/*
Copyright 2026 Arctel.net

Licensed under the Apache License, Version 2.0 (the "License");
you may not use this file except in compliance with the License.
You may obtain a copy of the License at

    http://www.apache.org/licenses/LICENSE-2.0

Unless required by applicable law or agreed to in writing, software
distributed under the License is distributed on an "AS IS" BASIS,
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
See the License for the specific language governing permissions and
limitations under the License.
*/

package cap

import (
	"context"
	"sync"
	"sync/atomic"
	"testing"
	"time"
)

func TestCapFullFlow(t *testing.T) {
	secret := []byte("a-very-long-secret-key-at-least-16-bytes")
	store := NewMemoryStore(1 * time.Minute)

	manager := NewManager(Config{
		Secret:              secret,
		ChallengeCount:      3, // small count for fast test
		ChallengeSize:       32,
		ChallengeDifficulty: 3, // small difficulty for fast test
		ChallengeTTL:        5 * time.Second,
		TokenTTL:            10 * time.Second,
	}, store)

	scope := "test-scope"
	ctx := context.Background()
	resp, err := manager.Generate(ctx, scope)
	if err != nil {
		t.Fatalf("Generate failed: %v", err)
	}

	if resp.Challenge.C != 3 {
		t.Errorf("Expected count 3, got %d", resp.Challenge.C)
	}

	// Solve the challenge (acting as client)
	solutions := Solve(resp.Token, resp.Challenge.C, resp.Challenge.S, resp.Challenge.D)

	// Redeem
	redeemResp, err := manager.Redeem(ctx, resp.Token, solutions, scope)
	if err != nil {
		t.Fatalf("Redeem failed: %v", err)
	}
	if !redeemResp.Success {
		t.Fatalf("Redeem returned success=false: %s", redeemResp.Error)
	}
	if redeemResp.Token == "" {
		t.Fatalf("Expected token, got empty")
	}

	// Verify the token
	valid, err := manager.VerifyToken(ctx, redeemResp.Token, scope)
	if err != nil {
		t.Fatalf("VerifyToken failed: %v", err)
	}
	if !valid {
		t.Fatalf("Expected redeem token to be valid")
	}

	// Verify token is one-time use
	validAgain, err := manager.VerifyToken(ctx, redeemResp.Token, scope)
	if err != nil {
		t.Fatalf("VerifyToken second call failed: %v", err)
	}
	if validAgain {
		t.Fatalf("Expected redeem token to be single-use (invalidated after verification)")
	}
}

// TestRedeemConcurrentRace verifies that when N goroutines simultaneously call
// Redeem with the same challenge JWT, exactly one succeeds and the rest are
// rejected with "already_redeemed". This guards against the TOCTOU fix.
func TestRedeemConcurrentRace(t *testing.T) {
	const goroutines = 50

	secret := []byte("race-test-secret-key-at-least-16-bytes")
	store := NewMemoryStore(1 * time.Minute)
	manager := NewManager(Config{
		Secret:              secret,
		ChallengeCount:      1,
		ChallengeSize:       32,
		ChallengeDifficulty: 3,
		ChallengeTTL:        30 * time.Second,
		TokenTTL:            30 * time.Second,
	}, store)

	ctx := context.Background()
	resp, err := manager.Generate(ctx, "login")
	if err != nil {
		t.Fatalf("Generate failed: %v", err)
	}
	solutions := Solve(resp.Token, resp.Challenge.C, resp.Challenge.S, resp.Challenge.D)

	var (
		wg      sync.WaitGroup
		success atomic.Int32
		barrier = make(chan struct{}) // synchronise goroutine start
	)

	for i := 0; i < goroutines; i++ {
		wg.Add(1)
		go func() {
			defer wg.Done()
			<-barrier // wait for the gun
			r, _ := manager.Redeem(ctx, resp.Token, solutions, "login")
			if r != nil && r.Success {
				success.Add(1)
			}
		}()
	}
	close(barrier) // fire all goroutines at once
	wg.Wait()

	if n := success.Load(); n != 1 {
		t.Fatalf("Expected exactly 1 successful Redeem, got %d", n)
	}
}

// TestVerifyTokenConcurrentRace verifies that when N goroutines simultaneously
// call VerifyToken with the same cap token, exactly one succeeds and the rest
// fail. This guards against the GetAndDelete fix.
func TestVerifyTokenConcurrentRace(t *testing.T) {
	const goroutines = 50

	secret := []byte("race-test-secret-key-at-least-16-bytes")
	store := NewMemoryStore(1 * time.Minute)
	manager := NewManager(Config{
		Secret:              secret,
		ChallengeCount:      1,
		ChallengeSize:       32,
		ChallengeDifficulty: 3,
		ChallengeTTL:        30 * time.Second,
		TokenTTL:            30 * time.Second,
	}, store)

	ctx := context.Background()
	resp, _ := manager.Generate(ctx, "login")
	solutions := Solve(resp.Token, resp.Challenge.C, resp.Challenge.S, resp.Challenge.D)
	redeemResp, err := manager.Redeem(ctx, resp.Token, solutions, "login")
	if err != nil || !redeemResp.Success {
		t.Fatalf("Redeem failed: %v %+v", err, redeemResp)
	}
	capToken := redeemResp.Token

	var (
		wg      sync.WaitGroup
		success atomic.Int32
		barrier = make(chan struct{})
	)

	for i := 0; i < goroutines; i++ {
		wg.Add(1)
		go func() {
			defer wg.Done()
			<-barrier
			ok, _ := manager.VerifyToken(ctx, capToken, "login")
			if ok {
				success.Add(1)
			}
		}()
	}
	close(barrier)
	wg.Wait()

	if n := success.Load(); n != 1 {
		t.Fatalf("Expected exactly 1 successful VerifyToken, got %d", n)
	}
}