package authclient

import (
	"context"
	"crypto"
	"crypto/rand"
	"crypto/rsa"
	"crypto/sha256"
	"encoding/base64"
	"encoding/json"
	"fmt"
	"io"
	"net"
	"net/http"
	"net/http/httptest"
	"net/url"
	"os"
	"path/filepath"
	"strings"
	"testing"
	"time"

	"keycape/internal/domain"
	"keycape/internal/server/oidc"
	"keycape/internal/server/telemetry"
)

type users struct{}

func (users) LookupUser(context.Context, string) (*domain.User, error) {
	return &domain.User{ID: "user:test", Username: "test"}, nil
}
func (users) LookupGroups(context.Context, string) ([]domain.Group, error)   { return nil, nil }
func (users) ValidatePassword(context.Context, string, string) (bool, error) { return true, nil }
func (users) ListUsers(context.Context) ([]domain.User, error)               { return nil, nil }

func provider(t *testing.T) (*Client, Discovery, *oidc.TokenHandler) {
	t.Helper()
	key, err := rsa.GenerateKey(rand.Reader, 2048)
	if err != nil {
		t.Fatal(err)
	}
	mux := http.NewServeMux()
	server := httptest.NewTLSServer(mux)
	t.Cleanup(server.Close)
	sessions := oidc.NewSessionStore()
	h := &oidc.TokenHandler{Issuer: server.URL, SigningKey: key, TokenLifetime: 15 * time.Minute, Sessions: sessions, Users: users{}, Emitter: telemetry.NoopEmitter{}, ClientConfig: map[string]*domain.Client{
		"service:consumer": {ClientID: "service:consumer", ClientType: "confidential", ClientSecret: "special+%: secret", GrantTypes: []string{"client_credentials"}, AllowedScopes: []string{"approval:read"}, Audience: "approval-engine", ServiceSubject: "service:test", Tenant: "tenant:test"},
		"human":            {ClientID: "human", AllowedScopes: []string{"openid", "approval:approve"}, Audience: "approval-engine"},
	}}
	mux.Handle("/token", h)
	keys := oidc.NewKeySet()
	keys.AddKey("key-1", &key.PublicKey)
	mux.Handle("/jwks", oidc.NewJWKSHandler(keys))
	d := Discovery{Issuer: server.URL, Authorization: server.URL + "/authorize", Token: server.URL + "/token", JWKS: server.URL + "/jwks"}
	mux.HandleFunc("/.well-known/openid-configuration", func(w http.ResponseWriter, r *http.Request) { json.NewEncoder(w).Encode(d) })
	mux.HandleFunc("/authorize", func(w http.ResponseWriter, r *http.Request) {
		q := r.URL.Query()
		// Record the redirect URI as the real /authorize does: the token
		// endpoint binds the exchange to it (KEY-WP-0016-T02).
		code := sessions.Create(&oidc.PKCESession{ClientID: q.Get("client_id"), Username: "test", Nonce: q.Get("nonce"), Scopes: strings.Fields(q.Get("scope")), PKCEChallenge: q.Get("code_challenge"), RedirectURI: q.Get("redirect_uri"), ExpiresAt: time.Now().Add(time.Minute)})
		target, _ := url.Parse(q.Get("redirect_uri"))
		params := target.Query()
		params.Set("state", q.Get("state"))
		params.Set("code", code)
		target.RawQuery = params.Encode()
		http.Redirect(w, r, target.String(), 302)
	})
	c, err := New(server.URL)
	if err != nil {
		t.Fatal(err)
	}
	c.HTTP.Transport = server.Client().Transport
	return c, d, h
}

func TestServiceExchangeAndClaimValidation(t *testing.T) {
	c, _, h := provider(t)
	ctx := context.Background()
	d, err := c.Discover(ctx)
	if err != nil {
		t.Fatal(err)
	}
	form := url.Values{"grant_type": {"client_credentials"}, "scope": {"approval:read"}}
	token, err := c.Exchange(ctx, d, form, "service:consumer", "special+%: secret", "approval-engine", "")
	if err != nil {
		t.Fatal(err)
	}
	if _, err = c.Verify(ctx, d, token.AccessToken, "other", ""); err == nil {
		t.Fatal("wrong audience accepted")
	}
	if _, err = c.Verify(ctx, d, token.AccessToken+"tampered", "approval-engine", ""); err == nil {
		t.Fatal("tampering accepted")
	}
	if _, err = c.Exchange(ctx, d, form, "service:consumer", "wrong", "approval-engine", ""); err == nil || strings.Contains(err.Error(), "special") {
		t.Fatal("wrong secret not safely rejected")
	}
	form.Set("scope", "approval:consume")
	if _, err = c.Exchange(ctx, d, form, "service:consumer", "special+%: secret", "approval-engine", ""); err == nil {
		t.Fatal("excess scope accepted")
	}
	form.Set("scope", "approval:read")
	h.TokenLifetime = -time.Minute
	if _, err = c.Exchange(ctx, d, form, "service:consumer", "special+%: secret", "approval-engine", ""); err == nil {
		t.Fatal("expired response accepted")
	}
}

