package httpapi

import (
	"bytes"
	"context"
	"encoding/json"
	"errors"
	"io"
	"log/slog"
	"net/http"
	"net/http/httptest"
	"strings"
	"testing"
	"time"

	"textmachine/platform/internal/auth"
)

type prober struct{ err error }

func (p prober) Ready(context.Context) error { return p.err }

type liveSessions struct{}

func (liveSessions) Lookup(context.Context, []byte, time.Time) (auth.Session, error) {
	return auth.Session{UserID: "u1", IdleExpiresAt: time.Now().Add(time.Hour), AbsoluteExpiresAt: time.Now().Add(time.Hour)}, nil
}
func (liveSessions) Touch(context.Context, []byte, time.Time, time.Duration) error { return nil }

type deadSessions struct{}

func (deadSessions) Lookup(context.Context, []byte, time.Time) (auth.Session, error) {
	return auth.Session{}, auth.ErrNoSession
}
func (deadSessions) Touch(context.Context, []byte, time.Time, time.Duration) error { return nil }

func newServer(t *testing.T, db Prober, sessions auth.SessionStore) (http.Handler, *bytes.Buffer) {
	t.Helper()
	var logs bytes.Buffer
	h, err := New(Deps{
		Log: slog.New(slog.NewJSONHandler(&logs, nil)),
		DB:  db,
		Auth: &auth.Authenticator{
			Sessions: sessions,
			IdleTTL:  time.Hour,
			Deny:     ProblemHandler(http.StatusUnauthorized, "Session missing or invalid"),
		},
	})
	if err != nil {
		t.Fatal(err)
	}
	return h, &logs
}

func TestHealthzIsIndependentOfTheDatabase(t *testing.T) {
	h, _ := newServer(t, prober{err: errors.New("down")}, deadSessions{})
	w := httptest.NewRecorder()
	h.ServeHTTP(w, httptest.NewRequest(http.MethodGet, "/healthz", nil))
	if w.Code != http.StatusOK {
		t.Fatalf("status = %d", w.Code)
	}
	// PT-34 and the no-store rule are applied to every response, not per handler.
	if got := w.Header().Get("X-Robots-Tag"); !strings.Contains(got, "noindex") {
		t.Fatalf("X-Robots-Tag = %q", got)
	}
	if got := w.Header().Get("Cache-Control"); got != "no-store" {
		t.Fatalf("Cache-Control = %q", got)
	}
	if w.Header().Get("X-Request-Id") == "" {
		t.Fatal("no request id")
	}
}

func TestReadyzFollowsTheDatabase(t *testing.T) {
	for name, tc := range map[string]struct {
		db   Prober
		want int
	}{
		"healthy":        {prober{}, http.StatusOK},
		"unreachable":    {prober{err: errors.New("down")}, http.StatusServiceUnavailable},
		"not configured": {nil, http.StatusServiceUnavailable},
	} {
		t.Run(name, func(t *testing.T) {
			h, _ := newServer(t, tc.db, deadSessions{})
			w := httptest.NewRecorder()
			h.ServeHTTP(w, httptest.NewRequest(http.MethodGet, "/readyz", nil))
			if w.Code != tc.want {
				t.Fatalf("status = %d, want %d", w.Code, tc.want)
			}
		})
	}
}

func TestAPISubtreeIsGuardedBeforeItIsRouted(t *testing.T) {
	h, logs := newServer(t, prober{}, deadSessions{})
	w := httptest.NewRecorder()
	h.ServeHTTP(w, httptest.NewRequest(http.MethodGet, "/v0/books", nil))
	if w.Code != http.StatusUnauthorized {
		t.Fatalf("status = %d, want 401: an anonymous caller must not be able to map the surface", w.Code)
	}
	assertProblem(t, w, http.StatusUnauthorized)
	// A rejected request must still be logged: an invisible 401 is an invisible brute force.
	if !strings.Contains(logs.String(), `"status":401`) {
		t.Fatalf("denial not logged: %s", logs.String())
	}
}

func TestAuthenticatedUnknownRouteIs404Problem(t *testing.T) {
	h, _ := newServer(t, prober{}, liveSessions{})
	w := httptest.NewRecorder()
	r := httptest.NewRequest(http.MethodGet, "/v0/nothing-here", nil)
	r.Header.Set("Authorization", "Bearer t")
	h.ServeHTTP(w, r)
	if w.Code != http.StatusNotFound {
		t.Fatalf("status = %d", w.Code)
	}
	assertProblem(t, w, http.StatusNotFound)
}

func TestAccessLogNamesTheRouteNotThePath(t *testing.T) {
	h, logs := newServer(t, prober{}, deadSessions{})
	h.ServeHTTP(httptest.NewRecorder(), httptest.NewRequest(http.MethodGet, "/healthz", nil))
	var line map[string]any
	if err := json.Unmarshal(bytes.TrimSpace(logs.Bytes()), &line); err != nil {
		t.Fatalf("log line: %v (%q)", err, logs.String())
	}
	if line["route"] != "GET /healthz" {
		t.Fatalf("route = %v; the pattern is what keeps ids out of the log", line["route"])
	}
	if line["status"] != float64(http.StatusOK) {
		t.Fatalf("status = %v", line["status"])
	}
}

func TestPanicBecomesAProblem(t *testing.T) {
	var logs bytes.Buffer
	inner := http.HandlerFunc(func(http.ResponseWriter, *http.Request) { panic("boom") })
	h := Recover(slog.New(slog.NewJSONHandler(&logs, nil)))(inner)
	w := httptest.NewRecorder()
	h.ServeHTTP(w, httptest.NewRequest(http.MethodGet, "/v0/books", nil))
	assertProblem(t, w, http.StatusInternalServerError)
}

