// Web Worker that runs the Bloch simulation off the main thread. It parses the
// .seq text, runs simulate(), streams throttled progress messages, and posts
// the raw signal back. Cancellation is handled by the main thread terminating
// the worker (no in-loop cancel needed).
import { parseSeq } from '../seq/parseSeq.ts'
import { simulate } from './simulate.ts'
import type { SimProgress } from './simulate.ts'
import type { Phantom } from '../phantom/phantomTypes.ts'

export interface RunMessage {
  type: 'run'
  seqText: string
  phantom: Phantom
}

export type WorkerOut =
  | { type: 'progress'; progress: SimProgress; elapsedMs: number }
  | {
      type: 'done'
      re: Float64Array
      im: Float64Array
      numReadouts: number
      samplesPerReadout: Int32Array
      offsets: Int32Array
      maxSamplesPerReadout: number
      elapsedMs: number
    }
  | { type: 'error'; message: string }

const ctx = self as unknown as Worker

ctx.onmessage = (ev: MessageEvent<RunMessage>) => {
  const msg = ev.data
  if (msg.type !== 'run') return
  const started = Date.now()
  try {
    const seq = parseSeq(msg.seqText)
    let lastPost = 0
    const result = simulate(seq, msg.phantom, {
      progressEvery: 128,
      onProgress: (progress) => {
        const now = Date.now()
        if (now - lastPost >= 100 || progress.fraction >= 1) {
          lastPost = now
          const out: WorkerOut = { type: 'progress', progress, elapsedMs: now - started }
          ctx.postMessage(out)
        }
      },
    })
    const out: WorkerOut = {
      type: 'done',
      re: result.re,
      im: result.im,
      numReadouts: result.numReadouts,
      samplesPerReadout: result.samplesPerReadout,
      offsets: result.offsets,
      maxSamplesPerReadout: result.maxSamplesPerReadout,
      elapsedMs: Date.now() - started,
    }
    ctx.postMessage(out, [result.re.buffer, result.im.buffer])
  } catch (err) {
    const out: WorkerOut = { type: 'error', message: err instanceof Error ? err.message : String(err) }
    ctx.postMessage(out)
  }
}