package platform

import (
	"context"
	"crypto/sha256"
	"encoding/base64"
	"encoding/json"
	"net/http"
	"net/http/httptest"
	"net/url"
	"strings"
	"testing"
	"time"
)

func TestNewPKCE(t *testing.T) {
	v, c, err := newPKCE()
	if err != nil {
		t.Fatalf("newPKCE: %v", err)
	}
	if len(v) != 64 {
		t.Errorf("verifier length = %d, want 64", len(v))
	}
	sum := sha256.Sum256([]byte(v))
	want := base64.RawURLEncoding.EncodeToString(sum[:])
	if c != want {
		t.Errorf("challenge = %q, want S256(verifier) = %q", c, want)
	}
	// two calls must differ
	v2, _, _ := newPKCE()
	if v == v2 {
		t.Error("two verifiers collided")
	}
}

// decodeBody reads a JSON request body into a map.
func decodeBody(t *testing.T, r *http.Request) map[string]string {
	t.Helper()
	var m map[string]string
	if err := json.NewDecoder(r.Body).Decode(&m); err != nil {
		t.Fatalf("decode body: %v", err)
	}
	return m
}

// TestLogin_Success drives the whole broker device-authorization loopback flow with a
// fake /device/token endpoint and a fake browser — no real network or prod dependency.
func TestLogin_Success(t *testing.T) {
	var gotBody map[string]string
	brokerSrv := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
		if r.URL.Path != "/device/token" {
			t.Errorf("token path = %s, want /device/token", r.URL.Path)
		}
		gotBody = decodeBody(t, r)
		w.Header().Set("Content-Type", "application/json")
		_ = json.NewEncoder(w).Encode(map[string]any{
			"id":             "sid-1",
			"app":            "cdrop",
			"access":         "at-123",
			"refresh":        "rtk-456",
			"access_expires": time.Now().Add(15 * time.Minute).Unix(),
		})
	}))
	defer brokerSrv.Close()

	cfg := OAuthConfig{BrokerURL: brokerSrv.URL, App: "cdrop"}

	// Fake browser: parse the /device/authorize URL, assert it carries app + PKCE,
	// then GET the loopback redirect with a code + the same state (approved).
	openURL := func(authURL string) {
		u, err := url.Parse(authURL)
		if err != nil {
			t.Errorf("parse authURL: %v", err)
			return
		}
		if !strings.HasSuffix(u.Path, "/device/authorize") {
			t.Errorf("authorize path = %s, want /device/authorize", u.Path)
		}
		q := u.Query()
		if q.Get("code_challenge") == "" || q.Get("code_challenge_method") != "S256" {
			t.Errorf("authorize request missing PKCE challenge: %v", q)
		}
		if q.Get("app") != "cdrop" {
			t.Errorf("authorize app = %q", q.Get("app"))
		}
		cb := q.Get("redirect_uri") + "?code=auth-code-xyz&state=" + url.QueryEscape(q.Get("state"))
		resp, err := http.Get(cb)
		if err != nil {
			t.Errorf("callback GET: %v", err)
			return
		}
		_ = resp.Body.Close()
	}

	tok, err := NewFlow(cfg, openURL).Login(context.Background())
	if err != nil {
		t.Fatalf("Login: %v", err)
	}
	if tok.AccessToken != "at-123" {
		t.Errorf("access = %q, want at-123", tok.AccessToken)
	}
	if tok.RefreshToken != "rtk-456" {
		t.Errorf("refresh = %q, want rtk-456", tok.RefreshToken)
	}
	if tok.ExpiresIn <= 0 || tok.ExpiresIn > 900 {
		t.Errorf("expires_in = %d, want ~900 (derived from access_expires)", tok.ExpiresIn)
	}

	// The exchange must carry the code, the PKCE verifier, and the same redirect_uri.
	if gotBody["code"] != "auth-code-xyz" {
		t.Errorf("code = %q", gotBody["code"])
	}
	if gotBody["code_verifier"] == "" {
		t.Error("token exchange missing code_verifier")
	}
	if !strings.HasPrefix(gotBody["redirect_uri"], "http://127.0.0.1:") {
		t.Errorf("redirect_uri = %q, want loopback", gotBody["redirect_uri"])
	}
}

func TestLogin_StateMismatch(t *testing.T) {
	cfg := OAuthConfig{BrokerURL: "https://sso.example.net", App: "cdrop"}
	openURL := func(authURL string) {
		u, _ := url.Parse(authURL)
		redirect := u.Query().Get("redirect_uri")
		resp, err := http.Get(redirect + "?code=c&state=WRONG-STATE")
		if err == nil {
			_ = resp.Body.Close()
		}
	}
	_, err := NewFlow(cfg, openURL).Login(context.Background())
	if err == nil || !strings.Contains(err.Error(), "state mismatch") {
		t.Fatalf("want state mismatch error, got %v", err)
	}
}

func TestLogin_IncompleteConfig(t *testing.T) {
	_, err := NewFlow(OAuthConfig{App: "only-app"}, func(string) {}).Login(context.Background())
	if err == nil {
		t.Fatal("want error for incomplete config, got nil")
	}
}

func TestRefresh_Success(t *testing.T) {
	var gotBody map[string]string
	brokerSrv := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
		if r.URL.Path != "/refresh" {
			t.Errorf("refresh path = %s, want /refresh", r.URL.Path)
		}
		gotBody = decodeBody(t, r)
		w.Header().Set("Content-Type", "application/json")
		_ = json.NewEncoder(w).Encode(map[string]any{
			"access":         "new-at",
			"refresh":        "new-rtk",
			"access_expires": time.Now().Add(15 * time.Minute).Unix(),
		})
	}))
	defer brokerSrv.Close()

	cfg := OAuthConfig{BrokerURL: brokerSrv.URL, App: "cdrop"}
	tok, err := NewFlow(cfg, func(string) {}).Refresh(context.Background(), "old-rtk")
	if err != nil {
		t.Fatalf("Refresh: %v", err)
	}
	if tok.AccessToken != "new-at" {
		t.Errorf("access = %q, want new-at", tok.AccessToken)
	}
	if tok.RefreshToken != "new-rtk" {
		t.Errorf("refresh = %q, want new-rtk (rotated)", tok.RefreshToken)
	}
	if gotBody["refresh"] != "old-rtk" {
		t.Errorf("sent refresh = %q, want old-rtk", gotBody["refresh"])
	}
}

func TestRefresh_EmptyToken(t *testing.T) {
	cfg := OAuthConfig{BrokerURL: "https://sso.example.net", App: "cdrop"}
	if _, err := NewFlow(cfg, func(string) {}).Refresh(context.Background(), ""); err == nil {
		t.Fatal("want error for empty refresh token")
	}
}
