aitbc/docs/bootstrap/blockchain_node.md

blockchain-node/ — Minimal Chain (asset-backed by compute)

0) TL;DR boot path for Windsurf

1. Create the service: apps/blockchain-node (Python, FastAPI, asyncio, uvicorn).
2. Data layer: sqlite via SQLModel (later: PostgreSQL).
3. P2P: WebSocket gossip (lib: websockets) with a simple overlay (peer table + heartbeats).
4. Consensus (MVP): PoA single-author (devnet) → upgrade to Compute-Backed Proof (CBP) after coordinator & miner telemetry are wired.
5. Block content: ComputeReceipts = “proofs of delivered AI work” signed by miners, plus standard transfers.
6. Minting: AIToken minted per verified compute unit (e.g., 1 AIT = 1,000 token-ops — calibrate later).
7. REST RPC: /rpc/* for clients & coordinator; /p2p/* for peers; /admin/* for node ops.
8. Ship a devnet script that starts: 1 bootstrap node, 1 coordinator-api mock, 1 miner mock, 1 client demo.

---

1) Goal & Scope

• Provide a minimal, testable blockchain node that issues AITokens only when real compute was delivered (asset-backed).
• Easy to run, easy to reset, deterministic devnet.
• Strong boundaries so coordinator-api (job orchestration) and miner-node (workers) can integrate quickly.

Out of scope (MVP):

• Smart contracts VM.
• Sharding/advanced networking.
• Custodial wallets. (Use local keypairs for dev.)

---

2) Core Concepts

2.1 Actors

• Client: pays AITokens to request compute jobs.
• Coordinator: matches jobs ↔ miners; returns signed receipts.
• Miner: executes jobs; produces ComputeReceipt signed with miner key.
• Blockchain Node: validates receipts, mints AIT for miners, tracks balances, finalizes blocks.

2.2 Asset-Backed Minting

• Unit of account: AIToken (AIT).
• A miner earns AIT when a ComputeReceipt is included in a block.
• A receipt is valid iff:
  1. Its job_id exists in coordinator logs,
  2. client_payment_tx covers the quoted price,
  3. miner_sig over (job_id, hash(output_meta), compute_units, price, nonce) is valid,
  4. Not previously claimed (receipt_id unique).

---

3) Minimal Architecture

blockchain-node/
  ├─ src/
  │  ├─ main.py                 # FastAPI entry
  │  ├─ p2p.py                  # WS gossip, peer table, block relay
  │  ├─ consensus.py            # PoA/CBP state machine
  │  ├─ types.py                # dataclasses / pydantic models
  │  ├─ state.py                # DB access (SQLModel), UTXO/Account
  │  ├─ mempool.py              # tx pool (transfers + receipts)
  │  ├─ crypto.py               # ed25519 keys, signatures, hashing
  │  ├─ receipts.py             # receipt validation (with coordinator)
  │  ├─ blocks.py               # block build/verify, difficulty stub
  │  ├─ rpc.py                  # REST/RPC routes for clients & ops
  │  └─ settings.py             # env config
  ├─ tests/
  │  └─ ...                     # unit & integration tests
  ├─ scripts/
  │  ├─ devnet_up.sh            # run bootstrap node + mocks
  │  └─ keygen.py               # create node/miner/client keys
  ├─ README.md
  └─ requirements.txt

---

4) Data Model (SQLModel)

4.1 Tables

• blocks(id, parent_id, height, timestamp, proposer, tx_count, hash, state_root, sig)
• tx(id, block_id, type, payload_json, sender, nonce, fee, sig, hash, status)
• accounts(address, balance, nonce, pubkey)
• receipts(receipt_id, job_id, client_addr, miner_addr, compute_units, price, output_hash, miner_sig, status)
• peers(node_id, addr, last_seen, score)
• params(key, value) — chain config (mint ratios, fee rate, etc.)

4.2 TX Types

• TRANSFER: move AIT from A → B
• RECEIPT_CLAIM: include a ComputeReceipt; mints to miner and settles client escrow
• STAKE/UNSTAKE (later)
• PARAM_UPDATE (PoA only, gated by admin key for devnet)

---

5) Block Format (JSON)

{
  "parent": "<block_hash>",
  "height": 123,
  "timestamp": 1699999999,
  "proposer": "<node_address>",
  "txs": ["<tx_hash>", "..."],
  "stateRoot": "<merkle_root_after_block>",
  "sig": "<proposer_signature_over_header>"
}

Header sign bytes = hash(parent|height|timestamp|proposer|stateRoot)

---

6) Consensus

6.1 MVP: PoA (Single Author)

• One configured PROPOSER_KEY creates blocks at fixed interval (e.g., 2s).
• Honest mode only for devnet; finality by canonical longest/height rule.

