graphql-request/src/layers/4_ResultSet/customScalars.ts

import type { ExecutionResult } from 'graphql'
import { standardScalarTypeNames } from '../../lib/graphql.js'
import { assertArray, mapValues } from '../../lib/prelude.js'
import type { Object$2, Schema } from '../1_Schema/__.js'
import { Output } from '../1_Schema/__.js'
import { readMaybeThunk } from '../1_Schema/core/helpers.js'
import type { GraphQLObject } from '../4_ResultSet/runtime.js'
import { assertGraphQLObject } from '../4_ResultSet/runtime.js'

export const decode = <$Data extends ExecutionResult['data']>(index: Schema.Object$2, data: $Data): $Data => {
  if (!data) return data
  return mapValues(data, (v, fieldName) => {
    const indexField = index.fields[fieldName]
    if (!indexField) throw new Error(`Field not found: ${String(fieldName)}`)

    const type = readMaybeThunk(indexField.type)
    const typeWithoutNonNull = Output.unwrapNullable(type) as Output.Named | Output.List<any>
    const v2 = decodeCustomScalarValue(typeWithoutNonNull, v as any)
    return v2
  }) as $Data
}

const decodeCustomScalarValue = (
  indexType: Output.Any,
  fieldValue: string | boolean | null | number | GraphQLObject | GraphQLObject[],
) => {
  if (fieldValue === null) return null

  const indexTypeDethunked = readMaybeThunk(indexType)
  const typeWithoutNonNull = Output.unwrapNullable(indexTypeDethunked) as Exclude<Output.Any, Output.Nullable<any>>

  if (typeWithoutNonNull.kind === `list`) {
    assertArray(fieldValue)
    return fieldValue.map((v2: any): any => {
      return decodeCustomScalarValue(typeWithoutNonNull.type, v2)
    })
  }

  if (typeWithoutNonNull.kind === `Scalar`) {
    if ((typeWithoutNonNull.name in standardScalarTypeNames)) {
      // todo test this case
      return fieldValue
    }
    if (typeof fieldValue === `object`) throw new Error(`Expected scalar. Got: ${String(fieldValue)}`)
    // @ts-expect-error fixme
    return typeWithoutNonNull.codec.decode(fieldValue)
  }

  if (typeWithoutNonNull.kind === `typename`) {
    return fieldValue
  }

  assertGraphQLObject(fieldValue)

  if (typeWithoutNonNull.kind === `Object`) {
    return decode(typeWithoutNonNull, fieldValue)
  }

  if (typeWithoutNonNull.kind === `Interface` || typeWithoutNonNull.kind === `Union`) {
    const possibleObjects = typeWithoutNonNull.kind === `Interface`
      ? typeWithoutNonNull.implementors
      : typeWithoutNonNull.members
    // todo handle aliases -- will require having the selection set available for reference too :/
    // eslint-disable-next-line
    // @ts-ignore infinite depth issue
    // eslint-disable-next-line
    const ObjectType = possibleObjects.find((ObjectType) => {
      if (fieldValue.__typename === ObjectType.fields.__typename.type.type) return true
      if (Object.keys(fieldValue).every(fieldName => ObjectType.fields[fieldName] !== undefined)) return true
      return false
    }) as undefined | Object$2
    if (!ObjectType) throw new Error(`Could not pick object for ${typeWithoutNonNull.kind} selection`)
    return decode(ObjectType, fieldValue)
  }

  return fieldValue
}