import { describe, it, expect, vi, beforeEach } from "vitest";
import express from "express";
import request from "supertest";

let app: express.Express;

beforeEach(async () => {
  vi.clearAllMocks();
  vi.resetModules();
  
  // Create a minimal test app that mimics the structure of the main app
  app = express();
  
  // Add request ID middleware (used by error handler)
  app.use((req, _res, next) => {
    req.requestId = "test-request-id";
    next();
  });
  
  // Add JSON parsing middleware
  app.use(express.json({ limit: "500kb" }));
  
  // Add test routes that can throw errors
  app.post("/v1/convert/html", (_req, _res, next) => {
    const err = new Error("Test API error");
    next(err);
  });
  
  app.get("/v1/test-error", (_req, _res, next) => {
    const err = new Error("Test V1 error");
    next(err);
  });
  
  app.get("/health/test-error", (_req, _res, next) => {
    const err = new Error("Test health error");
    next(err);
  });
  
  app.get("/non-api/test-error", (_req, _res, next) => {
    const err = new Error("Test non-API error");
    next(err);
  });
  
  // Import and add the global error handler from index.ts
  // We need to copy the exact error handler logic
  app.use((err: unknown, req: express.Request, res: express.Response, _next: express.NextFunction) => {
    const reqId = req.requestId || "unknown";
    
    // Check if this is a JSON parse error from express.json()
    if (err instanceof SyntaxError && 'status' in err && (err as Record<string, unknown>).status === 400 && 'body' in err) {
      if (!res.headersSent) {
        res.status(400).json({ error: "Invalid JSON in request body" });
      }
      return;
    }
    
    if (!res.headersSent) {
      const isApi = req.path.startsWith("/v1/") || req.path.startsWith("/health");
      if (isApi) {
        res.status(500).json({ error: "Internal server error" });
      } else {
        res.status(500).send("Internal server error");
      }
    }
  });
});

describe("global error handler", () => {
  it("returns 400 JSON response for invalid JSON body", async () => {
    const response = await request(app)
      .post("/v1/convert/html")
      .set("Content-Type", "application/json")
      .send("{ invalid json content")
      .expect(400);
    
    expect(response.body).toEqual({
      error: "Invalid JSON in request body"
    });
    expect(response.headers["content-type"]).toMatch(/application\/json/);
  });
  
  it("returns 500 JSON response for errors on /v1/* API paths", async () => {
    const response = await request(app)
      .get("/v1/test-error")
      .expect(500);
    
    expect(response.body).toEqual({
      error: "Internal server error"
    });
    expect(response.headers["content-type"]).toMatch(/application\/json/);
  });
  
  it("returns 500 JSON response for errors on /health API paths", async () => {
    const response = await request(app)
      .get("/health/test-error")
      .expect(500);
    
    expect(response.body).toEqual({
      error: "Internal server error"
    });
    expect(response.headers["content-type"]).toMatch(/application\/json/);
  });
  
  it("returns 500 plain text response for errors on non-API paths", async () => {
    const response = await request(app)
      .get("/non-api/test-error")
      .expect(500);
    
    expect(response.text).toBe("Internal server error");
    expect(response.headers["content-type"]).toMatch(/text\/html/);
  });
  
  it("handles POST requests with valid JSON but route throws error (API path)", async () => {
    const response = await request(app)
      .post("/v1/convert/html")
      .set("Content-Type", "application/json")
      .send({ html: "<h1>Test</h1>" })
      .expect(500);
    
    expect(response.body).toEqual({
      error: "Internal server error"
    });
    expect(response.headers["content-type"]).toMatch(/application\/json/);
  });
});