[1]+"."+self.cbParam2.currentText()
        tooltip = "E.g.\n%s = 2.0 * (%s)\n" %(p1, p2)
        tooltip += "%s = sqrt(%s) + 5"%(p1, p2)
        self.txtConstraint.setToolTip(tooltip)

    def onParamIndexChange(self, index):
        """
        Respond to parameter combo box changes
        """
        # Find out the signal source
        source = self.sender().objectName()
        if source == "cbParam1":
            self.txtParam.setText(self.tab_names[0] + ":" + self.cbParam1.currentText())
        else:
            self.txtConstraint.setText(self.tab_names[1] + "." + self.cbParam2.currentText())

    def onOperatorChange(self, index):
        """
        Respond to operator combo box changes
        """
        self.txtOperator.setText(self.cbOperator.currentText())

    def onRevert(self):
        """
        switch M1 <-> M2
        """
        # Switch parameters
        self.params[1], self.params[0] = self.params[0], self.params[1]
        self.tab_names[1], self.tab_names[0] = self.tab_names[0], self.tab_names[1]
        self.tabs[1], self.tabs[0] = self.tabs[0], self.tabs[1]
        # Try to swap parameter names in the line edit
        current_text = self.txtConstraint.text()
        new_text = current_text.replace(self.cbParam1.currentText(), self.cbParam2.currentText())
        self.txtConstraint.setText(new_text)
        # Update labels and tooltips
        index1 = self.cbParam1.currentIndex()
        index2 = self.cbParam2.currentIndex()
        indexOp = self.cbOperator.currentIndex()
        self.setupWidgets()

        # Original indices
        self.cbParam1.setCurrentIndex(index2)
        self.cbParam2.setCurrentIndex(index1)
        self.cbOperator.setCurrentIndex(indexOp)
        self.setupTooltip()

    def validateFormula(self):
        """
        Add visual cues when formula is incorrect
        """
        formula_is_valid = self.validateConstraint(self.txtConstraint.text())
        if not formula_is_valid:
            self.cmdOK.setEnabled(False)
            self.txtConstraint.setStyleSheet("QLineEdit {background-color: red;}")
        else:
            self.cmdOK.setEnabled(True)
            self.txtConstraint.setStyleSheet("QLineEdit {background-color: white;}")

    def validateConstraint(self, constraint_text):
        """
        Ensure the constraint has proper form
        """
        # 0. none or empty
        if not constraint_text or not isinstance(constraint_text, str):
            return False

        # M1.scale  --> model_str='M1', constraint_text='scale'
        param_str = self.cbParam2.currentText()
        constraint_text = constraint_text.strip()
        model_str = self.txtName2.text()

        # 0. Has to contain the model name
        if model_str != self.txtName2.text():
            return False

        # Remove model name from constraint
        constraint_text = constraint_text.replace(model_str+".",'')

        # 1. just the parameter
        if param_str == constraint_text:
            return True

        # 2. ensure the text contains parameter name
        parameter_string_start = constraint_text.find(param_str)
        if parameter_string_start < 0:
            return False

        # 3. replace parameter name with "1" and try to evaluate the expression
        try:
            expression_to_evaluate = constraint_text.replace(param_str, "1.0")
            eval(expression_to_evaluate)
        except Exception:
            # Too many cases to cover individually, just a blanket
            # Exception should be sufficient
            # Note that in current numpy things like sqrt(-1) don't
            # raise but just return warnings
            return False

        return True

    def constraint(self):
        """
        Return the generated constraint as tuple (model1, param1, operator, constraint)
        """
        return (self.txtName1.text(), self.cbParam1.currentText(), self.cbOperator.currentText(), self.txtConstraint.text())

    def onHelp(self):
        """
        Display related help section
        """
        try:
            help_location = GuiUtils.HELP_DIRECTORY_LOCATION + \
            "/user/qtgui/Perspectives/Fitting/fitting_help.html#simultaneous-fits-with-constraints"
            webbrowser.open('file://' + os.path.realpath(help_location))
        except AttributeError:
            # No manager defined - testing and standalone runs
            pass