"""Chapter-related queries.

Functions take an explicit sqlite3 connection with row_factory=sqlite3.Row
and return plain dicts. No Flask imports.
"""

from datetime import datetime

CHAPTER_COLUMNS = (
    "id, novel_id, volume, chapter_number, title, outline, content, "
    "word_count, status, created_at, updated_at"
)

ALLOWED_UPDATE_FIELDS = {
    "title",
    "outline",
    "content",
    "word_count",
    "status",
    "volume",
    "chapter_number",
}


def _rows(cur):
    return [dict(row) for row in cur.fetchall()]


def _now():
    return datetime.now().isoformat(timespec="seconds")


def list_chapters(db, novel_id):
    """All chapters of a novel ordered by volume, chapter_number."""
    return _rows(
        db.execute(
            f"SELECT {CHAPTER_COLUMNS} FROM chapters WHERE novel_id = ? "
            "ORDER BY volume, chapter_number",
            (novel_id,),
        )
    )


def get_chapter(db, chapter_id):
    """Single chapter row as dict, or None."""
    row = db.execute(
        f"SELECT {CHAPTER_COLUMNS} FROM chapters WHERE id = ?", (chapter_id,)
    ).fetchone()
    return dict(row) if row is not None else None


def get_chapter_by_number(db, novel_id, volume, chapter_number):
    """Chapter identified by novel + volume + chapter_number, or None."""
    row = db.execute(
        f"SELECT {CHAPTER_COLUMNS} FROM chapters "
        "WHERE novel_id = ? AND volume = ? AND chapter_number = ?",
        (novel_id, volume, chapter_number),
    ).fetchone()
    return dict(row) if row is not None else None


def create_chapter(db, novel_id, volume, chapter_number, title=None, outline=None, status="pending"):
    """Insert a new chapter and return its id."""
    now = _now()
    cur = db.execute(
        "INSERT INTO chapters (novel_id, volume, chapter_number, title, outline, status, created_at, updated_at) "
        "VALUES (?, ?, ?, ?, ?, ?, ?, ?)",
        (novel_id, volume, chapter_number, title, outline, status, now, now),
    )
    db.commit()
    return cur.lastrowid


def update_chapter(db, chapter_id, **fields):
    """Update allowed chapter fields."""
    updates = {k: v for k, v in fields.items() if k in ALLOWED_UPDATE_FIELDS}
    if not updates:
        return
    updates["updated_at"] = _now()
    assignments = ", ".join(f"{key} = ?" for key in updates)
    db.execute(
        f"UPDATE chapters SET {assignments} WHERE id = ?",
        (*updates.values(), chapter_id),
    )
    db.commit()


def get_previous_chapters(db, novel_id, volume, chapter_number, limit=2):
    """Chapters strictly before (volume, chapter_number), newest first, with content."""
    return _rows(
        db.execute(
            f"SELECT {CHAPTER_COLUMNS} FROM chapters "
            "WHERE novel_id = ? AND (volume < ? OR (volume = ? AND chapter_number < ?)) "
            "ORDER BY volume DESC, chapter_number DESC LIMIT ?",
            (novel_id, volume, volume, chapter_number, limit),
        )
    )


def list_done_chapters(db, novel_id, limit=20):
    """Done chapters, newest first."""
    return _rows(
        db.execute(
            f"SELECT {CHAPTER_COLUMNS} FROM chapters "
            "WHERE novel_id = ? AND status = 'done' "
            "ORDER BY volume DESC, chapter_number DESC LIMIT ?",
            (novel_id, limit),
        )
    )