import astropy.units as u
import ast
import math
import numpy as np
import os
from PyQt5.uic import loadUi
from PyQt5.QtCore import Qt
from qtpy.QtGui import QIcon
from qtpy.QtWidgets import (QMainWindow,QInputDialog,QApplication, QDialog,
                            QComboBox, QPushButton, QTreeWidget, QTreeWidgetItem,
                            QMessageBox)
import specutils
from specutils import Spectrum1D
import uuid

from ...core.plugin import plugin


@plugin('Arithmetic')
class Arithmetic(QDialog):
    """
    A plugin that can show a dialog to allow users to define derived variables.
    """
    def __init__(self, *args, **kwargs):
        """
        Equation editor main dialog. From this view you can add, edit, and remove
        arithmetic attributes.
        """
        super().__init__(parent=None)
        loadUi(os.path.abspath(
            os.path.join(os.path.dirname(__file__),
                         ".", "arithmetic_editor.ui")), self)

        self.setWindowTitle("Arithmetic")
        self.button_add_derived.clicked.connect(self.showDialog)
        self.button_edit_derived.clicked.connect(self.edit_expression)
        self.button_remove_derived.clicked.connect(self.remove_expression)

        self.is_editmode=False

        self.setModal(True)

    @plugin.tool_bar(name="Arithmetic", icon=QIcon(":/icons/014-calculator.svg"))
    def on_action_triggered(self):
        """Trigger the arithmetic UI when button is clicked."""
        self.show()

    def set_equation(self, eq_name=None, eq_expression=None):
        """Place equation in main dialog."""

        current_item = self.list_derived_components.currentItem()
        if current_item and eq_name == current_item.text(0):
            current_item.setText(1, eq_expression)
        else:
            new_row = QTreeWidgetItem()
            new_row.setText(0, eq_name)
            new_row.setText(1, eq_expression)

            self.list_derived_components.addTopLevelItem(new_row)

    def edit_expression(self):
        """Edit selected expression in main dialog"""
        if not self.list_derived_components.currentItem():
            QMessageBox.warning(self, "No Spectrum1D Objects",
                                "No selected expression to edit!")
        else:
            current_item = self.list_derived_components.currentItem()
            label = current_item.text(0)
            equation = current_item.text(1)
            self.editor = EquationEditor(self, label=label, equation=equation, parent=self)

    def remove_expression(self):
        """Remove selected expression in main diaglog"""
        if not self.list_derived_components.currentItem():
            QMessageBox.warning(self, "No Spectrum1D Objects",
                                "No selected expression to remove!")
        else:
            # Get current selected item and it's index in the QTreeWidget.
            current_item = self.list_derived_components.currentItem()
            index = self.list_derived_components.indexOfTopLevelItem(current_item)

            self.list_derived_components.takeTopLevelItem(index)

    def showDialog(self):
        """Show arithmetic editor"""
        self.editor = EquationEditor(self, parent=self)

    def find_matches(self, eq_name):
        """Checks for matching names"""
        matches = self.list_derived_components.findItems(eq_name, Qt.MatchExactly, 0)
        matches = [item.text(0) for item in matches]
        return matches


class EquationEditor(QDialog):
    """
    A Qt dialog where users can enter expressions to calculate variables
    derived from other variables.
    """
    tip_text = ("<b>Note:</b> The spectrum names in the expression should be surrounded "
                "by {{ }} brackets (e.g. {{{example1}}}), and you <br>"
                "you can use libraries imported in the namespace (numpy, specutils, etc). "
                "Objects returned from editor must be type Spectrum1D!<br><br>"
                "<b>Example expressions:</b><br><br>"
                "  - Double the flux of '{example1}': {{{example1}}} * 2<br>"
                "  - Add two Spectrum1D objects: {{{example1}}}*2 + {{{example2}}}<br>"
                "  - Subtract two Spectrum1D objects: {{{example1}}}*2 - {{{example2}}}<br>"
                "  - Use Spectrum1D API: Spectrum1D(spectral_axis={{{example1}}}.wavelength,flux={{{example1}}}.flux)")

    placeholder_text = ("Type any mathematical expression here - "
                        "you can include attribute names from the "
                        "drop-down below by selecting them and "
                        "clicking 'Insert'.")

