import { describe, it, expect } from "vitest";
import { resolveIdentity } from "../src/mcp.js";

function fakeExtra(header?: string): unknown {
  if (header === undefined) return {};
  return { requestInfo: { headers: { "x-mailbox": header } } };
}

describe("resolveIdentity", () => {
  it("prefers the explicit argument when present", () => {
    expect(resolveIdentity("alice", fakeExtra("bob"), "from")).toBe("alice");
  });

  it("falls back to X-Mailbox header when arg missing", () => {
    expect(resolveIdentity(undefined, fakeExtra("bob"), "from")).toBe("bob");
  });

  it("trims whitespace from explicit arg and header", () => {
    expect(resolveIdentity("  alice  ", fakeExtra(), "from")).toBe("alice");
    expect(resolveIdentity(undefined, fakeExtra("  bob  "), "name")).toBe("bob");
  });

  it("treats empty arg as missing and falls back", () => {
    expect(resolveIdentity("", fakeExtra("bob"), "name")).toBe("bob");
    expect(resolveIdentity("   ", fakeExtra("bob"), "name")).toBe("bob");
  });

  it("throws with a helpful message when neither is provided", () => {
    expect(() => resolveIdentity(undefined, fakeExtra(), "from")).toThrow(
      /Pass `from`.*SessionStart announcement/i,
    );
  });

  it("throws referencing the correct arg name", () => {
    expect(() => resolveIdentity(undefined, fakeExtra(), "name")).toThrow(
      /Pass `name`/,
    );
  });

  it("handles extra without requestInfo", () => {
    expect(() => resolveIdentity(undefined, {}, "from")).toThrow(/Pass `from`/);
    expect(() => resolveIdentity(undefined, null, "from")).toThrow(/Pass `from`/);
  });
});