// Copyright 2022 Princess B33f Heavy Industries / Dave Shanley
// SPDX-License-Identifier: MIT

package model

import (
	"fmt"
	"github.com/pb33f/libopenapi/datamodel/low"
	"github.com/pb33f/libopenapi/datamodel/low/base"
	v3 "github.com/pb33f/libopenapi/datamodel/low/v3"
	"gopkg.in/yaml.v3"
	"sort"
	"sync"
)

// SchemaChanges represent all changes to a base.Schema OpenAPI object. These changes are represented
// by all versions of OpenAPI.
//
// Any additions or removals to slice based results will be recorded in the PropertyChanges of the parent
// changes, and not the child for example, adding a new schema to `anyOf` will create a new change result in
// PropertyChanges.Changes, and not in the AnyOfChanges property.
type SchemaChanges struct {
	PropertyChanges
	DiscriminatorChanges  *DiscriminatorChanges
	AllOfChanges          []*SchemaChanges
	AnyOfChanges          []*SchemaChanges
	OneOfChanges          []*SchemaChanges
	NotChanges            []*SchemaChanges
	ItemsChanges          []*SchemaChanges
	SchemaPropertyChanges map[string]*SchemaChanges
	ExternalDocChanges    *ExternalDocChanges
	XMLChanges            *XMLChanges
	ExtensionChanges      *ExtensionChanges
}

// TotalChanges returns a count of the total number of changes made to this schema and all sub-schemas
func (s *SchemaChanges) TotalChanges() int {
	t := s.PropertyChanges.TotalChanges()
	if s.DiscriminatorChanges != nil {
		t += s.DiscriminatorChanges.TotalChanges()
	}
	if len(s.AllOfChanges) > 0 {
		for n := range s.AllOfChanges {
			t += s.AllOfChanges[n].TotalChanges()
		}
	}
	if len(s.AnyOfChanges) > 0 {
		for n := range s.AnyOfChanges {
			t += s.AnyOfChanges[n].TotalChanges()
		}
	}
	if len(s.OneOfChanges) > 0 {
		for n := range s.OneOfChanges {
			t += s.OneOfChanges[n].TotalChanges()
		}
	}
	if len(s.NotChanges) > 0 {
		for n := range s.NotChanges {
			t += s.NotChanges[n].TotalChanges()
		}
	}
	if len(s.ItemsChanges) > 0 {
		for n := range s.ItemsChanges {
			t += s.ItemsChanges[n].TotalChanges()
		}
	}
	if s.SchemaPropertyChanges != nil {
		for n := range s.SchemaPropertyChanges {
			t += s.SchemaPropertyChanges[n].TotalChanges()
		}
	}
	if s.ExternalDocChanges != nil {
		t += s.ExternalDocChanges.TotalChanges()
	}
	if s.XMLChanges != nil {
		t += s.XMLChanges.TotalChanges()
	}
	if s.ExtensionChanges != nil {
		t += s.ExtensionChanges.TotalChanges()
	}
	return t
}

// TotalBreakingChanges returns the total number of breaking changes made to this schema and all sub-schemas.
func (s *SchemaChanges) TotalBreakingChanges() int {
	t := s.PropertyChanges.TotalBreakingChanges()
	if s.DiscriminatorChanges != nil {
		t += s.DiscriminatorChanges.TotalBreakingChanges()
	}
	if len(s.AllOfChanges) > 0 {
		for n := range s.AllOfChanges {
			t += s.AllOfChanges[n].TotalBreakingChanges()
		}
	}
	if len(s.AllOfChanges) > 0 {
		for n := range s.AllOfChanges {
			t += s.AllOfChanges[n].TotalBreakingChanges()
		}
	}
	if len(s.AnyOfChanges) > 0 {
		for n := range s.AnyOfChanges {
			t += s.AnyOfChanges[n].TotalBreakingChanges()
		}
	}
	if len(s.OneOfChanges) > 0 {
		for n := range s.OneOfChanges {
			t += s.OneOfChanges[n].TotalBreakingChanges()
		}
	}
	if len(s.NotChanges) > 0 {
		for n := range s.NotChanges {
			t += s.NotChanges[n].TotalBreakingChanges()
		}
	}
	if len(s.ItemsChanges) > 0 {
		for n := range s.ItemsChanges {
			t += s.ItemsChanges[n].TotalBreakingChanges()
		}
	}
	if s.XMLChanges != nil {
		t += s.XMLChanges.TotalBreakingChanges()
	}
	if s.SchemaPropertyChanges != nil {
		for n := range s.SchemaPropertyChanges {
			t += s.SchemaPropertyChanges[n].TotalBreakingChanges()
		}
	}
	return t
}

