from datetime import datetime
from pathlib import Path
from shutil import copy2

from flask import flash
from sqlalchemy import select

from . import settings
from .exceptions import DataBaseImportException
from .models import (
    Appointment,
    Assistant,
    Experiment,
    Group,
    GroupExperiment,
    Part,
    PartStudent,
    Program,
    Semester,
    SemesterExperiment,
    Student,
    User,
    db,
    get_first,
)


def now():
    return datetime.now().strftime("%d_%m_%Y_%H_%M_%S")


def is_null(entry):
    return entry == "NULL" or entry == ""


def nullable(entry):
    if is_null(entry):
        return None

    return entry


def not_nullable(entry):
    if is_null(entry):
        raise DataBaseImportException("Unnullable entry is NULL!")

    return entry


def importFromFile(filePath):
    db_path = Path(settings["SQLITE_DB_PATH"])

    db_bk_dir = db_path.parent / "backups"
    db_bk_dir.mkdir(exist_ok=True)

    if filePath[-4:] != ".txt":
        raise DataBaseImportException(
            "The import file has to be a text file with txt extension (.txt at the end of the filename)!"
        )

    semesters = {}
    parts = {}
    students = {}
    groups = {}
    partStudents = {}
    experiments = {}
    groupExperiments = {}
    appointments = {}

    with open(filePath) as f:
        flash("Reading file...")

        expectingTable = True
        readHeader = False

        for line in f:
            line = line[:-1]

            if line == "":
                expectingTable = True
                continue

            if expectingTable:
                if line[0] != "#":
                    raise DataBaseImportException(f"Expected a Table name starting with # but got this line: {line}")

                expectingTable = False
                tableName = line[1:]

                if tableName == "Semester":
                    activeDict = semesters
                elif tableName == "Part":
                    activeDict = parts
                elif tableName == "Student":
                    activeDict = students
                elif tableName == "Group":
                    activeDict = groups
                elif tableName == "PartStudent":
                    activeDict = partStudents
                elif tableName == "Experiment":
                    activeDict = experiments
                elif tableName == "GroupExperiment":
                    activeDict = groupExperiments
                elif tableName == "Appointment":
                    activeDict = appointments
                else:
                    raise DataBaseImportException(f"{tableName} is not a valid table name!")

                readHeader = True
                continue

            cells = line.split("\t")

            if readHeader:
                readHeader = False
                activeDict["_header"] = cells

                for cell in cells:
                    activeDict[cell] = []

                continue

            cellsLen = len(cells)
            if cellsLen != len(activeDict["_header"]):
                raise DataBaseImportException(
                    f"The number of header cells is not equal to the number of row cells in row {cells}!"
                )

            for i in range(cellsLen):
                activeDict[activeDict["_header"][i]].append(cells[i])

    try:
        # Semester
        flash("Semester...")

        if len(semesters["label"]) != 1:
            raise DataBaseImportException("Only one semester is allowed in an import file!")

        semesterLabel = not_nullable(semesters["label"][0])
        semesterYear = int(not_nullable(semesters["year"][0]))
        dbSemester = get_first(select(Semester).where(Semester.label == semesterLabel, Semester.year == semesterYear))

        if dbSemester is None:
            raise DataBaseImportException(
                f"{semesterLabel}{semesterYear} does not exist in the database! Please make sure that you create the semester from the web interface first."
            )

        # Part
        flash("Part...")

        dbParts = {}
        for i, id in enumerate(parts["id"]):
            id = int(not_nullable(id))
            partNumber = int(not_nullable(parts["number"][i]))
            partProgramLabel = not_nullable(parts["program_label"][i])
            dbPart = get_first(
                select(Part)
                .join(Program)
                .where(
                    Part.number == partNumber,
                    Program.label == partProgramLabel,
                    Part.semester == dbSemester,
                )
            )

            if dbPart is None:
                raise DataBaseImportException(
                    f"Part with number {partNumber} and program label {partProgramLabel} does not exist in the database! Please make sure that you create parts from the web interface first."
                )

            dbParts[id] = dbPart

        # Student
        flash("Student...")

        dbStudents = {}
        for i, studentNumber in enumerate(students["student_number"]):
            studentNumber = int(not_nullable(studentNumber))
            dbStudent = get_first(select(Student).where(Student.student_number == studentNumber))

