package main

// The ≈ display's rate snapshot (fx.go): fetch, parse, last-good fallback,
// and the empty-until-fetched public shape.

import (
	"encoding/json"
	"net/http"
	"net/http/httptest"
	"testing"
)

const ecbSample = `<?xml version="1.0" encoding="UTF-8"?>
<gesmes:Envelope xmlns:gesmes="http://www.gesmes.org/xml/2002-08-01" xmlns="http://www.ecb.int/vocabulary/2002-08-01/eurofxref">
  <gesmes:subject>Reference rates</gesmes:subject>
  <Cube>
    <Cube time="2026-07-17">
      <Cube currency="USD" rate="1.0876"/>
      <Cube currency="GBP" rate="0.8433"/>
      <Cube currency="JPY" rate="170.61"/>
    </Cube>
  </Cube>
</gesmes:Envelope>`

func TestFXRefreshAndServe(t *testing.T) {
	feed := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
		w.Write([]byte(ecbSample))
	}))
	defer feed.Close()
	ts, s := newTestServer(t)

	get := func() (string, map[string]float64) {
		t.Helper()
		resp, err := http.Get(ts.URL + "/api/fx")
		if err != nil {
			t.Fatal(err)
		}
		defer resp.Body.Close()
		if resp.StatusCode != http.StatusOK {
			t.Fatalf("fx: HTTP %d", resp.StatusCode)
		}
		var body struct {
			Base  string             `json:"base"`
			Date  string             `json:"date"`
			Rates map[string]float64 `json:"rates"`
		}
		if err := json.NewDecoder(resp.Body).Decode(&body); err != nil {
			t.Fatal(err)
		}
		if body.Base != "EUR" {
			t.Fatalf("base = %q", body.Base)
		}
		return body.Date, body.Rates
	}

	// Before any fetch: an empty snapshot, still a clean 200 (the client just
	// shows no ≈ figure).
	if date, rates := get(); date != "" || len(rates) != 0 {
		t.Fatalf("pre-fetch snapshot = %q %v, want empty", date, rates)
	}

	if err := s.fx.refresh(http.DefaultClient, feed.URL); err != nil {
		t.Fatal(err)
	}
	date, rates := get()
	if date != "2026-07-17" || rates["USD"] != 1.0876 || rates["GBP"] != 0.8433 || len(rates) != 3 {
		t.Fatalf("snapshot = %q %v", date, rates)
	}

	// A failing feed keeps the last-good snapshot.
	feed.Close()
	if err := s.fx.refresh(http.DefaultClient, feed.URL); err == nil {
		t.Fatal("refresh against a dead feed reported success")
	}
	if date, rates := get(); date != "2026-07-17" || len(rates) != 3 {
		t.Fatalf("post-failure snapshot = %q %v, want last-good kept", date, rates)
	}

	// So does a feed that answers but parses to nothing.
	empty := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
		w.Write([]byte(`<Envelope><Cube><Cube time="2026-07-18"></Cube></Cube></Envelope>`))
	}))
	defer empty.Close()
	if err := s.fx.refresh(http.DefaultClient, empty.URL); err == nil {
		t.Fatal("empty feed reported success")
	}
	if date, _ := get(); date != "2026-07-17" {
		t.Fatalf("empty feed replaced the snapshot (date %q)", date)
	}
}