-- Ported from the SQLite migration of the same number. Same version, same
-- meaning, different spelling: SQLite's storage classes and PostgreSQL's types
-- do not line up, and one shared file would be a promise neither could keep.
--
-- Times are milliseconds since the epoch in BIGINT, exactly as in SQLite,
-- rather than TIMESTAMPTZ. The Go code reads and writes int64 milliseconds
-- everywhere; converting here would mean two time representations in one
-- codebase, and the conversion would be the thing that is wrong at 2am.

-- Server-side conversations, so a thread can continue on a different model
-- than it started on.
--
-- Off unless a project turns it on. Until this migration ran, llmgw stored no
-- message content anywhere — usage rows carry token counts and costs, never
-- text — and that stays true for every project that does not ask. An on-prem
-- gateway keeping nothing anyone typed is much easier to put in front of a
-- team than one keeping everything, so storing is a choice a project makes
-- rather than a default it discovers.

-- retention_hours is the switch and the limit at once. NULL means this project
-- stores nothing, which is every project that existed before this and every
-- one created since without asking.
--
-- One column rather than a boolean and a duration: a thread store with no
-- expiry is a transcript of everything a team ever typed, kept forever by
-- omission. Turning it on therefore requires saying for how long.
ALTER TABLE projects ADD COLUMN thread_retention_hours BIGINT;

CREATE TABLE threads (
  id         TEXT PRIMARY KEY,
  -- Scoped to a project, and checked on every read. Thread ids are opaque, but
  -- an unguessable id is a secret and secrets leak into logs, shell history
  -- and bug reports; the scope is what makes a leaked id useless to someone
  -- outside the project.
  project_id TEXT NOT NULL REFERENCES projects(id) ON DELETE CASCADE,
  created_at BIGINT NOT NULL,
  -- Touched on every append, so retention measures idleness rather than age:
  -- expiring a conversation someone is still having would be a strange way to
  -- keep a promise about storage.
  updated_at BIGINT NOT NULL
);
CREATE INDEX threads_by_project ON threads(project_id);
CREATE INDEX threads_by_updated ON threads(updated_at);

CREATE TABLE thread_messages (
  thread_id TEXT NOT NULL REFERENCES threads(id) ON DELETE CASCADE,
  -- Position rather than a timestamp, because order is the point and two
  -- messages can share a millisecond.
  seq     BIGINT NOT NULL,
  role    TEXT NOT NULL,
  content TEXT NOT NULL,
  -- Which model produced an assistant turn. A thread that moved between models
  -- otherwise reads as one voice, and when the answers disagree that is the
  -- first thing anyone wants to know.
  model TEXT,
  PRIMARY KEY (thread_id, seq)
);