func CompareSchemas(l, r *base.SchemaProxy) *SchemaChanges {
	sc := new(SchemaChanges)
	var changes []*Change

	// Added
	if l == nil && r != nil {
		CreateChange(&changes, ObjectAdded, v3.SchemaLabel,
			nil, nil, true, nil, r)
		sc.Changes = changes
	}

	// Removed
	if l != nil && r == nil {
		CreateChange(&changes, ObjectRemoved, v3.SchemaLabel,
			nil, nil, true, l, nil)
		sc.Changes = changes
	}

	if l != nil && r != nil {

		// if left proxy is a reference and right is a reference (we won't recurse into them)
		if l.IsSchemaReference() && r.IsSchemaReference() {
			// points to the same schema
			if l.GetSchemaReference() == r.GetSchemaReference() {
				// there is nothing to be done at this point.
				return nil
			} else {
				// references are different, that's all we care to know.
				CreateChange(&changes, Modified, v3.RefLabel,
					l.GetValueNode().Content[1], r.GetValueNode().Content[1], true, l.GetSchemaReference(),
					r.GetSchemaReference())
				sc.Changes = changes
				return sc
			}
		}

		// changed from inline to ref
		if !l.IsSchemaReference() && r.IsSchemaReference() {
			CreateChange(&changes, Modified, v3.RefLabel,
				l.GetValueNode(), r.GetValueNode().Content[1], true, l, r.GetSchemaReference())
			sc.Changes = changes
			return sc // we're done here
		}

		// changed from ref to inline
		if l.IsSchemaReference() && !r.IsSchemaReference() {
			CreateChange(&changes, Modified, v3.RefLabel,
				l.GetValueNode().Content[1], r.GetValueNode(), true, l.GetSchemaReference(), r)
			sc.Changes = changes
			return sc // done, nothing else to do.
		}

		lSchema := l.Schema()
		rSchema := r.Schema()

		if low.AreEqual(lSchema, rSchema) {
			// there is no point going on, we know nothing changed!
			return nil
		}

		// check XML
		checkSchemaXML(lSchema, rSchema, &changes, sc)

		// check examples
		checkExamples(lSchema, rSchema, &changes)

		// check schema core properties for changes.
		checkSchemaPropertyChanges(lSchema, rSchema, &changes, sc)

		// now for the confusing part, there is also a schema's 'properties' property to parse.
		// inception, eat your heart out.
		doneChan := make(chan bool)
		totalProperties := checkPropertiesPropertyOfASchema(lSchema, rSchema, &changes, sc, doneChan)

		// check polymorphic and multi-values async for speed.
		go extractSchemaChanges(lSchema.OneOf.Value, rSchema.OneOf.Value, v3.OneOfLabel,
			&sc.OneOfChanges, &changes, doneChan)

		go extractSchemaChanges(lSchema.AllOf.Value, rSchema.AllOf.Value, v3.AllOfLabel,
			&sc.AllOfChanges, &changes, doneChan)

		go extractSchemaChanges(lSchema.AnyOf.Value, rSchema.AnyOf.Value, v3.AnyOfLabel,
			&sc.AnyOfChanges, &changes, doneChan)

		go extractSchemaChanges(lSchema.Items.Value, rSchema.Items.Value, v3.ItemsLabel,
			&sc.ItemsChanges, &changes, doneChan)

		go extractSchemaChanges(lSchema.Not.Value, rSchema.Not.Value, v3.NotLabel,
			&sc.NotChanges, &changes, doneChan)

