GraphQL Resolvers - AnimeThemes Web

Overview

Resolvers are functions that fetch data for GraphQL queries. The AnimeThemes Web application uses a custom resolver system that translates GraphQL queries into REST API calls to the AnimeThemes API.

Schema Architecture

The GraphQL schema is built from multiple type definition files:

// src/lib/common/animethemes/type-defs.ts
const typeDefs = gql`
  type Query {
    anime(id: Int, slug: String): Anime
    animeAll(limit: Int, year: Int, season: String): [Anime!]!
    artist(id: Int, slug: String): Artist
    // ...
  }
  
  type Anime {
    id: Int!
    name: String!
    slug: String!
    themes: [Theme!]!
    // ...
  }
`;

Type definitions are located in:

/src/lib/common/animethemes/type-defs.ts - Main AnimeThemes types
/src/lib/server/animebracket/type-defs.ts - Anime bracket types

Resolver Pattern

Resolvers are organized by type and use helper functions to fetch data from the API:

const resolvers: Resolvers = {
  Query: {
    anime: createApiResolver<ApiAnimeShow>()({
      endpoint: (_, { slug }) => `/anime/${slug}`,
      extractFromResponse: (response) => response.anime,
    }),
  },
  
  Anime: {
    themes: createApiResolverNotNull<ApiAnimeShow<"animethemes">>()({
      extractFromParent: (anime) => anime.animethemes,
      endpoint: (anime) => `/anime/${anime.slug}`,
      extractFromResponse: (response) => response.anime.animethemes,
      type: "Anime",
      baseInclude: INCLUDES.Anime.themes,
    }),
  },
};

Resolver Helper Functions

The resolver system provides several helper functions:

createApiResolver

Creates a resolver that may return null.

createApiResolver<ApiAnimeShow>()({
  endpoint: (_, { slug }) => `/anime/${slug}`,
  extractFromResponse: (response) => response.anime,
})

Use cases:

Root queries that may not find a resource
Optional fields that may be null

createApiResolverNotNull

Creates a resolver that always returns a value (never null).

createApiResolverNotNull<ApiAnimeShow<"animethemes">>()({
  extractFromParent: (anime) => anime.animethemes,
  endpoint: (anime) => `/anime/${anime.slug}`,
  extractFromResponse: (response) => response.anime.animethemes,
  type: "Anime",
  baseInclude: INCLUDES.Anime.themes,
})

Use cases:

Required relationships
Non-nullable fields

createApiResolverPaginated

Creates a resolver for paginated list queries.

createApiResolverPaginated<ApiAnimeIndex>()({
  endpoint: () => `/anime`,
  extractFromResponse: (response) => response.anime,
})

Use cases:

Index pages (animeAll, artistAll, etc.)
Large collections of data

transformedResolver

Wraps a resolver with a transformation function.

transformedResolver(
  createApiResolverNotNull<ApiAnimeShow<"resources">>()({
    extractFromParent: (anime) => anime.resources,
    endpoint: (anime) => `/anime/${anime.slug}`,
    extractFromResponse: (response) => response.anime.resources,
    type: "Anime",
    baseInclude: INCLUDES.Anime.resources,
  }),
  (resources) => resources.map(({ animeresource, ...resource }) => 
    ({ ...animeresource, ...resource })
  )
)

Use cases:

Transforming API response shape
Merging pivot table data
Adding computed fields

Include System

The resolver system automatically manages API includes to fetch related data efficiently.

Include Constants

export const INCLUDES = {
  Anime: {
    synonyms: "animesynonyms",
    themes: "animethemes",
    series: "series",
    studios: "studios",
    resources: "resources",
    images: "images",
  },
  Theme: {
    song: "song",
    group: "group",
    anime: "anime",
    entries: "animethemeentries",
  },
  // ...
};

How Includes Work

When you query nested fields, the resolver:

Checks if data is already in parent
If not, constructs API request with includes
Fetches data with single API call
Caches result to avoid duplicate requests

Example:

query {
  anime(slug: "bakemonogatari") {
    name
    themes {
      type
      song {
        title
      }
    }
  }
}

Generates API request:

GET /anime/bakemonogatari?include=animethemes.song

Nested Includes

The system handles deeply nested includes:

query {
  anime(slug: "bakemonogatari") {
    themes {
      entries {
        videos {
          audio {
            filename
          }
        }
      }
    }
  }
}

