import type Chunk from './chunk.ts'
import type VirtualOffset from './virtualOffset.ts'

export function canMergeBlocks(chunk1: Chunk, chunk2: Chunk) {
  return (
    chunk2.minv.blockPosition - chunk1.maxv.blockPosition < 65_000 &&
    chunk2.maxv.blockPosition - chunk1.minv.blockPosition < 5_000_000
  )
}

export function optimizeChunks(chunks: Chunk[], lowest?: VirtualOffset) {
  const mergedChunks: Chunk[] = []
  let lastChunk: Chunk | undefined

  if (chunks.length === 0) {
    return chunks
  }

  chunks.sort(function (c0, c1) {
    const dif = c0.minv.blockPosition - c1.minv.blockPosition
    return dif === 0 ? c0.minv.dataPosition - c1.minv.dataPosition : dif
  })

  for (const chunk of chunks) {
    if (!lowest || chunk.maxv.compareTo(lowest) > 0) {
      if (lastChunk === undefined) {
        mergedChunks.push(chunk)
        lastChunk = chunk
      } else {
        if (canMergeBlocks(lastChunk, chunk)) {
          if (chunk.maxv.compareTo(lastChunk.maxv) > 0) {
            lastChunk.maxv = chunk.maxv
          }
        } else {
          mergedChunks.push(chunk)
          lastChunk = chunk
        }
      }
    }
  }

  return mergedChunks
}