import { EscPos, bitonalFromRGBA, rasterToEscPos } from '@sims/printing'

/**
 * Indic raster receipt (09-UX §5.3): ESC/POS text mode can't render Devanagari
 * or Malayalam, so non-Latin receipts are drawn to an offscreen canvas and sent
 * as a GS v 0 bit-image. Canvas is a browser API, so this lives in the app; the
 * thresholding + bit-packing are the pure @sims/printing package (raster.ts).
 *
 * v1 caveat (documented): browsers fall back to the OS fonts for canvas text, so
 * Devanagari/Malayalam coverage depends on the shop PC having a suitable font
 * (Windows ships Nirmala UI). The raster *pipeline* is what S2 delivers; bundled
 * canvas webfonts are a follow-up. Latin/ASCII always renders.
 */

/** Print-head pixel width: 384 dots for 2" (32 col), 576 for 3" (42 col). */
export function headWidth(cols: 32 | 42): number {
  return cols === 32 ? 384 : 576
}

export function renderRasterReceipt(lines: string[], opts: { width: 32 | 42; kickDrawer?: boolean }): Uint8Array {
  const W = headWidth(opts.width)
  const fontPx = opts.width === 32 ? 20 : 22
  const lineH = Math.round(fontPx * 1.35)
  const padTop = 8
  const padBottom = 24
  const H = padTop + lines.length * lineH + padBottom

  const canvas = document.createElement('canvas')
  canvas.width = W
  canvas.height = H
  const ctx = canvas.getContext('2d')
  if (ctx === null) throw new Error('Canvas 2D unavailable — cannot rasterize receipt')
  ctx.fillStyle = '#fff'
  ctx.fillRect(0, 0, W, H)
  ctx.fillStyle = '#000'
  ctx.textBaseline = 'top'
  // A font stack the browser can fall back to for Indic scripts on the shop PC.
  ctx.font = `${fontPx}px "Noto Sans", "Noto Sans Devanagari", "Nirmala UI", "Segoe UI", monospace`
  lines.forEach((text, i) => {
    const y = padTop + i * lineH
    if (i === 0) {
      ctx.textAlign = 'center'
      ctx.fillText(text, W / 2, y)
    } else {
      ctx.textAlign = 'left'
      ctx.fillText(text, 4, y)
    }
  })

  const img = ctx.getImageData(0, 0, W, H)
  const body = rasterToEscPos(bitonalFromRGBA(img.data, W, H))

  const head = new EscPos().init()
  if (opts.kickDrawer === true) head.drawerKick()
  const prefix = head.align('left').build()
  const tail = new EscPos().feed(4).cut().build()

  const out = new Uint8Array(prefix.length + body.length + tail.length)
  out.set(prefix, 0)
  out.set(body, prefix.length)
  out.set(tail, prefix.length + body.length)
  return out
}