Author Hodik Maksym

Project: Game Quest Parser (Course Project) Goal: To create a parser for a custom domain-specific language (DSL) for RPG games.

Game Quest Parser (GQDL)

Game Quest Parser is a robust command-line tool and library written in Rust for parsing the Game Quest Definition Language (GQDL).

It allows game developers to define RPG quests in a simple, human-readable text format and converts them into structured Rust objects. This project demonstrates the implementation of a Recursive Descent Parser from scratch, ensuring strict type safety and detailed error reporting.

Features

• Custom Grammar: Parses a structured language with nested blocks and key-value properties.
• Type Safety: Distinguishes between integers, booleans, strings, and lists.
• Error Handling: Provides descriptive errors using thiserror (library) and anyhow (CLI).
• CLI Tool: Includes a command-line interface built with clap.

Technical Description

The parsing process transforms raw text into a usable data structure through two main stages:

1. Lexical Analysis (Lexer)

The Lexer scans the source code character by character and groups them into Tokens.

• Input: active: true
• Output: [Token::Identifier("active"), Token::Colon, Token::True]

2. Syntactic Analysis (Parser)

The Parser iterates through the tokens and builds an Abstract Syntax Tree (AST) represented by the Quest struct. It validates the order of tokens against the defined grammar rules.

Data Flow Diagram:

[ Source File ] -> [ Lexer ] -> [ Token Stream ] -> [ Parser ] -> [ Quest Struct ]
                                                        |
                                               (Validates Grammar)

Grammar Rules The parser follows the EBNF (Extended Backus-Naur Form) grammar rules below:

EBNF

QUEST_DEF  ::= "quest" (IDENTIFIER | STRING) "{" BODY "}"
BODY       ::= PROPERTY (","? PROPERTY)*
PROPERTY   ::= KEY ":" VALUE
KEY        ::= "reward" | "active" | "step"
VALUE      ::= INTEGER | BOOLEAN | STRING

Example Input (test_quest.txt)

quest "The Lost Sword" {
    active: true,
    reward: 500,
    step: "Talk to the blacksmith",
    step: "Find the cave entrance",
    step: "Defeat the skeleton king"
}

Installation & Usage Prerequisites Rust and Cargo (latest stable version) CLI Commands

1. Parse a Quest File Reads the specified file and prints the parsed Rust structure. cargo run -- parse --file test_quest.txt
2. Show Credits Displays project information and author. cargo run -- credits
3. Help Displays all available commands and options. cargo run -- --help