Implement Bevy/DDlog scaffolding

[leynos]

Summary

• set up initial Bevy app and DDlog handle
• compile src/lille.dl in build.rs when ddlog executable is available
• expose new Bevy resource helpers
• document updated architecture and dependencies
• update contribution guide for new nixie Mermaid validator

Testing

• cargo fmt -- --check
• cargo clippy --quiet (fails: no matching package named differential-datalog)
• cargo test --quiet (fails: no matching package named differential-datalog)
• nixie docs/architecture.md

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https://chatgpt.com/codex/tasks/task_e_6845ea7092cc8322b351fa85a0033e6f

Summary by Sourcery

Set up foundational Bevy and DDlog scaffolding by replacing the legacy Piston loop with a Bevy App, inserting a placeholder DDlog handle resource, and extending the build script to compile the DDlog program when the compiler is present.

New Features:

• Introduce a minimal Bevy App setup with default plugins and a hello_world startup system
• Add a placeholder DdlogHandle resource and corresponding Bevy startup system
• Integrate DDlog compilation of src/lille.dl into the build process when the ddlog compiler is detected

Enhancements:

• Replace the custom game loop and Piston prototype with a Bevy-based application entry point
• Expose Bevy resource helpers and re-export key items in the crate’s public API
• Add Bevy as a project dependency in Cargo.toml

Build:

• Watch src/lille.dl for changes and invoke the ddlog compiler in build.rs if available
• Enhance build.rs to download a font fallback and emit warnings on failures

Documentation:

• Update architecture.md to document the new Bevy/DDlog scaffolding and legacy Piston prototype
• Revise AGENTS.md to use nixie for Mermaid diagram validation

[sourcery-ai]

Reviewer's Guide

Scaffolds a Bevy-based game runtime with placeholder DDlog integration by enhancing the build script to compile DDlog programs, refactoring the main loop into a Bevy App with systems, adding a ddlog_handle module, updating dependencies, and revising documentation to reflect the new architecture.

Sequence Diagram: New Application Startup Process

sequenceDiagram
    actor User
    participant MainFunction as "main()"
    participant BevyApp as "Bevy App"
    participant InitDdlogSystem as "init_ddlog_system()"
    participant HelloWorldSystem as "hello_world()"
    participant DdlogHandleResource as "DdlogHandle (Resource)"

    User->>MainFunction: Execute program
    MainFunction->>BevyApp: App::new()
    MainFunction->>BevyApp: .add_plugins(DefaultPlugins)
    MainFunction->>BevyApp: .add_startup_system(init_ddlog_system)
    MainFunction->>BevyApp: .add_systems(Startup, hello_world)
    MainFunction->>BevyApp: .run()
    BevyApp-->>InitDdlogSystem: Calls startup system
    InitDdlogSystem->>DdlogHandleResource: commands.insert_resource(DdlogHandle)
    InitDdlogSystem-->>BevyApp: Returns
    BevyApp-->>HelloWorldSystem: Calls startup system
    HelloWorldSystem->>HelloWorldSystem: info!("Hello Bevy!")
    HelloWorldSystem-->>BevyApp: Returns

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Sequence Diagram: DDlog Compilation in Build Process

sequenceDiagram
    participant CargoBuild as "cargo build"
    participant BuildScript as "build.rs"
    participant DDlogCompiler as "ddlog compiler"
    participant FileSystem as "File System"

    CargoBuild->>BuildScript: Executes
    BuildScript->>DDlogCompiler: Check availability (ddlog --version)
    DDlogCompiler-->>BuildScript: Reports availability
    alt ddlog compiler available
        BuildScript->>FileSystem: Check "src/lille.dl" existence
        FileSystem-->>BuildScript: Reports existence
        alt "src/lille.dl" exists
            BuildScript->>DDlogCompiler: Compile "src/lille.dl" (output "ddlog_lille")
            DDlogCompiler-->>BuildScript: Compilation status
        end
    else ddlog compiler not available
        BuildScript->>BuildScript: Log warning "ddlog compiler not found"
    end

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ER Diagram: New DdlogHandle Data Type (Unit Struct, Bevy Resource)

erDiagram
    DdlogHandle

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File-Level Changes

Change	Details	Files
Enhanced build script for font management and DDlog compilation	Added rerun-if-changed for src/lille.dl Imported Command to invoke external processes Implemented check and invocation of ddlog compiler with warnings Retained font download logic and FONT_PATH env var	build.rs
Refactored main to use Bevy App instead of Piston loop	Removed manual GameWorld and GraphicsContext loop Defined a hello_world startup system Configured App::new with DefaultPlugins and init_ddlog_system	src/main.rs
Introduced ddlog_handle module and updated library exports	Added DdlogHandle resource and init_ddlog_system system Reordered and re-exported ddlog_handle and existing components in lib.rs	src/ddlog_handle.rs src/lib.rs
Added Bevy dependency for new architecture scaffolding	Inserted bevy = { version = "0.12", default-features = false, features = ["bevy_winit"] }	Cargo.toml
Updated documentation for Bevy/DDlog transition and validation tool	Expanded architecture.md with phase description and legacy notes Replaced Mermaid validation script with nixie in AGENTS.md	docs/architecture.md AGENTS.md

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[sourcery-ai]

Hey @leynos - I've reviewed your changes and they look great!

Here's what I looked at during the review

• 🟡 General issues: 2 issues found
• 🟢 Security: all looks good
• 🟢 Testing: all looks good
• 🟢 Complexity: all looks good
• 🟢 Documentation: all looks good

---

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[leynos]

@sourcery-ai review

[sourcery-ai]

Hey @leynos - I've reviewed your changes and they look great!

Here's what I looked at during the review

• 🟡 General issues: 1 issue found
• 🟢 Security: all looks good
• 🟢 Testing: all looks good
• 🟢 Complexity: all looks good
• 🟢 Documentation: all looks good

---

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_{Help me be more useful! Please click 👍 or 👎 on each comment and I'll use the feedback to improve your reviews.}