Change development fund to be paid by mostrod #561

grunch · 2026-01-02T17:50:31Z

Summary by CodeRabbit

New Features
- Added asynchronous development fee payment system with automatic scheduling and retry capability.
- Simplified fee structure where development fees are tracked and paid separately, not deducted from buyer or seller transactions.
Changes
- Development fee calculations now unified at order acceptance time; buyers and sellers no longer bear direct development fee costs.

_{✏️ Tip: You can customize this high-level summary in your review settings.}

coderabbitai · 2026-01-02T17:50:42Z

Walkthrough

The changes refactor the development fee model to eliminate per-party fee splits. A new calculate_dev_fee() function centralizes fee computation based on the Mostro fee percentage. Dev fees are no longer deducted from buyer and seller amounts; instead, they are tracked separately and asynchronously paid by Mostrod through a scheduler job. All amount calculations across order flows are updated to remove per-user dev fee components.

Changes

Cohort / File(s)	Summary
Core dev_fee calculation `src/util.rs`, `docs/DEV_FEE.md`	Added public `calculate_dev_fee(total_mostro_fee: i64, percentage: f64) -> i64` function for deterministic fee computation. Wrapper `get_dev_fee()` remains for backwards compatibility. Documentation reflects new payment model.
Order amount calculations `src/flow.rs`, `src/app/add_invoice.rs`	Removed dev_fee split logic. Seller amounts now computed as `order.amount + order.fee`; buyer amounts as `order.amount - order.fee`. Hold invoice and order state updates simplified to exclude per-party dev_fee deductions.
Payment/refund flow `src/app/release.rs`	Updated retry failure and payment completion logic to deduct only `order.fee` (not dev_fee split) when computing buyer refund amounts. Simplified fee subtraction in both `check_failure_retries()` and `do_payment()` paths.

Sequence Diagram(s)

sequenceDiagram
    autonumber
    
    participant User as User/Buyer
    participant Mostrod as Mostrod
    participant DB as Database
    participant LND as LND/LNURL

    rect rgb(220, 240, 255)
    Note over Mostrod,DB: Order Take & Dev Fee Calculation
    Mostrod->>Mostrod: Take order & calculate<br/>dev_fee from Mostro fee %
    Mostrod->>DB: Store order with dev_fee<br/>(unpaid status)
    DB-->>Mostrod: Order persisted
    end

    rect rgb(240, 220, 255)
    Note over Mostrod,LND: Async Dev Fee Payment (Scheduler Job)
    par Every 60 seconds
        Mostrod->>DB: Query unpaid dev_fees<br/>(settled-hold-invoice/<br/>success statuses)
        DB-->>Mostrod: List of dev_fees
    end
    
    opt Dev fee amount valid
        Mostrod->>LND: Request payment via LNURL
        LND-->>Mostrod: Payment hash
        Mostrod->>DB: Update dev_fee_paid=true<br/>& dev_fee_payment_hash
        DB-->>Mostrod: Success
        Mostrod->>Mostrod: Log verification complete
    end
    
    opt Payment fails
        Mostrod->>Mostrod: Log retry attempt
    end
    end
    
    rect rgb(220, 255, 220)
    Note over User,DB: Seller/Buyer Amount Flows (No Dev Fee Split)
    Mostrod->>DB: Seller receives:<br/>order.amount + order.fee
    Mostrod->>DB: Buyer pays:<br/>order.amount - order.fee
    DB-->>User: Amounts exclude dev_fee
    end

Estimated code review effort

🎯 3 (Moderate) | ⏱️ ~20 minutes

Possibly related issues

Sustainable Development Fee Implementation for Mostro #549: Centralizes dev_fee calculation in src/util.rs with the new calculate_dev_fee() function and get_dev_fee() wrapper.
Change development fund to be paid by mostrod instead of users #560: Shifts dev_fee payment responsibility from users (buyer/seller split) to Mostrod, removing per-party fee deductions.

Possibly related PRs

feat: implement Phase 4 dev fee audit events via Nostr #559: Adds scheduler-based async dev_fee payment lifecycle alongside audit event publishing.
fix: correct amount calculations in seller/buyer messages #552: Updates amount calculations in add_invoice.rs, flow.rs, and util.rs to align seller/buyer messages with new fee model (order.amount ± order.fee).
fix: correct AddInvoice amount calculation on payment failure #524: Modifies retry/payment failure path in src/app/release.rs to simplify buyer amount computation.

Suggested reviewers

Catrya
arkanoider

Poem

🐰 A fee so clean, no split in sight,
Mostro hops in, pays the dev's delight!
Amounts ring true, no more subtraction,
Async magic—scheduler in action! 💫

Pre-merge checks and finishing touches

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Docstring Coverage	⚠️ Warning	Docstring coverage is 28.57% which is insufficient. The required threshold is 80.00%.	You can run `@coderabbitai generate docstrings` to improve docstring coverage.

✅ Passed checks (2 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title 'Change development fund to be paid by mostrod' directly and clearly summarizes the main change: shifting dev fee payment responsibility from users to Mostrod. It is concise, specific, and accurately reflects the core modification across all modified files.

✨ Finishing touches

📝 Generate docstrings

📜 Recent review details

Configuration used: Organization UI

Review profile: CHILL

Plan: Pro

📥 Commits

Reviewing files that changed from the base of the PR and between 12f9600 and da7aa23.