            if dbStudent is None:
                dbStudent = Student(
                    student_number=studentNumber,
                    first_name=not_nullable(students["first_name"][i]),
                    last_name=not_nullable(students["last_name"][i]),
                    uni_email=not_nullable(students["uni_email"][i]),
                    contact_email=nullable(students["contact_email"][i]),
                    bachelor_thesis=nullable(students["bachelor_thesis"][i]),
                    bachelor_thesis_work_group=nullable(students["bachelor_thesis_work_group"][i]),
                    note=nullable(students["note"][i]),
                )
                db.session.add(dbStudent)
            else:
                dbStudent.contact_email = nullable(students["contact_email"][i])
                dbStudent.bachelor_thesis = nullable(students["bachelor_thesis"][i])
                dbStudent.bachelor_thesis_work_group = nullable(students["bachelor_thesis_work_group"][i])
                dbStudent.note = nullable(students["note"][i])

            dbStudents[studentNumber] = dbStudent

        # Group
        flash("Group...")

        dbGroups = {}
        for i, id in enumerate(groups["id"]):
            id = int(not_nullable(id))
            program = get_first(select(Program).where(Program.label == not_nullable(groups["program_label"][i])))
            dbGroup = Group(
                number=int(not_nullable(groups["number"][i])),
                program=program,
                semester=dbSemester,
            )
            db.session.add(dbGroup)
            dbGroups[id] = dbGroup

        # PartStudent
        flash("PartStudent...")

        for i, studentNumber in enumerate(partStudents["student_number"]):
            studentNumber = int(not_nullable(studentNumber))
            dbPartStudent = PartStudent(
                student=dbStudents[studentNumber],
                part=dbParts[int(not_nullable(partStudents["part_id"][i]))],
                group=dbGroups[int(not_nullable(partStudents["group_id"][i]))],
            )
            db.session.add(dbPartStudent)

        # Experiment
        flash("Experiment...")

        dbSemesterExperiments = {}
        for i, id in enumerate(experiments["id"]):
            id = int(not_nullable(id))
            experimentNumber = int(not_nullable(experiments["number"][i]))

            experimentProgram = get_first(
                select(Program).where(Program.label == not_nullable(experiments["program_label"][i]))
            )
            dbExperiment = get_first(
                select(Experiment).where(Experiment.number == experimentNumber, Experiment.program == experimentProgram)
            )

            if dbExperiment is None:
                # TODO: Check if experimentProgram is None
                raise DataBaseImportException(
                    f"Experiment with number {experimentNumber} and program {experimentProgram} does not exist in the database. Please make sure that experiments are created from the web interface."
                )

            dbSemesterExperiment = get_first(
                select(SemesterExperiment).where(
                    SemesterExperiment.experiment == dbExperiment, SemesterExperiment.semester == dbSemester
                )
            )

            if dbSemesterExperiment is None:
                raise DataBaseImportException(
                    f"No semester experiment exists in the database to the experiment with number {experimentNumber} and program {experimentProgram}. Please make sure that semester experiments are created in the web interface. The problem might be that the experiment was not active while creating a new semester"
                )

            dbSemesterExperiments[id] = dbSemesterExperiment

        # GroupExperiment
        flash("GroupExperiment...")

        dbGroupExperiments = {}
        for i, id in enumerate(groupExperiments["id"]):
            id = int(not_nullable(id))
            dbGroupExperiment = GroupExperiment(
                semester_experiment=dbSemesterExperiments[int(not_nullable(groupExperiments["experiment_id"][i]))],
                group=dbGroups[int(not_nullable(groupExperiments["group_id"][i]))],
            )
            db.session.add(dbGroupExperiment)
            dbGroupExperiments[id] = dbGroupExperiment

        # Appointment
        flash("Appointment...")

        for i, date in enumerate(appointments["date"]):
            date = not_nullable(date)
            assistantEmail = not_nullable(appointments["assistant_email"][i])
            assistant = get_first(select(Assistant).join(User).where(User.email == assistantEmail))

            if assistant is None:
                raise DataBaseImportException(
                    f"Assistant with email {assistantEmail} does not exist in the database! Please make sure that you create assistants in the web interface."
                )

            dbAppointment = Appointment(
                date=datetime.strptime(date, "%d.%m.%Y").date(),
                special=bool(int(not_nullable(appointments["special"][i]))),
                group_experiment=dbGroupExperiments[int(not_nullable(appointments["group_experiment_id"][i]))],
                assistant=assistant,
            )
            db.session.add(dbAppointment)

        # Backup
        dest = db_bk_dir / f"before_{dbSemester}_import_{now()}.db"
        copy2(db_path, dest)

        flash(f"Made a backup of the database before committing the import at {dest}")

        db.session.commit()
    except Exception as ex:
        db.session.rollback()

        raise ex

    dest = db_bk_dir / f"after_{dbSemester}_import_{now()}.db"
    copy2(db_path, dest)

    flash(f"Made a backup of the database after the import at {dest}")

    flash("\nImport done!")
    flash("Please check that everything worked as expected. Restore the database backup otherwise!")