layoutAlgo.ts

interface RowSegment {
  width: number
  canStartLine?: boolean | undefined
  canEndLine?: boolean | undefined
}

// This implementation isn't fully currect since it never backtracks more than one element but it's good enough for now
export const sentenceLayoutAlgo = <T extends RowSegment>(
  rowSegments: T[],
  lineWidth: number,
): T[][] => {
  if (rowSegments.length === 0) {
    return []
  }

  const segments = [...rowSegments]

  const rows: T[][] = []

  let currentRow: T[] = [segments.shift()!]
  let currentRowWidth = currentRow[0].width

  while (segments.length > 0) {
    const segment = segments.shift()!

    if (currentRowWidth + segment.width <= lineWidth) {
      currentRow.push(segment)
      currentRowWidth += segment.width
    } else {
      const nextRow: T[] = []

      const lastOfCurrentRow = currentRow[currentRow.length - 1]
      if (lastOfCurrentRow.canEndLine && segment.canStartLine) {
        nextRow.push(segment)
        currentRowWidth = segment.width
      } else {
        nextRow.push(currentRow.pop()!)
        nextRow.push(segment)
        currentRowWidth = nextRow[0].width + nextRow[1].width
      }
      rows.push(currentRow)
      currentRow = nextRow
    }
  }

  rows.push(currentRow)

  return rows
}