text: // Copyright 2018 The Go Authors. All rights reserved.
  // Use of this source code is governed by a BSD-style
  // license that can be found in the LICENSE file.
  
  (() => {
  	if (typeof global !== "undefined") {
  		// global already exists
  	} else if (typeof window !== "undefined") {
  		window.global = window;
  	} else if (typeof self !== "undefined") {
  		self.global = self;
  	} else {
  		throw new Error("cannot export Go (neither global, window nor self is defined)");
  	}
  
  	// Map web browser API and Node.js API to a single common API (preferring web standards over Node.js API).
  	const isNodeJS = global.process && global.process.title === "node";
  	if (isNodeJS) {
  		global.require = require;
  		global.fs = require("fs");
  
  		const nodeCrypto = require("crypto");
  		global.crypto = {
  			getRandomValues(b) {
  				nodeCrypto.randomFillSync(b);
  			},
  		};
  
  		global.performance = {
  			now() {
  				const [sec, nsec] = process.hrtime();
  				return sec * 1000 + nsec / 1000000;
  			},
  		};
  
  		const util = require("util");
  		global.TextEncoder = util.TextEncoder;
  		global.TextDecoder = util.TextDecoder;
  	} else {
  		let outputBuf = "";
  		global.fs = {
  			constants: { O_WRONLY: -1, O_RDWR: -1, O_CREAT: -1, O_TRUNC: -1, O_APPEND: -1, O_EXCL: -1 }, // unused
  			writeSync(fd, buf) {
  				outputBuf += decoder.decode(buf);
  				const nl = outputBuf.lastIndexOf("\n");
  				if (nl != -1) {
  					console.log(outputBuf.substr(0, nl));
  					outputBuf = outputBuf.substr(nl + 1);
  				}
  				return buf.length;
  			},
  			write(fd, buf, offset, length, position, callback) {
  				if (offset !== 0 || length !== buf.length || position !== null) {
  					throw new Error("not implemented");
  				}
  				const n = this.writeSync(fd, buf);
  				callback(null, n);
  			},
  			open(path, flags, mode, callback) {
  				const err = new Error("not implemented");
  				err.code = "ENOSYS";
  				callback(err);
  			},
  			fsync(fd, callback) {
  				callback(null);
  			},
  		};
  	}
  
  	const encoder = new TextEncoder("utf-8");
  	const decoder = new TextDecoder("utf-8");
  
  	global.Go = class {
  		constructor() {
  			this.argv = ["js"];
  			this.env = {};
  			this.exit = (code) => {
  				if (code !== 0) {
  					console.warn("exit code:", code);
  				}
  			};
  			this._callbackTimeouts = new Map();
  			this._nextCallbackTimeoutID = 1;
  
  			const mem = () => {
  				// The buffer may change when requesting more memory.
  				return new DataView(this._inst.exports.mem.buffer);
  			}
  
  			const setInt64 = (addr, v) => {
  				mem().setUint32(addr + 0, v, true);
  				mem().setUint32(addr + 4, Math.floor(v / 4294967296), true);
  			}
  
  			const getInt64 = (addr) => {
  				const low = mem().getUint32(addr + 0, true);
  				const high = mem().getInt32(addr + 4, true);
  				return low + high * 4294967296;
  			}
  
  			const loadValue = (addr) => {
  				const f = mem().getFloat64(addr, true);
  				if (f === 0) {
  					return undefined;
  				}
  				if (!isNaN(f)) {
  					return f;
  				}
  
  				const id = mem().getUint32(addr, true);
  				return this._values[id];
  			}
  
  			const storeValue = (addr, v) => {
  				const nanHead = 0x7FF80000;
  
  				if (typeof v === "number") {
  					if (isNaN(v)) {
  						mem().setUint32(addr + 4, nanHead, true);
  						mem().setUint32(addr, 0, true);
  						return;
  					}
  					if (v === 0) {
  						mem().setUint32(addr + 4, nanHead, true);
  						mem().setUint32(addr, 1, true);
  						return;
  					}
  					mem().setFloat64(addr, v, true);
  					return;
  				}
  
  				switch (v) {
  					case undefined:
  						mem().setFloat64(addr, 0, true);
  						return;
  					case null:
  						mem().setUint32(addr + 4, nanHead, true);
  						mem().setUint32(addr, 2, true);
  						return;
  					case true:
  						mem().setUint32(addr + 4, nanHead, true);
  						mem().setUint32(addr, 3, true);
  						return;
  					case false:
  						mem().setUint32(addr + 4, nanHead, true);
  						mem().setUint32(addr, 4, true);
  						return;
  				}
  
  				let ref = this._refs.get(v);
  				if (ref === undefined) {
  					ref = this._values.length;
  					this._values.push(v);
  					this._refs.set(v, ref);
  				}
  				let typeFlag = 0;
  				switch (typeof v) {
  					case "string":
  						typeFlag = 1;
  						break;
  					case "symbol":
  						typeFlag = 2;
  						break;
  					case "function":
  						typeFlag = 3;
  						break;
  				}
  				mem().setUint32(addr + 4, nanHead | typeFlag, true);
  				mem().setUint32(addr, ref, true);
  			}
  