📒 Files selected for processing (5)

docs/DEV_FEE.md
src/app/add_invoice.rs
src/app/release.rs
src/flow.rs
src/util.rs

🧰 Additional context used

📓 Path-based instructions (3)

src/**/*.rs

📄 CodeRabbit inference engine (AGENTS.md)

Runtime code lives in src/ directory with subdirectories: src/app/ for order flows and business logic, src/lightning/ for LND bindings and Lightning helpers, src/rpc/ for gRPC service and types, and src/config/ for settings and loaders

Files:

src/app/add_invoice.rs
src/app/release.rs
src/flow.rs
src/util.rs

**/*.rs

📄 CodeRabbit inference engine (AGENTS.md)

**/*.rs: Use 4-space indent, snake_case for functions, PascalCase for types, and SCREAMING_SNAKE_CASE for constants in Rust code (Rust 2021 edition)
Document non-obvious public APIs with triple-slash /// documentation comments
Prefer tracing spans over ad-hoc logging in Rust code
Co-locate tests in their modules under mod tests blocks and name tests descriptively

Files:

src/app/add_invoice.rs
src/app/release.rs
src/flow.rs
src/util.rs

src/app/**

📄 CodeRabbit inference engine (AGENTS.md)

Mirror test fixtures under src/app/ directory where applicable

Files:

src/app/add_invoice.rs
src/app/release.rs

🧠 Learnings (7)

📓 Common learnings

Learnt from: grunch
Repo: MostroP2P/mostro PR: 554
File: docs/DEV_FEE_TECHNICAL_SPEC.md:1-434
Timestamp: 2025-12-17T13:04:13.036Z
Learning: In the Mostro development fee implementation, the Lightning address `mostro_p2psats.mobi` in src/config/constants.rs is temporary for testing purposes. The production address will be `developmentmostro.network` as documented in docs/DEV_FEE_TECHNICAL_SPEC.md. This intentional mismatch is planned to be resolved before production deployment.

📚 Learning: 2025-07-17T13:51:17.338Z

Learnt from: arkanoider
Repo: MostroP2P/mostro PR: 499
File: src/lightning/invoice.rs:108-114
Timestamp: 2025-07-17T13:51:17.338Z
Learning: In Lightning invoice validation for Mostro buy orders (src/lightning/invoice.rs), zero-amount invoices (amount_sat == 0) should always pass validation even when an expected amount is provided. This is because users can submit invoices at order creation time before knowing the exact satoshi amount they'll receive. The condition `if amount_sat != res && amount_sat != 0` correctly implements this by allowing zero-amount invoices to pass while enforcing exact amount matching for non-zero invoices.

Applied to files:

src/app/add_invoice.rs
src/app/release.rs
src/flow.rs
docs/DEV_FEE.md
src/util.rs

📚 Learning: 2025-06-25T22:48:44.741Z

Learnt from: Catrya
Repo: MostroP2P/mostro PR: 502
File: src/app/release.rs:52-55
Timestamp: 2025-06-25T22:48:44.741Z
Learning: The PaymentFailedInfo struct used in src/app/release.rs is defined in mostro-core PR #111, creating a cross-repository dependency that causes compilation errors until the dependency is resolved.

Applied to files:

src/app/release.rs
src/util.rs

📚 Learning: 2025-06-25T22:48:44.741Z

Learnt from: Catrya
Repo: MostroP2P/mostro PR: 502
File: src/app/release.rs:52-55
Timestamp: 2025-06-25T22:48:44.741Z
Learning: PaymentFailedInfo struct and Payload::PaymentFailed variant are defined in mostro-core PR #111, creating a cross-repository dependency with the Mostro repository that requires careful coordination of merging and version updates.

Applied to files:

src/app/release.rs
src/util.rs

📚 Learning: 2025-04-27T20:07:24.558Z

Learnt from: arkanoider
Repo: MostroP2P/mostro PR: 475
File: src/db.rs:792-802
Timestamp: 2025-04-27T20:07:24.558Z
Learning: The decrypt_data function from mostro_core::order returns a type that needs to be wrapped with MostroInternalErr to convert it to MostroError, so calls should keep the .map_err(MostroInternalErr) conversion.

Applied to files:

src/app/release.rs
src/util.rs

📚 Learning: 2025-12-17T13:04:13.036Z

Learnt from: grunch
Repo: MostroP2P/mostro PR: 554
File: docs/DEV_FEE_TECHNICAL_SPEC.md:1-434
Timestamp: 2025-12-17T13:04:13.036Z
Learning: In the Mostro development fee implementation, the Lightning address `mostro_p2psats.mobi` in src/config/constants.rs is temporary for testing purposes. The production address will be `developmentmostro.network` as documented in docs/DEV_FEE_TECHNICAL_SPEC.md. This intentional mismatch is planned to be resolved before production deployment.

Applied to files:

src/app/release.rs
docs/DEV_FEE.md
src/util.rs

📚 Learning: 2025-06-13T12:50:53.424Z

Learnt from: arkanoider
Repo: MostroP2P/mostro PR: 499
File: src/lightning/invoice.rs:21-27
Timestamp: 2025-06-13T12:50:53.424Z
Learning: `ln_exists(address: &str)` returns `Result<(), MostroError>`: `Ok(())` means the Lightning address exists (`tag == "payRequest"`), and `Err(_)` represents any invalid or unreachable address scenario.

Applied to files:

src/app/release.rs
src/util.rs

🪛 LanguageTool

docs/DEV_FEE.md

[grammar] ~11-~11: Ensure spelling is correct
Context: ...ity - Node operator contribution model (mostrod pays from its earnings, not users) ## ...