Wire /calculator to real ROI data and persistence

data/calculator-presets.json

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+[
+  {
+    "id": "solo-developer",
+    "name": "Solo Developer",
+    "description": "One builder automating repetitive coding and support tasks.",
+    "inputs": {
+      "agents": 1,
+      "hoursSavedPerAgentPerDay": 1.5,
+      "hourlyRate": 90,
+      "monthlyToolCosts": 149
+    }
+  },
+  {
+    "id": "small-team",
+    "name": "Small Team",
+    "description": "A startup squad using agents across product and operations.",
+    "inputs": {
+      "agents": 5,
+      "hoursSavedPerAgentPerDay": 2,
+      "hourlyRate": 75,
+      "monthlyToolCosts": 699
+    }
+  },
+  {
+    "id": "enterprise",
+    "name": "Enterprise",
+    "description": "Cross-functional enterprise deployment with strict SLAs.",
+    "inputs": {
+      "agents": 40,
+      "hoursSavedPerAgentPerDay": 1.75,
+      "hourlyRate": 95,
+      "monthlyToolCosts": 9500
+    }
+  },
+  {
+    "id": "agency",
+    "name": "Agency",
+    "description": "Client services team using agents to speed delivery.",
+    "inputs": {
+      "agents": 12,
+      "hoursSavedPerAgentPerDay": 2.5,
+      "hourlyRate": 85,
+      "monthlyToolCosts": 2200
+    }
+  }
+]

data/calculator-results.json

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+[
+  {
+    "id": "calc_seed_001",
+    "name": "Pilot - Internal Ops",
+    "inputs": {
+      "agents": 3,
+      "hoursSavedPerAgentPerDay": 1.8,
+      "hourlyRate": 70,
+      "monthlyToolCosts": 399
+    },
+    "results": {
+      "monthlySavings": 7917,
+      "annualRoi": 1984.21,
+      "paybackPeriodMonths": 0.05,
+      "efficiencyGainPercent": 22.5
+    },
+    "createdAt": "2026-01-03T14:23:00.000Z"
+  },
+  {
+    "id": "calc_seed_002",
+    "name": "Sales Enablement Rollout",
+    "inputs": {
+      "agents": 8,
+      "hoursSavedPerAgentPerDay": 1.25,
+      "hourlyRate": 65,
+      "monthlyToolCosts": 1200
+    },
+    "results": {
+      "monthlySavings": 13100,
+      "annualRoi": 1091.67,
+      "paybackPeriodMonths": 0.09,
+      "efficiencyGainPercent": 15.63
+    },
+    "createdAt": "2026-01-10T09:10:00.000Z"
+  },
+  {
+    "id": "calc_seed_003",
+    "name": "Agency Client Delivery",
+    "inputs": {
+      "agents": 10,
+      "hoursSavedPerAgentPerDay": 2.4,
+      "hourlyRate": 80,
+      "monthlyToolCosts": 2100
+    },
+    "results": {
+      "monthlySavings": 40140,
+      "annualRoi": 1911.43,
+      "paybackPeriodMonths": 0.05,
+      "efficiencyGainPercent": 30
+    },
+    "createdAt": "2026-01-22T18:47:00.000Z"
+  }
+]

