nikon4uk / py-chat-queries

Chat queries

• Read the guideline before start

Consider the following models:

1. User model with the following fields:
   • username - user's username
   • first_name - user's first_name
   • last_name - user's last_name
   • bio - any details such as age, country ot city
2. Chat model:
   • title - chat title
   • description - a short chat description
   • users - many-to-many field, chat participants
3. Message model:
   • text - message content
   • sent - time when message was sent
   • is_delivered - boolean value, True if message was delivered successfully
   • user - foreign key, points to the sender
   • chat - foreign key, points to the chat where the message was sent

Use the following command to load prepared data from fixture to test and debug your code:

python app/manage.py loaddata chat_data.json

Write some functions which should perform different queries on this domain:

1. get_messages_that_contain_word - function should return list of messages that contains word in its text. Use case-insensitive containment test.

2. get_untitled_chats - should return chats which title starts with "Untitled" string. For example, chats Untitled, Untitled(1), Untitled(2) should be considered as untitled.

3. get_users_who_sent_messages_in_2015 - should return list of tuples with first_name and last_name of users who sent messages in 2015. Use values_list.

4. get_actual_chats - should return list of the actual chats. Chats is actual when it is a message in it that was sent no later than 2020.

5. get_count_messages_sent_by_first_name - should return a list of Messages which text contains author's first_name.

6. get_users_who_sent_messages_starting_with_m_or_a - should return a list of users who sent at least one message starts with a or m. Use case-insensitive test.

7. get_delivered_or_admin_messages - should return a list of messages that was delivered or sent by a user whose username starts with "admin" prefix.

8. get_messages_sent_by_first_name - should return number of messages sent by all users with given first_name

9. get_top_users_by_number_of_the_messages - should return top-3 users by number of sent messages. They should have an additional field num_messages that should be equal to this number.

users = get_top_users_by_number_of_the_messages()
print(
    users[0].username,  # "user1"
    users[0].num_messages  # 7
)

Note: Use list() to convert QuerySet to the list.

Also, write two more functions which should user select_related and prefetch_related methods to decrease the number of queries to the database.

1. get_last_5_messages_dicts - should return list that contains five last messages. Each message should be represented as a dict with the following fields:
   • "from" - a username of the sender
   • "text" - text of the message

messages = get_last_5_messages_dicts()
print(message[3]) # {"from": "max", text: "Hello, mates!"}

2. get_chat_dicts - should return a list of chats represented by dicts. Each dict should contain the following fields:
   • "id" - chat id
   • "title" - chat title
   • "users" - a list of the participants' names

chats = get_chat_dicts()
# print(chats[0])
# {
#    "id": 1,
#    "title": "My family",
#    "participants": ["mom", "dad", "me"]
# }