		totalChecks := totalProperties + 5
		completedChecks := 0
		for completedChecks < totalChecks {
			select {
			case <-doneChan:
				completedChecks++
			}
		}
	}
	// done
	if changes != nil {
		sc.Changes = changes
	}
	return sc
}

func checkSchemaXML(lSchema *base.Schema, rSchema *base.Schema, changes *[]*Change, sc *SchemaChanges) {
	// XML removed
	if lSchema.XML.Value != nil && rSchema.XML.Value == nil {
		CreateChange(changes, ObjectRemoved, v3.XMLLabel,
			lSchema.XML.GetValueNode(), nil, true, lSchema.XML.GetValue(), nil)
	}
	// XML added
	if lSchema.XML.Value == nil && rSchema.XML.Value != nil {
		CreateChange(changes, ObjectAdded, v3.XMLLabel,
			nil, rSchema.XML.GetValueNode(), false, nil, rSchema.XML.GetValue())
	}

	// compare XML
	if lSchema.XML.Value != nil && rSchema.XML.Value != nil {
		if !low.AreEqual(lSchema.XML.Value, rSchema.XML.Value) {
			sc.XMLChanges = CompareXML(lSchema.XML.Value, rSchema.XML.Value)
		}
	}
}

func checkPropertiesPropertyOfASchema(
	lSchema *base.Schema,
	rSchema *base.Schema,
	changes *[]*Change,
	sc *SchemaChanges,
	doneChan chan bool) int {

	propChanges := make(map[string]*SchemaChanges)

	var lProps []string
	lEntities := make(map[string]*base.SchemaProxy)
	lKeyNodes := make(map[string]*yaml.Node)
	var rProps []string
	rEntities := make(map[string]*base.SchemaProxy)
	rKeyNodes := make(map[string]*yaml.Node)

	for w := range lSchema.Properties.Value {
		if !lSchema.Properties.Value[w].Value.IsSchemaReference() {
			lProps = append(lProps, w.Value)
			lEntities[w.Value] = lSchema.Properties.Value[w].Value
			lKeyNodes[w.Value] = w.KeyNode
		}
	}
	for w := range rSchema.Properties.Value {
		if !rSchema.Properties.Value[w].Value.IsSchemaReference() {
			rProps = append(rProps, w.Value)
			rEntities[w.Value] = rSchema.Properties.Value[w].Value
			rKeyNodes[w.Value] = w.KeyNode
		}
	}
	sort.Strings(lProps)
	sort.Strings(rProps)

	var propLock sync.Mutex
	checkProperty := func(key string, lp, rp *base.SchemaProxy, propChanges map[string]*SchemaChanges, done chan bool) {
		if lp != nil && rp != nil {
			ls := lp.Schema()
			rs := rp.Schema()
			if low.AreEqual(ls, rs) {
				done <- true
				return
			}
			s := CompareSchemas(lp, rp)
			propLock.Lock()
			propChanges[key] = s
			propLock.Unlock()
			done <- true
		}
	}

	totalProperties := 0
	if len(lProps) == len(rProps) {
		for w := range lProps {
			lp := lEntities[lProps[w]]
			rp := rEntities[rProps[w]]
			if lProps[w] == rProps[w] && lp != nil && rp != nil {
				totalProperties++
				go checkProperty(lProps[w], lp, rp, propChanges, doneChan)
			}

			// keys do not match, even after sorting, means a like for like replacement.
			if lProps[w] != rProps[w] {

				// old removed, new added.
				CreateChange(changes, ObjectAdded, v3.PropertiesLabel,
					nil, rKeyNodes[rProps[w]], false, nil, rEntities[rProps[w]])

				CreateChange(changes, ObjectRemoved, v3.PropertiesLabel,
					lKeyNodes[lProps[w]], nil, true, lEntities[lProps[w]], nil)
			}

