## Copyright © 2026 Olaf Kolkman
## SPDX-License-Identifier: GPL-3.0-or-later

from datetime import datetime, timezone
from uuid import uuid4

from backend.app.core.security import clean_url
from backend.app.database import get_connection

MAX_TAGS = 10


def normalize_tags(tags: list[str] | None) -> list[str]:
    normalized = []
    normalized_keys = set()
    for tag in tags or []:
        value = tag.strip()
        if value and not value.startswith('#'):
            value = f'#{value}'
        key = value.casefold()
        if value and key not in normalized_keys:
            normalized.append(value)
            normalized_keys.add(key)
    if len(normalized) > MAX_TAGS:
        raise ValueError(f'A link can have at most {MAX_TAGS} tags')
    return normalized


def save_link_tags(conn, link_id: str, tags: list[str]) -> None:
    canonical_tags = []
    for tag in tags:
        tag_row = conn.execute(
            'SELECT id FROM tags WHERE lower(name) = lower(?)',
            (tag,),
        ).fetchone()
        if tag_row is None:
            conn.execute(
                'INSERT INTO tags (id, name) VALUES (?, ?)',
                (str(uuid4()), tag),
            )
            tag_row = conn.execute('SELECT id FROM tags WHERE name = ?', (tag,)).fetchone()
        conn.execute(
            'INSERT OR IGNORE INTO link_tags (link_id, tag_id) VALUES (?, ?)',
            (link_id, tag_row['id']),
        )
        canonical_tags.append(conn.execute(
            'SELECT name FROM tags WHERE id = ?',
            (tag_row['id'],),
        ).fetchone()['name'])
    return canonical_tags


def get_link_tags(conn, link_id: str) -> list[str]:
    rows = conn.execute(
        '''
        SELECT tags.name FROM tags
        JOIN link_tags ON link_tags.tag_id = tags.id
        WHERE link_tags.link_id = ? ORDER BY tags.name
        ''',
        (link_id,),
    ).fetchall()
    return [row['name'] for row in rows]


def create_link(
    user_id: str,
    title: str,
    url: str,
    comment: str,
    timestamp: str | None,
    tags: list[str] | None = None,
):
    cleaned_url = clean_url(url)
    normalized_tags = normalize_tags(tags)
    created_at = datetime.now(timezone.utc).isoformat()
    record = {
        'id': str(uuid4()),
        'user_id': user_id,
        'title': title,
        'url': cleaned_url,
        'comment': comment,
        'timestamp': timestamp or created_at,
        'created_at': created_at,
        'updated_at': created_at,
        'is_public': 1,
    }
    with get_connection() as conn:
        conn.execute(
            '''
            INSERT INTO links (id, user_id, title, url, comment, timestamp, created_at, updated_at, is_public)
            VALUES (?, ?, ?, ?, ?, ?, ?, ?, ?)
            ''',
            (
                record['id'],
                record['user_id'],
                record['title'],
                record['url'],
                record['comment'],
                record['timestamp'],
                record['created_at'],
                record['updated_at'],
                record['is_public'],
            ),
        )
        stored_tags = save_link_tags(conn, record['id'], normalized_tags)
        conn.commit()
    record['tags'] = stored_tags
    return record


def list_public_links(username: str | None = None):
    with get_connection() as conn:
        rows = conn.execute(
            '''
            SELECT links.*, users.username, users.avatar_url, users.bio
            FROM links
            JOIN users ON users.id = links.user_id
            WHERE links.is_public = 1
              AND (? IS NULL OR users.username = ?)
            ORDER BY created_at DESC
            ''',
            (username, username),
        ).fetchall()
        records = [dict(row) for row in rows]
        for record in records:
            record['tags'] = get_link_tags(conn, record['id'])
    return records


def update_link(
    link_id: str,
    user_id: str,
    title: str,
    url: str,
    comment: str,
    tags: list[str] | None = None,
):
    cleaned_url = clean_url(url)
    normalized_tags = normalize_tags(tags)
    with get_connection() as conn:
        cursor = conn.execute(
            '''
            UPDATE links
            SET title = ?, url = ?, comment = ?, updated_at = CURRENT_TIMESTAMP
            WHERE id = ? AND user_id = ?
            ''',
            (title, cleaned_url, comment, link_id, user_id),
        )
        if cursor.rowcount == 0:
            return None
        conn.execute('DELETE FROM link_tags WHERE link_id = ?', (link_id,))
        stored_tags = save_link_tags(conn, link_id, normalized_tags)
        conn.commit()
        row = conn.execute('SELECT * FROM links WHERE id = ?', (link_id,)).fetchone()
        record = dict(row)
        record['tags'] = stored_tags
    return record


def list_public_users():
    with get_connection() as conn:
        rows = conn.execute(
            'SELECT username FROM users ORDER BY username'
        ).fetchall()
    return [row['username'] for row in rows]


def list_tags():
    with get_connection() as conn:
        rows = conn.execute('SELECT name FROM tags ORDER BY name').fetchall()
    tags = []
    seen = set()
    for row in rows:
        if row['name'].casefold() not in seen:
            tags.append(row['name'])
            seen.add(row['name'].casefold())
    return tags


def list_user_labels(user_id: str):
    with get_connection() as conn:
        rows = conn.execute(
            'SELECT id, name, created_by FROM tags WHERE created_by = ? ORDER BY name',
            (user_id,),
        ).fetchall()
    return [dict(row) for row in rows]


def create_label(user_id: str, name: str):
    normalized = normalize_tags([name])
    label = normalized[0] if normalized else ''
    if not label:
        raise ValueError('Label cannot be empty')
    with get_connection() as conn:
        existing = conn.execute(
            'SELECT id FROM tags WHERE lower(name) = lower(?)', (label,)
        ).fetchone()
        if existing:
            raise ValueError('Label already exists')
        label_id = str(uuid4())
        conn.execute(
            'INSERT INTO tags (id, name, created_by) VALUES (?, ?, ?)',
            (label_id, label, user_id),
        )
        conn.commit()
    return {'id': label_id, 'name': label, 'created_by': user_id}


def update_label(label_id: str, user_id: str, name: str):
    normalized = normalize_tags([name])
    if not normalized:
        raise ValueError('Label cannot be empty')
    with get_connection() as conn:
        current = conn.execute(
            'SELECT id, name, created_by FROM tags WHERE id = ?', (label_id,)
        ).fetchone()
        if current is None or current['created_by'] != user_id:
            return None
        duplicate = conn.execute(
            'SELECT id FROM tags WHERE lower(name) = lower(?) AND id != ?',
            (normalized[0], label_id),
        ).fetchone()
        if duplicate:
            raise ValueError('Label already exists')
        conn.execute('UPDATE tags SET name = ? WHERE id = ?', (normalized[0], label_id))
        conn.commit()
    return {'id': label_id, 'name': normalized[0], 'created_by': user_id}


def delete_label(label_id: str, user_id: str | None = None, is_admin: bool = False):
    with get_connection() as conn:
        current = conn.execute(
            'SELECT id, created_by FROM tags WHERE id = ?', (label_id,)
        ).fetchone()
        if current is None or (not is_admin and current['created_by'] != user_id):
            return False
        conn.execute('DELETE FROM tags WHERE id = ?', (label_id,))
        conn.commit()
    return True