6.2 Upgrade: Compute-Backed Proof (CBP)

• Each block’s work score = total compute_units in included receipts.
• Proposer election = weighted round-robin by recent work score and stake (later).
• Slashing: submitting invalid receipts reduces score; repeated offenses → temp ban.

---

7) Receipt Validation (Coordinator Check)

receipts.py performs:

1. Coordinator attestation (HTTP call to coordinator-api):
   • /attest/receipt with job_id, client, miner, price, compute_units, output_hash.
   • Returns {exists: bool, paid: bool, not_double_spent: bool, quote: {...}}.
2. Signature check: verify miner_sig with miner’s pubkey.
3. Economic checks: ensure client_payment_tx exists & covers price + fee.

For devnet without live coordinator, ship a mock that returns deterministic attestation for known job_id ranges.

---

8) Fees & Minting

• Fee model (MVP): fee = base_fee + k * payload_size.
• Minting:
  • Miner gets: mint = compute_units * MINT_PER_UNIT.
  • Coordinator gets: coord_cut = mint * COORDINATOR_RATIO.
  • Chain treasury (optional): small %, configurable in params.

---

9) RPC Surface (FastAPI)

9.1 Public

• POST /rpc/sendTx → {txHash}
• GET /rpc/getTx/{txHash} → {status, receipt}
• GET /rpc/getBlock/{heightOrHash}
• GET /rpc/getHead → {height, hash}
• GET /rpc/getBalance/{address} → {balance, nonce}
• POST /rpc/estimateFee → {fee}

9.2 Coordinator-facing

• POST /rpc/submitReceipt (alias of sendTx with type RECEIPT_CLAIM)
• POST /rpc/attest (devnet mock only)

9.3 Admin (devnet)

• POST /admin/paramSet (PoA only)
• POST /admin/peers/add {addr}
• POST /admin/mintFaucet {address, amount} (devnet)

9.4 P2P (WS)

• GET /p2p/peers → list
• WS /p2p/ws → subscribe to gossip: {"type":"block"|"tx"|"peer","data":...}

---

10) Keys & Crypto

• ed25519 for account & node keys.
• Address = bech32(hrp="ait", sha256(pubkey)[0:20]).
• Sign bytes:
  • TX: hash(type|sender|nonce|fee|payload_json_canonical)
  • Block: header hash as above.

Ship scripts/keygen.py for dev use.

---

11) Mempool Rules

• Accept if:
  • sig valid,
  • nonce == account.nonce + 1,
  • fee >= minFee,
  • For RECEIPT_CLAIM: passes receipts.validate() optimistically (soft-accept), then revalidate at block time.

Replacement: higher-fee replaces same (sender, nonce).

---

12) Node Lifecycle

Start:

1. Load config, open DB, ensure genesis.
2. Connect to bootstrap peers (if any).
3. Start RPC (FastAPI) + P2P WS server.
4. Start block proposer (if PoA key present).
5. Start peer heartbeats + gossip loops.

Shutdown:

• Graceful: flush mempool snapshot, close DB.

---

13) Genesis

• genesis.json:
  • chain_id, timestamp, accounts (faucet), params (mint ratios, base fee), authorities (PoA keys).

Provide scripts/make_genesis.py.

---

14) Devnet: End-to-End Demo

14.1 Components

• blockchain-node (this repo)
• coordinator-api (mock): /attest/receipt returns valid for job_id in [1..1_000_000]
• miner-node (mock): posts RECEIPT_CLAIM for synthetic jobs
• client-web (demo): sends TRANSFER & displays balances

14.2 Flow

1. Client pays price to escrow address (coordinator).
2. Miner executes job; coordinator verifies output.
3. Miner submits ComputeReceipt → included in next block.
4. Mint AIT to miner; escrow settles; client charged.

