refactor: create json schema ref resolver

Author: ivan-tymoshenko

index.js

@@ -9,6 +9,7 @@ const { randomUUID } = require('crypto')
 
 const validate = require('./schema-validator')
 const Serializer = require('./serializer')
+const RefResolver = require('./ref-resolver')
 const buildAjv = require('./ajv')
 
 let largeArraySize = 2e4
@@ -58,19 +59,12 @@ function resolveRef (location, ref) {
   const jsonPointer = ref.slice(hashIndex) || '#'
 
   const schemaRef = schemaId + jsonPointer
+  const schema = refResolver.getSchema(schemaRef)
 
-  let ajvSchema
-  try {
-    ajvSchema = ajvInstance.getSchema(schemaRef)
-  } catch (error) {
+  if (schema === undefined) {
     throw new Error(`Cannot find reference "${ref}"`)
   }
 
-  if (ajvSchema === undefined) {
-    throw new Error(`Cannot find reference "${ref}"`)
-  }
-
-  const schema = ajvSchema.schema
   if (schema.$ref !== undefined) {
     return resolveRef({ schema, schemaId, jsonPointer }, schema.$ref)
   }
@@ -83,6 +77,7 @@ const objectReferenceSerializersMap = new Map()
 
 let rootSchemaId = null
 let ajvInstance = null
+let refResolver = null
 let contextFunctions = null
 
 function build (schema, options) {
@@ -95,11 +90,13 @@ function build (schema, options) {
   options = options || {}
 
   ajvInstance = buildAjv(options.ajv)
+  refResolver = new RefResolver()
   rootSchemaId = schema.$id || randomUUID()
 
   isValidSchema(schema)
   extendDateTimeType(schema)
   ajvInstance.addSchema(schema, rootSchemaId)
+  refResolver.addSchema(schema, rootSchemaId)
 
   if (options.schema) {
     const externalSchemas = clone(options.schema)
@@ -114,8 +111,9 @@ function build (schema, options) {
         schemaKey = key + externalSchema.$id // relative URI
       }
 
-      if (ajvInstance.getSchema(schemaKey) === undefined) {
+      if (refResolver.getSchema(schemaKey) === undefined) {
         ajvInstance.addSchema(externalSchema, schemaKey)
+        refResolver.addSchema(externalSchema, key)
       }
     }
   }
@@ -178,6 +176,7 @@ function build (schema, options) {
   const stringifyFunc = contextFunc(ajvInstance, serializer)
 
   ajvInstance = null
+  refResolver = null
   rootSchemaId = null
   contextFunctions = null
   arrayItemsReferenceSerializersMap.clear()
@@ -493,6 +492,7 @@ function mergeAllOfSchema (location, schema, mergedSchema) {
 
   mergedSchema.$id = `merged_${randomUUID()}`
   ajvInstance.addSchema(mergedSchema)
+  refResolver.addSchema(mergedSchema)
   location.schemaId = mergedSchema.$id
   location.jsonPointer = '#'
 }

ref-resolver.js

@@ -0,0 +1,67 @@
+'use strict'
+
+class RefResolver {
+  constructor () {
+    this.refs = {}
+  }
+
+  addSchema (schema, schemaKey) {
+    if (schema === null) return
+
+    if (schema.$id !== undefined && schema.$id.charAt(0) !== '#') {
+      schemaKey = schema.$id
+    }
+
+    this.refs[schemaKey] = { schema, anchors: {} }
+    this.resolveSchema(schema, schemaKey, '')
+  }
+
+  getSchema (schemaReference) {
+    const [schemaKey, jsonPointer] = schemaReference.split('#')
+    const schema = this.refs[schemaKey]
+
+    if (schema === undefined) {
+      return undefined
+    }
+
+    return schema.anchors[jsonPointer] || getDataByJSONPointer(schema.schema, jsonPointer)
+  }
+
+  resolveSchema (schema, schemaKey, jsonPointer) {
+    const schemaId = schema.$id
+    if (schemaId !== undefined && typeof schemaId === 'string') {
+      if (schemaId.charAt(0) === '#') {
+        this.refs[schemaKey].anchors[schemaId.slice(1)] = schema
+      } else {
+        this.refs[schemaId] = { schema, anchors: {} }
+      }
+    }
+
+    for (const key in schema) {
+      if (typeof schema[key] === 'object' && schema[key] !== null) {
+        this.resolveSchema(schema[key], schemaKey, jsonPointer + '/' + key)
+      }
+    }
+  }
+}
+
+function getDataByJSONPointer (data, jsonPointer) {
+  const parts = jsonPointer.split('/')
+  let current = data
+  for (let i = 0; i < parts.length; i++) {
+    const part = parts[i]
+    if (part === '') {
+      continue
+    }
+    if (part.charAt(0) === '#') {
+      continue
+    }
+    if (current[part] === undefined) {
+      return undefined
+    }
+    current = current[part]
+  }
+  return current
+}
+
+module.exports = RefResolver