from django.db import connection

from zerver.models import UserProfile, Recipient

from typing import Any, Dict, List, Tuple

def generate_topic_history_from_db_rows(rows: List[Tuple[str, int]]) -> List[Dict[str, Any]]:
    canonical_topic_names = {}  # type: Dict[str, Tuple[int, str]]

    # Sort rows by max_message_id so that if a topic
    # has many different casings, we use the most
    # recent row.
    rows = sorted(rows, key=lambda tup: tup[1])

    for (topic_name, max_message_id) in rows:
        canonical_name = topic_name.lower()
        canonical_topic_names[canonical_name] = (max_message_id, topic_name)

    history = []
    for canonical_topic, (max_message_id, topic_name) in canonical_topic_names.items():
        history.append(dict(
            name=topic_name,
            max_id=max_message_id)
        )
    return sorted(history, key=lambda x: -x['max_id'])

def get_topic_history_for_stream(user_profile: UserProfile,
                                 recipient: Recipient,
                                 public_history: bool) -> List[Dict[str, Any]]:
    cursor = connection.cursor()
    if public_history:
        query = '''
        SELECT
            "zerver_message"."subject" as topic,
            max("zerver_message".id) as max_message_id
        FROM "zerver_message"
        WHERE (
            "zerver_message"."recipient_id" = %s
        )
        GROUP BY (
            "zerver_message"."subject"
        )
        ORDER BY max("zerver_message".id) DESC
        '''
        cursor.execute(query, [recipient.id])
    else:
        query = '''
        SELECT
            "zerver_message"."subject" as topic,
            max("zerver_message".id) as max_message_id
        FROM "zerver_message"
        INNER JOIN "zerver_usermessage" ON (
            "zerver_usermessage"."message_id" = "zerver_message"."id"
        )
        WHERE (
            "zerver_usermessage"."user_profile_id" = %s AND
            "zerver_message"."recipient_id" = %s
        )
        GROUP BY (
            "zerver_message"."subject"
        )
        ORDER BY max("zerver_message".id) DESC
        '''
        cursor.execute(query, [user_profile.id, recipient.id])
    rows = cursor.fetchall()
    cursor.close()

    return generate_topic_history_from_db_rows(rows)

def get_topic_history_for_web_public_stream(recipient: Recipient) -> List[Dict[str, Any]]:
    cursor = connection.cursor()
    query = '''
    SELECT
        "zerver_message"."subject" as topic,
        max("zerver_message".id) as max_message_id
    FROM "zerver_message"
    WHERE (
        "zerver_message"."recipient_id" = %s
    )
    GROUP BY (
        "zerver_message"."subject"
    )
    ORDER BY max("zerver_message".id) DESC
    '''
    cursor.execute(query, [recipient.id])
    rows = cursor.fetchall()
    cursor.close()

    return generate_topic_history_from_db_rows(rows)