Squid Snowbridge project

A Squid project to index snowbridge transfers. It accumulates transfer events from multiple chains(i.e. Ethereum, Bridgehub, Assethub) and serves them via GraphQL API.

Summary

• Quickstart
• Development flow
  • Database Schema
  • Entity classes
  • DB migrations
  • Typegen for Events, Extrinsics and Storage Calls
• Conventions

Prerequisites

• node 20.x
• docker
• npm -- note that yarn package manager is not supported

Quickly running the sample

Example commands below use sqd. Please install it before proceeding.

# 1. Install dependencies
npm ci

# 2. Copy the env and make change if necessary
cp .env.example .env

# 3. Start target Postgres database and detach
sqd up

# 4. Build the project
sqd build

# 5. Generate database migration
sqd migration:clean && sqd migration && sqd migration:apply

# 6. Start the squid processor for ethereum
sqd process:ethereum

# 7. Start the squid processor for bridgehub
sqd process:bridgehub

# 8. Start the squid processor for assethub
sqd process:assethub

# 9. Start the graphql api
sqd serve

A GraphiQL playground will be available at localhost:4350/graphql.

Dev flow

1. Define database schema

Start development by defining the schema of the target database via schema.graphql. Schema definition consists of regular graphql type declarations annotated with custom directives. Full description of schema.graphql dialect is available here.

2. Generate TypeORM classes

Mapping developers use TypeORM entities to interact with the target database during data processing. All necessary entity classes are generated by the squid framework from schema.graphql. This is done by running npx squid-typeorm-codegen or (equivalently) sqd codegen command.

3. Generate database migration

All database changes are applied through migration files located at db/migrations. squid-typeorm-migration(1) tool provides several commands to drive the process. It is all TypeORM under the hood.

# Connect to database, analyze its state and generate migration to match the target schema.
# The target schema is derived from entity classes generated earlier.
# Don't forget to compile your entity classes beforehand!
npx squid-typeorm-migration generate

# Create template file for custom database changes
npx squid-typeorm-migration create

# Apply database migrations from `db/migrations`
npx squid-typeorm-migration apply

# Revert the last performed migration
npx squid-typeorm-migration revert

Available sqd shortcuts:

# Build the project, remove any old migrations, then run `npx squid-typeorm-migration generate`
sqd migration:generate

# Run npx squid-typeorm-migration apply
sqd migration:apply

4. Generate TypeScript definitions for chain events, calls and storage

This is an optional part, but it is very advisable.

Event, call and runtime storage data come to mapping handlers as raw untyped json. While it is possible to work with raw untyped json data, it's extremely error-prone and the json structure may change over time due to runtime upgrades.

Squid framework provides a tool for generating type-safe wrappers around events, calls and runtime storage items for each historical change in the spec version. See the typegen page for different chains.

Project conventions

Squid tools assume a certain project layout.

• All compiled js files must reside in lib and all TypeScript sources in src. The layout of lib must reflect src.
• All TypeORM classes must be exported by src/model/index.ts (lib/model module).
• Database schema must be defined in schema.graphql.
• Database migrations must reside in db/migrations and must be plain js files.
• squid-*(1) executables consult .env file for a number of environment variables.

See the full desription in the documentation.

Graphql server extensions

Basically transfer status should be resolved by these two queries.

• transferStatusToPolkadots
• transferStatusToEthereums

It is possible to extend squid-graphql-server(1) with custom type-graphql resolvers and to add request validation. For more details, consult docs.