From 221e3256ee7e6f2c22f0d86ef91bc44afa075816 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Olav=20Sundf=C3=B8r?= <olav@sundfoer.com>
Date: Mon, 10 May 2021 23:39:57 +0200
Subject: [PATCH 1/3] playing around with typed env

---
 packages/common/src/env.ts | 126 +++++++++++++++++++++++++++++++++++++
 1 file changed, 126 insertions(+)
 create mode 100644 packages/common/src/env.ts

diff --git a/packages/common/src/env.ts b/packages/common/src/env.ts
new file mode 100644
index 00000000..5be01eee
--- /dev/null
+++ b/packages/common/src/env.ts
@@ -0,0 +1,126 @@
+import { logger } from "./logger/logger";
+
+/**
+ * IF this works, create new module
+ */
+/* type Specification =
+  | "string"
+  | "number"
+  | string[]
+  | [min: number, max: number];
+const _env = <T extends string>(input: { [key in T]: Specification }) => {};
+
+type SecondSpecification =
+  | "string"
+  | "number"
+  | `between ${number} and ${number}`;
+
+const _around = <T extends Specification>(
+  input: { [key in SecondSpecification]: string }
+) => {};
+
+const envs = ["test", "development", "production"] as const;
+type Env = typeof envs[number];
+
+type MyEnvironment = "PORT" | "API_KEY" | "AGE";
+const env = _env<MyEnvironment>({
+  PORT: "number",
+  AGE: [13, 99],
+  API_KEY: "string",
+});
+ */
+/* type Validator = (key: string) => boolean;
+const _validator = <T extends string>(input: { [key in T]: Validator }) => {
+  Object.keys(input).map((key) => {
+    const validator = input[key] as Validator;
+    const value = process.env[key];
+    if (!validator(value))
+      throw `${key} in env did not pass validator. (value: ${value})`;
+  });
+};
+ */
+/* const guarantee = <T>(value: any, boolean: boolean): value is T => boolean;
+
+const validators = {
+  string: <T extends string>(value: T): T => {
+    guarantee(value, typeof value === "string");
+    return value;
+  },
+  number: <T extends string>(value: T): number => {
+    if (!guarantee<number>(value, parseInt(value) !== NaN)) throw "";
+    return value;
+  },
+  range: <T extends number>(from: number, to: number) => (
+    value: any
+  ): number => {
+    if (
+      !guarantee<T>(
+        value,
+        validators.number(value) && value >= from && value < to
+      )
+    )
+      throw "";
+    return value;
+  },
+};
+
+_validator({
+  PORT: validators.range(8000, 9000),
+  SERIAL: validators.number,
+  API_KEY: validators.string,
+}); */
+
+type Validators = {
+  number: () => Validator<number>;
+  string: () => Validator<string>;
+  range: (from: number, to: number) => Validator<number>;
+  oneof: <T extends string>(values: T) => Validator<T>;
+};
+const validators: Validators = {
+  number: () => (value: string) => {
+    //TODO: validate
+    return () => -1;
+  },
+  string: () => (value: string) => {
+    //TODO: validate
+    return () => value;
+  },
+  range: (from: number, to: number) => (value: string) => {
+    //TODO: value
+    return () => -1;
+  },
+  oneof: <T extends string>(values: string) => () => {
+    //TODO: validate
+    return () => null as T;
+  },
+};
+
+type Validator<G> = (input: string) => () => G;
+const _env = <T extends string>(
+  input: { [key in T]: Validator<any> }
+): {
+  [key in T]: any;
+} => {
+  return Object.keys(input)
+    .map((key: T) => ({ key, get: input[key](key) }))
+    .map((a) => ({
+      [a.key]: a.get,
+    }))
+    .reduce((a, b) => ({
+      ...a,
+      ...b,
+    })) as {
+    [key in T]: any;
+  };
+};
+
+const env = _env({
+  PORT: validators.range(100, 200),
+  API_KEY: validators.range(1, 2),
+  //API_KEY: validators.string(),
+});
+
+//FIXME: values are any..
+const getPort = validators.range(1, 2)(process.env.PORT);
+const port = getPort();
+console.log(port);

From de7b0757a39f4b183e8e00fc590acb9147212c3d Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Olav=20Sundf=C3=B8r?= <olav@sundfoer.com>
Date: Sat, 15 May 2021 16:55:55 +0000
Subject: [PATCH 2/3] practiced some tdd on env module

