flake.nix

{
  description = "Rust Agentic Environment (Nightly + Diagnostics Tracking)";

  inputs = {
    nixpkgs.url = "github:NixOS/nixpkgs/nixos-unstable";
    flake-utils.url = "github:numtide/flake-utils";
    # REQUIRED: The overlay to get the Nightly compiler
    rust-overlay.url = "github:oxalica/rust-overlay";
  };

  outputs = { self, nixpkgs, flake-utils, rust-overlay }:
    flake-utils.lib.eachDefaultSystem (system:
      let
        # Apply the overlay to nixpkgs
        overlays = [ (import rust-overlay) ];
        pkgs = import nixpkgs {
          inherit system overlays;
        };

        # ---------------------------------------------------------------------
        # NIGHTLY TOOLCHAIN
        # We need this specific version to access -Z flags.
        # We include 'rust-src' for rust-analyzer support.
        # ---------------------------------------------------------------------
        rustToolchain = pkgs.rust-bin.nightly.latest.default.override {
          extensions = [ "rust-src" "rust-analyzer" "clippy" "rustfmt" ];
        };

        # ---------------------------------------------------------------------
        # 1. AGENT-CHECK (The Diagnostic Tracker)
        # ---------------------------------------------------------------------
        # -Z track-diagnostics: Debugs where the error was created.
        # --message-format short: Keeps it readable for the Agent.
        agentCheck = pkgs.writeShellScriptBin "agent-check" ''
          echo "🦀 [Check] Verifying Syntax (Nightly Diagnostics)..."
          ${rustToolchain}/bin/cargo check \
            -Z track-diagnostics \
            --message-format short \
            --color never \
            --quiet
        '';

        # ---------------------------------------------------------------------
        # 2. AGENT-LINT (Nightly Clippy)
        # ---------------------------------------------------------------------
        agentLint = pkgs.writeShellScriptBin "agent-lint" ''
          echo "🧹 [Lint] Running Nightly Clippy..."
          ${rustToolchain}/bin/cargo clippy \
            --message-format short \
            --color never \
            -- \
            -D warnings \
            -D clippy::unwrap_used \
            -D unsafe_code
        '';

        # ---------------------------------------------------------------------
        # 3. AGENT-AUDIT (Security)
        # ---------------------------------------------------------------------
        agentAudit = pkgs.writeShellScriptBin "agent-audit" ''
          echo "🔒 [Audit] Scanning dependencies..."
          ${pkgs.cargo-audit}/bin/cargo-audit --color never
        '';

        # ---------------------------------------------------------------------
        # AGENT CONTEXT
        # ---------------------------------------------------------------------
        agentContext = ''
          # Rust Agent Protocol (Nightly Edition)

          ## 🌙 NIGHTLY TOOLCHAIN ACTIVE
          You are using the **Nightly** compiler.
          - Syntax check uses \`-Z track-diagnostics\`.
          - If the compiler outputs internal path traces, focus on the "created at" location to understand the *root cause* of the error.

          ## 🚨 STRICT GUARDRAILS
          1. **NO \`Cargo.toml\` EDITS:** Use \`cargo add\`.
          2. **NO UNWRAPS:** Panics are banned.
          3. **NO UNSAFE:** Unsafe code is banned.

          ## 🛠 COMMANDS
          | Command | Purpose | Output Style |
          | :--- | :--- | :--- |
          | \`agent-check\` | **Deep Diagnostic Check.** | \`file:line:col: error\` + Diagnostic Trace |
          | \`agent-lint\` | **Security/Perf Check.** | Short format. |
          | \`agent-audit\` | **CVE Scan.** | Database output. |
        '';

      in
      {
        devShells.default = pkgs.mkShell {
          buildInputs = [
            rustToolchain # The Nightly Compiler
            pkgs.cargo-audit
            pkgs.pkg-config
            pkgs.openssl
            
            # Agent Scripts
            agentCheck
            agentLint
            agentAudit
          ];

          shellHook = ''
            echo "🌙 Initializing Rust Nightly Environment..."
            echo "   (Enabled: -Z track-diagnostics)"

            echo "${agentContext}" > AGENT_CONTEXT.md
            
            # Configure sparse registry for speed
            mkdir -p .cargo
            echo '[registry]' > .cargo/config.toml
            echo 'default = "sparse"' >> .cargo/config.toml

            if [ ! -f Cargo.toml ]; then
               cargo init --quiet
               cargo add tokio --features full --quiet
               cargo add anyhow --quiet
            fi
          '';
        };
      }
    );
}