CREATE TABLE IF NOT EXISTS ai_conversation (
    id UUID PRIMARY KEY DEFAULT gen_random_uuid(),
    user_id UUID NOT NULL,
    project_id UUID,
    scope VARCHAR(16) NOT NULL,
    title VARCHAR(512),
    model VARCHAR(128) NOT NULL DEFAULT 'gpt-4',
    model_config JSONB,
    status VARCHAR(32) NOT NULL DEFAULT 'active',
    root_message_id UUID,
    fork_count INT NOT NULL DEFAULT 0,
    is_shared BOOLEAN NOT NULL DEFAULT false,
    message_count INT NOT NULL DEFAULT 0,
    token_usage_total INT,
    created_at TIMESTAMPTZ NOT NULL DEFAULT NOW(),
    updated_at TIMESTAMPTZ NOT NULL DEFAULT NOW()
);

CREATE INDEX IF NOT EXISTS idx_ai_conv_user_id ON ai_conversation (user_id);
CREATE INDEX IF NOT EXISTS idx_ai_conv_project_id ON ai_conversation (project_id);
CREATE INDEX IF NOT EXISTS idx_ai_conv_scope ON ai_conversation (scope);
CREATE INDEX IF NOT EXISTS idx_ai_conv_user_created ON ai_conversation (user_id, created_at DESC);
CREATE INDEX IF NOT EXISTS idx_ai_conv_project_created ON ai_conversation (project_id, created_at DESC);