---

15) Testing Strategy

15.1 Unit

• crypto: keygen, sign/verify, address derivation
• state: balances, nonce, persistence
• receipts: signature + coordinator mock
• blocks: header hash, stateRoot

15.2 Integration

• Single node PoA: produce N blocks; submit transfers/receipts; assert balances.
• Two nodes P2P: block/tx relay; head convergence.

15.3 Property tests

• Nonce monotonicity; no double-spend; unique receipts.

---

16) Observability

• Structured logs (JSON) with component, event, height, latency_ms.
• /rpc/metrics (Prometheus format) — block time, mempool size, peers.

---

17) Configuration (ENV)

• CHAIN_ID=ait-devnet
• DB_PATH=./data/chain.db
• P2P_BIND=0.0.0.0:7070
• RPC_BIND=0.0.0.0:8080
• BOOTSTRAP_PEERS=ws://host:7070,...
• PROPOSER_KEY=... (optional for non-authors)
• MINT_PER_UNIT=1000
• COORDINATOR_RATIO=0.05

Provide .env.example.

---

18) Minimal API Payloads

18.1 TRANSFER

{
  "type": "TRANSFER",
  "sender": "ait1...",
  "nonce": 1,
  "fee": 10,
  "payload": {"to":"ait1...","amount":12345},
  "sig": "<ed25519>"
}

18.2 RECEIPT_CLAIM

{
  "type": "RECEIPT_CLAIM",
  "sender": "ait1miner...",
  "nonce": 7,
  "fee": 50,
  "payload": {
    "receipt_id": "rcpt_7f3a...",
    "job_id": "job_42",
    "client_addr": "ait1client...",
    "miner_addr": "ait1miner...",
    "compute_units": 2500,
    "price": 50000,
    "output_hash": "sha256:abcd...",
    "miner_sig": "<sig_over_core_fields>"
  },
  "sig": "<miner_account_sig>"
}

---

19) Security Notes (MVP)

• Devnet PoA means trust in proposer; do not expose to internet without firewall.
• Enforce coordinator host allowlist for attest calls.
• Rate-limit /rpc/sendTx.

---

20) Roadmap

1. ✅ PoA devnet with receipts.
2. 🔜 CBP proposer selection from rolling work score.
3. 🔜 Stake & slashing.
4. 🔜 Replace SQLite with PostgreSQL.
5. 🔜 Snapshots & fast-sync.
6. 🔜 Light client (SPV of receipts & balances).

---

21) Developer Tasks (Windsurf Order)

1. Scaffold project & requirements.txt:

   • fastapi, uvicorn[standard], sqlmodel, pydantic, websockets, pyyaml, python-dotenv, ed25519, orjson.

2. Implement:

   • crypto.py, types.py, state.py.
   • rpc.py (public routes).
   • mempool.py.
   • blocks.py (build/validate).
   • consensus.py (PoA tick).
   • p2p.py (WS server + simple gossip).
   • receipts.py (mock coordinator).

3. Wire main.py:

   • Start RPC, P2P, PoA loops.

4. Scripts:

   • scripts/keygen.py, scripts/make_genesis.py, scripts/devnet_up.sh.

5. Tests:

   • Add unit + an integration test that mints on a receipt.

6. Docs:

   • Update README.md with curl examples.

---

22) Curl Snippets (Dev)

• Faucet (dev only):

curl -sX POST localhost:8080/admin/mintFaucet -H 'content-type: application/json' \
  -d '{"address":"ait1client...","amount":1000000}'

• Transfer:

curl -sX POST localhost:8080/rpc/sendTx -H 'content-type: application/json' \
  -d @transfer.json

• Submit Receipt:

curl -sX POST localhost:8080/rpc/submitReceipt -H 'content-type: application/json' \
  -d @receipt_claim.json

---

23) Definition of Done (MVP)

• Node produces blocks on PoA.
• Can transfer AIT between accounts.
• Can submit a valid ComputeReceipt → miner balance increases; escrow decreases.
• Two nodes converge on same head via P2P.
• Basic metrics exposed.

---

24) Next Files to Create

• src/main.py
• src/crypto.py
• src/types.py
• src/state.py
• src/mempool.py
• src/blocks.py
• src/consensus.py
• src/p2p.py
• src/receipts.py
• src/rpc.py
• scripts/keygen.py, scripts/devnet_up.sh
• .env.example, README.md, requirements.txt