# Install Graph CLI
npm install -g @graphprotocol/graph-cli

# Verify
graph --version

# Initialize from existing contract
graph init --product subgraph-studio \
  --from-contract 0x... \
  --network mainnet \
  --abi ./abi.json \
  my-subgraph

cd my-subgraph

my-subgraph/
├── subgraph.yaml          # Manifest
├── schema.graphql         # GraphQL schema
├── src/
│   └── mapping.ts         # Event handlers
├── abis/
│   └── Contract.json      # Contract ABIs
├── tests/
│   └── contract.test.ts   # Unit tests
└── package.json

specVersion: 0.0.5
schema:
  file: ./schema.graphql
dataSources:
  - kind: ethereum
    name: Token
    network: mainnet
    source:
      address: "0x..."
      abi: Token
      startBlock: 18000000
    mapping:
      kind: ethereum/events
      apiVersion: 0.0.7
      language: wasm/assemblyscript
      entities:
        - Transfer
        - Account
      abis:
        - name: Token
          file: ./abis/Token.json
      eventHandlers:
        - event: Transfer(indexed address,indexed address,uint256)
          handler: handleTransfer
        - event: Approval(indexed address,indexed address,uint256)
          handler: handleApproval
      callHandlers:
        - function: transfer(address,uint256)
          handler: handleTransferCall
      blockHandlers:
        - handler: handleBlock
      file: ./src/mapping.ts

# schema.graphql

type Token @entity {
  id: ID!
  name: String!
  symbol: String!
  decimals: Int!
  totalSupply: BigInt!
  holders: [Account!]! @derivedFrom(field: "token")
}

type Account @entity {
  id: ID!
  token: Token!
  balance: BigInt!
  transfersFrom: [Transfer!]! @derivedFrom(field: "from")
  transfersTo: [Transfer!]! @derivedFrom(field: "to")
}

type Transfer @entity {
  id: ID!
  from: Account!
  to: Account!
  value: BigInt!
  timestamp: BigInt!
  blockNumber: BigInt!
  transactionHash: Bytes!
}

# For aggregations
type DailyVolume @entity {
  id: ID!  # date string
  date: BigInt!
  volume: BigInt!
  txCount: Int!
}

// src/mapping.ts
import { Transfer as TransferEvent } from "../generated/Token/Token";
import { Token, Account, Transfer, DailyVolume } from "../generated/schema";
import { BigInt, Bytes, Address } from "@graphprotocol/graph-ts";

export function handleTransfer(event: TransferEvent): void {
  // Create Transfer entity
  let transfer = new Transfer(
    event.transaction.hash.toHex() + "-" + event.logIndex.toString()
  );
  transfer.from = getOrCreateAccount(event.params.from).id;
  transfer.to = getOrCreateAccount(event.params.to).id;
  transfer.value = event.params.value;
  transfer.timestamp = event.block.timestamp;
  transfer.blockNumber = event.block.number;
  transfer.transactionHash = event.transaction.hash;
  transfer.save();

  // Update account balances
  updateAccountBalance(event.params.from, event.params.value.neg());
  updateAccountBalance(event.params.to, event.params.value);

  // Update daily volume
  updateDailyVolume(event.block.timestamp, event.params.value);
}

function getOrCreateAccount(address: Address): Account {
  let id = address.toHex();
  let account = Account.load(id);

  if (account == null) {
    account = new Account(id);
    account.token = "token-id";
    account.balance = BigInt.fromI32(0);
    account.save();
  }

  return account;
}

function updateAccountBalance(address: Address, delta: BigInt): void {
  let account = getOrCreateAccount(address);
  account.balance = account.balance.plus(delta);
  account.save();
}

function updateDailyVolume(timestamp: BigInt, value: BigInt): void {
  let dayId = timestamp.toI32() / 86400;
  let id = dayId.toString();

  let volume = DailyVolume.load(id);
  if (volume == null) {
    volume = new DailyVolume(id);
    volume.date = BigInt.fromI32(dayId * 86400);
    volume.volume = BigInt.fromI32(0);
    volume.txCount = 0;
  }

  volume.volume = volume.volume.plus(value);
  volume.txCount = volume.txCount + 1;
  volume.save();
}

# subgraph.yaml - for factory patterns
templates:
  - kind: ethereum
    name: Pool
    network: mainnet
    source:
      abi: Pool
    mapping:
      kind: ethereum/events
      apiVersion: 0.0.7
      language: wasm/assemblyscript
      entities:
        - Pool
        - Swap
      abis:
        - name: Pool
          file: ./abis/Pool.json
      eventHandlers:
        - event: Swap(indexed address,uint256,uint256)
          handler: handleSwap
      file: ./src/pool.ts

// src/factory.ts
import { Pool as PoolTemplate } from "../generated/templates";

export function handlePoolCreated(event: PoolCreated): void {
  // Create data source for new pool
  PoolTemplate.create(event.params.pool);

  // Create Pool entity
  let pool = new Pool(event.params.pool.toHex());
  pool.save();
}

# Generate code from schema
graph codegen

# Build subgraph
graph build

# Authenticate
graph auth --studio <deploy-key>

# Deploy to Subgraph Studio
graph deploy --studio my-subgraph

# Deploy to hosted service (deprecated)
graph deploy --node https://api.thegraph.com/deploy/ \
  --ipfs https://api.thegraph.com/ipfs/ \
  username/my-subgraph

# Example queries
query RecentTransfers {
  transfers(first: 10, orderBy: timestamp, orderDirection: desc) {
    id
    from {
      id
      balance
    }
    to {
      id
      balance
    }
    value
    timestamp
  }
}

query TopHolders {
  accounts(first: 10, orderBy: balance, orderDirection: desc) {
    id
    balance
  }
}

query DailyVolumes {
  dailyVolumes(first: 30, orderBy: date, orderDirection: desc) {
    date
    volume
    txCount
  }
}

// tests/token.test.ts
import { assert, test, clearStore } from "matchstick-as";
import { handleTransfer } from "../src/mapping";
import { createTransferEvent } from "./utils";

test("Creates Transfer entity", () => {
  let event = createTransferEvent(
    "0x1234...",
    "0x5678...",
    "1000000000000000000"
  );

  handleTransfer(event);

  assert.entityCount("Transfer", 1);
  clearStore();
});