-- Cohorts table
CREATE TABLE IF NOT EXISTS cohorts (
    id UUID PRIMARY KEY DEFAULT gen_random_uuid(),
    organization_id UUID NOT NULL,
    name TEXT NOT NULL,
    description TEXT,
    created_at TIMESTAMPTZ NOT NULL DEFAULT NOW(),
    updated_at TIMESTAMPTZ NOT NULL DEFAULT NOW(),
    CONSTRAINT cohorts_organization_id_fkey FOREIGN KEY (organization_id) REFERENCES organizations(id) ON DELETE CASCADE
);

-- User-Cohort relationship table (M:N)
CREATE TABLE IF NOT EXISTS user_cohorts (
    id UUID PRIMARY KEY DEFAULT gen_random_uuid(),
    cohort_id UUID NOT NULL,
    user_id UUID NOT NULL,
    assigned_at TIMESTAMPTZ NOT NULL DEFAULT NOW(),
    CONSTRAINT user_cohorts_cohort_id_fkey FOREIGN KEY (cohort_id) REFERENCES cohorts(id) ON DELETE CASCADE,
    CONSTRAINT user_cohorts_user_id_fkey FOREIGN KEY (user_id) REFERENCES users(id) ON DELETE CASCADE,
    CONSTRAINT user_cohorts_unique UNIQUE (cohort_id, user_id)
);

-- Indexes for performance
CREATE INDEX IF NOT EXISTS idx_cohorts_organization_id ON cohorts(organization_id);
CREATE INDEX IF NOT EXISTS idx_user_cohorts_cohort_id ON user_cohorts(cohort_id);
CREATE INDEX IF NOT EXISTS idx_user_cohorts_user_id ON user_cohorts(user_id);