		}
	}

	// something removed
	if len(lProps) > len(rProps) {
		for w := range lProps {
			if w < len(rProps) {
				totalProperties++
				go checkProperty(lProps[w], lEntities[lProps[w]], rEntities[rProps[w]], propChanges, doneChan)
			}
			if w >= len(rProps) {
				CreateChange(changes, ObjectRemoved, v3.PropertiesLabel,
					lKeyNodes[lProps[w]], nil, true, lEntities[lProps[w]], nil)
			}
		}
	}

	// something added
	if len(rProps) > len(lProps) {
		for w := range rProps {
			if w < len(lProps) {
				totalProperties++
				go checkProperty(rProps[w], lEntities[lProps[w]], rEntities[rProps[w]], propChanges, doneChan)
			}
			if w >= len(lProps) {
				CreateChange(changes, ObjectAdded, v3.PropertiesLabel,
					nil, rKeyNodes[rProps[w]], false, nil, rEntities[rProps[w]])
			}
		}
	}
	sc.SchemaPropertyChanges = propChanges
	return totalProperties
}

func checkSchemaPropertyChanges(
	lSchema *base.Schema,
	rSchema *base.Schema,
	changes *[]*Change, sc *SchemaChanges) {

	var props []*PropertyCheck

	// $schema (breaking change)
	props = append(props, &PropertyCheck{
		LeftNode:  lSchema.SchemaTypeRef.ValueNode,
		RightNode: rSchema.SchemaTypeRef.ValueNode,
		Label:     v3.SchemaDialectLabel,
		Changes:   changes,
		Breaking:  true,
		Original:  lSchema,
		New:       rSchema,
	})

	// ExclusiveMaximum
	props = append(props, &PropertyCheck{
		LeftNode:  lSchema.ExclusiveMaximum.ValueNode,
		RightNode: rSchema.ExclusiveMaximum.ValueNode,
		Label:     v3.ExclusiveMaximumLabel,
		Changes:   changes,
		Breaking:  true,
		Original:  lSchema,
		New:       rSchema,
	})

	// ExclusiveMinimum
	props = append(props, &PropertyCheck{
		LeftNode:  lSchema.ExclusiveMinimum.ValueNode,
		RightNode: rSchema.ExclusiveMinimum.ValueNode,
		Label:     v3.ExclusiveMinimumLabel,
		Changes:   changes,
		Breaking:  true,
		Original:  lSchema,
		New:       rSchema,
	})

	// Type
	props = append(props, &PropertyCheck{
		LeftNode:  lSchema.Type.ValueNode,
		RightNode: rSchema.Type.ValueNode,
		Label:     v3.TypeLabel,
		Changes:   changes,
		Breaking:  true,
		Original:  lSchema,
		New:       rSchema,
	})

	// Title
	props = append(props, &PropertyCheck{
		LeftNode:  lSchema.Title.ValueNode,
		RightNode: rSchema.Title.ValueNode,
		Label:     v3.TitleLabel,
		Changes:   changes,
		Breaking:  false,
		Original:  lSchema,
		New:       rSchema,
	})

	// MultipleOf
	props = append(props, &PropertyCheck{
		LeftNode:  lSchema.MultipleOf.ValueNode,
		RightNode: rSchema.MultipleOf.ValueNode,
		Label:     v3.MultipleOfLabel,
		Changes:   changes,
		Breaking:  true,
		Original:  lSchema,
		New:       rSchema,
	})

	// Maximum
	props = append(props, &PropertyCheck{
		LeftNode:  lSchema.Maximum.ValueNode,
		RightNode: rSchema.Maximum.ValueNode,
		Label:     v3.MaximumLabel,
		Changes:   changes,
		Breaking:  true,
		Original:  lSchema,
		New:       rSchema,
	})

	// Minimum
	props = append(props, &PropertyCheck{
		LeftNode:  lSchema.Minimum.ValueNode,
		RightNode: rSchema.Minimum.ValueNode,
		Label:     v3.MinimumLabel,
		Changes:   changes,
		Breaking:  true,
		Original:  lSchema,
		New:       rSchema,
	})