Generates:

GET /anime/bakemonogatari?include=animethemes.animethemeentries.videos.audio

Root Query Resolvers

Single Resource Queries

Query: {
  anime: createApiResolver<ApiAnimeShow>()({
    endpoint: (_, { slug }) => `/anime/${slug}`,
    extractFromResponse: (response) => response.anime,
  }),
  
  artist: createApiResolver<ApiArtistShow>()({
    endpoint: (_, { slug }) => `/artist/${slug}`,
    extractFromResponse: (response) => response.artist,
  }),
  
  theme: createApiResolver<ApiThemeShow>()({
    endpoint: (_, { id }) => `/animetheme/${id}`,
    extractFromResponse: (response) => response.animetheme,
  }),
}

List Queries

Query: {
  animeAll: createApiResolverPaginated<ApiAnimeIndex>()({
    endpoint: () => `/anime`,
    extractFromResponse: (response) => response.anime,
  }),
  
  themeAll: createApiResolverPaginated<ApiThemeIndex>()({
    endpoint: (_, { orderBy, orderDesc, has }) =>
      `/animetheme?sort=${orderDesc ? "-" : ""}${orderBy}&filter[has]=${has}`,
    extractFromResponse: (response) => response.animethemes,
  }),
}

Special Queries

Query: {
  // Constructed from API data
  year: (_, { value }) => ({ value }),
  
  // Nested scope
  me: () => ({}),
}

Type Resolvers

Field Resolvers

Resolve specific fields on types:

Anime: {
  // Fetch related themes
  themes: createApiResolverNotNull<ApiAnimeShow<"animethemes">>()({
    extractFromParent: (anime) => anime.animethemes,
    endpoint: (anime) => `/anime/${anime.slug}`,
    extractFromResponse: (response) => response.anime.animethemes,
    type: "Anime",
    baseInclude: INCLUDES.Anime.themes,
  }),
  
  // Fetch images
  images: createApiResolverNotNull<ApiAnimeShow<"images">>()({
    extractFromParent: (anime) => anime.images,
    endpoint: (anime) => `/anime/${anime.slug}`,
    extractFromResponse: (response) => response.anime.images,
    type: "Anime",
    baseInclude: INCLUDES.Anime.images,
  }),
}

Default Values

Provide default values for nullable fields:

Theme: {
  sequence: (theme) => theme.sequence || 0,
}

Entry: {
  version: (entry) => entry.version || 1,
}

Enum Resolvers

Map internal values to GraphQL enum values:

VideoOverlap: {
  NONE: "None",
  TRANSITION: "Transition",
  OVER: "Over",
}

Data Transformation

Some resolvers transform API responses to match the GraphQL schema:

Merging Pivot Data

Artist: {
  performances: transformedResolver(
    createApiResolverNotNull<ApiArtistShow<"songs">>()({
      extractFromParent: (artist) => artist.songs,
      endpoint: (artist) => `/artist/${artist.slug}`,
      extractFromResponse: (response) => response.artist.songs,
      type: "Artist",
      baseInclude: INCLUDES.Artist.performances,
    }),
    (songs, artist) => songs.map((song) => 
      ({ ...song.artistsong, song, artist })
    )
  ),
}

This merges pivot table data (artistsong) with the related models.

Flattening Resources

Anime: {
  resources: transformedResolver(
    createApiResolverNotNull<ApiAnimeShow<"resources">>()({
      extractFromParent: (anime) => anime.resources,
      endpoint: (anime) => `/anime/${anime.slug}`,
      extractFromResponse: (response) => response.anime.resources,
      type: "Anime",
      baseInclude: INCLUDES.Anime.resources,
    }),
    (resources) => resources.map(({ animeresource, ...resource }) => 
      ({ ...animeresource, ...resource })
    )
  ),
}

Pagination

Paginated resolvers handle large datasets:

Query: {
  animeAll: createApiResolverPaginated<ApiAnimeIndex>()({
    endpoint: () => `/anime`,
    extractFromResponse: (response) => response.anime,
  }),
}

The system:

Respects the limit parameter
Uses default page size from config
Fetches pages sequentially
Aggregates results

Context and Caching

API Request Context

export interface ApiResolverContext {
  apiRequests: number;
  req?: IncomingMessage;
  // ...
}

