First commit, basic SQLite store, worker, and server

store.go

@@ -0,0 +1,59 @@
+package main
+
+import (
+	"database/sql"
+	_ "modernc.org/sqlite"
+)
+
+const schema = `
+CREATE TABLE IF NOT EXISTS runs (
+	id          INTEGER PRIMARY KEY,
+	chapter_id  INTEGER NOT NULL,
+	department  TEXT    NOT NULL,
+	rep_user_id INTEGER NOT NULL,
+	status      TEXT    NOT NULL,
+	started_at  TEXT    NOT NULL DEFAULT CURRENT_TIMESTAMP,
+	ended_at    TEXT
+);
+
+CREATE UNIQUE INDEX IF NOT EXISTS one_run_per_dept
+	ON runs(chapter_id, department) WHERE status = 'running';
+`
+
+type SQLStore struct{ db *sql.DB }
+
+func OpenStore(path string) (*SQLStore, error) {
+	db, err := sql.Open("sqlite",
+		"file:"+path+"?_pragma=journal_mode(WAL)&_pragma=busy_timeout(5000)")
+	if err != nil {
+		return nil, err
+	}
+	db.SetMaxOpenConns(1)
+	if _, err := db.Exec(schema); err != nil {
+		return nil, err
+	}
+	return &SQLStore{db: db}, nil
+}
+
+func (s *SQLStore) AcquireLock(chapterID int64, dept string, repID int64) (int64, error) {
+	res, err := s.db.Exec(
+		`INSERT INTO runs (chapter_id, department, rep_user_id, status)
+		 VALUES (?, ?, ?, 'running')`, chapterID, dept, repID)
+	if err != nil {
+		return 0, ErrLocked // refine: only on constraint violation
+	}
+	return res.LastInsertId()
+}
+
+func (s *SQLStore) ReleaseLock(runID int64) error {
+	_, err := s.db.Exec(
+		`UPDATE runs SET status='done', ended_at=CURRENT_TIMESTAMP WHERE id=?`, runID)
+	return err
+}
+
+func (s *SQLStore) SweepStaleLocks() error {
+	_, err := s.db.Exec(
+		`UPDATE runs SET status='crashed', ended_at=CURRENT_TIMESTAMP
+		 WHERE status='running'`)
+	return err
+}