chore: Move fee breakdown logic (#578)

src/types/feeBreakdown.ts

@@ -0,0 +1,21 @@
+export interface FeeBreakdown {
+  amount: {
+    calculated: number;
+    payable: number;
+    reduction: number;
+    vat: number;
+  };
+  reductions: string[];
+  exemptions: string[];
+}
+
+export interface PassportFeeFields {
+  "application.fee.calculated": number;
+  "application.fee.payable": number;
+  "application.fee.payable.vat": number;
+  "application.fee.reduction.alternative": boolean;
+  "application.fee.reduction.parishCouncil": boolean;
+  "application.fee.reduction.sports": boolean;
+  "application.fee.exemption.disability": boolean;
+  "application.fee.exemption.resubmission": boolean;
+}

src/types/index.ts

@@ -4,6 +4,7 @@ export * from "./bops";
 export * from "./component";
 export * from "./data";
 export * from "./export";
+export * from "./feeBreakdown";
 export * from "./flags";
 export * from "./flow";
 export * from "./gov-uk-payment";

src/utils/feeBreakdown.test.ts

@@ -0,0 +1,285 @@
+import { PassportFeeFields } from "../types";
+import {
+  calculateReduction,
+  getFeeBreakdown,
+  toFeeBreakdown,
+  toNumber,
+} from "./feeBreakdown";
+
+describe("toNumber() helper function", () => {
+  it("outputs a number when passed a number", () => {
+    const input = 12;
+    const output = toNumber(input);
+
+    expect(output).toEqual(input);
+  });
+
+  it("outputs a number when passed a number tuple", () => {
+    const input: [number] = [12];
+    const output = toNumber(input);
+
+    expect(output).toEqual(12);
+  });
+});
+
+describe("calculateReduction() helper function", () => {
+  it("correctly outputs the reduction when a calculated value is provided", () => {
+    const input: PassportFeeFields = {
+      "application.fee.calculated": 100,
+      "application.fee.payable": 50,
+      "application.fee.payable.vat": 0,
+      "application.fee.reduction.alternative": false,
+      "application.fee.reduction.parishCouncil": false,
+      "application.fee.reduction.sports": false,
+      "application.fee.exemption.disability": false,
+      "application.fee.exemption.resubmission": false,
+    };
+    const reduction = calculateReduction(input);
+
+    expect(reduction).toEqual(50);
+  });
+
+  it("defaults to 0 when calculated is 0", () => {
+    const input: PassportFeeFields = {
+      "application.fee.calculated": 0,
+      "application.fee.payable": 100,
+      "application.fee.payable.vat": 0,
+      "application.fee.reduction.alternative": false,
+      "application.fee.reduction.parishCouncil": false,
+      "application.fee.reduction.sports": false,
+      "application.fee.exemption.disability": false,
+      "application.fee.exemption.resubmission": false,
+    };
+    const reduction = calculateReduction(input);
+
+    expect(reduction).toEqual(0);
+  });
+});
+
+describe("toFeeBreakdown() helper function", () => {
+  it("correctly maps fields", () => {
+    const input: PassportFeeFields = {
+      "application.fee.calculated": 100,
+      "application.fee.payable": 50,
+      "application.fee.payable.vat": 10,
+      "application.fee.reduction.alternative": false,
+      "application.fee.reduction.parishCouncil": false,
+      "application.fee.reduction.sports": false,
+      "application.fee.exemption.disability": false,
+      "application.fee.exemption.resubmission": false,
+    };
+
+    const { amount } = toFeeBreakdown(input);
+
+    expect(amount.calculated).toEqual(input["application.fee.calculated"]);
+    expect(amount.payable).toEqual(input["application.fee.payable"]);
+    expect(amount.vat).toEqual(input["application.fee.payable.vat"]);
+    expect(amount.reduction).toEqual(50);
+  });
+
+  it("sets calculated to payable amount if no calculated value is provided", () => {
+    const input: PassportFeeFields = {
+      "application.fee.calculated": 0,
+      "application.fee.payable.vat": 10,
+      "application.fee.payable": 50,
+      "application.fee.reduction.alternative": false,
+      "application.fee.reduction.parishCouncil": false,
+      "application.fee.reduction.sports": false,
+      "application.fee.exemption.disability": false,
+      "application.fee.exemption.resubmission": false,
+    };
+
+    const { amount } = toFeeBreakdown(input);
+
+    expect(amount.calculated).toEqual(input["application.fee.payable"]);
+  });
+});
+
+describe("getFeeBreakdown() function", () => {
+  describe("valid data", () => {
+    it("returns a fee breakdown for number inputs", () => {
+      const mockPassportData = {
+        "application.fee.calculated": 1000,
+        "application.fee.payable": 800,
+        "application.fee.payable.vat": 160,
+        "some.other.fields": ["abc", "xyz"],
+      };
+
+      const result = getFeeBreakdown(mockPassportData);
+
+      expect(result).toEqual({
+        amount: {
+          calculated: 1000,
+          payable: 800,
+          reduction: 200,
+          vat: 160,
+        },
+        exemptions: [],
+        reductions: [],
+      });
+    });
+
+    it("returns a fee breakdown for number tuple inputs", () => {
+      const mockPassportData = {
+        "application.fee.calculated": [1000],
+        "application.fee.payable": [800],
+        "application.fee.payable.vat": [160],
+        "some.other.fields": ["abc", "xyz"],
