locations.js

import {qs, sprint, locationOf, defer} from "./utils/core";
import Queue from "./utils/queue";
import EpubCFI from "./epubcfi";
import { EVENTS } from "./utils/constants";
import EventEmitter from "event-emitter";

/**
 * Find Locations for a Book
 * @param {Spine} spine
 * @param {request} request
 * @param {number} [pause=100]
 */
class Locations {
	constructor(spine, request, pause) {
		this.spine = spine;
		this.request = request;
		this.pause = pause || 100;

		this.q = new Queue(this);
		this.epubcfi = new EpubCFI();

		this._locations = [];
		this.total = 0;

		this.break = 150;

		this._current = 0;

		this.currentLocation = '';
		this._currentCfi ='';
		this.processingTimeout = undefined;
	}

	/**
	 * Load all of sections in the book to generate locations
	 * @param  {int} chars how many chars to split on
	 * @return {object} locations
	 */
	generate(chars) {

		if (chars) {
			this.break = chars;
		}

		this.q.pause();

		this.spine.each(function(section) {
			if (section.linear) {
				this.q.enqueue(this.process.bind(this), section);
			}
		}.bind(this));

		return this.q.run().then(function() {
			this.total = this._locations.length - 1;

			if (this._currentCfi) {
				this.currentLocation = this._currentCfi;
			}

			return this._locations;
			// console.log(this.percentage(this.book.rendition.location.start), this.percentage(this.book.rendition.location.end));
		}.bind(this));

	}

	createRange () {
		return {
			startContainer: undefined,
			startOffset: undefined,
			endContainer: undefined,
			endOffset: undefined
		};
	}

	process(section) {

		return section.load(this.request)
			.then(function(contents) {
				var completed = new defer();
				var locations = this.parse(contents, section.cfiBase);
				this._locations = this._locations.concat(locations);

				section.unload();

				this.processingTimeout = setTimeout(() => completed.resolve(locations), this.pause);
				return completed.promise;
			}.bind(this));

	}

	parse(contents, cfiBase, chars) {
		var locations = [];
		var range;
		var doc = contents.ownerDocument;
		var body = qs(doc, "body");
		var counter = 0;
		var prev;
		var _break = chars || this.break;
		var parser = function(node) {
			var len = node.length;
			var dist;
			var pos = 0;

			if (node.textContent.trim().length === 0) {
				return false; // continue
			}

			// Start range
			if (counter == 0) {
				range = this.createRange();
				range.startContainer = node;
				range.startOffset = 0;
			}

			dist = _break - counter;

			// Node is smaller than a break,
			// skip over it
			if(dist > len){
				counter += len;
				pos = len;
			}


			while (pos < len) {
				dist = _break - counter;

				if (counter === 0) {
					// Start new range
					pos += 1;
					range = this.createRange();
					range.startContainer = node;
					range.startOffset = pos;
				}

				// pos += dist;

				// Gone over
				if(pos + dist >= len){
					// Continue counter for next node
					counter += len - pos;
					// break
					pos = len;
				// At End
				} else {
					// Advance pos
					pos += dist;

					// End the previous range
					range.endContainer = node;
					range.endOffset = pos;
					// cfi = section.cfiFromRange(range);
					let cfi = new EpubCFI(range, cfiBase).toString();
					locations.push(cfi);
					counter = 0;
				}
			}
			prev = node;
		};

		sprint(body, parser.bind(this));

		// Close remaining
		if (range && range.startContainer && prev) {
			range.endContainer = prev;
			range.endOffset = prev.length;
			let cfi = new EpubCFI(range, cfiBase).toString();
			locations.push(cfi);
			counter = 0;
		}

		return locations;
	}

	/**
	 * Get a location from an EpubCFI
	 * @param {EpubCFI} cfi
	 * @return {number}
	 */
	locationFromCfi(cfi){
		let loc;
		if (EpubCFI.prototype.isCfiString(cfi)) {
			cfi = new EpubCFI(cfi);
		}
		// Check if the location has not been set yet
		if(this._locations.length === 0) {
			return -1;
		}

		loc = locationOf(cfi, this._locations, this.epubcfi.compare);

		if (loc > this.total) {
			return this.total;
		}

		return loc;
	}

	/**
	 * Get a percentage position in locations from an EpubCFI
	 * @param {EpubCFI} cfi
	 * @return {number}
	 */
	percentageFromCfi(cfi) {
		if(this._locations.length === 0) {
			return null;
		}
		// Find closest cfi
		var loc = this.locationFromCfi(cfi);
		// Get percentage in total
		return this.percentageFromLocation(loc);
	}

	/**
	 * Get a percentage position from a location index
	 * @param {number} location
	 * @return {number}
	 */
	percentageFromLocation(loc) {
		if (!loc || !this.total) {
			return 0;
		}

		return (loc / this.total);
	}

	/**
	 * Get an EpubCFI from location index
	 * @param {number} loc
	 * @return {EpubCFI} cfi
	 */
	cfiFromLocation(loc){
		var cfi = -1;
		// check that pg is an int
		if(typeof loc != "number"){
			loc = parseInt(loc);
		}

		if(loc >= 0 && loc < this._locations.length) {
			cfi = this._locations[loc];
		}

		return cfi;
	}

	/**
	 * Get an EpubCFI from location percentage
	 * @param {number} percentage
	 * @return {EpubCFI} cfi
	 */
	cfiFromPercentage(percentage){
		let loc;
		if (percentage > 1) {
			console.warn("Normalize cfiFromPercentage value to between 0 - 1");
		}

		// Make sure 1 goes to very end
		if (percentage >= 1) {
			let cfi = new EpubCFI(this._locations[this.total]);
			cfi.collapse();
			return cfi.toString();
		}

		loc = Math.ceil(this.total * percentage);
		return this.cfiFromLocation(loc);
	}

	/**
	 * Load locations from JSON
	 * @param {json} locations
	 */
	load(locations){
		if (typeof locations === "string") {
			this._locations = JSON.parse(locations);
		} else {
			this._locations = locations;
		}
		this.total = this._locations.length - 1;
		return this._locations;
	}

	/**
	 * Save locations to JSON
	 * @return {json}
	 */
	save(){
		return JSON.stringify(this._locations);
	}

	getCurrent(){
		return this._current;
	}

	setCurrent(curr){
		var loc;

		if(typeof curr == "string"){
			this._currentCfi = curr;
		} else if (typeof curr == "number") {
			this._current = curr;
		} else {
			return;
		}

		if(this._locations.length === 0) {
			return;
		}

		if(typeof curr == "string"){
			loc = this.locationFromCfi(curr);
			this._current = loc;
		} else {
			loc = curr;
		}

		this.emit(EVENTS.LOCATIONS.CHANGED, {
			percentage: this.percentageFromLocation(loc)
		});
	}

	/**
	 * Get the current location
	 */
	get currentLocation() {
		return this._current;
	}

	/**
	 * Set the current location
	 */
	set currentLocation(curr) {
		this.setCurrent(curr);
	}

	/**
	 * Locations length
	 */
	length () {
		return this._locations.length;
	}

	destroy () {
		this.spine = undefined;
		this.request = undefined;
		this.pause = undefined;

		this.q.stop();
		this.q = undefined;
		this.epubcfi = undefined;

		this._locations = undefined
		this.total = undefined;

		this.break = undefined;
		this._current = undefined;

		this.currentLocation = undefined;
		this._currentCfi = undefined;
		clearTimeout(this.processingTimeout);
	}
}

EventEmitter(Locations.prototype);

export default Locations;