src/app/api/calculator/route.ts

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+import { promises as fs } from "fs";
+import path from "path";
+import { NextRequest, NextResponse } from "next/server";
+
+type CalculatorInputs = {
+  agents: number;
+  hoursSavedPerAgentPerDay: number;
+  hourlyRate: number;
+  monthlyToolCosts: number;
+};
+
+type CalculatorResults = {
+  monthlySavings: number;
+  annualRoi: number;
+  paybackPeriodMonths: number | null;
+  efficiencyGainPercent: number;
+};
+
+type SavedCalculation = {
+  id: string;
+  name: string;
+  inputs: CalculatorInputs;
+  results: CalculatorResults;
+  createdAt: string;
+};
+
+type SaveCalculationBody = {
+  name?: unknown;
+  inputs?: unknown;
+  results?: unknown;
+};
+
+const PRESETS_PATH = path.join(process.cwd(), "data", "calculator-presets.json");
+const RESULTS_PATH = path.join(process.cwd(), "data", "calculator-results.json");
+
+function isFiniteNumber(value: unknown): value is number {
+  return typeof value === "number" && Number.isFinite(value);
+}
+
+function isInputs(value: unknown): value is CalculatorInputs {
+  if (!value || typeof value !== "object") {
+    return false;
+  }
+
+  const inputs = value as Partial<CalculatorInputs>;
+
+  return (
+    isFiniteNumber(inputs.agents) &&
+    isFiniteNumber(inputs.hoursSavedPerAgentPerDay) &&
+    isFiniteNumber(inputs.hourlyRate) &&
+    isFiniteNumber(inputs.monthlyToolCosts)
+  );
+}
+
+function isResults(value: unknown): value is CalculatorResults {
+  if (!value || typeof value !== "object") {
+    return false;
+  }
+
+  const results = value as Partial<CalculatorResults>;
+
+  const paybackValid =
+    results.paybackPeriodMonths === null || isFiniteNumber(results.paybackPeriodMonths);
+
+  return (
+    isFiniteNumber(results.monthlySavings) &&
+    isFiniteNumber(results.annualRoi) &&
+    paybackValid &&
+    isFiniteNumber(results.efficiencyGainPercent)
+  );
+}
+
+async function readJsonFile<T>(filePath: string, fallback: T): Promise<T> {
+  try {
+    const raw = await fs.readFile(filePath, "utf8");
+    return JSON.parse(raw) as T;
+  } catch {
+    return fallback;
+  }
+}
+
+async function writeResults(results: SavedCalculation[]): Promise<void> {
+  const dir = path.dirname(RESULTS_PATH);
+  await fs.mkdir(dir, { recursive: true });
+  await fs.writeFile(RESULTS_PATH, JSON.stringify(results, null, 2), "utf8");
+}
+
+export async function GET() {
+  try {
+    const presets = await readJsonFile(PRESETS_PATH, []);
+
+    if (!Array.isArray(presets)) {
+      return NextResponse.json({ error: "Invalid presets format" }, { status: 500 });
+    }
+
+    return NextResponse.json({ presets });
+  } catch (error) {
+    console.error("Failed to load calculator presets", error);
+    return NextResponse.json({ error: "Failed to load calculator presets" }, { status: 500 });
+  }
+}
+
+export async function POST(request: NextRequest) {
+  try {
+    const body = (await request.json()) as SaveCalculationBody;
+
+    const name = typeof body.name === "string" ? body.name.trim() : "";
+    const inputs = body.inputs;
+    const results = body.results;
+
+    if (!name) {
+      return NextResponse.json({ error: "name is required" }, { status: 400 });
+    }
+
+    if (!isInputs(inputs)) {
+      return NextResponse.json(
+        { error: "inputs must include agents, hoursSavedPerAgentPerDay, hourlyRate, and monthlyToolCosts" },
+        { status: 400 }
+      );
+    }
+
+    if (!isResults(results)) {
+      return NextResponse.json(
+        {
+          error:
+            "results must include monthlySavings, annualRoi, paybackPeriodMonths, and efficiencyGainPercent",
+        },
+        { status: 400 }
+      );
+    }
+
+    const existingResults = await readJsonFile<SavedCalculation[]>(RESULTS_PATH, []);
+    const safeResults = Array.isArray(existingResults) ? existingResults : [];
+
+    const record: SavedCalculation = {
+      id: `calc_${Date.now()}_${Math.random().toString(36).slice(2, 8)}`,
+      name,
+      inputs,
+      results,
+      createdAt: new Date().toISOString(),
+    };
+
+    safeResults.unshift(record);
+    await writeResults(safeResults);
+
+    return NextResponse.json({ calculation: record }, { status: 201 });
+  } catch (error) {
+    console.error("Failed to save calculator result", error);
+    return NextResponse.json({ error: "Failed to save calculator result" }, { status: 500 });
+  }
+}