import { GrowingByteBuffer } from './growing-byte-buffer'

export const QUICK_OPEN_LISTING_MAX_RESULTS = 20_001
export const QUICK_OPEN_LISTING_MAX_RETAINED_PATHS = 100_000
export const QUICK_OPEN_LISTING_MAX_RETAINED_PATH_BYTES = 32 * 1024 * 1024
export const QUICK_OPEN_LISTING_MAX_PATH_BYTES = 64 * 1024

export type QuickOpenListingBudget = {
  retainedPathCount: number
  retainedPathBytes: number
  maxRetainedPaths: number
  maxRetainedPathBytes: number
  maxPathBytes: number
}

export function resolveQuickOpenResultLimit(requested?: number): number {
  if (requested === undefined || requested === Number.POSITIVE_INFINITY) {
    return QUICK_OPEN_LISTING_MAX_RESULTS
  }
  if (!Number.isFinite(requested)) {
    return 0
  }
  return Math.min(Math.max(Math.trunc(requested), 0), QUICK_OPEN_LISTING_MAX_RESULTS)
}

export function createQuickOpenListingBudget(
  limits: Partial<
    Pick<QuickOpenListingBudget, 'maxRetainedPaths' | 'maxRetainedPathBytes' | 'maxPathBytes'>
  > = {}
): QuickOpenListingBudget {
  const maxRetainedPaths = limits.maxRetainedPaths ?? QUICK_OPEN_LISTING_MAX_RETAINED_PATHS
  const maxRetainedPathBytes =
    limits.maxRetainedPathBytes ?? QUICK_OPEN_LISTING_MAX_RETAINED_PATH_BYTES
  const maxPathBytes = limits.maxPathBytes ?? QUICK_OPEN_LISTING_MAX_PATH_BYTES
  for (const [name, value] of Object.entries({
    maxRetainedPaths,
    maxRetainedPathBytes,
    maxPathBytes
  })) {
    if (!Number.isSafeInteger(value) || value < 0) {
      throw new RangeError(`${name} must be a non-negative safe integer`)
    }
  }
  return {
    retainedPathCount: 0,
    retainedPathBytes: 0,
    maxRetainedPaths,
    maxRetainedPathBytes,
    maxPathBytes
  }
}

export function retainQuickOpenPath(
  paths: Set<string>,
  path: string,
  budget: QuickOpenListingBudget
): boolean {
  if (paths.has(path)) {
    return false
  }
  const pathBytes = Buffer.byteLength(path, 'utf8')
  if (pathBytes > budget.maxPathBytes) {
    throw new Error(`Quick Open file path exceeded ${budget.maxPathBytes} bytes`)
  }
  if (budget.retainedPathCount >= budget.maxRetainedPaths) {
    throw new Error(`Quick Open file listing exceeded ${budget.maxRetainedPaths} retained paths`)
  }
  if (pathBytes > budget.maxRetainedPathBytes - budget.retainedPathBytes) {
    throw new Error(
      `Quick Open file listing exceeded ${budget.maxRetainedPathBytes} retained path bytes`
    )
  }
  budget.retainedPathCount++
  budget.retainedPathBytes += pathBytes
  paths.add(path)
  return true
}

export type QuickOpenPathAccumulatorResult = 'continue' | 'stopped' | 'path-too-large'

export class QuickOpenSubprocessPathAccumulator {
  private readonly field = new GrowingByteBuffer()

  constructor(
    private readonly delimiter: number,
    private readonly maxPathBytes = QUICK_OPEN_LISTING_MAX_PATH_BYTES
  ) {
    if (!Number.isInteger(delimiter) || delimiter < 0 || delimiter > 0xff) {
      throw new RangeError('Quick Open path delimiter must be one byte')
    }
    if (!Number.isSafeInteger(maxPathBytes) || maxPathBytes < 0) {
      throw new RangeError('Quick Open path limit must be a non-negative safe integer')
    }
  }

  push(
    rawChunk: Buffer | string,
    onPath: (path: string) => boolean
  ): QuickOpenPathAccumulatorResult {
    const chunk = Buffer.isBuffer(rawChunk) ? rawChunk : Buffer.from(rawChunk, 'utf8')
    let cursor = 0
    while (cursor < chunk.length) {
      const delimiter = chunk.indexOf(this.delimiter, cursor)
      const end = delimiter === -1 ? chunk.length : delimiter
      const segmentBytes = end - cursor
      if (this.field.byteLength + segmentBytes > this.maxPathBytes) {
        this.clear()
        return 'path-too-large'
      }
      if (delimiter !== -1 && this.field.byteLength === 0) {
        if (!onPath(chunk.toString('utf8', cursor, end))) {
          return 'stopped'
        }
      } else if (segmentBytes > 0) {
        // Why: copying prevents a short residual path from retaining the whole read buffer.
        this.field.append(chunk.subarray(cursor, end))
        if (delimiter !== -1 && !onPath(this.take())) {
          return 'stopped'
        }
      } else if (delimiter !== -1 && !onPath(this.take())) {
        return 'stopped'
      }
      if (delimiter === -1) {
        return 'continue'
      }
      cursor = delimiter + 1
    }
    return 'continue'
  }

  finish(): string | null {
    return this.field.byteLength > 0 ? this.take() : null
  }

  clear(): void {
    this.field.clear()
  }

  private take(): string {
    return this.field.takeString()
  }
}