// This file is part of meshoptimizer library and is distributed under the terms of MIT License.
// Copyright (C) 2016-2023, by Arseny Kapoulkine (arseny.kapoulkine@gmail.com)
var MeshoptDecoder = (function() {
	"use strict";

	var instance;
	var supported = false;

	var ready = (instantiateWasm = {}) => {

		if (typeof instantiateWasm !== 'function') {
			return Promise.reject(new Error('No wasm support detected'));
		}

		return instantiateWasm().then(function(result) {
			supported = true;
			instance = result.instance;
			instance.exports.__wasm_call_ctors();
		});
	}

	function decode(fun, target, count, size, source, filter) {
		var sbrk = instance.exports.sbrk;
		var count4 = (count + 3) & ~3;
		var tp = sbrk(count4 * size);
		var sp = sbrk(source.length);
		var heap = new Uint8Array(instance.exports.memory.buffer);
		heap.set(source, sp);
		var res = fun(tp, count, size, sp, source.length);
		if (res == 0 && filter) {
			filter(tp, count4, size);
		}
		target.set(heap.subarray(tp, tp + count * size));
		sbrk(tp - sbrk(0));
		if (res != 0) {
			throw new Error("Malformed buffer data: " + res);
		}
	}

	var filters = {
		NONE: "",
		OCTAHEDRAL: "meshopt_decodeFilterOct",
		QUATERNION: "meshopt_decodeFilterQuat",
		EXPONENTIAL: "meshopt_decodeFilterExp",
	};

	var decoders = {
		ATTRIBUTES: "meshopt_decodeVertexBuffer",
		TRIANGLES: "meshopt_decodeIndexBuffer",
		INDICES: "meshopt_decodeIndexSequence",
	};

	var workers = [];
	var requestId = 0;

	function createWorker(url) {
		var worker = {
			object: new Worker(url),
			pending: 0,
			requests: {}
		};

		worker.object.onmessage = function(event) {
			var data = event.data;

			worker.pending -= data.count;
			worker.requests[data.id][data.action](data.value);

			delete worker.requests[data.id];
		};

		return worker;
	}

	function initWorkers(count) {
		var source =
			"var instance; var ready = WebAssembly.instantiate(new Uint8Array([" + new Uint8Array(unpack(wasm)) + "]), {})" +
			".then(function(result) { instance = result.instance; instance.exports.__wasm_call_ctors(); });" +
			"self.onmessage = workerProcess;" +
			decode.toString() + workerProcess.toString();

		var blob = new Blob([source], {type: 'text/javascript'});
		var url = URL.createObjectURL(blob);

		for (var i = 0; i < count; ++i) {
			workers[i] = createWorker(url);
		}

		URL.revokeObjectURL(url);
	}

	function decodeWorker(count, size, source, mode, filter) {
		var worker = workers[0];

		for (var i = 1; i < workers.length; ++i) {
			if (workers[i].pending < worker.pending) {
				worker = workers[i];
			}
		}

		return new Promise(function (resolve, reject) {
			var data = new Uint8Array(source);
			var id = requestId++;

			worker.pending += count;
			worker.requests[id] = { resolve: resolve, reject: reject };
			worker.object.postMessage({ id: id, count: count, size: size, source: data, mode: mode, filter: filter }, [ data.buffer ]);
		});
	}

	function workerProcess(event) {
		ready.then(function() {
			var data = event.data;
			try {
				var target = new Uint8Array(data.count * data.size);
				decode(instance.exports[data.mode], target, data.count, data.size, data.source, instance.exports[data.filter]);
				self.postMessage({ id: data.id, count: data.count, action: "resolve", value: target }, [ target.buffer ]);
			} catch (error) {
				self.postMessage({ id: data.id, count: data.count, action: "reject", value: error });
			}
		});
	}

	return {
		ready: ready,
		supported: supported,
		useWorkers: function(count) {
			initWorkers(count);
		},
		decodeVertexBuffer: function(target, count, size, source, filter) {
			decode(instance.exports.meshopt_decodeVertexBuffer, target, count, size, source, instance.exports[filters[filter]]);
		},
		decodeIndexBuffer: function(target, count, size, source) {
			decode(instance.exports.meshopt_decodeIndexBuffer, target, count, size, source);
		},
		decodeIndexSequence: function(target, count, size, source) {
			decode(instance.exports.meshopt_decodeIndexSequence, target, count, size, source);
		},
		decodeGltfBuffer: function(target, count, size, source, mode, filter) {
			decode(instance.exports[decoders[mode]], target, count, size, source, instance.exports[filters[filter]]);
		},
		decodeGltfBufferAsync: function(count, size, source, mode, filter) {
			if (workers.length > 0) {
				return decodeWorker(count, size, source, decoders[mode], filters[filter]);
			}

			return ready.then(function() {
				var target = new Uint8Array(count * size);
				decode(instance.exports[decoders[mode]], target, count, size, source, instance.exports[filters[filter]]);
				return target;
			});
		}
	};
})();

export default MeshoptDecoder;