export interface ChapterItem {
  rawTitle:string
  title:string
  /**
   * the chapter content
   */
  text:string
  /**
   * the chapter number
   */
  number:number
  key:string
  indexOf:number
}

export type Chapters = ChapterItem[]

function formatLines(text:string){
  const lines = text.split('\n')
    // .reduce<string[]>((result,line)=>{
    //   const childLines = line.split('\r\n').map(childLine=>{
    //       return childLine.split("\r")
    //     })
    //   return result.concat(
    //     ...childLines
    //   )
    // },[])


  return lines
}



export function splitChapter(text:string){
  const lines = formatLines(text)
  
  const chapters:Chapters = []

  /**
   * the chapters array index, not the chapter number
   * like pointer
   */
  let chapterIndex = -1
  let offset = 0
  for(let lineIndex=0;lineIndex<lines.length;lineIndex++) {
    const lineText = lines[lineIndex]
    offset += lineText.length
    if(!lineText || !lineText.trim()) {
      continue
    }
    const title = getChapterTitle(lineText)
    if(title!==null){
      ++chapterIndex;
      chapters[chapterIndex] = {
        rawTitle:lineText,
        title,
        text:"",
        number:chapterIndex+1,
        key:generateKey(),
        indexOf:Math.max(0,offset-1)
      }
      // lastLineOffset+=lineText.length
      continue
    }
    if(chapterIndex===-1) {
      chapterIndex = 0
      chapters[chapterIndex] = {
        title:"",
        rawTitle:"",
        text:lineText+"\n",
        number:1,
        key:generateKey(),
        indexOf:Math.max(0,offset)
      }
      continue
    }
    const chapter = chapters[chapterIndex]
    chapter.text += lineText
    // chapter.indexOf = lastLineOffset+lineText.length
    // lastLineOffset = chapter.indexOf
  }

  console.info("chapters",chapters)
  return chapters
}

function getChapterTitle(text:string){
  const matchTitleSpecialCharRegexp = /[^\s\da-z]/i
  // example: Chapter 1
  if(/^chapter\s*\d+/i.test(text)) {
    return text.replace(/^chapter\s*\d+/i,"").replace(matchTitleSpecialCharRegexp,"").trim()
  }

  // example Chapter: title
  // example Chapter 2: title
  // example Chapter one: title
  // example Chapter One: "title"
  // example Chapter One: [title]
  // example Chapter III: [title]
  // example Chapter: [title]
  if(/^chapter\s*.*[^\s\da-z]([\s\da-z]+)/i.test(text)) {
    return text.replace(/^chapter\s*.*[^\s\da-z]([\s\da-z]+)/i,"$1").replace(matchTitleSpecialCharRegexp,"").trim()
  }

  if(
    /^([-=+<>#\*])\1{2,}$/.test(text)
  ) {
    return ""
  }

  if(/SPLIT\s*CHAPTER/.test(text)) return ""
  if(/CHAPTER\s*SPLIT/.test(text)) return ""

  return null
}

function randomString(count:number) {
    const seeds = ['0','1','2','3','4','5','6','7','8','9','A','B','C','D','E','F','G','H','I','J','K','L','M','N','O','P','Q','R','S','T','U','V','W','X','Y','Z','a','b','c','d','e','f','g','h','i','j','k','l','m','n','o','p','q','r','s','t','u','v','w','x','y','z'];
    return Array(count).fill("").map(()=>{
      const index = Math.floor(Math.random() * 1000) % (seeds.length)
      return seeds[index]
    }).join("")

}

const generateKey = () => randomString(20)

export async function readFile(file:File){
  const reader = new FileReader()
      
  const promise = new Promise<string>((resolve,reject)=>{
    reader.addEventListener("loadend",function(){
      let txt = reader.result as unknown as string
      txt = txt.replace('\r\n','\n').replace('\r','\n')
      resolve(reader.result as unknown as string)
    })
    reader.addEventListener("error",reject)
  })

  reader.readAsText(file,"utf-8")

  return promise
}