all: add flake.nix setup and CLAUDE.md documentation

Author: fubhy

.gitignore

@@ -32,4 +32,12 @@ lcov.info
 
 # Docker volumes and debug logs
 .postgres
-logfile
+logfile
+
+# Nix related files
+.direnv
+.envrc
+.data
+
+# Local claude settings
+.claude/settings.local.json

CLAUDE.md

@@ -0,0 +1,194 @@
+# CLAUDE.md
+
+This file provides guidance to Claude Code (claude.ai/code) when working with code in this repository.
+
+## Project Overview
+
+Graph Node is a Rust-based decentralized blockchain indexing protocol that enables efficient querying of blockchain data through GraphQL. It's the core component of The Graph protocol, written as a Cargo workspace with multiple crates organized by functionality.
+
+## Essential Development Commands
+
+### Unit Tests
+
+Unit tests are inlined with source code
+
+```bash
+# REQUIRED: Export database connection string before running unit tests
+export THEGRAPH_STORE_POSTGRES_DIESEL_URL="postgresql://graph:graph@127.0.0.1:5432/graph-test"
+
+# Run unit tests (integration tests are excluded due to missing environment dependencies)
+cargo test --workspace --exclude graph-tests
+
+# Run specific tests
+cargo test -p graph data_source::common::tests
+cargo test <specific_test_name>
+```
+
+### Integration Tests
+
+⚠️ **Only run integration tests when explicitly requested or when changes require full system testing**
+
+Integration tests require environment dependencies that can be provided **EITHER** through Docker & Docker Compose **OR** through Nix. They are more complex to run than unit tests. They test the full system end-to-end and should not be run by default during development. Use unit tests for regular development and only run integration tests when:
+
+- Explicitly asked to do so
+- Making changes to integration/end-to-end functionality
+- Debugging issues that require full system testing
+- Preparing releases or major changes
+
+**Prerequisites:**
+1. Docker and Docker Compose **OR** Nix (for operating environment dependencies)
+2. Yarn (v1)
+3. Foundry (for smart contract compilation)
+
+**Running Integration Tests:**
+```bash
+# Run all integration tests
+cargo test -p graph-tests --test integration_tests -- --nocapture
+
+# Run a specific integration test case (e.g., "grafted" test case)
+TEST_CASE=grafted cargo test -p graph-tests --test integration_tests -- --nocapture
+```
+
+**Important Notes:**
+- Integration tests take significant time (several minutes)
+- Tests automatically reset the database between runs
+- Logs are written to `tests/integration-tests/graph-node.log`
+
+### Code Quality
+```bash
+# 🚨 MANDATORY: Format all code IMMEDIATELY after any .rs file edit
+cargo fmt --all
+
+# 🚨 MANDATORY: Check code for warnings and errors - MUST have zero warnings
+cargo check
+```
+
+🚨 **CRITICAL REQUIREMENTS for ANY implementation**:
+- **🚨 MANDATORY**: `cargo fmt --all` MUST be run before any commit
+- **🚨 MANDATORY**: `cargo check` MUST show zero warnings before any commit
+- **🚨 MANDATORY**: The unit test suite MUST pass before any commit
+
+Forgetting any of these means you failed to follow instructions. Before any commit or PR, ALL of the above MUST be satisfied! No exceptions!
+
+## High-Level Architecture
+
+### Core Components
+- **`graph/`**: Core abstractions, traits, and shared types
+- **`node/`**: Main executable and CLI (graphman)
+- **`chain/`**: Blockchain-specific adapters (ethereum, near, substreams)
+- **`runtime/`**: WebAssembly runtime for subgraph execution
+- **`store/`**: PostgreSQL-based storage layer
+- **`graphql/`**: GraphQL query execution engine
+- **`server/`**: HTTP/WebSocket APIs
+
+### Data Flow
+```
+Blockchain → Chain Adapter → Block Stream → Trigger Processing → Runtime → Store → GraphQL API
+```
+
+1. **Chain Adapters** connect to blockchain nodes and convert data to standardized formats
+2. **Block Streams** provide event-driven streaming of blockchain blocks
+3. **Trigger Processing** matches blockchain events to subgraph handlers
