parsecap.js

const {createCAPobj,stringify,getline,floor}=require("./cap");

const pageofx=(cap,db)=>{
	const arr=db.getpageline(cap.bkseq);
	let prev=0,l=0;
	for (var i=0;i<arr.length;i++) {
		if (arr[i]>cap.bk0) {
			if (i==0) return {_:0,x:cap.bk0,_w:arr[1]-arr[0]};
			return {_:i, x:cap.bk0-arr[i-1], _w:arr[i]-arr[i-1] };
		}
	}
	let _w=1;
	const nextarr=db.getpageline(cap.bkseq+1)
	if (nextarr) {
		const nextbookstart=db.bookstarts[cap.bkseq];
		_w=nextbookstart-arr[arr.length-1];
	} else {
		const thisbookstart=db.bookstarts[cap.bkseq];
		_w=db.totalline-thisbookstart-arr[arr.length-1];
	}
	const _=arr.length-1;
	const x=cap.bk0-arr[arr.length-1];
	return {_,x,_w};
}

const CAPx0=(cap,db)=>{
	let bookstart=db.bookstarts[cap.bkseq];
	let x=cap.x;
	let p=cap._;

	if (p==-1) {
		let bk0=cap.bk0; 
		if (bk0==-1) bk0=0;
		return bookstart+bk0+x;
	}

	const parr=db.getpageline(cap.bkseq);

	if (p>parr.length)	p=parr.length;

	let pstart=0;   //若p=0, 則起始行必為0
	if (p!=0) {
		if (p<1) p=1;
		//while (p&&p<parr.length && !parr[p]) p++;//新版無跳頁，會重復前個數字
		pstart=parr[p-1]; 	 //pageline[i-1]是dbp=i 的起始行。	
	}
	x+=pstart;
	x0=bookstart+x;
	return x0;
}
const recal=(cap,db)=>{
	cap.x0=CAPx0(cap,db);
	cap.bk0=cap.x0-db.bookstarts[cap.bkseq];
	const pp=pageofx(cap,db);
	cap=Object.assign(cap,pp);
}
const bindMethods=(cap,db)=>{
	cap.bkx=(cap.bkseq+1)+"_x"+(cap.bk0);
	cap.prevp=prevp.bind(cap);
	cap.nextp=nextp.bind(cap);
	cap.floor=floor.bind(cap);
	cap.stringify=stringify.bind(cap);
	cap.getline=getline.bind(cap);
	cap.stringify=stringify.bind(cap);
	Object.defineProperty(cap,"db",{get:()=>db});
}
const nextp=function(){
	const np=createCAPobj(this,{y:0,z:0,_:this._+1});
	recal(np,this.db);
	bindMethods(np,this.db);
	return np;
}
const prevp=function(){
	const pv=createCAPobj(this ,{y:0,z:0,_:this._-1});
	recal(pv,this.db);
	bindMethods(pv,this.db);
	pv.floor();
	return pv;
}
const parseCAP=(str,db)=>{
	let out={};
	if (typeof str=='number' || parseInt(str).toString()==str) {//absolute jsdb line number
		const obj=db.pagefromx0(str);
		obj.bk=db.booknames[obj.bkseq];
		obj.x0=str;
		out=createCAPobj(obj);
	} else if (typeof str=='string') {
		const at=str.indexOf("_");
		if (at==-1) throw "invalid address "+str;
		const arr=[];

		str.substr(at).replace(/([a-z_]\d+)/g,(m,m1)=>arr.push(m1));

		let bk=str.substr(0,at);
		let bkseq=-1;
		if (parseInt(bk).toString()===bk) {
			bkseq=parseInt(bk)-1;
			if (bkseq<0) bkseq=0;
			bk=db.booknames[bkseq];
		} else {
			bkseq=db.booknames.indexOf(bk);
			if (bkseq==-1) {
				return null;
			}
		}
		const o={bk,bkseq};
		arr.forEach(item=>{
			const k=item[0];
			const v=parseInt(item.substr(1))||0;
			o[k]=v;
			if (k=="z" && v==0) o[k]=-1;//ends with z without number
		});
		out=createCAPobj(o);
	} else throw "invalid parsecap param"
 	recal(out,db);
	bindMethods(out,db);
	return out;
}
module.exports=parseCAP;