---
 packages/common/src/env.test.ts | 95 +++++++++++++++++++++++++++++++++
 packages/common/src/env.ts      |  6 +++
 2 files changed, 101 insertions(+)
 create mode 100644 packages/common/src/env.test.ts
 create mode 100644 packages/common/src/env.ts

diff --git a/packages/common/src/env.test.ts b/packages/common/src/env.test.ts
new file mode 100644
index 00000000..cd5ddc62
--- /dev/null
+++ b/packages/common/src/env.test.ts
@@ -0,0 +1,95 @@
+import { getEnv } from "./env";
+describe("the module for picking up env variables", () => {
+  it("is a function does not return null", () => {
+    const env = getEnv({});
+    expect(env).not.toBeNull();
+  });
+
+  it("is a function that does not return undefined", () => {
+    const env = getEnv({});
+    expect(env).not.toBeUndefined();
+  });
+
+  it("throws if one of its input is not in the env", () => {
+    expect(() => {
+      getEnv({
+        NOT_IN_ENV: "string",
+      });
+    }).toThrow();
+  });
+
+  it("throws with appropriate error if key is not in the environment", () => {
+    expect(() => {
+      getEnv({
+        NOT_IN_ENV: "string",
+      });
+    }).toThrowError(`NOT_IN_ENV was expected to be in environment`);
+  });
+
+  const withEnvironment = <T>(
+    environment: T,
+    action: (environment: T) => void
+  ) => () => {
+    const previousEnv = process.env;
+    process.env = (environment as any) as NodeJS.ProcessEnv;
+
+    action(environment);
+    process.env = previousEnv;
+  };
+
+  describe("withEnvironment helper", () => {
+    it(
+      "does change process.env",
+      withEnvironment(
+        {
+          TEST: "value",
+        },
+        (environment) => {
+          expect(process.env.TEST).toEqual("value");
+        }
+      )
+    );
+
+    it(
+      "does return test key in callback",
+      withEnvironment(
+        {
+          KEY_NAME: "TEST_VALUE",
+        },
+        (environment) => {
+          expect(environment.KEY_NAME).toEqual("TEST_VALUE");
+        }
+      )
+    );
+
+    it(
+      "returns environment exactly equal to process.env",
+      withEnvironment(
+        {
+          KEY: "VALUE",
+        },
+        (environment) => {
+          expect(environment).toEqual(process.env);
+        }
+      )
+    );
+
+    it(
+      "does not have other keys in env than the ones specified",
+      withEnvironment({ KEY: "VALUE" }, (environment) => {
+        expect(process.env).toEqual({ KEY: "VALUE" });
+      })
+    );
+    it(
+      "does not have any other keys in object than the ones specified",
+      withEnvironment(
+        {
+          KEY: "VALUE",
+        },
+        (environment) => {
+          expect(environment).toEqual({ KEY: "VALUE" });
+        }
+      )
+    );
+  });
+});
diff --git a/packages/common/src/env.ts b/packages/common/src/env.ts
new file mode 100644
index 00000000..b557c725
--- /dev/null
+++ b/packages/common/src/env.ts
@@ -0,0 +1,6 @@
+export const getEnv = <T>(input: T) => {
+  Object.keys(input).forEach((key) => {
+    if (!process.env[key]) throw `${key} was expected to be in environment`;
+  });
+  return {};
+};

From a4cd7b8103199fb6990a223a47c7ea42cae9bc85 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Olav=20Sundf=C3=B8r?= <olav@sundfoer.com>
Date: Mon, 24 May 2021 16:05:55 +0200
Subject: [PATCH 3/3] matchers working, FIX: no typing

---
 packages/common/src/env.test.ts | 82 ++++++++++++++++++++++++++++-----
 packages/common/src/env.ts      | 47 +++++++++++++++++--
 2 files changed, 112 insertions(+), 17 deletions(-)

diff --git a/packages/common/src/env.test.ts b/packages/common/src/env.test.ts
index cd5ddc62..49996c0d 100644
--- a/packages/common/src/env.test.ts
+++ b/packages/common/src/env.test.ts
@@ -1,4 +1,5 @@
-import { getEnv } from "./env";
+import faker from "faker";
+import { getEnv, isString, isInteger } from "./env";
 describe("the module for picking up env variables", () => {
   it("is a function does not return null", () => {
     const env = getEnv({});
@@ -13,7 +14,7 @@ describe("the module for picking up env variables", () => {
   it("throws if one of its input is not in the env", () => {
     expect(() => {
       getEnv({
-        NOT_IN_ENV: "string",
+        NOT_IN_ENV: isString,
       });
     }).toThrow();
   });
@@ -21,21 +22,20 @@ describe("the module for picking up env variables", () => {
   it("throws with appropriate error if key is not in the environment", () => {
     expect(() => {
       getEnv({
-        NOT_IN_ENV: "string",
+        NOT_IN_ENV: isString,
       });
     }).toThrowError(`NOT_IN_ENV was expected to be in environment`);
   });
 