  			const loadSlice = (addr) => {
  				const array = getInt64(addr + 0);
  				const len = getInt64(addr + 8);
  				return new Uint8Array(this._inst.exports.mem.buffer, array, len);
  			}
  
  			const loadSliceOfValues = (addr) => {
  				const array = getInt64(addr + 0);
  				const len = getInt64(addr + 8);
  				const a = new Array(len);
  				for (let i = 0; i < len; i++) {
  					a[i] = loadValue(array + i * 8);
  				}
  				return a;
  			}
  
  			const loadString = (addr) => {
  				const saddr = getInt64(addr + 0);
  				const len = getInt64(addr + 8);
  				return decoder.decode(new DataView(this._inst.exports.mem.buffer, saddr, len));
  			}
  
  			const timeOrigin = Date.now() - performance.now();
  			this.importObject = {
  				go: {
  					// func wasmExit(code int32)
  					"runtime.wasmExit": (sp) => {
  						const code = mem().getInt32(sp + 8, true);
  						this.exited = true;
  						delete this._inst;
  						delete this._values;
  						delete this._refs;
  						this.exit(code);
  					},
  
  					// func wasmWrite(fd uintptr, p unsafe.Pointer, n int32)
  					"runtime.wasmWrite": (sp) => {
  						const fd = getInt64(sp + 8);
  						const p = getInt64(sp + 16);
  						const n = mem().getInt32(sp + 24, true);
  						fs.writeSync(fd, new Uint8Array(this._inst.exports.mem.buffer, p, n));
  					},
  
  					// func nanotime() int64
  					"runtime.nanotime": (sp) => {
  						setInt64(sp + 8, (timeOrigin + performance.now()) * 1000000);
  					},
  
  					// func walltime() (sec int64, nsec int32)
  					"runtime.walltime": (sp) => {
  						const msec = (new Date).getTime();
  						setInt64(sp + 8, msec / 1000);
  						mem().setInt32(sp + 16, (msec % 1000) * 1000000, true);
  					},
  
  					// func scheduleCallback(delay int64) int32
  					"runtime.scheduleCallback": (sp) => {
  						const id = this._nextCallbackTimeoutID;
  						this._nextCallbackTimeoutID++;
  						this._callbackTimeouts.set(id, setTimeout(
  							() => { this._resolveCallbackPromise(); },
  							getInt64(sp + 8) + 1, // setTimeout has been seen to fire up to 1 millisecond early
  						));
  						mem().setInt32(sp + 16, id, true);
  					},
  
  					// func clearScheduledCallback(id int32)
  					"runtime.clearScheduledCallback": (sp) => {
  						const id = mem().getInt32(sp + 8, true);
  						clearTimeout(this._callbackTimeouts.get(id));
  						this._callbackTimeouts.delete(id);
  					},
  
  					// func getRandomData(r []byte)
  					"runtime.getRandomData": (sp) => {
  						crypto.getRandomValues(loadSlice(sp + 8));
  					},
  
  					// func stringVal(value string) ref
  					"syscall/js.stringVal": (sp) => {
  						storeValue(sp + 24, loadString(sp + 8));
  					},
  
  					// func valueGet(v ref, p string) ref
  					"syscall/js.valueGet": (sp) => {
  						storeValue(sp + 32, Reflect.get(loadValue(sp + 8), loadString(sp + 16)));
  					},
  
  					// func valueSet(v ref, p string, x ref)
  					"syscall/js.valueSet": (sp) => {
  						Reflect.set(loadValue(sp + 8), loadString(sp + 16), loadValue(sp + 32));
  					},
  
  					// func valueIndex(v ref, i int) ref
  					"syscall/js.valueIndex": (sp) => {
  						storeValue(sp + 24, Reflect.get(loadValue(sp + 8), getInt64(sp + 16)));
  					},
  
  					// valueSetIndex(v ref, i int, x ref)
  					"syscall/js.valueSetIndex": (sp) => {
  						Reflect.set(loadValue(sp + 8), getInt64(sp + 16), loadValue(sp + 24));
  					},
  
  					// func valueCall(v ref, m string, args []ref) (ref, bool)
  					"syscall/js.valueCall": (sp) => {
  						try {
  							const v = loadValue(sp + 8);
  							const m = Reflect.get(v, loadString(sp + 16));
  							const args = loadSliceOfValues(sp + 32);
  							storeValue(sp + 56, Reflect.apply(m, v, args));
  							mem().setUint8(sp + 64, 1);
  						} catch (err) {
  							storeValue(sp + 56, err);
  							mem().setUint8(sp + 64, 0);
  						}
  					},
  
  					// func valueInvoke(v ref, args []ref) (ref, bool)
  					"syscall/js.valueInvoke": (sp) => {
  						try {
  							const v = loadValue(sp + 8);
  							const args = loadSliceOfValues(sp + 16);
  							storeValue(sp + 40, Reflect.apply(v, undefined, args));
  							mem().setUint8(sp + 48, 1);
  						} catch (err) {
  							storeValue(sp + 40, err);
  							mem().setUint8(sp + 48, 0);
  						}
  					},
  