	// MaxLength
	props = append(props, &PropertyCheck{
		LeftNode:  lSchema.MaxLength.ValueNode,
		RightNode: rSchema.MaxLength.ValueNode,
		Label:     v3.MaxLengthLabel,
		Changes:   changes,
		Breaking:  true,
		Original:  lSchema,
		New:       rSchema,
	})

	// MinLength
	props = append(props, &PropertyCheck{
		LeftNode:  lSchema.MinLength.ValueNode,
		RightNode: rSchema.MinLength.ValueNode,
		Label:     v3.MinLengthLabel,
		Changes:   changes,
		Breaking:  true,
		Original:  lSchema,
		New:       rSchema,
	})

	// Pattern
	props = append(props, &PropertyCheck{
		LeftNode:  lSchema.Pattern.ValueNode,
		RightNode: rSchema.Pattern.ValueNode,
		Label:     v3.PatternLabel,
		Changes:   changes,
		Breaking:  true,
		Original:  lSchema,
		New:       rSchema,
	})

	// Format
	props = append(props, &PropertyCheck{
		LeftNode:  lSchema.Format.ValueNode,
		RightNode: rSchema.Format.ValueNode,
		Label:     v3.FormatLabel,
		Changes:   changes,
		Breaking:  true,
		Original:  lSchema,
		New:       rSchema,
	})

	// MaxItems
	props = append(props, &PropertyCheck{
		LeftNode:  lSchema.MaxItems.ValueNode,
		RightNode: rSchema.MaxItems.ValueNode,
		Label:     v3.MaxItemsLabel,
		Changes:   changes,
		Breaking:  true,
		Original:  lSchema,
		New:       rSchema,
	})

	// MinItems
	props = append(props, &PropertyCheck{
		LeftNode:  lSchema.MinItems.ValueNode,
		RightNode: rSchema.MinItems.ValueNode,
		Label:     v3.MinItemsLabel,
		Changes:   changes,
		Breaking:  true,
		Original:  lSchema,
		New:       rSchema,
	})

	// MaxProperties
	props = append(props, &PropertyCheck{
		LeftNode:  lSchema.MaxProperties.ValueNode,
		RightNode: rSchema.MaxProperties.ValueNode,
		Label:     v3.MaxPropertiesLabel,
		Changes:   changes,
		Breaking:  true,
		Original:  lSchema,
		New:       rSchema,
	})

	// MinProperties
	props = append(props, &PropertyCheck{
		LeftNode:  lSchema.MinProperties.ValueNode,
		RightNode: rSchema.MinProperties.ValueNode,
		Label:     v3.MinPropertiesLabel,
		Changes:   changes,
		Breaking:  true,
		Original:  lSchema,
		New:       rSchema,
	})

	// UniqueItems
	props = append(props, &PropertyCheck{
		LeftNode:  lSchema.UniqueItems.ValueNode,
		RightNode: rSchema.UniqueItems.ValueNode,
		Label:     v3.UniqueItemsLabel,
		Changes:   changes,
		Breaking:  true,
		Original:  lSchema,
		New:       rSchema,
	})

	// AdditionalProperties
	props = append(props, &PropertyCheck{
		LeftNode:  lSchema.AdditionalProperties.ValueNode,
		RightNode: rSchema.AdditionalProperties.ValueNode,
		Label:     v3.AdditionalPropertiesLabel,
		Changes:   changes,
		Breaking:  false,
		Original:  lSchema,
		New:       rSchema,
	})

	// Description
	props = append(props, &PropertyCheck{
		LeftNode:  lSchema.Description.ValueNode,
		RightNode: rSchema.Description.ValueNode,
		Label:     v3.DescriptionLabel,
		Changes:   changes,
		Breaking:  false,
		Original:  lSchema,
		New:       rSchema,
	})

	// ContentEncoding
	props = append(props, &PropertyCheck{
		LeftNode:  lSchema.ContentEncoding.ValueNode,
		RightNode: rSchema.ContentEncoding.ValueNode,
		Label:     v3.ContentEncodingLabel,
		Changes:   changes,
		Breaking:  true,
		Original:  lSchema,
		New:       rSchema,
	})