+      };
+
+      const result = getFeeBreakdown(mockPassportData);
+
+      expect(result).toEqual({
+        amount: {
+          calculated: 1000,
+          payable: 800,
+          reduction: 200,
+          vat: 160,
+        },
+        exemptions: [],
+        reductions: [],
+      });
+    });
+
+    it("parses 'true' reduction values to a list of keys", () => {
+      const mockPassportData = {
+        "application.fee.calculated": 1000,
+        "application.fee.payable": 800,
+        "application.fee.payable.vat": 160,
+        "application.fee.reduction.alternative": ["true"],
+        "application.fee.reduction.parishCouncil": ["true"],
+        "some.other.fields": ["abc", "xyz"],
+      };
+
+      const result = getFeeBreakdown(mockPassportData);
+
+      expect(result?.reductions).toHaveLength(2);
+      expect(result?.reductions).toEqual(
+        expect.arrayContaining(["alternative", "parishCouncil"]),
+      );
+    });
+
+    it("does not parse 'false' reduction values to a list of keys", () => {
+      const mockPassportData = {
+        "application.fee.calculated": 1000,
+        "application.fee.payable": 800,
+        "application.fee.payable.vat": 160,
+        "application.fee.reduction.alternative": ["false"],
+        "application.fee.reduction.parishCouncil": ["false"],
+        "some.other.fields": ["abc", "xyz"],
+      };
+
+      const result = getFeeBreakdown(mockPassportData);
+
+      expect(result?.reductions).toHaveLength(0);
+    });
+
+    it("does not parse non-schema reduction values", () => {
+      const mockPassportData = {
+        "application.fee.calculated": 1000,
+        "application.fee.payable": 800,
+        "application.fee.payable.vat": 160,
+        "application.fee.reduction.alternative": ["true"],
+        "application.fee.reduction.parishCouncil": ["false"],
+        "application.fee.reduction.someReason": ["true"],
+        "application.fee.reduction.someOtherReason": ["false"],
+        "some.other.fields": ["abc", "xyz"],
+      };
+
+      const result = getFeeBreakdown(mockPassportData);
+
+      expect(result?.reductions).toEqual(
+        expect.not.arrayContaining(["someReason"]),
+      );
+      expect(result?.reductions).toEqual(
+        expect.not.arrayContaining(["someOtherReason"]),
+      );
+    });
+
+    it("parses 'true' exemption values to a list of keys", () => {
+      const mockPassportData = {
+        "application.fee.calculated": 1000,
+        "application.fee.payable": 800,
+        "application.fee.payable.vat": 160,
+        "application.fee.exemption.disability": ["true"],
+        "application.fee.exemption.resubmission": ["true"],
+        "some.other.fields": ["abc", "xyz"],
+      };
+
+      const result = getFeeBreakdown(mockPassportData);
+
+      expect(result?.exemptions).toHaveLength(2);
+      expect(result?.exemptions).toEqual(
+        expect.arrayContaining(["disability", "resubmission"]),
+      );
+    });
+
+    it("does not parse 'false' exemption values to a list of keys", () => {
+      const mockPassportData = {
+        "application.fee.calculated": 1000,
+        "application.fee.payable": 800,
+        "application.fee.payable.vat": 160,
+        "application.fee.exemption.disability": ["false"],
+        "application.fee.exemption.resubmission": ["false"],
+        "some.other.fields": ["abc", "xyz"],
+      };
+
+      const result = getFeeBreakdown(mockPassportData);
+
+      expect(result?.exemptions).toHaveLength(0);
+    });
+
+    it("does not parse non-schema exemption values", () => {
+      const mockPassportData = {
+        "application.fee.calculated": 1000,
+        "application.fee.payable": 800,
+        "application.fee.payable.vat": 160,
+        "application.fee.exemption.disability": ["false"],
+        "application.fee.exemption.resubmission": ["false"],
+        "application.fee.exemption.someReason": ["true"],
+        "application.fee.exemption.someOtherReason": ["false"],
+        "some.other.fields": ["abc", "xyz"],
+      };
+
+      const result = getFeeBreakdown(mockPassportData);
+
+      expect(result?.exemptions).toEqual(
+        expect.not.arrayContaining(["someReason"]),
+      );
+      expect(result?.exemptions).toEqual(
+        expect.not.arrayContaining(["someOtherReason"]),
+      );
+    });
+  });
+
+  describe("invalid inputs", () => {
+    it("returns undefined for missing data", () => {
+      const mockPassportData = {
+        "some.other.fields": ["abc", "xyz"],
+      };
+
+      expect(() => getFeeBreakdown(mockPassportData)).toThrow();
+    });
+
+    it("returns undefined for partial data", () => {
+      const mockPassportData = {
+        "application.fee.calculated": [1000],
+        "application.fee.payable.vat": [160],
+        "some.other.fields": ["abc", "xyz"],
+      };
+
+      expect(() => getFeeBreakdown(mockPassportData)).toThrow();
+    });
+
+    it("returns undefined for incorrect data", () => {
+      const mockPassportData = {
+        "application.fee.calculated": "some string",
+        "application.fee.payable": [800, 700],
+        "application.fee.payable.vat": false,
+        "some.other.fields": ["abc", "xyz"],
+      };
+
+      expect(() => getFeeBreakdown(mockPassportData)).toThrow();
+    });
+  });
+});