From ab53f080b2cbf8a4e6ce3e9e4394684e38459fc8 Mon Sep 17 00:00:00 2001
From: Sven Slootweg <admin@cryto.net>
Date: Wed, 5 Jul 2023 01:29:40 +0200
Subject: [PATCH] Initial commit

---
 README.md    |   3 ++
 index.js     | 133 +++++++++++++++++++++++++++++++++++++++++++++++++++
 package.json |   8 ++++
 3 files changed, 144 insertions(+)
 create mode 100644 README.md
 create mode 100644 index.js
 create mode 100644 package.json

diff --git a/README.md b/README.md
new file mode 100644
index 0000000..56f77bf
--- /dev/null
+++ b/README.md
@@ -0,0 +1,3 @@
+# @joepie91/result
+
+A rudimentary result type. Work in progress.
diff --git a/index.js b/index.js
new file mode 100644
index 0000000..9be77de
--- /dev/null
+++ b/index.js
@@ -0,0 +1,133 @@
+"use strict";
+
+function createResultObject(isSuccessful, containedValue) {
+	return {
+		__isResultType: true,
+		isOK: isSuccessful,
+		isError: !isSuccessful,
+		error: function () {
+			if (!isSuccessful) {
+				return containedValue;
+			} else {
+				// FIXME: Clearer error message, definitely a bug!
+				throw new Error(`The Result is in a success state`);
+			}
+		},
+		value: function () {
+			if (isSuccessful) {
+				return containedValue;
+			} else {
+				throw containedValue;
+			}
+		},
+		valueOr: function (defaultValue) {
+			if (isSuccessful) {
+				return containedValue;
+			} else {
+				return defaultValue;
+			}
+		},
+		mapTo: function ({ ok, error }) {
+			let okMapper = ok ?? ((value) => Result.ok(value));
+			let errorMapper = error ?? ((error) => Result.error(error));
+
+			if (this.isOK) {
+				let mapped = okMapper(containedValue);
+
+				return (Result.isResult(mapped))
+					? mapped
+					: Result.ok(mapped);
+			} else {
+				let mapped = errorMapper(containedValue);
+
+				return (Result.isResult(mapped))
+					? mapped
+					: Result.error(mapped);
+			}
+		},
+		// valueOr: function (errorCode, errorMessage) {
+		// 	if (isSuccessful) {
+		// 		return containedValue;
+		// 	} else {
+		// 		// FIXME: Integrate with error-chain somehow?
+		// 		let error = new Error(errorMessage);
+		// 		error.code = errorCode;
+		// 		throw error;
+		// 	}
+		// },
+		// FIXME: Chaining, Promise chain integration?
+		// FIXME: Serialization
+		// FIXME: Chaining with error filtering
+	};
+}
+
+let Result = module.exports = {
+	isResult: function (value) {
+		return (value != null && value.__isResultType === true);
+	},
+	ok: function (value) {
+		// Emulate what Promises do on `resolve(...)`
+		if (this.isResult(value)) {
+			return value;
+		} else {
+			return createResultObject(true, value);
+		}
+	},
+	error: function (error) {
+		return createResultObject(false, error);
+	},
+	wrap: function (callback) {
+		// Always returns a Result
+		try {
+			let result = callback();
+			return this.ok(result);
+		} catch (error) {
+			return this.error(error);
+		}
+	},
+	wrapAsync: function (callback) {
+		// Always returns a Promise that resolves to a Result
+		return new Promise((resolve, _reject) => {
+			resolve(callback());
+		}).then((result) => {
+			return this.ok(result);
+		}).catch((error) => {
+			return this.error(error);
+		});
+	},
+	// The below methods are used when it's unknown whether something will produce a Result or just return/throw
+	unwrapValue: function (value) {
+		if (Result.isResult(value)) {
+			return value.unwrap();
+		} else {
+			return value;
+		}
+	},
+	unwrap: function (callback) {
+		return Result.unwrapValue(callback());
+	},
+	unwrapAsync: function (callback) {
+		return new Promise((resolve, _reject) => {
+			resolve(callback());
+		}).then((result) => {
+			return Result.unwrapValue(result);
+		});
+	}
+};
+
+
+/* IDEA:
+
+result.mapTo({
+	ok: (value) => value * 2,
+	error: (error) => chain(error, ErrorType, "Foo Bar")
+})
+
+result.mapTo({
+	// can return either a result or any value
+	ok: (value) => value * 2,
+	// can return either a result or an Error
+	error: (_error) => result.ok(0)
+})
+
+*/
diff --git a/package.json b/package.json
new file mode 100644
index 0000000..9349d39
--- /dev/null
+++ b/package.json
@@ -0,0 +1,8 @@
+{
+  "name": "@joepie91/result",
+  "version": "0.1.0",
+  "main": "index.js",
+  "repository": "https://git.cryto.net/joepie91/result.git",
+  "author": "Sven Slootweg <admin@cryto.net>",
+  "license": "WTFPL OR CC0-1.0"
+}