from flask import current_app
from flask import g
import sqlite3

from .book import Book

def get_db():
    """Connect to the application's configured database. The connection
    is unique for each request and will be reused if this is called
    again.
    """
    if "db" not in g:
        g.db = sqlite3.connect(
            current_app.config["DATABASE"], detect_types=sqlite3.PARSE_DECLTYPES
        )
        g.db.row_factory = sqlite3.Row

    return g.db

def get_book(isbn):
    db = get_db()

    data = db.execute(
        """
        SELECT * FROM book WHERE isbn=?
        """,
        (isbn,)
    ).fetchone()

    if data is None:
        raise IndexError("Book not in db")

    book = Book(isbn)
    book._manual_load(
        data["title"],
        publisher=data["publisher"],
        publish_date=data["publish_date"],
        author=data["author"],
        count=data["count"],
        category=data["category"] if data["category"] != "" else None
    )
    return book

def delete_book(isbn):
    db = get_db()

    data = db.execute(
        """
        DELETE FROM book WHERE isbn=?
        """,
        (isbn,)
    )
    db.commit()

def increment_count(book):
    if book.count == -1:
        book = get_book(book.isbn)

    db = get_db()
    db.execute(
        """
        UPDATE book SET count=?
        WHERE isbn=?
        """,
        (book.count+1, book.isbn)
    )
    db.commit()

def add_book(book):
    try:
        book = get_book(book.isbn)
        increment_count(book)
        return "duplicate"
    except IndexError:
        if book.count == -1:
            book.count = 1

        db = get_db()
        db.execute(
            """
            INSERT INTO book (isbn, count, title, author, publisher, publish_date, category)
            VALUES (?, ?, ?, ?, ?, ?, ?)
            """,
            (book.isbn, book.count, book.title, book.author, book.publisher, book.publish_date, book.category)
        )
        db.commit()
        return "added"

def update_book(book):
    db = get_db()
    db.execute(
        """
        UPDATE book SET count=?, title=?, author=?, publisher=?, publish_date=?, category=?
        WHERE isbn=?
        """,
        (book.count, book.title, book.author, book.publisher, book.publish_date, book.category, book.isbn)
    )
    db.commit()
    return "updated"

def get_all_books():
    def count_none(book):
        count = 0
        if book.title is None:
            count += 1
        if book.author is None:
            count += 1
        if book.publish_date is None:
            count += 1
        if book.publisher is None:
            count += 1
        if book.category is None:
            count += 1
        return -count

    db = get_db()

    data = db.execute(
        """
        SELECT * FROM book
        """
    ).fetchall()

    books = []
    for data_row in data:
        book = Book(data_row["isbn"])
        book._manual_load(
            data_row["title"],
            publisher=data_row["publisher"],
            publish_date=data_row["publish_date"],
            author=data_row["author"],
            count=data_row["count"],
            category=data_row["category"] if data_row["category"] != "" else None
        )
        books.append(book)
    
    return sorted(books, key=count_none)

def get_categories():
    db = get_db()

    data = db.execute(
        """
        SELECT DISTINCT category FROM book
        """
    ).fetchall()

    return [row["category"] for row in data]