package appview

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

	"github.com/go-chi/chi/v5"
)

// catalogRouter wires the production registration, mountCatalogRefusal, over a
// stand-in for the distribution app, so the test can tell an intercepted request
// from one that reached the library. Calling the real helper rather than
// restating its routes keeps the test from drifting away from NewServer.
func catalogRouter() (chi.Router, *bool) {
	reachedDistribution := false
	r := chi.NewRouter()
	// Registered first on purpose: chi must prefer the static patterns below
	// even when the wildcard is declared ahead of them.
	r.Handle("/v2/*", http.HandlerFunc(func(w http.ResponseWriter, _ *http.Request) {
		reachedDistribution = true
		w.Header().Set("Content-Type", "application/json")
		_, _ = w.Write([]byte(`{"repositories":[]}`))
	}))
	mountCatalogRefusal(r)
	return r, &reachedDistribution
}

// TestCatalogUnsupported pins the contract: /v2/_catalog answers UNSUPPORTED
// with 405 for every parameter shape, so no query string can change the answer.
func TestCatalogUnsupported(t *testing.T) {
	paths := []string{
		"/v2/_catalog",
		"/v2/_catalog?n=1",
		"/v2/_catalog?n=1000",
		"/v2/_catalog?n=0",
		"/v2/_catalog?n=-1",
		"/v2/_catalog?n=abc",
		"/v2/_catalog?last=foo",
		"/v2/_catalog?n=1000&last=foo",
		"/v2/_catalog/",
		"/v2/_catalog/?n=1000",
	}
	methods := []string{http.MethodGet, http.MethodHead, http.MethodPost, http.MethodDelete}

	for _, path := range paths {
		for _, method := range methods {
			t.Run(method+" "+path, func(t *testing.T) {
				router, reached := catalogRouter()
				rec := httptest.NewRecorder()
				router.ServeHTTP(rec, httptest.NewRequest(method, path, nil))

				if *reached {
					t.Fatalf("request reached the distribution handler, chi routed %q to the wildcard", path)
				}
				if rec.Code != http.StatusMethodNotAllowed {
					t.Errorf("status = %d, want %d", rec.Code, http.StatusMethodNotAllowed)
				}
				if ct := rec.Header().Get("Content-Type"); ct != "application/json" {
					t.Errorf("Content-Type = %q, want application/json", ct)
				}

				var body struct {
					Errors []struct {
						Code    string `json:"code"`
						Message string `json:"message"`
					} `json:"errors"`
				}
				if err := json.Unmarshal(rec.Body.Bytes(), &body); err != nil {
					t.Fatalf("decode body %q: %v", rec.Body.String(), err)
				}
				if len(body.Errors) != 1 {
					t.Fatalf("got %d errors, want 1: %s", len(body.Errors), rec.Body.String())
				}
				if body.Errors[0].Code != "UNSUPPORTED" {
					t.Errorf("code = %q, want UNSUPPORTED", body.Errors[0].Code)
				}
				if body.Errors[0].Message == "" {
					t.Error("message is empty, it should explain why there is no catalog")
				}
			})
		}
	}
}

// TestCatalogResponseIsIdentical asserts the stronger property: not merely that
// every form is UNSUPPORTED, but that every form produces byte-identical output,
// so no parameter is left able to influence the answer.
func TestCatalogResponseIsIdentical(t *testing.T) {
	paths := []string{
		"/v2/_catalog",
		"/v2/_catalog?n=1",
		"/v2/_catalog?n=1000",
		"/v2/_catalog?n=0",
		"/v2/_catalog?n=-1",
		"/v2/_catalog?n=abc",
		"/v2/_catalog?last=foo",
		"/v2/_catalog/",
	}

	var wantCode int
	var wantBody string
	for i, path := range paths {
		router, _ := catalogRouter()
		rec := httptest.NewRecorder()
		router.ServeHTTP(rec, httptest.NewRequest(http.MethodGet, path, nil))
		if i == 0 {
			wantCode, wantBody = rec.Code, rec.Body.String()
			continue
		}
		if rec.Code != wantCode || rec.Body.String() != wantBody {
			t.Errorf("%s returned %d %q, want %d %q", path, rec.Code, rec.Body.String(), wantCode, wantBody)
		}
	}
}

// TestCatalogDoesNotShadowRepositories guards the interception's blast radius:
// real repository paths must still reach the distribution handler.
func TestCatalogDoesNotShadowRepositories(t *testing.T) {
	paths := []string{
		"/v2/",
		"/v2/alice.example.com/nginx/tags/list",
		"/v2/alice.example.com/_catalog/manifests/latest",
		"/v2/_catalogue/nginx/tags/list",
	}
	for _, path := range paths {
		t.Run(path, func(t *testing.T) {
			router, reached := catalogRouter()
			rec := httptest.NewRecorder()
			router.ServeHTTP(rec, httptest.NewRequest(http.MethodGet, path, nil))
			if !*reached {
				t.Errorf("%s was intercepted, it should reach the distribution handler (got %d %q)", path, rec.Code, rec.Body.String())
			}
		})
	}
}

// TestCatalogSends405Allow pins the Allow header RFC 9110 requires on a 405.
//
// 15.5.6 and 10.2.1 both state it as a MUST: "An origin server MUST generate an
// Allow header field in a 405 (Method Not Allowed) response." UNSUPPORTED maps
// to 405, so the header has to be there. The value is empty on purpose —
// 10.2.1: "An empty Allow field value indicates that the resource allows no
// methods" — which is the truth for a catalog that does not exist.
//
// Asserted via the header map rather than the raw wire because Go writes an
// empty field value as "Allow: " and a client reads it back as present with an
// empty string, which is the distinction that matters: present-and-empty is
// compliant, absent is not.
func TestCatalogSends405Allow(t *testing.T) {
	r, _ := catalogRouter()

	for _, method := range []string{http.MethodGet, http.MethodHead, http.MethodPost} {
		for _, path := range []string{"/v2/_catalog", "/v2/_catalog/", "/v2/_catalog?n=1000"} {
			req := httptest.NewRequest(method, path, nil)
			rec := httptest.NewRecorder()
			r.ServeHTTP(rec, req)

			if rec.Code != http.StatusMethodNotAllowed {
				t.Errorf("%s %s: status = %d, want %d", method, path, rec.Code, http.StatusMethodNotAllowed)
			}
			values, present := rec.Result().Header["Allow"]
			if !present {
				t.Errorf("%s %s: no Allow header on a 405; RFC 9110 15.5.6 makes it a MUST", method, path)
				continue
			}
			if len(values) != 1 || values[0] != "" {
				t.Errorf("%s %s: Allow = %q, want exactly one empty value (RFC 9110 10.2.1: the resource allows no methods)",
					method, path, values)
			}
		}
	}
}