vChewing-macOS/Packages/vChewing_LangModelAssembly/Sources/LangModelAssembly/LMConsolidator.swift

// (c) 2021 and onwards The vChewing Project (MIT-NTL License).
// ====================
// This code is released under the MIT license (SPDX-License-Identifier: MIT)
// ... with NTL restriction stating that:
// No trademark license is granted to use the trade names, trademarks, service
// marks, or product names of Contributor, except as required to fulfill notice
// requirements defined in MIT License.

import Foundation
import LineReader
import Shared

public extension vChewingLM {
  enum LMConsolidator {
    public static let kPragmaHeader = "# 𝙵𝙾𝚁𝙼𝙰𝚃 𝚘𝚛𝚐.𝚊𝚝𝚎𝚕𝚒𝚎𝚛𝙸𝚗𝚖𝚞.𝚟𝚌𝚑𝚎𝚠𝚒𝚗𝚐.𝚞𝚜𝚎𝚛𝙻𝚊𝚗𝚐𝚞𝚊𝚐𝚎𝙼𝚘𝚍𝚎𝚕𝙳𝚊𝚝𝚊.𝚏𝚘𝚛𝚖𝚊𝚝𝚝𝚎𝚍"

    /// 檢查給定檔案的標頭是否正常。
    /// - Parameter path: 給定檔案路徑。
    /// - Returns: 結果正常則為真，其餘為假。
    public static func checkPragma(path: String) -> Bool {
      if FileManager.default.fileExists(atPath: path) {
        do {
          guard let fileHandle = FileHandle(forReadingAtPath: path) else {
            throw FileErrors.fileHandleError("")
          }
          let lineReader = try LineReader(file: fileHandle)
          for strLine in lineReader { // 不需要 i=0，因為第一遍迴圈就出結果。
            if strLine != kPragmaHeader {
              vCLog("Header Mismatch, Starting In-Place Consolidation.")
              return false
            } else {
              vCLog("Header Verification Succeeded: \(strLine).")
              return true
            }
          }
        } catch {
          vCLog("Header Verification Failed: File Access Error.")
          return false
        }
      }
      vCLog("Header Verification Failed: File Missing.")
      return false
    }

    /// 檢查檔案是否以空行結尾，如果缺失則補充之。
    /// - Parameter path: 給定檔案路徑。
    /// - Returns: 結果正常或修復順利則為真，其餘為假。
    @discardableResult public static func fixEOF(path: String) -> Bool {
      var fileSize: UInt64?
      do {
        let dict = try FileManager.default.attributesOfItem(atPath: path)
        if let value = dict[FileAttributeKey.size] as? UInt64 { fileSize = value }
      } catch {
        vCLog("EOF Fix Failed: File Missing at \(path).")
        return false
      }
      guard let fileSize = fileSize else { return false }
      guard let writeFile = FileHandle(forUpdatingAtPath: path) else {
        vCLog("EOF Fix Failed: File Not Writable at \(path).")
        return false
      }
      defer { writeFile.closeFile() }
      /// 注意：Swift 版 LMConsolidator 並未在此安排對 EOF 的去重複工序。
      /// 但這個函式執行完之後往往就會 consolidate() 整理格式，所以不會有差。
      writeFile.seek(toFileOffset: fileSize - 1)
      if writeFile.readDataToEndOfFile().first != 0x0A {
        vCLog("EOF Missing Confirmed, Start Fixing.")
        var newData = Data()
        newData.append(0x0A)
        writeFile.write(newData)
        vCLog("EOF Successfully Assured.")
      }
      return false
    }

    /// 統整給定的字串。
    /// - Parameters:
    ///   - text: 操作對象。
    ///   - shouldCheckPragma: 是否在檔案標頭完好無損的情況下略過對格式的整理。
    public static func consolidate(text strProcessed: inout String, pragma shouldCheckPragma: Bool) {
      var pragmaResult: Bool {
        let realPragmaHeader = kPragmaHeader + "\n"
        if strProcessed.count <= kPragmaHeader.count { return false }
        let range = 0 ..< (realPragmaHeader.count)
        let fetchedPragma = ContiguousArray(strProcessed.utf8CString[range])
        return fetchedPragma == realPragmaHeader.utf8CString
      }

      if shouldCheckPragma, pragmaResult { return }

      // Step 1: Consolidating formats per line.
      // -------
      // CJKWhiteSpace (\x{3000}) to ASCII Space
      // NonBreakWhiteSpace (\x{A0}) to ASCII Space
      // Tab to ASCII Space
      // 統整連續空格為一個 ASCII 空格
      strProcessed.regReplace(pattern: #"( +|　+| +|\t+)+"#, replaceWith: " ")
      // 去除行尾行首空格
      strProcessed.regReplace(pattern: #"(^ | $)"#, replaceWith: "")
      strProcessed.regReplace(pattern: #"(\n | \n)"#, replaceWith: "\n")
      // CR & FF to LF, 且去除重複行
      strProcessed.regReplace(pattern: #"(\f+|\r+|\n+)+"#, replaceWith: "\n")
      strProcessed.regReplace(pattern: "^\(kPragmaHeader)$", replaceWith: "")
      if strProcessed.prefix(1) == " " { // 去除檔案開頭空格
        strProcessed.removeFirst()
      }
      if strProcessed.suffix(1) == " " { // 去除檔案結尾空格
        strProcessed.removeLast()
      }

      // Step 3: Deduplication.
      let arrData = strProcessed.split(separator: "\n")
      // 下面兩行的 reversed 是首尾顛倒，免得破壞最新的 override 資訊。
      let arrDataDeduplicated = Array(NSOrderedSet(array: arrData.reversed()).array as! [String])
      strProcessed = arrDataDeduplicated.reversed().joined(separator: "\n") + "\n"

      // Step 4: Remove duplicated newlines at the end of the file.
      strProcessed.regReplace(pattern: #"\n+"#, replaceWith: "\n")

      // Step 5: Add pragma header back.
      strProcessed = kPragmaHeader + "\n" + strProcessed // Add Pragma Header
    }

    /// 統整給定的檔案的格式。
    /// - Parameters:
    ///   - path: 給定檔案路徑。
    ///   - shouldCheckPragma: 是否在檔案標頭完好無損的情況下略過對格式的整理。
    /// - Returns: 若整理順利或無須整理，則為真；反之為假。
    @discardableResult public static func consolidate(path: String, pragma shouldCheckPragma: Bool) -> Bool {
      let pragmaResult = checkPragma(path: path)
      if shouldCheckPragma {
        if pragmaResult {
          return true
        }
      }

      let urlPath = URL(fileURLWithPath: path)
      if FileManager.default.fileExists(atPath: path) {
        do {
          var strProcessed = try String(contentsOf: urlPath, encoding: .utf8)
          consolidate(text: &strProcessed, pragma: shouldCheckPragma)
          // Write consolidated file contents.
          try strProcessed.write(to: urlPath, atomically: false, encoding: .utf8)
        } catch {
          vCLog("Consolidation Failed w/ File: \(path), error: \(error)")
          return false
        }
        vCLog("Either Consolidation Successful Or No-Need-To-Consolidate.")
        return true
      }
      vCLog("Consolidation Failed: File Missing at \(path).")
      return false
    }
  }
}