Create book.proto

src/proto/book.proto

+syntax = "proto3";
+
+option java_multiple_files = true;
+option java_package = "org.ds.proto";
+
+enum BookType {
+  UNKNOWN = 0;
+  FICTION = 1;
+  SCIENCE = 2;
+  TECHNOLOGY = 3;
+  HISTORY = 4;
+}
+
+message Author {
+  string name = 1;
+  string country = 2;
+  string email = 3;
+}
+
+message Publisher {
+  string name = 1;
+  string city = 2;
+  int32 established_year = 3;
+}
+
+message Book {
+  string title = 1;
+  Author author = 2;              // nested message
+  string isbn = 3;
+  int32 publication_year = 4;
+  BookType type = 5;              // enum
+  Publisher publisher = 6;        // nested message
+  repeated string genres = 7;     // repeated field
+  double price = 8;
+  bool available = 9;
+  int32 page_count = 10;
+}
+
+message Library {
+  repeated Book books = 1;
+}
+
+service LibraryService {
+  rpc AddBook(Book) returns (OperationResponse);
+  rpc FindBooks(SearchRequest) returns (Library);
+  rpc GetBook(BookRequest) returns (Book);
+}
+
+message OperationResponse {
+  bool success = 1;
+  string message = 2;
+  string book_id = 3;
+}
+
+message SearchRequest {
+  string query = 1;
+  BookType type = 2;
+}
+
+message BookRequest {
+  string isbn = 1;
+}
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