+4. **Runtime** executes subgraph code in WebAssembly sandbox
+5. **Store** persists entities with block-level granularity
+6. **GraphQL** processes queries and returns results
+
+### Key Abstractions
+- **`Blockchain`** trait: Core blockchain interface
+- **`Store`** trait: Storage abstraction with read/write variants
+- **`RuntimeHost`**: WASM execution environment
+- **`TriggerData`**: Standardized blockchain events
+- **`EventConsumer`/`EventProducer`**: Component communication
+
+### Architecture Patterns
+- **Event-driven**: Components communicate through async streams and channels
+- **Trait-based**: Extensive use of traits for abstraction and modularity
+- **Async/await**: Tokio-based async runtime throughout
+- **Multi-shard**: Database sharding for scalability
+- **Sandboxed execution**: WASM runtime with gas metering
+
+## Development Guidelines
+
+### Commit Convention
+Use format: `{crate-name}: {description}`
+- Single crate: `store: Support 'Or' filters`
+- Multiple crates: `core, graphql: Add event source to store`
+- All crates: `all: {description}`
+
+### Git Workflow
+- Rebase on master (don't merge master into feature branch)
+- Keep commits logical and atomic
+- Squash commits to clean up history before merging
+
+## Crate Structure
+
+### Core Crates
+- **`graph`**: Shared types, traits, and utilities
+- **`node`**: Main binary and component wiring
+- **`core`**: Business logic and subgraph management
+
+### Blockchain Integration
+- **`chain/ethereum`**: Ethereum chain support
+- **`chain/near`**: NEAR protocol support
+- **`chain/substreams`**: Substreams data source support
+
+### Infrastructure
+- **`store/postgres`**: PostgreSQL storage implementation
+- **`runtime/wasm`**: WebAssembly runtime and host functions
+- **`graphql`**: Query processing and execution
+- **`server/`**: HTTP/WebSocket servers
+
+### Key Dependencies
+- **`diesel`**: PostgreSQL ORM
+- **`tokio`**: Async runtime
+- **`tonic`**: gRPC framework
+- **`wasmtime`**: WebAssembly runtime
+- **`web3`**: Ethereum interaction
+
+## Test Environment Requirements
+
+### Process Compose Setup (Recommended)
+
+The repository includes a process-compose-flake setup that provides native, declarative service management.
+
+**Unit Tests:**
+```bash
+# Human: Start PostgreSQL + IPFS for unit tests in a separate terminal
+# PostgreSQL: localhost:5432, IPFS: localhost:5001
+nix run .#unit
+
+# Claude must export the database connection string before running unit tests
+export THEGRAPH_STORE_POSTGRES_DIESEL_URL="postgresql://graph:graph@127.0.0.1:5432/graph-test"
+
+# Claude can then run unit tests
+cargo test --workspace --exclude graph-tests
+```
+
+**Integration Tests:**
+```bash
+# Human: Start all services for integration tests in a separate terminal
+# PostgreSQL: localhost:3011, IPFS: localhost:3001, Anvil: localhost:3021
+nix run .#integration
+
+# Claude can then run integration tests
+cargo test -p graph-tests --test integration_tests
+```
+
+**Services Configuration:**
+The services are configured to use the test suite default ports for unit- and integration tests respectively.
+
+| Service | Unit Tests Port | Integration Tests Port | Database/Config |
+|---------|-----------------|------------------------|-----------------|
+| PostgreSQL | 5432 | 3011 | `graph-test` / `graph-node` |
+| IPFS | 5001 | 3001 | Data in `./.data/unit` or `./.data/integration` |
+| Anvil (Ethereum) | - | 3021 | Deterministic test chain |
+
+**Service Configuration:**
+The setup combines built-in services-flake services with custom multiService modules:
+
+**Built-in Services:**
+- **PostgreSQL**: Uses services-flake's postgres service with a helper function (`mkPostgresConfig`) that provides graph-specific defaults including required extensions.
+
+**Custom Services** (located in `./nix`):
+- `ipfs.nix`: IPFS (kubo) with automatic initialization and configurable ports  
+- `anvil.nix`: Ethereum test chain with deterministic configuration