-- Share links table: enables students to submit TFEs via unique, optional-password-protected URLs
CREATE TABLE IF NOT EXISTS share_links (
    id INTEGER PRIMARY KEY AUTOINCREMENT,
    slug TEXT NOT NULL UNIQUE,               -- Format: YYYYMMDD-<random>, e.g. 20260416-a3f9k2
    password_hash TEXT,                      -- bcrypt hash; NULL = no password required
    is_active INTEGER NOT NULL DEFAULT 1,    -- 1 = active, 0 = disabled
    usage_count INTEGER NOT NULL DEFAULT 0,  -- Number of successful submissions via this link
    created_by INTEGER NOT NULL,             -- admin user ID (references admin_sessions or admin_users)
    created_at DATETIME DEFAULT CURRENT_TIMESTAMP,
    expires_at DATETIME                      -- NULL = never expires
);

CREATE INDEX IF NOT EXISTS idx_share_links_slug ON share_links(slug);
CREATE INDEX IF NOT EXISTS idx_share_links_active ON share_links(is_active);