package content

import (
	"bytes"
	"crypto/sha256"
	"encoding/hex"
	"testing"
)

func TestBindStableHash(t *testing.T) {
	payload := Phase1Rendered{
		"title":  "Approve policy change v3",
		"action": "sign",
		"detail": map[string]any{"policy_id": "pol-42"},
	}
	a, err := Bind(payload)
	if err != nil {
		t.Fatalf("Bind: %v", err)
	}
	b, err := Bind(payload)
	if err != nil {
		t.Fatalf("Bind again: %v", err)
	}
	if a.ContentHash != b.ContentHash {
		t.Errorf("content_hash not stable: %q vs %q", a.ContentHash, b.ContentHash)
	}
	if !bytes.Equal(a.ContentCanonical, b.ContentCanonical) {
		t.Errorf("canonical bytes not stable")
	}
	if bytes.Equal(a.Salt, b.Salt) {
		t.Errorf("salt should be random (equal across two calls)")
	}
	if bytes.Equal(a.Nonce, b.Nonce) {
		t.Errorf("nonce should be random (equal across two calls)")
	}
}

func TestBindRejectsNil(t *testing.T) {
	if _, err := Bind(nil); err == nil {
		t.Fatalf("Bind(nil) must error")
	}
}

func TestVerificationDigitsFormat(t *testing.T) {
	b, err := Bind(Phase1Rendered{"k": "v"})
	if err != nil {
		t.Fatal(err)
	}
	if l := len(b.VerificationDigits); l != 6 {
		t.Errorf("want 6 digits, got %d (%q)", l, b.VerificationDigits)
	}
	for _, r := range b.VerificationDigits {
		if r < '0' || r > '9' {
			t.Errorf("non-digit %q in verification digits %q", r, b.VerificationDigits)
		}
	}
}

func TestChallengeFor_Deterministic(t *testing.T) {
	b, err := Bind(Phase1Rendered{"k": "v"})
	if err != nil {
		t.Fatal(err)
	}
	got := ChallengeFor(b.Nonce, b.ContentCanonical)
	if !bytes.Equal(got, b.Challenge) {
		t.Errorf("ChallengeFor must reproduce the challenge")
	}
	// Flip a byte in canonical content — challenge must change.
	alt := append([]byte(nil), b.ContentCanonical...)
	alt[0] ^= 0xff
	if bytes.Equal(ChallengeFor(b.Nonce, alt), b.Challenge) {
		t.Errorf("challenge did not change when canonical content was tampered")
	}
}

func TestRehashCanonicalMatchesBind(t *testing.T) {
	b, err := Bind(Phase1Rendered{"foo": "bar"})
	if err != nil {
		t.Fatal(err)
	}
	if got := RehashCanonical(b.ContentCanonical); got != b.ContentHash {
		t.Errorf("RehashCanonical=%q want %q", got, b.ContentHash)
	}
	// Sanity: computed independently
	sum := sha256.Sum256(b.ContentCanonical)
	if "sha256:"+hex.EncodeToString(sum[:]) != b.ContentHash {
		t.Errorf("ContentHash does not match computed sha256")
	}
}