-- Conversations table for chat persistence
CREATE TABLE IF NOT EXISTS conversations (
    id              UUID PRIMARY KEY DEFAULT gen_random_uuid(),
    project_id      TEXT NOT NULL,
    title           TEXT NOT NULL,
    created_at      TIMESTAMPTZ NOT NULL DEFAULT NOW(),
    updated_at      TIMESTAMPTZ NOT NULL DEFAULT NOW(),
    last_message_at TIMESTAMPTZ
);

-- Messages table for conversation history
CREATE TABLE IF NOT EXISTS messages (
    id              UUID PRIMARY KEY DEFAULT gen_random_uuid(),
    conversation_id UUID NOT NULL REFERENCES conversations(id) ON DELETE CASCADE,
    role            VARCHAR(20) NOT NULL,  -- 'user', 'assistant', 'system'
    content         TEXT NOT NULL,
    created_at      TIMESTAMPTZ NOT NULL DEFAULT NOW()
);

-- Indexes for efficient querying
CREATE INDEX IF NOT EXISTS idx_conversations_project
    ON conversations(project_id, last_message_at DESC NULLS LAST);

CREATE INDEX IF NOT EXISTS idx_messages_conversation
    ON messages(conversation_id, created_at ASC);

-- Update trigger for conversations.updated_at
CREATE OR REPLACE FUNCTION update_conversations_updated_at()
RETURNS TRIGGER AS $$
BEGIN
    NEW.updated_at = NOW();
    RETURN NEW;
END;
$$ LANGUAGE plpgsql;

CREATE TRIGGER conversations_updated_at
    BEFORE UPDATE ON conversations
    FOR EACH ROW
    EXECUTE FUNCTION update_conversations_updated_at();

-- Trigger to update last_message_at when a message is added
CREATE OR REPLACE FUNCTION update_conversation_last_message()
RETURNS TRIGGER AS $$
BEGIN
    UPDATE conversations
    SET last_message_at = NEW.created_at
    WHERE id = NEW.conversation_id;
    RETURN NEW;
END;
$$ LANGUAGE plpgsql;

CREATE TRIGGER message_updates_conversation
    AFTER INSERT ON messages
    FOR EACH ROW
    EXECUTE FUNCTION update_conversation_last_message();

COMMENT ON TABLE conversations IS 'Chat conversations for project architect service';
COMMENT ON TABLE messages IS 'Messages within conversations';