POC generating types from JSON schema

There are tools out there that do this, no need to reinvent the wheel

test/generate-typescript/type-declaration-from-schema.test.js

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+/* eslint-disable no-use-before-define */
+
+function generateObjectType(schema) {
+  const properties = Object.keys(schema.properties)
+    .map((key) => {
+      const property = schema.properties[key];
+
+      return `${key}: ${generateType(property)}`;
+    })
+    .join(", ");
+
+  return `{ ${properties} }`;
+}
+
+function generateType(schema) {
+  if (schema.type === "string") {
+    return "string";
+  }
+
+  if (schema.type === "integer") {
+    return "number";
+  }
+
+  if (schema.type === "object") {
+    return generateObjectType(schema);
+  }
+
+  if (schema.type === "array") {
+    return `${generateType(schema.items)}[]`;
+  }
+
+  return `/* unknown type: ${schema.type} */`;
+}
+
+function generateTypeDeclaration(name, schema) {
+  return `export type ${name} = ${generateType(schema)};`;
+}
+
+describe("typeScript generator", () => {
+  it("creates a type declaration for a simple string", () => {
+    const code = generateTypeDeclaration("foo", { type: "string" });
+
+    expect(code).toBe("export type foo = string;");
+  });
+
+  it("creates a type declaration for an integer", () => {
+    const code = generateTypeDeclaration("foo", { type: "integer" });
+
+    expect(code).toBe("export type foo = number;");
+  });
+
+  it("creates a type declaration for an object", () => {
+    const code = generateTypeDeclaration("foo", {
+      type: "object",
+
+      properties: {
+        id: {
+          type: "integer",
+          format: "int64",
+        },
+
+        name: {
+          type: "string",
+        },
+      },
+
+      required: ["name"],
+
+      example: {
+        name: "Puma",
+        id: 1,
+      },
+    });
+
+    expect(code).toBe("export type foo = { id: number, name: string };");
+  });
+
+  it("creates a type declaration for an array", () => {
+    const code = generateTypeDeclaration("foo", {
+      type: "array",
+
+      items: {
+        type: "string",
+      },
+    });
+
+    expect(code).toBe("export type foo = string[];");
+  });
+
+  it("creates a type declaration for an array of objects", () => {
+    const code = generateTypeDeclaration("foo", {
+      type: "array",
+
+      items: {
+        type: "object",
+
+        properties: {
+          id: {
+            type: "integer",
+            format: "int64",
+          },
+
+          name: {
+            type: "string",
+          },
+        },
+      },
+    });
+
+    expect(code).toBe("export type foo = { id: number, name: string }[];");
+  });
+});