-- Cipher schema. The server is a "dumb" key directory + relay.
-- It stores ONLY public keys and ciphertext. Private keys never leave the client.

-- A user account. Identified by username; discoverable by other users.
CREATE TABLE users (
  id            TEXT PRIMARY KEY,          -- uuid
  username      TEXT NOT NULL UNIQUE,      -- lowercase handle, e.g. "alice"
  display_name  TEXT NOT NULL,
  pw_hash       TEXT NOT NULL,             -- PBKDF2(password) — account auth only, unrelated to E2E keys
  pw_salt       TEXT NOT NULL,
  created_at    INTEGER NOT NULL
);
CREATE INDEX idx_users_username ON users(username);

-- A device belonging to a user. Each device has its own Signal identity.
-- Multi-device: a user may register several (phone, desktop) via QR linking.
CREATE TABLE devices (
  id                 TEXT PRIMARY KEY,     -- uuid
  user_id            TEXT NOT NULL REFERENCES users(id) ON DELETE CASCADE,
  registration_id    INTEGER NOT NULL,     -- Signal registrationId
  identity_key       TEXT NOT NULL,        -- base64 public identity key
  signed_prekey_id   INTEGER NOT NULL,
  signed_prekey_pub  TEXT NOT NULL,        -- base64
  signed_prekey_sig  TEXT NOT NULL,        -- base64 signature over signed_prekey_pub
  created_at         INTEGER NOT NULL,
  last_seen          INTEGER NOT NULL
);
CREATE INDEX idx_devices_user ON devices(user_id);

-- One-time prekeys. Server hands one out per session-init request, then deletes it.
CREATE TABLE one_time_prekeys (
  device_id   TEXT NOT NULL REFERENCES devices(id) ON DELETE CASCADE,
  prekey_id   INTEGER NOT NULL,
  prekey_pub  TEXT NOT NULL,               -- base64
  PRIMARY KEY (device_id, prekey_id)
);
CREATE INDEX idx_otk_device ON one_time_prekeys(device_id);

-- Bearer auth sessions (account-level). Token proves control of the account.
CREATE TABLE sessions (
  token       TEXT PRIMARY KEY,            -- random opaque token
  user_id     TEXT NOT NULL REFERENCES users(id) ON DELETE CASCADE,
  device_id   TEXT NOT NULL REFERENCES devices(id) ON DELETE CASCADE,
  created_at  INTEGER NOT NULL,
  expires_at  INTEGER NOT NULL
);
CREATE INDEX idx_sessions_user ON sessions(user_id);

-- Web Push subscriptions for wake-on-message notifications (endpoint is opaque).
CREATE TABLE push_subs (
  device_id   TEXT PRIMARY KEY REFERENCES devices(id) ON DELETE CASCADE,
  endpoint    TEXT NOT NULL,
  p256dh      TEXT NOT NULL,
  auth        TEXT NOT NULL,
  created_at  INTEGER NOT NULL
);