package filestore

import (
	"bytes"
	"crypto/sha256"
	"encoding/hex"
	"errors"
	"os"
	"path/filepath"
	"testing"
)

// TestStoreCommitsAndReusesImmutableFile 验证 Commit 首次写入会创建文件且 Reused 为 false，
// 第二次写入相同身份时按幂等返回 Reused 为 true 且路径一致。
func TestStoreCommitsAndReusesImmutableFile(t *testing.T) {
	t.Parallel()
	store, err := New(t.TempDir())
	if err != nil {
		t.Fatalf("create file store: %v", err)
	}
	content := []byte("signed update package")
	identity := identityOf(content)
	committed, err := store.Commit("transactions/one/package.zip", bytes.NewReader(content), identity)
	if err != nil {
		t.Fatalf("commit file: %v", err)
	}
	if committed.Reused {
		t.Fatal("new file reported as reused")
	}
	actual, err := os.ReadFile(committed.Path)
	if err != nil || !bytes.Equal(actual, content) {
		t.Fatalf("read committed file: content=%q err=%v", actual, err)
	}
	reused, err := store.Commit("transactions/one/package.zip", bytes.NewReader(content), identity)
	if err != nil {
		t.Fatalf("reuse committed file: %v", err)
	}
	if !reused.Reused || reused.Path != committed.Path {
		t.Fatalf("unexpected reused file: %+v", reused)
	}
}

// TestStoreInspectsCommittedIdentityWithoutMutation 验证 Inspect 能校验已提交文件的身份、
// 正确处理不存在的文件或目录，并对身份不符返回 ErrDestinationConflict。
func TestStoreInspectsCommittedIdentityWithoutMutation(t *testing.T) {
	t.Parallel()
	store, err := New(t.TempDir())
	if err != nil {
		t.Fatalf("create file store: %v", err)
	}
	content := []byte("immutable backend jar")
	identity := identityOf(content)
	if _, err := store.Commit("releases/backend.jar", bytes.NewReader(content), identity); err != nil {
		t.Fatalf("commit file: %v", err)
	}
	inspected, found, err := store.Inspect("releases/backend.jar", identity)
	if err != nil || !found || inspected.Path == "" || !inspected.Reused {
		t.Fatalf("inspect committed file: file=%+v found=%t err=%v", inspected, found, err)
	}
	_, found, err = store.Inspect("releases/missing.jar", identity)
	if err != nil || found {
		t.Fatalf("inspect missing file: found=%t err=%v", found, err)
	}
	_, found, err = store.Inspect("missing/directory/backend.jar", identity)
	if err != nil || found {
		t.Fatalf("inspect file below missing directory: found=%t err=%v", found, err)
	}
	_, _, err = store.Inspect("releases/backend.jar", identityOf([]byte("different")))
	if !errors.Is(err, ErrDestinationConflict) {
		t.Fatalf("expected immutable identity conflict, got %v", err)
	}
}

// TestStoreRejectsMismatchAndNeverPublishesInvalidFile 验证身份不符时 Commit 返回错误，
// 且目标路径上不会留下任何已发布的文件。
func TestStoreRejectsMismatchAndNeverPublishesInvalidFile(t *testing.T) {
	t.Parallel()
	root := t.TempDir()
	store, err := New(root)
	if err != nil {
		t.Fatalf("create file store: %v", err)
	}
	content := []byte("actual")
	expected := identityOf([]byte("different"))
	expected.Size = int64(len(content))
	_, err = store.Commit("package.zip", bytes.NewReader(content), expected)
	if err == nil {
		t.Fatal("SHA-256 mismatch was accepted")
	}
	if _, statErr := os.Stat(filepath.Join(root, "package.zip")); !errors.Is(statErr, os.ErrNotExist) {
		t.Fatalf("invalid destination was published: %v", statErr)
	}
}

// TestStoreRejectsNilSource 验证 Commit 传入 nil source 时会被拒绝。
func TestStoreRejectsNilSource(t *testing.T) {
	t.Parallel()
	store, err := New(t.TempDir())
	if err != nil {
		t.Fatalf("create file store: %v", err)
	}
	if _, err := store.Commit("package.zip", nil, identityOf(nil)); err == nil {
		t.Fatal("nil file source was accepted")
	}
}

// TestStoreRejectsExistingDifferentContentAndPathEscape 验证目标已存在不同内容时返回
// ErrDestinationConflict，且通过 ../ 越界的相对路径会被拒绝。
func TestStoreRejectsExistingDifferentContentAndPathEscape(t *testing.T) {
	t.Parallel()
	root := t.TempDir()
	store, err := New(root)
	if err != nil {
		t.Fatalf("create file store: %v", err)
	}
	if err := os.WriteFile(filepath.Join(root, "package.zip"), []byte("old"), 0o640); err != nil {
		t.Fatalf("seed destination: %v", err)
	}
	_, err = store.Commit("package.zip", bytes.NewReader([]byte("new")), identityOf([]byte("new")))
	if !errors.Is(err, ErrDestinationConflict) {
		t.Fatalf("expected destination conflict, got %v", err)
	}
	_, err = store.Commit("../outside", bytes.NewReader(nil), identityOf(nil))
	if err == nil {
		t.Fatal("path traversal was accepted")
	}
}

// TestStoreRejectsSymlinkedParentOutsideRoot 验证父目录为指向根目录之外的符号链接时，
// Commit 会被拒绝，防止文件通过符号链接写出存储根目录。
func TestStoreRejectsSymlinkedParentOutsideRoot(t *testing.T) {
	t.Parallel()
	root := t.TempDir()
	outside := t.TempDir()
	if err := os.Symlink(outside, filepath.Join(root, "linked")); err != nil {
		t.Fatalf("create parent symlink: %v", err)
	}
	store, err := New(root)
	if err != nil {
		t.Fatalf("create file store: %v", err)
	}
	_, err = store.Commit("linked/package.zip", bytes.NewReader(nil), identityOf(nil))
	if err == nil {
		t.Fatal("symlinked parent outside root was accepted")
	}
}

// identityOf 根据 content 计算其 SHA-256 摘要并返回对应的 Identity，供测试构造期望身份。
func identityOf(content []byte) Identity {
	digest := sha256.Sum256(content)
	return Identity{Size: int64(len(content)), SHA256: hex.EncodeToString(digest[:])}
}