	// ContentMediaType
	props = append(props, &PropertyCheck{
		LeftNode:  lSchema.ContentMediaType.ValueNode,
		RightNode: rSchema.ContentMediaType.ValueNode,
		Label:     v3.ContentMediaType,
		Changes:   changes,
		Breaking:  true,
		Original:  lSchema,
		New:       rSchema,
	})

	// Default
	props = append(props, &PropertyCheck{
		LeftNode:  lSchema.Default.ValueNode,
		RightNode: rSchema.Default.ValueNode,
		Label:     v3.DefaultLabel,
		Changes:   changes,
		Breaking:  true,
		Original:  lSchema,
		New:       rSchema,
	})

	// Nullable
	props = append(props, &PropertyCheck{
		LeftNode:  lSchema.Nullable.ValueNode,
		RightNode: rSchema.Nullable.ValueNode,
		Label:     v3.NullableLabel,
		Changes:   changes,
		Breaking:  true,
		Original:  lSchema,
		New:       rSchema,
	})

	// ReadOnly
	props = append(props, &PropertyCheck{
		LeftNode:  lSchema.ReadOnly.ValueNode,
		RightNode: rSchema.ReadOnly.ValueNode,
		Label:     v3.ReadOnlyLabel,
		Changes:   changes,
		Breaking:  true,
		Original:  lSchema,
		New:       rSchema,
	})

	// WriteOnly
	props = append(props, &PropertyCheck{
		LeftNode:  lSchema.WriteOnly.ValueNode,
		RightNode: rSchema.WriteOnly.ValueNode,
		Label:     v3.WriteOnlyLabel,
		Changes:   changes,
		Breaking:  true,
		Original:  lSchema,
		New:       rSchema,
	})

	// Example
	props = append(props, &PropertyCheck{
		LeftNode:  lSchema.Example.ValueNode,
		RightNode: rSchema.Example.ValueNode,
		Label:     v3.ExampleLabel,
		Changes:   changes,
		Breaking:  false,
		Original:  lSchema,
		New:       rSchema,
	})

	// Deprecated
	props = append(props, &PropertyCheck{
		LeftNode:  lSchema.Deprecated.ValueNode,
		RightNode: rSchema.Deprecated.ValueNode,
		Label:     v3.DeprecatedLabel,
		Changes:   changes,
		Breaking:  false,
		Original:  lSchema,
		New:       rSchema,
	})

	// Required
	j := make(map[string]int)
	k := make(map[string]int)
	for i := range lSchema.Required.Value {
		j[lSchema.Required.Value[i].Value] = i
	}
	for i := range rSchema.Required.Value {
		k[rSchema.Required.Value[i].Value] = i
	}
	for g := range k {
		if _, ok := j[g]; !ok {
			CreateChange(changes, PropertyAdded, v3.RequiredLabel,
				nil, rSchema.Required.Value[k[g]].GetValueNode(), true, nil,
				rSchema.Required.Value[k[g]].GetValue)
		}
	}
	for g := range j {
		if _, ok := k[g]; !ok {
			CreateChange(changes, PropertyRemoved, v3.RequiredLabel,
				lSchema.Required.Value[j[g]].GetValueNode(), nil, true, lSchema.Required.Value[j[g]].GetValue,
				nil)
		}
	}

	// Enums
	j = make(map[string]int)
	k = make(map[string]int)
	for i := range lSchema.Enum.Value {
		j[fmt.Sprint(lSchema.Enum.Value[i].Value)] = i
	}
	for i := range rSchema.Enum.Value {
		k[fmt.Sprint(rSchema.Enum.Value[i].Value)] = i
	}
	for g := range k {
		if _, ok := j[g]; !ok {
			CreateChange(changes, PropertyAdded, v3.EnumLabel,
				nil, rSchema.Enum.Value[k[g]].GetValueNode(), false, nil,
				rSchema.Enum.Value[k[g]].GetValue)
		}
	}
	for g := range j {
		if _, ok := k[g]; !ok {
			CreateChange(changes, PropertyRemoved, v3.EnumLabel,
				lSchema.Enum.Value[j[g]].GetValueNode(), nil, true, lSchema.Enum.Value[j[g]].GetValue,
				nil)
		}
	}

