package packetpath

import "testing"

func TestMeetsPathTrust_DefaultThreshold(t *testing.T) {
	// nil cfg → DefaultMinHashBytesForMapping (1): everything is trusted, which
	// is the pre-#1784 behaviour. This test is the guard on that promise: if the
	// default is ever raised, upgrading instances silently lose a large share of
	// their mapping evidence with no UI control to opt back out.
	cases := []struct {
		prefixBytes int
		want        bool
	}{
		{0, true},
		{1, true},
		{2, true},
		{3, true},
	}
	for _, c := range cases {
		if got := MeetsPathTrust(c.prefixBytes, nil); got != c.want {
			t.Errorf("MeetsPathTrust(%d, nil) = %v, want %v", c.prefixBytes, got, c.want)
		}
	}
}

func TestMeetsPathTrust_TrustAllOptIn(t *testing.T) {
	cfg := &TrustConfig{MinHashBytesForMapping: 1}
	for _, prefixBytes := range []int{0, 1, 2, 3} {
		if !MeetsPathTrust(prefixBytes, cfg) {
			t.Errorf("MeetsPathTrust(%d, minBytes=1) = false, want true", prefixBytes)
		}
	}
}

func TestMeetsPathTrust_Exclude1Byte(t *testing.T) {
	// minHashBytesForMapping: 2 — recommended for denser meshes.
	cfg := &TrustConfig{MinHashBytesForMapping: 2}
	cases := []struct {
		prefixBytes int
		want        bool
	}{
		{0, false},
		{1, false},
		{2, true},
		{3, true},
	}
	for _, c := range cases {
		if got := MeetsPathTrust(c.prefixBytes, cfg); got != c.want {
			t.Errorf("MeetsPathTrust(%d, minBytes=2) = %v, want %v", c.prefixBytes, got, c.want)
		}
	}
}

func TestMeetsPathTrust_ZeroValueOptIn(t *testing.T) {
	// A zero-value MinHashBytesForMapping (the JSON field absent) must resolve to
	// DefaultMinHashBytesForMapping, not be read as an explicit opt-in to some
	// other number. Asserted against the constant rather than against a literal
	// so this keeps testing the property if the default is ever changed again.
	unset := &TrustConfig{}
	if got := unset.MinHashBytesOrDefault(); got != DefaultMinHashBytesForMapping {
		t.Errorf("unset.MinHashBytesOrDefault() = %d, want %d", got, DefaultMinHashBytesForMapping)
	}
	// And it must behave identically to a config that names the default outright.
	explicit := &TrustConfig{MinHashBytesForMapping: DefaultMinHashBytesForMapping}
	for _, prefixBytes := range []int{0, 1, 2, 3} {
		if MeetsPathTrust(prefixBytes, unset) != MeetsPathTrust(prefixBytes, explicit) {
			t.Errorf("prefixBytes=%d: unset and explicit-default disagree", prefixBytes)
		}
	}
	// An explicit stricter setting must still be honoured over the default.
	strict := &TrustConfig{MinHashBytesForMapping: 2}
	if MeetsPathTrust(1, strict) {
		t.Error("MeetsPathTrust(1, minBytes=2) = true, want false — an explicit setting must win")
	}
}

func TestMeetsPathTrust_ConservativeThreshold3(t *testing.T) {
	cfg := &TrustConfig{MinHashBytesForMapping: 3}
	cases := []struct {
		prefixBytes int
		want        bool
	}{
		{0, false},
		{1, false},
		{2, false},
		{3, true},
	}
	for _, c := range cases {
		if got := MeetsPathTrust(c.prefixBytes, cfg); got != c.want {
			t.Errorf("MeetsPathTrust(%d, minBytes=3) = %v, want %v", c.prefixBytes, got, c.want)
		}
	}
}

func TestMinHashBytesOrDefault(t *testing.T) {
	var nilCfg *TrustConfig
	if got := nilCfg.MinHashBytesOrDefault(); got != DefaultMinHashBytesForMapping {
		t.Errorf("nil.MinHashBytesOrDefault() = %d, want %d", got, DefaultMinHashBytesForMapping)
	}
	unset := &TrustConfig{}
	if got := unset.MinHashBytesOrDefault(); got != DefaultMinHashBytesForMapping {
		t.Errorf("unset.MinHashBytesOrDefault() = %d, want %d", got, DefaultMinHashBytesForMapping)
	}
	explicit := &TrustConfig{MinHashBytesForMapping: 1}
	if got := explicit.MinHashBytesOrDefault(); got != 1 {
		t.Errorf("explicit(1).MinHashBytesOrDefault() = %d, want 1", got)
	}
	explicit2 := &TrustConfig{MinHashBytesForMapping: 2}
	if got := explicit2.MinHashBytesOrDefault(); got != 2 {
		t.Errorf("explicit(2).MinHashBytesOrDefault() = %d, want 2", got)
	}
	negative := &TrustConfig{MinHashBytesForMapping: -5}
	if got := negative.MinHashBytesOrDefault(); got != DefaultMinHashBytesForMapping {
		t.Errorf("negative.MinHashBytesOrDefault() = %d, want %d (defensive fallback)", got, DefaultMinHashBytesForMapping)
	}
}

func TestMinHashBytesOrDefault_ClampsAboveMax(t *testing.T) {
	cases := []int{4, 5, 99}
	for _, v := range cases {
		cfg := &TrustConfig{MinHashBytesForMapping: v}
		if got := cfg.MinHashBytesOrDefault(); got != MaxHashBytes {
			t.Errorf("MinHashBytesForMapping: %d -> MinHashBytesOrDefault() = %d, want %d (clamped)", v, got, MaxHashBytes)
		}
	}
}

func TestMinHashBytesOrDefault_ExactlyMax(t *testing.T) {
	cfg := &TrustConfig{MinHashBytesForMapping: MaxHashBytes}
	if got := cfg.MinHashBytesOrDefault(); got != MaxHashBytes {
		t.Errorf("MinHashBytesOrDefault() = %d, want %d (exactly max, no clamp needed)", got, MaxHashBytes)
	}
}

func TestMeetsPathTrust_ClampedThresholdOnlyTrustsMaxBytes(t *testing.T) {
	cfg := &TrustConfig{MinHashBytesForMapping: 99}
	cases := []struct {
		prefixBytes int
		want        bool
	}{
		{0, false},
		{1, false},
		{2, false},
		{3, true},
	}
	for _, c := range cases {
		if got := MeetsPathTrust(c.prefixBytes, cfg); got != c.want {
			t.Errorf("MeetsPathTrust(%d, minBytes=99->clamped) = %v, want %v", c.prefixBytes, got, c.want)
		}
	}
}