Valve Hammer FGd Editor

Purpose & User Intent: This tool provides a dedicated parser, validator, and generator workflow for Valve Hammer Editor FGDs.
Target users include level designers, modders, and tooling engineers who author or update FGDs to define entity classes, keyvalues, and behavior properties used by Source-engine maps. It addresses structural mistakes, invalid keys, and inconsistent definitions that slow iteration and cause map build failures.
Core Logic & Features: The tool parses FGD text, builds an internal representation, and enforces domain rules such as required blocks (entities, properties) and valid key names. Required features include FGD_text input, engine_version awareness, and optional_batch_processing. Advanced features cover dependency checks, cross-field validation, and auto-fix suggestions. Outputs include a validated draft, an error report, and a diff suitable for version control.
Algorithms & Calculations: Parsing follows the FGD grammar, tokenization, and block validation. It enforces naming conventions, checks for missing required blocks, and validates cross-field references (entity to property mappings). When available, it computes minimal safe changes and emits a structured diff to facilitate review. Error severity levels distinguish fatal, error, and warning.
Error & Edge Cases: Handles missing inputs, empty FGD content, unknown keys, deprecated blocks, and engine_version mismatches. If external references are unresolved or the file encoding is invalid, it reports precise locations and suggested corrections. Large FGDs are processed in streaming passes to minimize memory use.
Industry/Region & Localization: Follows Source engine data conventions and UTF-8 text encoding. Engine_version and target_game support common regional builds; no localization of content is performed beyond metadata.
Assumptions & Exclusions: Assumes textual FGD definitions for Source-era entities. Does not compile maps, modify textures, or alter runtime assets. UI rendering or editor integration details are out of scope.