-  const withEnvironment = <T>(
-    environment: T,
-    action: (environment: T) => void
-  ) => () => {
-    const previousEnv = process.env;
-    process.env = (environment as any) as NodeJS.ProcessEnv;
+  const withEnvironment =
+    <T>(environment: T, action: (environment: T) => void) =>
+    () => {
+      const previousEnv = process.env;
+      process.env = environment as any as NodeJS.ProcessEnv;
 
-    action(environment);
-    process.env = previousEnv;
-  };
+      action(environment);
+      process.env = previousEnv;
+    };
 
   describe("withEnvironment helper", () => {
     it(
@@ -91,5 +91,63 @@ describe("the module for picking up env variables", () => {
         }
       )
     );
+
+    it(
+      "Does return an object with the KEY from input",
+      withEnvironment({ KEY: "VALUE" }, () => {
+        const env = getEnv({ KEY: isString });
+        expect(env.KEY).toBeDefined();
+        expect(env.KEY).toEqual("VALUE");
+      })
+    );
+
+    it(
+      "Accepts key with type of Validator",
+      withEnvironment({ API_KEY: "some_key" }, () => {
+        const env = getEnv({ API_KEY: isString });
+        expect(env.API_KEY).toBeDefined();
+      })
+    );
+
+    it(
+      "Does not accept an argument that's not a validator",
+      withEnvironment({ PORT: faker.datatype.number() }, () => {
+        expect(() => {
+          //@ts-expect-error
+          getEnv({ PORT: "NOT_A_VALIDATOR" });
+        }).toThrow(); //will throw because "NOT_A_VALIDATOR" is not a function
+      })
+    );
+
+    it("Does return a value with the expeted type", () =>
+      withEnvironment({ PORT: faker.datatype.number() }, () => {
+        const acceptingNumber = (input: number) => {};
+        const env = getEnv({ PORT: isInteger });
+
+        //NOTE: if this does not compile, consider test failing
+        acceptingNumber(env.PORT);
+      }));
+
+    describe("isInteger validator", () => {
+      it(
+        "Fails if is not number",
+        withEnvironment({ PORT: faker.lorem.word(10) }, (environment) => {
+          expect(() => {
+            getEnv({ PORT: isInteger });
+          }).toThrowError(
+            `PORT did not match its validator. Found: ${environment.PORT}`
+          );
+        })
+      );
+
+      it(
+        "Does not fail if it is an integer",
+        withEnvironment({ PORT: faker.datatype.number() }, () => {
+          expect(() => {
+            getEnv({ PORT: isInteger });
+          }).not.toThrow();
+        })
+      );
+    });
   });
 });
diff --git a/packages/common/src/env.ts b/packages/common/src/env.ts
index b557c725..f34b6fbb 100644
--- a/packages/common/src/env.ts
+++ b/packages/common/src/env.ts
@@ -1,6 +1,43 @@
-export const getEnv = <T>(input: T) => {
-  Object.keys(input).forEach((key) => {
-    if (!process.env[key]) throw `${key} was expected to be in environment`;
-  });
-  return {};
+type PossibleTypes = string | number;
+type Validator = <T extends PossibleTypes>(
+  value: any
+) => boolean /* value is T */;
+//const a: Validator = (p: any): p is string => true;
+//a("thing");
+
+export const getEnv = <G extends string, T extends { [key in G]: Validator }>(
+  input: T
+) =>
+  Object.keys(input)
+    .map((key: G) => {
+      const actualValue = process.env[key];
+      if (!actualValue) throw `${key} was expected to be in environment`;
+
+      const validator = input[key];
+      if (!validator(actualValue))
+        throw `${key} did not match its validator. Found: ${actualValue}`;
+
+      return {
+        [key as G]: actualValue,
+      };
+    })
+    .reduce((a, b) => ({
+      ...a,
+      ...b,
+    }));
+
+export const isString = (input: any): boolean /* input is string */ =>
+  typeof input === "string" && isNaN(parseInt(input));
+
+const env = getEnv({
+  KEY: isString,
+});
+
+export const isInteger = (input: any): boolean /* input is number */ =>
+  !isNaN(parseInt(input));
+
+const isFloat = (input: any) => parseFloat(input) !== NaN;
+const isBetween = (min: number, max: number) => (input: string) => {
+  const number = parseFloat(input);
+  return number !== NaN || (number < max && number > min);
 };