// apps/hq/test/concurrency.test.ts — D24 (red-team): SQLite transaction serialization.
import { describe, it, expect } from 'vitest'
import { openDb } from '../src/db'

describe('SqliteDb.transaction serialization (D24)', () => {
  it('overlapping transactions do not interleave — a concurrent counter stays consistent', async () => {
    const db = openDb(':memory:')
    await db.exec(`CREATE TABLE ctr (id INTEGER PRIMARY KEY, n INTEGER NOT NULL)`)
    await db.run(`INSERT INTO ctr (id, n) VALUES (1, 0)`)
    // 50 read-modify-write transactions fired concurrently. Without serialization the
    // read-then-write would race and lose increments; the mutex makes the final count exact.
    const bump = () => db.transaction(async () => {
      const row = (await db.get<{ n: number }>(`SELECT n FROM ctr WHERE id=1`))!
      // Yield the event loop mid-transaction — the moment a naive impl would interleave.
      await Promise.resolve()
      await db.run(`UPDATE ctr SET n=? WHERE id=1`, row.n + 1)
    })
    await Promise.all(Array.from({ length: 50 }, bump))
    expect((await db.get<{ n: number }>(`SELECT n FROM ctr WHERE id=1`))!.n).toBe(50)
    await db.close()
  })

  it('a nested transaction still commits with its parent (savepoint), and rolls back alone on inner failure', async () => {
    const db = openDb(':memory:')
    await db.exec(`CREATE TABLE t (k TEXT PRIMARY KEY)`)
    // Outer commits; a caught inner failure rolls back only the savepoint.
    await db.transaction(async () => {
      await db.run(`INSERT INTO t (k) VALUES ('outer')`)
      await db.transaction(async () => {
        await db.run(`INSERT INTO t (k) VALUES ('inner')`)
        throw new Error('inner boom')
      }).catch(() => undefined)
    })
    expect(await db.get(`SELECT k FROM t WHERE k='outer'`)).toBeDefined()
    expect(await db.get(`SELECT k FROM t WHERE k='inner'`)).toBeUndefined()
    // An outer failure rolls back everything including the nested savepoint work.
    await db.transaction(async () => {
      await db.run(`INSERT INTO t (k) VALUES ('a')`)
      await db.transaction(async () => { await db.run(`INSERT INTO t (k) VALUES ('b')`) })
      throw new Error('outer boom')
    }).catch(() => undefined)
    expect(await db.get(`SELECT k FROM t WHERE k='a'`)).toBeUndefined()
    expect(await db.get(`SELECT k FROM t WHERE k='b'`)).toBeUndefined()
    await db.close()
  })
})