type urlWriter struct{ urls chan string }

func (w urlWriter) Write(p []byte) (int, error) {
	for _, line := range strings.Split(string(p), "\n") {
		if strings.HasPrefix(line, "https://") {
			w.urls <- line
		}
	}
	return len(p), nil
}

func TestBrowserLoginPKCEAndState(t *testing.T) {
	c, d, _ := provider(t)
	listener, err := net.Listen("tcp", "127.0.0.1:0")
	if err != nil {
		t.Fatal(err)
	}
	redirect := "http://" + listener.Addr().String() + "/callback"
	listener.Close()
	ctx, cancel := context.WithTimeout(context.Background(), 10*time.Second)
	defer cancel()
	urls := make(chan string, 1)
	completed := make(chan error, 1)
	go func() {
		_, err := c.Login(ctx, d, "human", "approval-engine", "openid approval:approve", redirect, urlWriter{urls})
		completed <- err
	}()
	var address string
	select {
	case address = <-urls:
	case err := <-completed:
		t.Fatal(err)
	case <-ctx.Done():
		t.Fatal("no login URL")
	}
	// A forged callback must not consume the real login attempt.
	res, err := http.Get(redirect + "?state=forged&code=forged")
	if err != nil {
		t.Fatal(err)
	}
	res.Body.Close()
	if res.StatusCode != 400 {
		t.Fatal("forged state accepted")
	}
	browser := &http.Client{Transport: c.HTTP.Transport, Timeout: 5 * time.Second}
	res, err = browser.Get(address)
	if err != nil {
		t.Fatal(err)
	}
	io.Copy(io.Discard, res.Body)
	res.Body.Close()
	select {
	case err := <-completed:
		if err != nil {
			t.Fatal(err)
		}
	case <-ctx.Done():
		t.Fatal("login did not finish")
	}
}

func TestLoginRejectsUnsafeCallbacks(t *testing.T) {
	c, d, _ := provider(t)
	for _, callback := range []string{"http://example.com:8000/callback", "http://localhost:8000/callback", "http://127.0.0.1:0/callback", "http://127.0.0.1:8000/callback?extra=yes"} {
		if _, err := c.Login(context.Background(), d, "human", "approval-engine", "openid", callback, io.Discard); err == nil {
			t.Fatalf("accepted %s", callback)
		}
	}
}

func TestOutputProtection(t *testing.T) {
	dir := t.TempDir()
	path := filepath.Join(dir, "token.json")
	file, err := reserveOutput(path)
	if err != nil {
		t.Fatalf("reserve %s: %v", path, err)
	}
	file.Close()
	info, _ := os.Stat(path)
	if info.Mode().Perm() != 0600 {
		t.Fatal("file not private")
	}
	if _, err = reserveOutput(path); err == nil {
		t.Fatal("overwrote existing file")
	}
	link := filepath.Join(dir, "link")
	if err = os.Symlink(path, link); err != nil {
		t.Fatal(err)
	}
	if _, err = reserveOutput(link); err == nil {
		t.Fatal("followed output symlink")
	}
	repo := filepath.Join(dir, "repo")
	os.Mkdir(repo, 0700)
	os.WriteFile(filepath.Join(repo, ".git"), []byte("gitdir: elsewhere"), 0600)
	if _, err = reserveOutput(filepath.Join(repo, "token")); err == nil {
		t.Fatal("allowed token in worktree")
	}
}

func TestDiscoveryAndRedirectBoundaries(t *testing.T) {
	for _, issuer := range []string{"http://example.com", "https://user:pass@example.com", "https://example.com?secret=value"} {
		if _, err := New(issuer); err == nil {
			t.Fatal("unsafe issuer accepted")
		}
	}
	mux := http.NewServeMux()
	server := httptest.NewTLSServer(mux)
	defer server.Close()
	c, _ := New(server.URL)
	c.HTTP.Transport = server.Client().Transport
	mux.HandleFunc("/.well-known/openid-configuration", func(w http.ResponseWriter, r *http.Request) {
		fmt.Fprintf(w, `{"issuer":%q,"authorization_endpoint":"https://evil.example/a","token_endpoint":"https://evil.example/t","jwks_uri":"https://evil.example/j"}`, server.URL)
	})
	if _, err := c.Discover(context.Background()); err == nil {
		t.Fatal("cross-origin discovery accepted")
	}
	mux.HandleFunc("/redirect", func(w http.ResponseWriter, r *http.Request) { http.Redirect(w, r, "https://evil.example", 307) })
	var out any
	if err := c.request(context.Background(), "POST", server.URL+"/redirect", nil, "id", "secret", &out); err == nil {
		t.Fatal("followed credential redirect")
	}
}

