CREATE TABLE IF NOT EXISTS conversations (
    id UUID PRIMARY KEY DEFAULT uuidv7(),
    user_id UUID NOT NULL REFERENCES users(id) ON DELETE CASCADE,
    mod_id UUID REFERENCES users(id) ON DELETE SET NULL,
    status SMALLINT NOT NULL DEFAULT 1, -- 1: waiting, 2: active, 3: resolved
    closed_at TIMESTAMPTZ,
    created_at TIMESTAMPTZ NOT NULL DEFAULT NOW(),
    updated_at TIMESTAMPTZ NOT NULL DEFAULT NOW()
);

CREATE INDEX idx_conversations_user_id ON conversations (user_id);
CREATE INDEX idx_conversations_mod_id ON conversations (mod_id);
CREATE INDEX idx_conversations_status ON conversations (status);

CREATE TABLE IF NOT EXISTS messages (
    id UUID PRIMARY KEY DEFAULT uuidv7(),
    conversation_id UUID NOT NULL REFERENCES conversations(id) ON DELETE CASCADE,
    sender_id UUID NOT NULL REFERENCES users(id) ON DELETE CASCADE,
    content TEXT NOT NULL,
    created_at TIMESTAMPTZ NOT NULL DEFAULT NOW()
);

CREATE INDEX idx_messages_conversation_id ON messages (conversation_id);
CREATE INDEX idx_messages_created_at ON messages (created_at DESC);

CREATE TABLE IF NOT EXISTS chatbot_histories (
    id UUID PRIMARY KEY DEFAULT uuidv7(),
    user_id UUID NOT NULL REFERENCES users(id) ON DELETE CASCADE,
    question TEXT NOT NULL,
    answer TEXT NOT NULL,
    created_at TIMESTAMPTZ NOT NULL DEFAULT NOW()
);

CREATE INDEX idx_chatbot_histories_user_id ON chatbot_histories (user_id, created_at DESC);