#!/usr/bin/env python3
"""Модуль для работы с сериями"""
from db_utils import get_cursor


def get_series_by_letter(letter=''):
    """Возвращает серии по первой букве"""
    conn, cur = get_cursor()

    if letter:
        cur.execute("""
            SELECT s.id, s.name, s.name_hash,
                   COUNT(DISTINCT b.id) as books_count
            FROM series s
            LEFT JOIN books b ON b.series_id = s.id
            WHERE s.name ILIKE %s
            GROUP BY s.id, s.name, s.name_hash
            ORDER BY s.name
            LIMIT 100
        """, (letter + '%',))
    else:
        cur.execute("""
            SELECT DISTINCT lower(substring(name, 1, 1)) as letter,
                   COUNT(*) as cnt
            FROM series
            WHERE name ~ '^[а-яА-Яa-zA-Z]'
            GROUP BY lower(substring(name, 1, 1))
            ORDER BY letter
        """)

    result = cur.fetchall()
    conn.close()
    return result


def get_series_by_hash(series_hash):
    """Возвращает серию по хешу"""
    conn, cur = get_cursor()

    cur.execute("""
        SELECT id, name, name_hash
        FROM series
        WHERE name_hash = %s
    """, (series_hash,))

    series = cur.fetchone()
    conn.close()
    return series


def get_series_books(series_id):
    """Возвращает все книги серии"""
    conn, cur = get_cursor()

    cur.execute("""
        SELECT b.id, b.title, b.language, b.series_number,
               string_agg(DISTINCT a.full_name, ', ' ORDER BY ba.position) as authors
        FROM books b
        JOIN book_authors ba ON ba.book_id = b.id
        JOIN authors a ON a.id = ba.author_id
        WHERE b.series_id = %s
        GROUP BY b.id, b.title, b.language, b.series_number
        ORDER BY b.series_number NULLS LAST, b.title
    """, (series_id,))

    books = cur.fetchall()
    conn.close()
    return books