-- AP A1.1 — CadenceInstance (minimal): eine offene Instanz pro Recurring, Tages-Tracking

CREATE TABLE cadence_instances (
    id UUID PRIMARY KEY DEFAULT gen_random_uuid(),
    tenant_id UUID NOT NULL REFERENCES tenants(id) ON DELETE CASCADE,
    recurring_element_id UUID NOT NULL REFERENCES recurring_elements(id) ON DELETE CASCADE,
    status VARCHAR(32) NOT NULL DEFAULT 'open'
        CHECK (status IN ('open', 'completed')),
    due_at TIMESTAMPTZ NOT NULL,
    completed_at TIMESTAMPTZ NULL,
    measurement_note TEXT NOT NULL DEFAULT '',
    created_at TIMESTAMPTZ NOT NULL DEFAULT NOW(),
    updated_at TIMESTAMPTZ NOT NULL DEFAULT NOW()
);

CREATE INDEX idx_cadence_instances_tenant_recurring
    ON cadence_instances(tenant_id, recurring_element_id);

CREATE INDEX idx_cadence_instances_open_due
    ON cadence_instances(tenant_id, due_at)
    WHERE status = 'open';

CREATE UNIQUE INDEX idx_cadence_instances_one_open_per_recurring
    ON cadence_instances(recurring_element_id)
    WHERE status = 'open';