"use strict";

const sax = require("sax");
const unreachable = require("@joepie91/unreachable")("detect-svg-scripts");

const { validateArguments } = require("@validatem/core");
const either = require("@validatem/either");
const required = require("@validatem/required");
const isString = require("@validatem/is-string");
const isBuffer = require("@validatem/is-buffer");
const isNodeStream = require("@validatem/is-node-stream");

module.exports = function detectSVGScripts(svgFile) {
	validateArguments(arguments, {
		svgFile: [ required, either([ isString, isBuffer, isNodeStream.anyReadable ]) ]
	});

	let parser = sax.createStream(false);

	if (typeof svgFile === "string" || Buffer.isBuffer(svgFile)) {
		// Make sure that all event listeners have been attached before we feed in any data
		process.nextTick(() => {
			parser.end(svgFile);
		});
	} else {
		svgFile.pipe(parser);
	}

	return new Promise((resolve, reject) => {
		let occurrences = [];

		function detachListeners() {
			parser.removeListener("end", onEnd);
			parser.removeListener("error", onError);
			parser.removeListener("opentag", onTag);
		}

		function onEnd() {
			resolve(occurrences);
			detachListeners();
		}

		function onError(error) {
			reject(error);
			detachListeners();
		}
		
		function onTag(tag) {
			let normalizedTag = tag.name
				.toLowerCase()
				.replace(/.+:([^:]+)$/, (_, actualTag) => actualTag);
	
			let normalizedAttributes = Object.entries(tag.attributes)
				.map(([ attribute, value ]) => [ attribute.toLowerCase(), value ]);
			
			if (normalizedTag === "script") {
				let externalSources = normalizedAttributes
					.filter(([ attribute, _value ]) => attribute === "src")
					.map(([ _attribute, value ]) => value);

				if (externalSources.length === 1) {
					occurrences.push({
						type: "externalScriptFile",
						tag: tag,
						file: externalSources[0]
					});
				} else if (externalSources.length === 0) {
					occurrences.push({
						type: "inlineScriptTag",
						tag: tag
					});
				} else {
					unreachable("Encountered more than one 'src' key");
				}
			}
	
			// https://developer.mozilla.org/en-US/docs/Web/SVG/Attribute/Events
			let eventHandlers = normalizedAttributes
				.filter(([ attribute, _value ]) => attribute.startsWith("on"));
	
			for (let [ attribute, _value ] of eventHandlers) {
				occurrences.push({
					type: "eventHandler",
					tag: tag,
					attribute: attribute
				});
			}
		}

		parser.on("error", onError);
		parser.on("end", onEnd);
		parser.on("opentag", onTag);
	});
};