package server

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

	"cc.tiredsysadmin.keeporg/internal/store"
)

// fakeIdP is the smallest thing that behaves like an OIDC provider: a
// discovery document, an authorization endpoint that redirects straight
// back, a token endpoint and a userinfo endpoint.
type fakeIdP struct {
	*httptest.Server
	subject, email, username string
	// tokenAuth records the client credentials the server presented.
	tokenAuth [2]string
	authCalls int
}

func newFakeIdP(t *testing.T, subject, email, username string) *fakeIdP {
	idp := &fakeIdP{subject: subject, email: email, username: username}
	mux := http.NewServeMux()
	idp.Server = httptest.NewServer(mux)
	t.Cleanup(idp.Close)

	mux.HandleFunc("GET /.well-known/openid-configuration", func(w http.ResponseWriter, r *http.Request) {
		_ = json.NewEncoder(w).Encode(map[string]string{
			"issuer":                 idp.URL,
			"authorization_endpoint": idp.URL + "/authorize",
			"token_endpoint":         idp.URL + "/token",
			"userinfo_endpoint":      idp.URL + "/userinfo",
		})
	})
	mux.HandleFunc("GET /authorize", func(w http.ResponseWriter, r *http.Request) {
		idp.authCalls++
		q := r.URL.Query()
		back, err := url.Parse(q.Get("redirect_uri"))
		if err != nil {
			http.Error(w, "bad redirect_uri", http.StatusBadRequest)
			return
		}
		rq := back.Query()
		rq.Set("code", "authorization-code")
		rq.Set("state", q.Get("state"))
		back.RawQuery = rq.Encode()
		http.Redirect(w, r, back.String(), http.StatusFound)
	})
	mux.HandleFunc("POST /token", func(w http.ResponseWriter, r *http.Request) {
		user, pass, _ := r.BasicAuth()
		idp.tokenAuth = [2]string{user, pass}
		_ = r.ParseForm()
		if r.FormValue("code") != "authorization-code" {
			http.Error(w, "bad code", http.StatusBadRequest)
			return
		}
		_ = json.NewEncoder(w).Encode(map[string]any{
			"access_token": "an-access-token", "token_type": "Bearer", "expires_in": 300,
		})
	})
	mux.HandleFunc("GET /userinfo", func(w http.ResponseWriter, r *http.Request) {
		if r.Header.Get("Authorization") != "Bearer an-access-token" {
			http.Error(w, "unauthorized", http.StatusUnauthorized)
			return
		}
		_ = json.NewEncoder(w).Encode(map[string]string{
			"sub": idp.subject, "email": idp.email, "preferred_username": idp.username,
		})
	})
	return idp
}

// withOIDC configures a harness against this provider.
func (idp *fakeIdP) withOIDC(autoCreate bool, defaultGroup string) func(*Config) {
	return func(c *Config) {
		c.OIDC = OIDCConfig{
			Issuer: idp.URL, ClientID: "keeporg", ClientSecret: "a-client-secret",
			AutoCreate: autoCreate, DefaultGroupID: defaultGroup,
		}
	}
}

func TestOIDCSignsInToTheWebInterface(t *testing.T) {
	idp := newFakeIdP(t, "subject-1", "sso@example.com", "ssouser")
	h := newHarnessWith(t, idp.withOIDC(true, "everyone"))
	b := newBrowser(t, h)

	// The sign-in page offers it, and following that link is the whole flow.
	status, page := b.get("/web")
	if status != http.StatusOK || !strings.Contains(page, "/oidc/login") {
		t.Fatalf("the sign-in page does not offer single sign-on:\n%s", page)
	}
	status, page = b.get("/oidc/login")
	if status != http.StatusOK {
		t.Fatalf("oidc login: %d\n%s", status, page)
	}
	if !strings.Contains(page, "Your vaults") {
		t.Fatalf("single sign-on did not land on the vault list:\n%s", page)
	}
	if b.cookie() == "" {
		t.Fatal("no session cookie after signing in with single sign-on")
	}
	if idp.authCalls != 1 {
		t.Fatalf("the provider's authorize endpoint was called %d times", idp.authCalls)
	}
	if idp.tokenAuth != [2]string{"keeporg", "a-client-secret"} {
		t.Fatalf("the server authenticated to the token endpoint as %v", idp.tokenAuth)
	}

