-- SRS schema. D1 owns SRS state (stage, next_review, attempts, gates,
-- boosts); GitHub issues own the catalog columns, reconciled nightly.
CREATE TABLE problems (
  lc_number   INTEGER PRIMARY KEY,
  issue       INTEGER NOT NULL,
  topic_issue INTEGER NOT NULL,
  title       TEXT NOT NULL,
  difficulty  TEXT NOT NULL,               -- easy|medium|hard
  set_label   TEXT NOT NULL,               -- core|optional|deferred
  stage       TEXT NOT NULL DEFAULT 'new', -- new|+2|+5|+10|retired
  next_review TEXT,                        -- YYYY-MM-DD ET, NULL when retired/unsolved
  defer_until TEXT                         -- deferred Hards: 2026-09-28+
);

CREATE TABLE attempts (
  id        INTEGER PRIMARY KEY AUTOINCREMENT,
  lc_number INTEGER NOT NULL REFERENCES problems(lc_number),
  date      TEXT NOT NULL,
  kind      TEXT NOT NULL,                 -- first|review|drill|gate
  result    TEXT NOT NULL,                 -- pass|fail
  source    TEXT NOT NULL                  -- email|webhook|import
);

-- One-tap email links must be idempotent (same link twice = no-op), but
-- /done webhook corrections (pass then fail, same day) must stay legal —
-- so uniqueness applies to email-sourced attempts only.
CREATE UNIQUE INDEX attempts_email_once
  ON attempts (lc_number, date, kind) WHERE source = 'email';
CREATE INDEX attempts_by_date ON attempts (date);

CREATE TABLE topics (
  issue     INTEGER PRIMARY KEY,
  name      TEXT NOT NULL,
  misses    INTEGER NOT NULL DEFAULT 0,
  boost     INTEGER NOT NULL DEFAULT 0,
  milestone INTEGER                        -- phase; from the topic issue
);

CREATE TABLE gates (
  week      INTEGER PRIMARY KEY,           -- ISO week
  issue     INTEGER,
  problems  TEXT NOT NULL,                 -- JSON array of lc_numbers
  pass_rate REAL,
  closed_on TEXT
);

CREATE TABLE drill_pool_used (lc_number INTEGER PRIMARY KEY);

-- Digest idempotency: one email per ET date.
CREATE TABLE email_log (
  date    TEXT PRIMARY KEY,                -- YYYY-MM-DD ET
  sent_at TEXT NOT NULL
);