//===----------------------------------------------------------------------===//
//
// This source file is part of the Swift.org open source project
//
// Copyright (c) 2014 - 2018 Apple Inc. and the Swift project authors
// Licensed under Apache License v2.0 with Runtime Library Exception
//
// See https://swift.org/LICENSE.txt for license information
// See https://swift.org/CONTRIBUTORS.txt for the list of Swift project authors
//
//===----------------------------------------------------------------------===//

import SKTestSupport
import SKUtilities
import XCTest

/// A linear congruential generator with user-specified seed value. Useful for generating a predictable "random" number sequence.
private struct SimpleLCG: RandomNumberGenerator {

  var state: UInt64

  package init(seed: UInt64) {
    state = seed
  }

  package mutating func next() -> UInt64 {
    state = state &* 6_364_136_223_846_793_005 &+ 1_442_695_040_888_963_407
    return state
  }
}

final class LineTablePerfTests: PerfTestCase {

  func testLineTableAppendPerf() {

    let characters: [Character] =
      [
        "\t", "\n",
      ] + (32...126).map { Character(UnicodeScalar($0)) }

    #if DEBUG || !ENABLE_PERF_TESTS
    let iterations = 1_000
    #else
    let iterations = 10_000
    #endif

    self.measure {
      var lcg = SimpleLCG(seed: 1)
      var t = LineTable("")
      var line = 0
      var col = 0
      for _ in 1...iterations {
        let c = characters.randomElement(using: &lcg)!
        t.replace(fromLine: line, utf16Offset: col, toLine: line, utf16Offset: col, with: String(c))
        col += 1
        if c == "\n" {
          line += 1
          col = 0
        }
      }
    }
  }

  func testLineTableSingleCharEditPerf() {
    let characters: [Character] =
      [
        "\t", "\n",
      ] + (32...126).map { Character(UnicodeScalar($0)) }

    #if DEBUG || !ENABLE_PERF_TESTS
    let iterations = 1_000
    let size = 1_000
    #else
    let iterations = 10_000
    let size = 10_000
    #endif

    self.measureMetrics([.wallClockTime], automaticallyStartMeasuring: false) {
      var lcg = SimpleLCG(seed: 1)
      var str = ""
      for _ in 1...size {
        str += String(characters.randomElement(using: &lcg)!)
      }

      var t = LineTable(str)

      self.startMeasuring()

      for _ in 1...iterations {
        let line = (0..<(t.lineCount - 1)).randomElement(using: &lcg) ?? 0
        let col = (0..<t.line(at: line)!.utf16.count).randomElement(using: &lcg) ?? 0
        let len = t.line(at: line)!.isEmpty ? 0 : Bool.random() ? 1 : 0
        var newText = String(characters.randomElement(using: &lcg)!)
        if len == 1 && Bool.random(using: &lcg) {
          newText = ""  // deletion
        }

        t.replace(fromLine: line, utf16Offset: col, utf16Length: len, with: newText)
      }

      self.stopMeasuring()
    }
  }
}