func TestServerRefusesToBuildWithoutAnAuthenticator(t *testing.T) {
	if _, err := New(Deps{Log: slog.Default()}); err == nil {
		t.Fatal("the API subtree may not be mounted unguarded")
	}
}

func assertProblem(t *testing.T, w *httptest.ResponseRecorder, status int) {
	t.Helper()
	if got := w.Header().Get("Content-Type"); got != "application/problem+json" {
		t.Fatalf("content-type = %q", got)
	}
	var p Problem
	if err := json.Unmarshal(w.Body.Bytes(), &p); err != nil {
		t.Fatalf("body: %v (%q)", err, w.Body.String())
	}
	if p.Status != status || p.Title == "" {
		t.Fatalf("problem = %+v", p)
	}
	// Engine vocabulary must never reach a client (contract §2.12).
	if strings.Contains(p.Detail, "sqlite") || strings.Contains(p.Detail, "pgx") {
		t.Fatalf("internals leaked into detail: %q", p.Detail)
	}
}

// stubLogin stands in for the sign-in flow: it only has to prove that the mount is wired the way
// the flow expects — starting a login without a session, ending one only with a session.
type stubLogin struct{}

func (stubLogin) Routes(guard func(http.Handler) http.Handler) http.Handler {
	mux := http.NewServeMux()
	mux.Handle("GET /auth/login", http.HandlerFunc(func(w http.ResponseWriter, _ *http.Request) {
		w.WriteHeader(http.StatusSeeOther)
	}))
	mux.Handle("POST /auth/logout", guard(http.HandlerFunc(func(w http.ResponseWriter, _ *http.Request) {
		w.WriteHeader(http.StatusNoContent)
	})))
	return mux
}

// The sign-in subtree is half-guarded on purpose, and the halves must not swap: the endpoint that
// CREATES a session cannot require one, and the endpoint that ends a session must.
// Mutation caught: wrapping the whole subtree in the guard, or mounting it without one.
func TestSignInSubtreeIsGuardedInHalves(t *testing.T) {
	var logs bytes.Buffer
	h, err := New(Deps{
		Log:   slog.New(slog.NewJSONHandler(&logs, nil)),
		Login: stubLogin{},
		Auth: &auth.Authenticator{
			Sessions: deadSessions{},
			IdleTTL:  time.Hour,
			Deny:     ProblemHandler(http.StatusUnauthorized, "Session missing or invalid"),
		},
	})
	if err != nil {
		t.Fatal(err)
	}

	rec := httptest.NewRecorder()
	h.ServeHTTP(rec, httptest.NewRequest(http.MethodGet, "/auth/login", nil))
	if rec.Code != http.StatusSeeOther {
		t.Fatalf("starting a login = %d, want 303: it cannot require the session it is about to create", rec.Code)
	}

	rec = httptest.NewRecorder()
	h.ServeHTTP(rec, httptest.NewRequest(http.MethodPost, "/auth/logout", nil))
	if rec.Code != http.StatusUnauthorized {
		t.Fatalf("signing out without a session = %d, want 401", rec.Code)
	}

	// And the subtree is under the CSRF check: a cross-site POST must not reach it.
	req := httptest.NewRequest(http.MethodPost, "/auth/logout", nil)
	req.Header.Set("Sec-Fetch-Site", "cross-site")
	rec = httptest.NewRecorder()
	h.ServeHTTP(rec, req)
	if rec.Code != http.StatusForbidden {
		t.Fatalf("cross-site sign-out = %d, want 403", rec.Code)
	}
}

// PD-53. The body cap is registered per ROUTE and never as a blanket layer above them, and the
// third case below is the measured reason: http.MaxBytesReader wrapping an already wrapped body
// keeps the TIGHTER limit, so a route could never raise its own above a shared default. Reintroduce
// an outer LimitBody and the upload route silently gets the small cap instead of its own.
// Mutation caught: adding a blanket LimitBody in New; removing LimitBody from guard.
func TestBodyCapIsPerRouteBecauseNestingOnlyTightens(t *testing.T) {
	drain := http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
		if _, err := io.Copy(io.Discard, r.Body); err != nil {
			WriteProblem(w, http.StatusRequestEntityTooLarge, "Request body too large", "")
			return
		}
		w.WriteHeader(http.StatusOK)
	})
	for name, tc := range map[string]struct {
		h    http.Handler
		body int
		want int
	}{
		"at the cap":   {LimitBody(10)(drain), 10, http.StatusOK},
		"over the cap": {LimitBody(10)(drain), 11, http.StatusRequestEntityTooLarge},
		"a route with its own larger cap gets it": {LimitBody(1000)(drain), 11, http.StatusOK},
		"a larger cap nested inside a smaller one does NOT raise it": {
			LimitBody(10)(LimitBody(1000)(drain)), 11, http.StatusRequestEntityTooLarge},
	} {
		t.Run(name, func(t *testing.T) {
			w := httptest.NewRecorder()
			r := httptest.NewRequest(http.MethodPost, "/v0/books", bytes.NewReader(make([]byte, tc.body)))
			tc.h.ServeHTTP(w, r)
			if w.Code != tc.want {
				t.Fatalf("status = %d, want %d", w.Code, tc.want)
			}
		})
	}
}

// The default is for contract routes carrying JSON of a few kilobytes. A band rather than the exact
// number: what matters is that nobody quietly turns the shared default into an upload allowance —
// the upload route is supposed to register its own, larger cap (PD-35).
func TestDefaultBodyCapStaysAContractSizedNumber(t *testing.T) {
	if DefaultMaxBody < 64<<10 || DefaultMaxBody > 4<<20 {
		t.Fatalf("DefaultMaxBody = %d: outside the band a contract route needs; an upload route registers its own cap",
			DefaultMaxBody)
	}
}