	// Discriminator
	if lSchema.Discriminator.Value != nil && rSchema.Discriminator.Value != nil {
		// check if hash matches, if not then compare.
		if lSchema.Discriminator.Value.Hash() != rSchema.Discriminator.Value.Hash() {
			sc.DiscriminatorChanges = CompareDiscriminator(lSchema.Discriminator.Value, rSchema.Discriminator.Value)
		}
	}
	// added Discriminator
	if lSchema.Discriminator.Value == nil && rSchema.Discriminator.Value != nil {
		CreateChange(changes, ObjectAdded, v3.DiscriminatorLabel,
			nil, rSchema.Discriminator.ValueNode, true, nil, rSchema.Discriminator.Value)
	}
	// removed Discriminator
	if lSchema.Discriminator.Value != nil && rSchema.Discriminator.Value == nil {
		CreateChange(changes, ObjectRemoved, v3.DiscriminatorLabel,
			lSchema.Discriminator.ValueNode, nil, true, lSchema.Discriminator.Value, nil)
	}

	// ExternalDocs
	if lSchema.ExternalDocs.Value != nil && rSchema.ExternalDocs.Value != nil {
		// check if hash matches, if not then compare.
		if lSchema.ExternalDocs.Value.Hash() != rSchema.ExternalDocs.Value.Hash() {
			sc.ExternalDocChanges = CompareExternalDocs(lSchema.ExternalDocs.Value, rSchema.ExternalDocs.Value)
		}
	}
	// added ExternalDocs
	if lSchema.ExternalDocs.Value == nil && rSchema.ExternalDocs.Value != nil {
		CreateChange(changes, ObjectAdded, v3.ExternalDocsLabel,
			nil, rSchema.ExternalDocs.ValueNode, false, nil, rSchema.ExternalDocs.Value)
	}
	// removed ExternalDocs
	if lSchema.ExternalDocs.Value != nil && rSchema.ExternalDocs.Value == nil {
		CreateChange(changes, ObjectRemoved, v3.ExternalDocsLabel,
			lSchema.ExternalDocs.ValueNode, nil, false, lSchema.ExternalDocs.Value, nil)
	}

	// check extensions
	sc.ExtensionChanges = CompareExtensions(lSchema.Extensions, rSchema.Extensions)

	// check core properties
	CheckProperties(props)
}

func checkExamples(lSchema *base.Schema, rSchema *base.Schema, changes *[]*Change) {
	// check examples (3.1+)
	var lExampKey, rExampKey []string
	lExampN := make(map[string]*yaml.Node)
	rExampN := make(map[string]*yaml.Node)
	lExampVal := make(map[string]any)
	rExampVal := make(map[string]any)

	// create keys by hashing values
	if lSchema.Examples.ValueNode != nil {
		for i := range lSchema.Examples.ValueNode.Content {
			key := low.GenerateHashString(lSchema.Examples.ValueNode.Content[i].Value)
			lExampKey = append(lExampKey, key)
			lExampVal[key] = lSchema.Examples.ValueNode.Content[i].Value
			lExampN[key] = lSchema.Examples.ValueNode.Content[i]

		}
	}
	if rSchema.Examples.ValueNode != nil {
		for i := range rSchema.Examples.ValueNode.Content {
			key := low.GenerateHashString(rSchema.Examples.ValueNode.Content[i].Value)
			rExampKey = append(rExampKey, key)
			rExampVal[key] = rSchema.Examples.ValueNode.Content[i].Value
			rExampN[key] = rSchema.Examples.ValueNode.Content[i]
		}
	}

