✨ TASK

Convert the Solidity contract below into a single‑file Cairo 1 implementation for Starknet.

• Preserve the external API (function names, params, events).
• Re‑implement business logic 1‑for‑1, adjusting only where Cairo semantics differ.
• Optimise for clarity over micro‑gas; follow current Cairo best‑practices.

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📜 Solidity Source (start)

<Paste the exact Solidity contract here>

📜 Solidity Source (end)

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🧩 Provide example user‑inputs (when relevant)

If any external/public function accepts free‑form or ambiguous payloads (e.g. bytes, string, dynamic arrays, mixed structs), add 2 – 3 representative examples immediately below ­— formatted as JSON snippets.

// Example payloads ─ remove if not needed
{
  "createOrder": {
    "id": "0xabc…",
    "amount": "1000000000000000000",
    "token": "0x1234…"
  },
  "metaTx": {
    "deadline": 1699999999,
    "signature": "0xdeadbeef…"
  }
}

These help the generator infer the correct Cairo types and packing strategy.

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🛠 DELIVERABLE

Return only the Cairo file contents — no extra prose:

1. File name: <originalName>.cairo (snake_case).
2. Builds cleanly with the latest toolchain (scarb build).
3. No TODOs or placeholders; concise inline docstrings are fine.

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⚙️ REQUIREMENTS

Topic	Requirement
Syntax	Cairo 1
Imports	Use OpenZeppelin‑Cairo ≥ 0.13.0 when an analogue exists (Ownable, IERC20, non_reentrant, Mapping, etc.).
Storage	Mirror Solidity structs/enums in #[storage] struct Storage { … } or OZ Mappings.
Errors	Convert custom errors to #[derive(Error)] enums or panic_with_reason("ErrorName") — names must match.
Events	Re‑declare every Solidity event as a #[event] struct with the same field order & names.
Type widths	Use Uint256 for token amounts & large counters; u8/u64 for small fields & timestamps.
Re‑entrancy	Protect mutating externals with @non_reentrant.
Ownership	Implement only_owner gating via OZ Ownable.
Hash & Sig checks	EVM sigs: starknet_keccak + verify_eth_signature. Starknet sigs: ecdsa::verify.
Time	Replace block.timestamp with get_block_timestamp().
Storage refunds	Where Solidity does delete, call .pop(key) (or equivalent) to reclaim fees.
Constants	Solidity immutable → Cairo const or constructor‑set storage vars, whichever preserves behaviour.

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🏗 STRUCTURE GUIDE

1. Imports & use statements

2. #[storage] struct Storage

3. Custom error enum (#[derive(Error)])

4. #[event] structs

5. User‑defined enums / helper structs

6. Contract impl block

   • constructor( … )
   • External/public functions (keep Solidity order)
   • Internal helpers

7. Optional snforge unit‑test stubs under #[cfg(test)]

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🟢 ACCEPTANCE CRITERIA

• scarb build prints zero warnings.
• Function selectors & event topic hashes are byte‑identical to the Solidity originals.
• All revert paths mirror Solidity behaviour in snforge tests.
• README stays clean — no additional commentary beyond this template.

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📦 Reference Scarb.toml snippet (latest versions — July 2025)

[package]
name    = "translated_contract"
version = "0.1.0"
edition = "2023_10"

[dependencies]
# Core Cairo / Starknet (Keccak, secp256k1, ECDSA helpers, etc.)
starknet = ">=2.11.4"           # use the latest stable tag

# OpenZeppelin Cairo contracts (Ownable, IERC20, non_reentrant, Mapping…)
openzeppelin = { git = "https://github.com/OpenZeppelin/cairo-contracts.git", tag = "v2.0.0" }

# (Add any extra libs the generator requires here)

Tip: always run scarb update before compiling to pull the newest minor releases.