func TestNonceMismatchAndCancelledLogin(t *testing.T) {
	c, d, _ := provider(t)
	form := url.Values{"grant_type": {"client_credentials"}, "scope": {"approval:read"}}
	token, err := c.Exchange(context.Background(), d, form, "service:consumer", "special+%: secret", "approval-engine", "")
	if err != nil {
		t.Fatal(err)
	}
	if _, err = c.Verify(context.Background(), d, token.AccessToken, "approval-engine", "required-nonce"); err == nil {
		t.Fatal("missing nonce accepted")
	}
	listener, err := net.Listen("tcp", "127.0.0.1:0")
	if err != nil {
		t.Fatal(err)
	}
	redirect := "http://" + listener.Addr().String() + "/callback"
	listener.Close()
	ctx, cancel := context.WithCancel(context.Background())
	cancel()
	if _, err = c.Login(ctx, d, "human", "approval-engine", "openid", redirect, io.Discard); err == nil {
		t.Fatal("cancelled login succeeded")
	}
	listener, err = net.Listen("tcp", strings.TrimPrefix(strings.TrimSuffix(redirect, "/callback"), "http://"))
	if err != nil {
		t.Fatal("listener not released")
	}
	listener.Close()
}

// The caller-side verifier moved onto internal/jose (KEY-WP-0019-T05). The
// existing tamper case proves the signature is checked at all; these two prove
// the parts of the move that a byte-level tamper cannot reach. A token signed
// by an unpublished key under a kid the provider does publish fails only if key
// selection is bound to the published set, not merely if the bytes are intact.
// A key set carrying an undersized modulus must deny the login rather than fall
// through to the claims, which is ParseJWKS strictness being applied on this
// path and not only in the adapter.
func TestVerifyRejectsForeignSignatureAndUnusableKeySet(t *testing.T) {
	c, d, _ := provider(t)
	ctx := context.Background()

	foreign, err := rsa.GenerateKey(rand.Reader, 2048)
	if err != nil {
		t.Fatal(err)
	}
	now := time.Now()
	forged := signToken(t, foreign, "key-1", map[string]any{
		"iss": c.Issuer,
		"aud": "approval-engine",
		"sub": "service:test",
		"iat": now.Unix(),
		"exp": now.Add(time.Minute).Unix(),
	})
	if _, err := c.Verify(ctx, d, forged, "approval-engine", ""); err == nil {
		t.Fatal("token signed by an unpublished key accepted")
	}

	// A key set the client cannot use must deny, not fall through to the
	// claims. The token here is otherwise genuine.
	genuine := signToken(t, foreign, "key-1", map[string]any{
		"iss": c.Issuer, "aud": "approval-engine", "sub": "service:test",
		"iat": now.Unix(), "exp": now.Add(time.Minute).Unix(),
	})
	broken := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, _ *http.Request) {
		fmt.Fprint(w, `{"keys":[{"kty":"RSA","kid":"key-1","n":"AQAB","e":"AQAB"}]}`)
	}))
	t.Cleanup(broken.Close)
	if _, err := c.Verify(ctx, Discovery{Issuer: d.Issuer, JWKS: broken.URL}, genuine, "approval-engine", ""); err == nil {
		t.Fatal("undersized key in the published set accepted")
	}
}

// signToken builds an RS256 JWT with the given kid and claims.
func signToken(t *testing.T, key *rsa.PrivateKey, kid string, claims map[string]any) string {
	t.Helper()
	enc := func(v any) string {
		raw, err := json.Marshal(v)
		if err != nil {
			t.Fatal(err)
		}
		return base64.RawURLEncoding.EncodeToString(raw)
	}
	input := enc(map[string]any{"alg": "RS256", "typ": "JWT", "kid": kid}) + "." + enc(claims)
	digest := sha256.Sum256([]byte(input))
	signature, err := rsa.SignPKCS1v15(rand.Reader, key, crypto.SHA256, digest[:])
	if err != nil {
		t.Fatal(err)
	}
	return input + "." + base64.RawURLEncoding.EncodeToString(signature)
}