	// if examples equal lengths, check for equality
	if len(lExampKey) == len(rExampKey) {
		for i := range lExampKey {
			if lExampKey[i] != rExampKey[i] {
				CreateChange(changes, Modified, v3.ExamplesLabel,
					lExampN[lExampKey[i]], rExampN[rExampKey[i]], false,
					lExampVal[lExampKey[i]], rExampVal[rExampKey[i]])
			}
		}
	}
	// examples were removed.
	if len(lExampKey) > len(rExampKey) {
		for i := range lExampKey {
			if i < len(rExampKey) && lExampKey[i] != rExampKey[i] {
				CreateChange(changes, Modified, v3.ExamplesLabel,
					lExampN[lExampKey[i]], rExampN[rExampKey[i]], false,
					lExampVal[lExampKey[i]], rExampVal[rExampKey[i]])
			}
			if i >= len(rExampKey) {
				CreateChange(changes, ObjectRemoved, v3.ExamplesLabel,
					lExampN[lExampKey[i]], nil, false,
					lExampVal[lExampKey[i]], nil)
			}
		}
	}

	// examples were added
	if len(lExampKey) < len(rExampKey) {
		for i := range rExampKey {
			if i < len(lExampKey) && lExampKey[i] != rExampKey[i] {
				CreateChange(changes, Modified, v3.ExamplesLabel,
					lExampN[lExampKey[i]], rExampN[rExampKey[i]], false,
					lExampVal[lExampKey[i]], rExampVal[rExampKey[i]])
			}
			if i >= len(lExampKey) {
				CreateChange(changes, ObjectAdded, v3.ExamplesLabel,
					nil, rExampN[rExampKey[i]], false,
					nil, rExampVal[rExampKey[i]])
			}
		}
	}
}

func extractSchemaChanges(
	lSchema []low.ValueReference[*base.SchemaProxy],
	rSchema []low.ValueReference[*base.SchemaProxy],
	label string,
	sc *[]*SchemaChanges,
	changes *[]*Change,
	done chan bool) {

	// if there is nothing here, there is nothing to do.
	if lSchema == nil && rSchema == nil {
		done <- true
		return
	}

	x := "%x"
	// create hash key maps to check equality
	lKeys := make([]string, 0, len(lSchema))
	rKeys := make([]string, 0, len(rSchema))
	lEntities := make(map[string]*base.SchemaProxy)
	rEntities := make(map[string]*base.SchemaProxy)
	for h := range lSchema {
		q := lSchema[h].Value
		if !q.IsSchemaReference() {
			w := q.Schema()
			z := fmt.Sprintf(x, w.Hash())
			lKeys = append(lKeys, z)
			lEntities[z] = q
		}
	}
	for h := range rSchema {
		q := rSchema[h].Value
		if !q.IsSchemaReference() {
			w := q.Schema()
			z := fmt.Sprintf(x, w.Hash())
			rKeys = append(rKeys, z)
			rEntities[z] = q
		}
	}

	// sort slices so that like for like is all sequenced.
	sort.Strings(lKeys)
	sort.Strings(rKeys)

	// check for identical lengths
	if len(lKeys) == len(rKeys) {
		for w := range lKeys {
			// keys are different, which means there are changes.
			if lKeys[w] != rKeys[w] {
				*sc = append(*sc, CompareSchemas(lEntities[lKeys[w]], rEntities[rKeys[w]]))
			}
		}
	}

	// things were removed
	if len(lKeys) > len(rKeys) {
		for w := range lKeys {
			if w < len(rKeys) && lKeys[w] != rKeys[w] {
				*sc = append(*sc, CompareSchemas(lEntities[lKeys[w]], rEntities[rKeys[w]]))
			}
			if w >= len(rKeys) {
				CreateChange(changes, ObjectRemoved, label,
					lEntities[lKeys[w]].GetValueNode(), nil, true, lEntities[lKeys[w]], nil)
			}
		}
	}

	// things were added
	if len(rKeys) > len(lKeys) {
		for w := range rKeys {
			if w < len(lKeys) && rKeys[w] != lKeys[w] {
				*sc = append(*sc, CompareSchemas(lEntities[lKeys[w]], rEntities[rKeys[w]]))
			}
			if w >= len(lKeys) {
				CreateChange(changes, ObjectAdded, label,
					nil, rEntities[rKeys[w]].GetValueNode(), false, nil, rEntities[rKeys[w]])
			}
		}
	}
	done <- true
}