package challenge

import (
	"testing"
	"time"
)

func TestNewGenerator(t *testing.T) {
	config := TestConfig()
	generator := NewGenerator(config)

	if generator == nil {
		t.Fatal("expected generator to be created")
	}

	if generator.config != config {
		t.Error("expected generator to store config reference")
	}
}

func TestGenerator_GenerateChallenge(t *testing.T) {
	config := TestConfig()
	generator := NewGenerator(config)

	challenge, err := generator.GenerateChallenge()
	if err != nil {
		t.Fatalf("expected no error, got: %v", err)
	}

	// Validate basic properties
	if challenge.Difficulty != config.DefaultDifficulty {
		t.Errorf("expected difficulty %d, got %d", config.DefaultDifficulty, challenge.Difficulty)
	}

	if challenge.Resource != config.Resource {
		t.Errorf("expected resource %s, got %s", config.Resource, challenge.Resource)
	}

	if len(challenge.Random) != config.RandomBytes {
		t.Errorf("expected %d random bytes, got %d", config.RandomBytes, len(challenge.Random))
	}

	if len(challenge.HMAC) == 0 {
		t.Error("expected HMAC to be set")
	}

	if challenge.Timestamp <= 0 {
		t.Error("expected positive timestamp")
	}

	// Verify timestamp is recent (within last minute)
	now := time.Now().Unix()
	if challenge.Timestamp < now-60 || challenge.Timestamp > now {
		t.Errorf("expected timestamp to be recent, got %d (now: %d)", challenge.Timestamp, now)
	}
}

func TestGenerator_GenerateChallengeWithOptions(t *testing.T) {
	config := TestConfig()
	generator := NewGenerator(config)

	customDifficulty := 8
	challenge, err := generator.GenerateChallenge(WithDifficulty(customDifficulty))
	if err != nil {
		t.Fatalf("expected no error, got: %v", err)
	}

	if challenge.Difficulty != customDifficulty {
		t.Errorf("expected custom difficulty %d, got %d", customDifficulty, challenge.Difficulty)
	}
}

func TestGenerator_GenerateChallengeValidation(t *testing.T) {
	config := TestConfig()
	generator := NewGenerator(config)

	tests := []struct {
		name       string
		difficulty int
		expectErr  bool
	}{
		{
			name:       "valid difficulty within range",
			difficulty: 5,
			expectErr:  false,
		},
		{
			name:       "difficulty too low",
			difficulty: config.MinDifficulty - 1,
			expectErr:  true,
		},
		{
			name:       "difficulty too high",
			difficulty: config.MaxDifficulty + 1,
			expectErr:  true,
		},
	}

	for _, tt := range tests {
		t.Run(tt.name, func(t *testing.T) {
			_, err := generator.GenerateChallenge(WithDifficulty(tt.difficulty))

			if tt.expectErr && err == nil {
				t.Error("expected error but got none")
			}

			if !tt.expectErr && err != nil {
				t.Errorf("expected no error but got: %v", err)
			}

			if err != nil && err != ErrInvalidDifficulty {
				t.Errorf("expected ErrInvalidDifficulty, got: %v", err)
			}
		})
	}
}

func TestGenerator_HMACIntegrity(t *testing.T) {
	config := TestConfig()
	generator := NewGenerator(config)

	challenge, err := generator.GenerateChallenge()
	if err != nil {
		t.Fatalf("unexpected error: %v", err)
	}

	// Verify HMAC with original secret
	err = challenge.VerifyHMAC(config.HMACSecret)
	if err != nil {
		t.Fatalf("expected HMAC verification to pass, got: %v", err)
	}

	// Verify HMAC fails with different secret
	differentConfig := TestConfig()
	err = challenge.VerifyHMAC(differentConfig.HMACSecret)
	if err != ErrInvalidHMAC {
		t.Fatalf("expected ErrInvalidHMAC with different secret, got: %v", err)
	}
}

func TestGenerator_RandomnessUniqueness(t *testing.T) {
	config := TestConfig()
	generator := NewGenerator(config)

	// Generate multiple challenges and ensure they have different random values
	challenges := make([]*Challenge, 10)
	for i := range challenges {
		challenge, err := generator.GenerateChallenge()
		if err != nil {
			t.Fatalf("unexpected error generating challenge %d: %v", i, err)
		}
		challenges[i] = challenge
	}

	// Check that all random values are different
	for i := 0; i < len(challenges); i++ {
		for j := i + 1; j < len(challenges); j++ {
			if string(challenges[i].Random) == string(challenges[j].Random) {
				t.Errorf("challenges %d and %d have identical random values: %x", i, j, challenges[i].Random)
			}
		}
	}
}

func TestWithDifficulty(t *testing.T) {
	challenge := &Challenge{Difficulty: 4}
	option := WithDifficulty(8)

	option(challenge)

	if challenge.Difficulty != 8 {
		t.Errorf("expected difficulty 8, got %d", challenge.Difficulty)
	}
}