Request Counting

The context tracks API requests for performance monitoring:

const { data, apiRequests } = await fetchData<Query>(query);
console.log(`Made ${apiRequests} API requests`);

Deduplication

The resolver system deduplicates requests within a single query execution using:

Parent data checking (extractFromParent)
Shared include paths
Request batching with p-limit

Error Handling

Resolvers handle errors gracefully:

// Nullable resolvers return null on error
anime: createApiResolver<ApiAnimeShow>()({
  endpoint: (_, { slug }) => `/anime/${slug}`,
  extractFromResponse: (response) => response.anime,
})
// Returns null if anime not found

// Non-null resolvers throw errors
themes: createApiResolverNotNull<ApiAnimeShow<"animethemes">>()({
  // ...
})
// Throws error if themes cannot be fetched

Best Practices

1. Use Fragments

Define reusable fragments on components:

MyComponent.fragments = {
  anime: gql`
    fragment MyComponentAnime on Anime {
      id
      name
      slug
    }
  `,
};

2. Minimize Over-fetching

Only query fields you need:

# Good
query {
  anime(slug: $slug) {
    name
    year
  }
}

# Avoid
query {
  anime(slug: $slug) {
    # All fields
    id
    name
    slug
    year
    season
    synopsis
    # ...
  }
}

3. Use Appropriate Resolver Types

Use createApiResolver for nullable fields
Use createApiResolverNotNull for required fields
Use createApiResolverPaginated for lists
Use transformedResolver for data transformation

4. Leverage Includes

Let the resolver system handle includes automatically:

# This query automatically includes themes.song.artists
query {
  anime(slug: $slug) {
    themes {
      song {
        title
        performances {
          artist {
            name
          }
        }
      }
    }
  }
}

Custom Resolvers

Some resolvers use custom logic:

Bracket Resolvers

// src/lib/server/animebracket/resolvers.ts
Query: {
  bracket: async (_, { slug }) => {
    const bracket = await fetchJson<SourceBracket>(
      `https://animebracket.com/api/bracket/${slug}`
    );
    // Custom transformation
    return transformBracket(bracket);
  },
}

Season Resolvers

Season: {
  anime: createApiResolverPaginated<ApiAnimeIndex>()({
    endpoint: (season) => 
      `/anime?filter[year]=${season.year.value}&filter[season]=${season.value}`,
    extractFromResponse: (response) => response.anime,
    type: "Anime",
  }),
}

Next Steps

GraphQL Queries - Learn how to write queries
GraphQL Types - Explore available types
Working with API - Guide to using the AnimeThemes API

Hooks

Context

Utilities

GraphQL Schema

​Overview

​Schema Architecture

​Resolver Pattern

​Resolver Helper Functions

​createApiResolver

​createApiResolverNotNull

​createApiResolverPaginated

​transformedResolver

​Include System

​Include Constants

​How Includes Work

​Nested Includes

​Root Query Resolvers

​Single Resource Queries

​List Queries

​Special Queries

​Type Resolvers

​Field Resolvers

​Default Values

​Enum Resolvers

​Data Transformation

​Merging Pivot Data

​Flattening Resources

​Pagination

​Context and Caching

​API Request Context

​Request Counting

​Deduplication

​Error Handling

​Best Practices

​1. Use Fragments

​2. Minimize Over-fetching

​3. Use Appropriate Resolver Types

​4. Leverage Includes

​Custom Resolvers

​Bracket Resolvers

​Season Resolvers

​Next Steps

Build docs developers (and LLMs) love

Overview

Schema Architecture

Resolver Pattern

Resolver Helper Functions

createApiResolver

createApiResolverNotNull

createApiResolverPaginated

transformedResolver

Include System

Include Constants

How Includes Work

Nested Includes

Root Query Resolvers

Single Resource Queries

List Queries

Special Queries

Type Resolvers

Field Resolvers

Default Values

Enum Resolvers

Data Transformation

Merging Pivot Data

Flattening Resources

Pagination

Context and Caching

API Request Context

Request Counting

Deduplication

Error Handling

Best Practices

1. Use Fragments

2. Minimize Over-fetching

3. Use Appropriate Resolver Types

4. Leverage Includes

Custom Resolvers

Bracket Resolvers

Season Resolvers

Next Steps