  					// func valueNew(v ref, args []ref) (ref, bool)
  					"syscall/js.valueNew": (sp) => {
  						try {
  							const v = loadValue(sp + 8);
  							const args = loadSliceOfValues(sp + 16);
  							storeValue(sp + 40, Reflect.construct(v, args));
  							mem().setUint8(sp + 48, 1);
  						} catch (err) {
  							storeValue(sp + 40, err);
  							mem().setUint8(sp + 48, 0);
  						}
  					},
  
  					// func valueLength(v ref) int
  					"syscall/js.valueLength": (sp) => {
  						setInt64(sp + 16, parseInt(loadValue(sp + 8).length));
  					},
  
  					// valuePrepareString(v ref) (ref, int)
  					"syscall/js.valuePrepareString": (sp) => {
  						const str = encoder.encode(String(loadValue(sp + 8)));
  						storeValue(sp + 16, str);
  						setInt64(sp + 24, str.length);
  					},
  
  					// valueLoadString(v ref, b []byte)
  					"syscall/js.valueLoadString": (sp) => {
  						const str = loadValue(sp + 8);
  						loadSlice(sp + 16).set(str);
  					},
  
  					// func valueInstanceOf(v ref, t ref) bool
  					"syscall/js.valueInstanceOf": (sp) => {
  						mem().setUint8(sp + 24, loadValue(sp + 8) instanceof loadValue(sp + 16));
  					},
  
  					"debug": (value) => {
  						console.log(value);
  					},
  				}
  			};
  		}
  
  		async run(instance) {
  			this._inst = instance;
  			this._values = [ // TODO: garbage collection
  				NaN,
  				0,
  				null,
  				true,
  				false,
  				global,
  				this._inst.exports.mem,
  				this,
  			];
  			this._refs = new Map();
  			this._callbackShutdown = false;
  			this.exited = false;
  
  			const mem = new DataView(this._inst.exports.mem.buffer)
  
  			// Pass command line arguments and environment variables to WebAssembly by writing them to the linear memory.
  			let offset = 4096;
  
  			const strPtr = (str) => {
  				let ptr = offset;
  				new Uint8Array(mem.buffer, offset, str.length + 1).set(encoder.encode(str + "\0"));
  				offset += str.length + (8 - (str.length % 8));
  				return ptr;
  			};
  
  			const argc = this.argv.length;
  
  			const argvPtrs = [];
  			this.argv.forEach((arg) => {
  				argvPtrs.push(strPtr(arg));
  			});
  
  			const keys = Object.keys(this.env).sort();
  			argvPtrs.push(keys.length);
  			keys.forEach((key) => {
  				argvPtrs.push(strPtr(`${key}=${this.env[key]}`));
  			});
  
  			const argv = offset;
  			argvPtrs.forEach((ptr) => {
  				mem.setUint32(offset, ptr, true);
  				mem.setUint32(offset + 4, 0, true);
  				offset += 8;
  			});
  
  			while (true) {
  				const callbackPromise = new Promise((resolve) => {
  					this._resolveCallbackPromise = () => {
  						if (this.exited) {
  							throw new Error("bad callback: Go program has already exited");
  						}
  						setTimeout(resolve, 0); // make sure it is asynchronous
  					};
  				});
  				this._inst.exports.run(argc, argv);
  				if (this.exited) {
  					break;
  				}
  				await callbackPromise;
  			}
  		}
  
  		static _makeCallbackHelper(id, pendingCallbacks, go) {
  			return function () {
  				pendingCallbacks.push({ id: id, args: arguments });
  				go._resolveCallbackPromise();
  			};
  		}
  
  		static _makeEventCallbackHelper(preventDefault, stopPropagation, stopImmediatePropagation, fn) {
  			return function (event) {
  				if (preventDefault) {
  					event.preventDefault();
  				}
  				if (stopPropagation) {
  					event.stopPropagation();
  				}
  				if (stopImmediatePropagation) {
  					event.stopImmediatePropagation();
  				}
  				fn(event);
  			};
  		}
  	}
  
  	if (isNodeJS) {
  		if (process.argv.length < 3) {
  			process.stderr.write("usage: go_js_wasm_exec [wasm binary] [arguments]\n");
  			process.exit(1);
  		}
  
  		const go = new Go();
  		go.argv = process.argv.slice(2);
  		go.env = process.env;
  		go.exit = process.exit;
  		WebAssembly.instantiate(fs.readFileSync(process.argv[2]), go.importObject).then((result) => {
  			process.on("exit", (code) => { // Node.js exits if no callback is pending
  				if (code === 0 && !go.exited) {
  					// deadlock, make Go print error and stack traces
  					go._callbackShutdown = true;
  					go._inst.exports.run();
  				}
  			});
  			return go.run(result.instance);
  		}).catch((err) => {
  			throw err;
  		});
  	}
  })();
  