fvtt-lethal-fantasy/module/documents/roll-damage.mjs

/**
 * Evaluate a spell/miracle damage formula with per-die explosion, then post to chat.
 * Explosion dice are shown manually via showForRoll; the main roll is shown automatically
 * by toMessage() (which triggers Dice So Nice via its createChatMessage hook).
 * Append "NE" to the formula to disable explosion.
 *
 * @param {string} formula    Dice formula, e.g. "1d8", "2d6", "1d8NE"
 * @param {Object} rollOpts   Options for LethalFantasyRoll (rollType, actorId, defenderId, etc.)
 * @returns {Promise<ChatMessage>}
 */
export async function rollSpellDamageToMessage(formula, rollOpts) {
  const roll = new this(formula, {}, rollOpts)
  await roll.evaluate()
  const shouldExplode = !/NE$/i.test(formula)
  const diceResults = []
  let diceSum = 0
  for (const term of roll.dice) {
    const singleDice = `1D${term.faces}`
    const termResults = Array.from(term.results)
    for (const r of termResults) {
      let diceResult = r.result
      diceResults.push({ dice: singleDice.toUpperCase(), value: diceResult })
      diceSum += diceResult
      if (shouldExplode && term.faces > 0) {
        while (diceResult === term.faces) {
          const xr = await new Roll(singleDice).evaluate()
          // Optional chaining guards against unexpected roll structure
          diceResult = xr.dice?.[0]?.results?.[0]?.result ?? (term.faces - 1)
          diceResults.push({ dice: `${singleDice.toUpperCase()}-1`, value: diceResult - 1 })
          diceSum += (diceResult - 1)
          term.results.push({ result: diceResult, active: true })
        }
      }
    }
  }
  roll.options.diceResults = diceResults
  roll.options.rollTotal = diceSum
  return roll.toMessage()
}