.

migrations/20250510184011_channel_message.sql

@@ -0,0 +1,105 @@
+CREATE TABLE IF NOT EXISTS "channel"
+(
+    "id"        UUID    NOT NULL PRIMARY KEY DEFAULT uuid_generate_v7(),
+    "name"      VARCHAR NOT NULL,
+    "type"      INT2    NOT NULL,
+    "position"  INT2    NOT NULL,
+    "server_id" UUID REFERENCES "server" ("id") ON DELETE CASCADE,      -- only for server channels
+    "parent"    UUID    REFERENCES "channel" ("id") ON DELETE SET NULL, -- only for server channels
+    "owner_id"  UUID    REFERENCES "user" ("id") ON DELETE SET NULL     -- only for group channels
+);
+
+-- only for dm or group channels
+CREATE TABLE IF NOT EXISTS "channel_recipient"
+(
+    "channel_id" UUID NOT NULL REFERENCES "channel" ("id") ON DELETE CASCADE,
+    "user_id"    UUID NOT NULL REFERENCES "user" ("id") ON DELETE CASCADE,
+    PRIMARY KEY ("channel_id", "user_id")
+);
+
+CREATE TABLE IF NOT EXISTS "message"
+(
+    "id"         UUID NOT NULL PRIMARY KEY DEFAULT uuid_generate_v7(),
+    "author_id"  UUID NOT NULL REFERENCES "user" ("id") ON DELETE CASCADE,
+    "channel_id" UUID NOT NULL REFERENCES "channel" ("id") ON DELETE CASCADE,
+    "content"    TEXT NOT NULL
+);
+
+CREATE TABLE IF NOT EXISTS "message_attachment"
+(
+    "message_id" UUID NOT NULL REFERENCES "message" ON DELETE CASCADE,
+    "file_id"    UUID NOT NULL REFERENCES "file" ON DELETE CASCADE,
+    "order"      INT2 NOT NULL,
+    PRIMARY KEY ("message_id", "file_id")
+);
+
+ALTER TABLE "channel"
+    ADD COLUMN "last_message_id" UUID REFERENCES "message" ("id") ON DELETE SET NULL;
+
+
+CREATE OR REPLACE FUNCTION create_dm_channel(
+    user1_id UUID,
+    user2_id UUID,
+    channel_type INT2
+)
+    RETURNS UUID
+    LANGUAGE plpgsql
+AS
+$$
+DECLARE
+    new_channel_id UUID;
+    channel_name   VARCHAR;
+BEGIN
+    -- Validate parameters
+    IF user1_id IS NULL OR user2_id IS NULL THEN
+        RAISE EXCEPTION 'Both user IDs must be provided';
+    END IF;
+
+    IF user1_id = user2_id THEN
+        RAISE EXCEPTION 'Cannot create a DM channel with the same user';
+    END IF;
+
+-- Check if users exist
+    IF NOT exists (SELECT 1 FROM "user" WHERE id = user1_id) OR
+       NOT exists (SELECT 1 FROM "user" WHERE id = user2_id) THEN
+        RAISE EXCEPTION 'One or both users do not exist';
+    END IF;
+
+-- Check if DM already exists between these users
+    IF exists (SELECT 1
+               FROM channel c
+                        JOIN channel_recipient cr1 ON c.id = cr1.channel_id AND cr1.user_id = user1_id
+                        JOIN channel_recipient cr2 ON c.id = cr2.channel_id AND cr2.user_id = user2_id
+               WHERE c.type = channel_type
+                 AND (SELECT count(*) FROM channel_recipient WHERE channel_id = c.id) = 2) THEN
+        -- Find and return the existing channel ID
+        SELECT c.id
+        INTO new_channel_id
+        FROM channel c
+                 JOIN channel_recipient cr1 ON c.id = cr1.channel_id AND cr1.user_id = user1_id
+                 JOIN channel_recipient cr2 ON c.id = cr2.channel_id AND cr2.user_id = user2_id
+        WHERE c.type = channel_type
+          AND (SELECT count(*) FROM channel_recipient WHERE channel_id = c.id) = 2
+        LIMIT 1;
+
+        RAISE NOTICE 'DM channel already exists between these users with ID: %', new_channel_id;
+        RETURN new_channel_id;
+    END IF;
+
+-- Generate channel name (conventionally uses user IDs in DMs)
+    channel_name := concat(user1_id, '-', user2_id);
+
+    -- Create new channel
+    INSERT INTO "channel" ("name", "type", "position")
+    VALUES (channel_name, channel_type, 0)
+    RETURNING id INTO new_channel_id;
+
+-- Add both users as recipients
+    INSERT INTO "channel_recipient" ("channel_id", "user_id")
+    VALUES (new_channel_id, user1_id),
+           (new_channel_id, user2_id);
+
+    RAISE NOTICE 'DM channel created with ID: %', new_channel_id;
+    RETURN new_channel_id;
+END;
+$$;