    def __init__(self, equation_editor, label=None, equation=None, parent=None):
        """Dialog where you specify equation names and expressions."""
        super(EquationEditor, self).__init__(parent)
        loadUi(os.path.abspath(
            os.path.join(os.path.dirname(__file__),
                         ".", "equation_editor.ui")), self)

        self.setWindowTitle("Equation Editor")

        self._equation_editor = equation_editor

        if not self._equation_editor.hub.data_items:
            self.msgbox = QMessageBox.warning(self._equation_editor, "No Spectrum1D Objects",
                                "There is no data loaded into your SpecViz session!")
        else:
            self.is_addmode = label is None

            example1 = 'SPECTRUM1'
            example2 = 'SPECTRUM2'
            self.example_label.setText(self.tip_text.format(example1=example1,
                                                            example2=example2))

            if label is not None:
                self.text_label.setText(label)
                self.text_label.setDisabled(True)
            else:
                self.text_label.setPlaceholderText("New attribute name")
            if equation is not None:
                self.expression.insertPlainText(equation)
            else:
                self.expression.setPlaceholderText(self.placeholder_text)

            self.combosel_data.addItems([item.name for item in self._equation_editor.hub.data_items])

            self.combosel_component.addItems(['wavelength', 'velocity',
                                              'frequency', 'flux'])

            self.button_insert_spectrum.clicked.connect(self._insert_spectrum)
            self.button_insert_component.clicked.connect(self._insert_component)

            self.button_ok.clicked.connect(self._assign_components)
            self.button_cancel.clicked.connect(self._close_dialog)

            self.text_label.textChanged.connect(self._update_status)
            self.expression.textChanged.connect(self._update_status)
            self._update_status()

            self.setModal(True)
            self.show()

    def _get_eq_name(self):
        """Get user input name of equation"""
        return self.text_label.text().strip()

    def _get_raw_command(self):
        """Return text entered into the editor"""
        return self.expression.toPlainText().strip()

    def _insert_component(self):
        """Insert data item components into editor"""
        label = self.combosel_component.currentText()
        self.expression.insertPlainText('.' + self.combosel_component.currentText())

    def _insert_spectrum(self):
        """Insert data item components into editor"""
        label = self.combosel_data.currentText()
        self.expression.insertPlainText('{' + label + '}')

    def _assign_components(self):
        """Assign arithmetic components to UI"""
        self.eq_name = self._get_eq_name()
        self.eq_expression = self._get_raw_command()

        self._equation_editor.set_equation(self.eq_name, self.eq_expression)

        self._equation_editor.hub.workspace.model.add_data(
            spec=self.evaluated_arith, name=self.eq_name)

        self._close_dialog()

    def _close_dialog(self):
        self.close()

    def _item_from_name(self, name):
        """Get data item based on name"""
        return next((x.spectrum for x in self._equation_editor.hub.data_items
                     if x.name == name))

    def _duplicate_component(self, compname):
        if compname in self._equation_editor.find_matches(compname):
            return True
        if compname in [x.name for x in self._equation_editor.hub.data_items]:
            return True

        return False

    def _update_status(self):
        """Check status of entered arithmetic"""
        # If the text hasn't changed, no need to check again
        if hasattr(self, '_cache') and self._cache == (self.text_label.text(),
                                                       self._get_raw_command()):
            return

        if self.text_label.text() == "":
            self.label_status.setStyleSheet('color: red')
            self.label_status.setText("Attribute name not set")
            self.button_ok.setEnabled(False)

        elif self.is_addmode and self._duplicate_component(self.text_label.text()):
            self.label_status.setStyleSheet('color: red')
            self.label_status.setText("Component name already exists.")
            self.button_ok.setEnabled(False)

        elif self._get_raw_command() == "":
            self.label_status.setText("")
            self.button_ok.setEnabled(False)

        else:
            try:
                dict_map = {x.name: "self._item_from_name('{}')".format(x.name)
                            for x in self._equation_editor.hub.data_items}
                raw_str = self._get_raw_command()
                self.evaluated_arith = eval(raw_str.format(**dict_map))
                if not isinstance(self.evaluated_arith,
                                  specutils.spectra.spectrum1d.Spectrum1D):

                    raise ValueError("Arithmetic Editor must return ",
                                     "Spectrum1D object not {}".\
                                     format(type(self.evaluated_arith)))
            except SyntaxError:
                self.label_status.setStyleSheet('color: red')
                self.label_status.setText("Incomplete or invalid syntax")
                self.button_ok.setEnabled(False)
            except Exception as exc:
                self.label_status.setStyleSheet('color: red')
                self.label_status.setText(str(exc))
                self.button_ok.setEnabled(False)
            else:
                self.label_status.setStyleSheet('color: green')
                self.label_status.setText("Valid expression")
                self.button_ok.setEnabled(True)

        self._cache = self.text_label.text(), self._get_raw_command()
