package mw

import (
	"net/http"
	"net/http/httptest"
	"testing"

	"code.nochebuena.dev/einherjar/core/logz"
)

// A resolver that continues the client's X-Request-ID lands in both the context
// and the response header.
func TestRequestIDFrom_HonoursInbound(t *testing.T) {
	const inbound = "client-supplied-123"

	var ctxID string
	h := RequestIDFrom(func(r *http.Request) string {
		return r.Header.Get("X-Request-ID")
	})(http.HandlerFunc(func(_ http.ResponseWriter, r *http.Request) {
		ctxID = logz.GetRequestID(r.Context())
	}))

	req := httptest.NewRequest(http.MethodGet, "/", nil)
	req.Header.Set("X-Request-ID", inbound)
	rec := httptest.NewRecorder()
	h.ServeHTTP(rec, req)

	if ctxID != inbound {
		t.Errorf("context request id = %q, want %q", ctxID, inbound)
	}
	if got := rec.Header().Get("X-Request-ID"); got != inbound {
		t.Errorf("response header = %q, want %q", got, inbound)
	}
}

// Deliberate regression: RequestID(gen) always generates and never honours an
// inbound X-Request-ID. Callers that want to continue a client id use RequestIDFrom.
func TestRequestID_AlwaysGenerates_IgnoresInbound(t *testing.T) {
	const inbound = "client-supplied-123"
	const generated = "generated-999"

	var ctxID string
	h := RequestID(func() string { return generated })(
		http.HandlerFunc(func(_ http.ResponseWriter, r *http.Request) {
			ctxID = logz.GetRequestID(r.Context())
		}))

	req := httptest.NewRequest(http.MethodGet, "/", nil)
	req.Header.Set("X-Request-ID", inbound)
	rec := httptest.NewRecorder()
	h.ServeHTTP(rec, req)

	if ctxID != generated {
		t.Errorf("context request id = %q, want generated %q (inbound must be ignored)", ctxID, generated)
	}
	if got := rec.Header().Get("X-Request-ID"); got != generated {
		t.Errorf("response header = %q, want %q", got, generated)
	}
}

// The resolver runs exactly once per request.
func TestRequestIDFrom_ResolverCalledOnce(t *testing.T) {
	calls := 0
	h := RequestIDFrom(func(*http.Request) string {
		calls++
		return "id"
	})(http.HandlerFunc(func(http.ResponseWriter, *http.Request) {}))

	h.ServeHTTP(httptest.NewRecorder(), httptest.NewRequest(http.MethodGet, "/", nil))

	if calls != 1 {
		t.Errorf("resolver called %d times, want 1", calls)
	}
}

// An empty resolver result attaches nothing: no context id and no response header,
// rather than a silently-empty value.
func TestRequestIDFrom_EmptyResult_AttachesNothing(t *testing.T) {
	var ctxID string
	h := RequestIDFrom(func(*http.Request) string { return "" })(
		http.HandlerFunc(func(_ http.ResponseWriter, r *http.Request) {
			ctxID = logz.GetRequestID(r.Context())
		}))

	req := httptest.NewRequest(http.MethodGet, "/", nil)
	req.Header.Set("X-Request-ID", "should-be-ignored")
	rec := httptest.NewRecorder()
	h.ServeHTTP(rec, req)

	if ctxID != "" {
		t.Errorf("context request id = %q, want empty (nothing attached)", ctxID)
	}
	if vals := rec.Header().Values("X-Request-ID"); len(vals) != 0 {
		t.Errorf("X-Request-ID header = %v on empty resolve; want absent", vals)
	}
}