package parsemail

import (
	"crypto/ecdsa"
	"crypto/elliptic"
	"crypto/rand"
	"crypto/rsa"
	"crypto/x509"
	"encoding/pem"
	"os"
	"path/filepath"
	"testing"

	"git.pcux.cn/xuans/Smail/config"
)

func TestLoadPrivateKeyAcceptsStrongRSAKey(t *testing.T) {
	path := writeDKIMTestKey(t, 2048)
	signer, err := loadPrivateKey(path)
	if err != nil {
		t.Fatal(err)
	}
	privateKey, ok := signer.(*rsa.PrivateKey)
	if !ok || privateKey.N.BitLen() < 2048 {
		t.Fatal("应加载至少 2048 位的 RSA DKIM 私钥")
	}
}

func TestLoadPrivateKeyRejectsWeakRSAKey(t *testing.T) {
	path := writeDKIMTestKey(t, 1024)
	if _, err := loadPrivateKey(path); err == nil {
		t.Fatal("弱 RSA DKIM 私钥应被拒绝")
	}
}

func TestLoadPrivateKeyRejectsUnexpectedPKCS8Type(t *testing.T) {
	root, directory := prepareDKIMTestDirectory(t)
	privateKey, err := ecdsa.GenerateKey(elliptic.P256(), rand.Reader)
	if err != nil {
		t.Fatal(err)
	}
	encoded, err := x509.MarshalPKCS8PrivateKey(privateKey)
	if err != nil {
		t.Fatal(err)
	}
	path := filepath.Join(directory, "dkim.priv")
	if err := os.WriteFile(path, pem.EncodeToMemory(&pem.Block{Type: "PRIVATE KEY", Bytes: encoded}), 0600); err != nil {
		t.Fatal(err)
	}
	config.ROOT_PATH = root + string(os.PathSeparator)
	if _, err := loadPrivateKey(path); err == nil {
		t.Fatal("非 RSA PKCS8 私钥应被安全拒绝")
	}
}

func TestLoadPrivateKeyRejectsSymlink(t *testing.T) {
	root, directory := prepareDKIMTestDirectory(t)
	outside := filepath.Join(t.TempDir(), "outside.key")
	if err := os.WriteFile(outside, []byte("outside"), 0600); err != nil {
		t.Fatal(err)
	}
	path := filepath.Join(directory, "dkim.priv")
	if err := os.Symlink(outside, path); err != nil {
		t.Skipf("当前环境不支持符号链接测试: %v", err)
	}
	config.ROOT_PATH = root + string(os.PathSeparator)
	if _, err := loadPrivateKey(path); err == nil {
		t.Fatal("DKIM 私钥符号链接应被拒绝")
	}
}

func writeDKIMTestKey(t *testing.T, bits int) string {
	t.Helper()
	root, directory := prepareDKIMTestDirectory(t)
	privateKey, err := rsa.GenerateKey(rand.Reader, bits)
	if err != nil {
		t.Fatal(err)
	}
	encoded, err := x509.MarshalPKCS8PrivateKey(privateKey)
	if err != nil {
		t.Fatal(err)
	}
	path := filepath.Join(directory, "dkim.priv")
	if err := os.WriteFile(path, pem.EncodeToMemory(&pem.Block{Type: "PRIVATE KEY", Bytes: encoded}), 0600); err != nil {
		t.Fatal(err)
	}
	config.ROOT_PATH = root + string(os.PathSeparator)
	return path
}

func prepareDKIMTestDirectory(t *testing.T) (string, string) {
	t.Helper()
	oldRoot := config.ROOT_PATH
	root := t.TempDir()
	t.Cleanup(func() { config.ROOT_PATH = oldRoot })
	directory := filepath.Join(root, "config", "dkim")
	if err := os.MkdirAll(directory, 0700); err != nil {
		t.Fatal(err)
	}
	return root, directory
}