package metrics

import (
	"io"
	"net/http"
	"net/http/httptest"
	"strings"
	"testing"
	"time"
)

func TestRegistry_ObserveAndExpose(t *testing.T) {
	t.Parallel()

	r := New()
	// Three observations on the same series; one falls into each
	// representative band.
	r.Observe("/query", "2xx", 4*time.Millisecond)   // ≤ 5ms
	r.Observe("/query", "2xx", 20*time.Millisecond)  // ≤ 25ms
	r.Observe("/query", "2xx", 600*time.Millisecond) // ≤ 1s

	req := httptest.NewRequest(http.MethodGet, "/metrics", nil)
	rec := httptest.NewRecorder()
	r.Handler().ServeHTTP(rec, req)

	body := rec.Body.String()

	mustContain := []string{
		`# TYPE brain_query_duration_seconds histogram`,
		`brain_query_duration_seconds_bucket{path="/query",status="2xx",le="0.005"} 1`,
		`brain_query_duration_seconds_bucket{path="/query",status="2xx",le="0.025"} 2`,
		`brain_query_duration_seconds_bucket{path="/query",status="2xx",le="1.0"} 3`,
		`brain_query_duration_seconds_bucket{path="/query",status="2xx",le="+Inf"} 3`,
		`brain_query_duration_seconds_count{path="/query",status="2xx"} 3`,
	}
	for _, want := range mustContain {
		if !strings.Contains(body, want) {
			t.Errorf("missing line: %q\n--- body ---\n%s", want, body)
		}
	}

	if got := rec.Header().Get("Content-Type"); !strings.HasPrefix(got, "text/plain") {
		t.Errorf("content-type = %q, want text/plain prefix", got)
	}
}

func TestRegistry_LabelsByStatus(t *testing.T) {
	t.Parallel()

	r := New()
	r.Observe("/query", "2xx", time.Millisecond)
	r.Observe("/query", "5xx", time.Millisecond)
	r.Observe("/write", "2xx", time.Millisecond)

	rec := httptest.NewRecorder()
	r.Handler().ServeHTTP(rec, httptest.NewRequest(http.MethodGet, "/metrics", nil))
	body := rec.Body.String()

	for _, want := range []string{
		`brain_query_duration_seconds_count{path="/query",status="2xx"} 1`,
		`brain_query_duration_seconds_count{path="/query",status="5xx"} 1`,
		`brain_query_duration_seconds_count{path="/write",status="2xx"} 1`,
	} {
		if !strings.Contains(body, want) {
			t.Errorf("missing %q in body:\n%s", want, body)
		}
	}
}

func TestMiddleware_RecordsTiming(t *testing.T) {
	t.Parallel()

	r := New()
	handler := r.Middleware(http.HandlerFunc(func(w http.ResponseWriter, _ *http.Request) {
		time.Sleep(2 * time.Millisecond)
		w.WriteHeader(http.StatusOK)
		_, _ = io.WriteString(w, "ok")
	}))

	srv := httptest.NewServer(handler)
	defer srv.Close()

	resp, err := http.Get(srv.URL + "/query")
	if err != nil {
		t.Fatalf("get: %v", err)
	}
	_ = resp.Body.Close()

	if resp.StatusCode != http.StatusOK {
		t.Fatalf("status %d, want 200", resp.StatusCode)
	}

	// Exposition should now include /query.
	rec := httptest.NewRecorder()
	r.Handler().ServeHTTP(rec, httptest.NewRequest(http.MethodGet, "/metrics", nil))
	body := rec.Body.String()
	if !strings.Contains(body, `path="/query"`) {
		t.Errorf("expected /query series, got body:\n%s", body)
	}
	if !strings.Contains(body, `status="2xx"`) {
		t.Errorf("expected 2xx status class, got body:\n%s", body)
	}
}

func TestStatusRecorder_DefaultsTo200(t *testing.T) {
	t.Parallel()

	r := New()
	handler := r.Middleware(http.HandlerFunc(func(w http.ResponseWriter, _ *http.Request) {
		_, _ = w.Write([]byte("hello"))
	}))

	rec := httptest.NewRecorder()
	handler.ServeHTTP(rec, httptest.NewRequest(http.MethodGet, "/x", nil))

	if rec.Code != http.StatusOK {
		t.Errorf("code %d, want 200", rec.Code)
	}
}