-- Agent variant configurations: alternative model/prompt/parameter sets per agent.
-- Each agent can have multiple variants for A/B testing, model comparison,
-- and iterative prompt engineering. At most one variant per agent is active.

CREATE TABLE IF NOT EXISTS agent_variants (
    id UUID PRIMARY KEY DEFAULT gen_random_uuid(),
    agent_id UUID NOT NULL REFERENCES ai_agents(id) ON DELETE CASCADE,
    variant_name VARCHAR(200) NOT NULL,
    variant_slug VARCHAR(200) NOT NULL,
    description TEXT NOT NULL DEFAULT '',
    model_provider VARCHAR(50) NOT NULL DEFAULT 'ollama',
    model_name VARCHAR(200) NOT NULL,
    system_prompt TEXT NOT NULL DEFAULT '',
    user_prompt_template TEXT NOT NULL DEFAULT '',
    prompt_version VARCHAR(100) NOT NULL DEFAULT '',
    temperature FLOAT DEFAULT 0.0,
    max_tokens INTEGER DEFAULT 32768,
    context_window INTEGER DEFAULT 0,       -- Ollama num_ctx; 0 = use model default
    input_token_limit INTEGER DEFAULT 0,    -- max input tokens before truncation; 0 = no limit
    token_budget INTEGER DEFAULT 0,         -- total tokens per hour; 0 = unlimited
    timeout_seconds INTEGER DEFAULT 120,
    max_retries INTEGER DEFAULT 2,
    is_active BOOLEAN NOT NULL DEFAULT FALSE,
    created_at TIMESTAMPTZ NOT NULL DEFAULT NOW(),
    updated_at TIMESTAMPTZ NOT NULL DEFAULT NOW()
);

-- Each agent can have many variants, but variant slugs must be unique per agent.
CREATE UNIQUE INDEX IF NOT EXISTS idx_agent_variants_slug
    ON agent_variants(agent_id, variant_slug);

-- At most one active variant per agent (database-enforced invariant).
CREATE UNIQUE INDEX IF NOT EXISTS idx_agent_variants_active
    ON agent_variants(agent_id) WHERE is_active = TRUE;

-- Fast lookup by agent.
CREATE INDEX IF NOT EXISTS idx_agent_variants_agent
    ON agent_variants(agent_id);

-- Add variant_id to performance log for per-variant attribution.
-- Nullable so existing rows are unaffected; ON DELETE SET NULL preserves
-- historical log entries when a variant is removed.
ALTER TABLE agent_performance_log
    ADD COLUMN IF NOT EXISTS variant_id UUID REFERENCES agent_variants(id) ON DELETE SET NULL;

CREATE INDEX IF NOT EXISTS idx_agent_perf_variant
    ON agent_performance_log(variant_id, recorded_at DESC);