QUICKSIR

*Buyer–Seller Chat
Enable real-time or near real-time communication between buyers and sellers for a specific ad.

*Message Delivery
Ensure that messages (text or image) are correctly sent, stored, and displayed in the correct order.

*Read / Unread Status
Track whether a message has been read by the receiver to improve communication clarity.

***Table: chats

id-INT (PK)-Unique chat ID

ad_id-INT (FK)-Ad related to the chat

buyer_id-INT (FK)-User interested in the ad

seller_id-INT (FK)-Owner of the ad

last_message_at-DATETIME-Timestamp of last message

*Each record represents one conversation for a specific ad.

*Prevents multiple chat threads for the same buyer and seller.

*last_message_at helps in sorting recent chats.

***Table: chat_messages

*id-INT (PK)-Unique message ID

*chat_id-INT (FK)-Related chat

*sender_id-INT (FK)-Message sender

*message_type-ENUM-text / image

*message_text-TEXT-Message content

*created_at-DATETIME-Message sent time

*Stores individual messages in a chat.

*message_type differentiates between text and image messages.

*Messages are always linked to a valid chat using chat_id.

****Validations

*A chat can be initiated only after an ad is published.

*A chat is allowed only between the ad owner (seller) and an interested user (buyer).

*A unique chat must exist for each ad–buyer–seller combination.

*Only the sender or receiver can view messages in a chat.

*Messages must be displayed in chronological order.

*Empty messages are not allowed.

*Only valid file types (e.g., JPG, PNG) are allowed for image messages.

*Deleted or blocked users cannot send messages.