	// The account was provisioned, linked to the subject, and put in the
	// configured group.
	var linked *store.User
	h.srv.Store().Read(func(st *store.State) {
		linked = st.UserByOIDC(idp.URL, "subject-1")
	})
	if linked == nil {
		t.Fatal("no account was linked to the identity")
	}
	if linked.Username != "ssouser" || linked.Email != "sso@example.com" {
		t.Fatalf("provisioned account = %+v", linked)
	}
	var inGroup bool
	h.srv.Store().Read(func(st *store.State) {
		for _, m := range st.Memberships {
			if m.UserID == linked.ID && m.GroupID == "everyone" {
				inGroup = true
			}
		}
	})
	if !inGroup {
		t.Fatal("the new account did not join the default group")
	}
}

func TestOIDCApprovesAWaitingClient(t *testing.T) {
	idp := newFakeIdP(t, "subject-2", "dev@example.com", "devuser")
	h := newHarnessWith(t, idp.withOIDC(true, "everyone"))

	status, start := h.call("POST", "/api/v1/auth/device/start", "", map[string]string{"label": "laptop"})
	if status != http.StatusOK {
		t.Fatalf("device start: %d %v", status, start)
	}
	userCode := start["user_code"].(string)

	b := newBrowser(t, h)
	status, page := b.get("/oidc/login?code=" + url.QueryEscape(userCode))
	if status != http.StatusOK || !strings.Contains(page, "Device approved") {
		t.Fatalf("device approval through single sign-on: %d\n%s", status, page)
	}
	// A device approval must not also hand the browser a session cookie.
	if b.cookie() != "" {
		t.Fatal("approving a device set a web session cookie")
	}

	status, body := h.call("POST", "/api/v1/auth/device/poll", "",
		map[string]string{"device_code": start["device_code"].(string)})
	if status != http.StatusOK || body["token"] == "" {
		t.Fatalf("poll after single sign-on: %d %v", status, body)
	}
	if u := body["user"].(map[string]any); u["username"] != "devuser" {
		t.Fatalf("the session belongs to %v", u["username"])
	}
}

func TestOIDCLinksAnExistingAccountByUsername(t *testing.T) {
	idp := newFakeIdP(t, "subject-3", "", "admin")
	h := newHarnessWith(t, idp.withOIDC(false, ""))
	b := newBrowser(t, h)

	if _, page := b.get("/oidc/login"); !strings.Contains(page, "Your vaults") {
		t.Fatalf("an existing account was not matched:\n%s", page)
	}
	var u *store.User
	h.srv.Store().Read(func(st *store.State) { u = st.Users["admin"] })
	if u.OIDCSubject != "subject-3" {
		t.Fatalf("the existing account was not linked: %+v", u)
	}
}

func TestOIDCRefusesAnUnknownIdentityWhenProvisioningIsOff(t *testing.T) {
	idp := newFakeIdP(t, "subject-4", "stranger@example.com", "stranger")
	h := newHarnessWith(t, idp.withOIDC(false, ""))
	b := newBrowser(t, h)

	_, page := b.get("/oidc/login")
	if !strings.Contains(page, "no account is linked") {
		t.Fatalf("an unknown identity was let in:\n%s", page)
	}
	if b.cookie() != "" {
		t.Fatal("a session cookie was issued to an unknown identity")
	}
}

func TestOIDCCallbackRejectsAnUnknownState(t *testing.T) {
	idp := newFakeIdP(t, "subject-5", "", "someone")
	h := newHarnessWith(t, idp.withOIDC(true, ""))
	b := newBrowser(t, h)

	_, page := b.get("/oidc/callback?code=authorization-code&state=not-a-real-state")
	if !strings.Contains(page, "expired") {
		t.Fatalf("a forged callback was accepted:\n%s", page)
	}
	if b.cookie() != "" {
		t.Fatal("a forged callback issued a session cookie")
	}
}

func TestSignInPageHidesSingleSignOnWhenItIsNotConfigured(t *testing.T) {
	b := newBrowser(t, newHarness(t))
	_, page := b.get("/web")
	if strings.Contains(page, "oidc/login") {
		t.Fatal("single sign-on is offered although no provider is configured")
	}
}