CLOUDP-236398: Add validation logic for paths

tools/cli/internal/cli/merge/merge.go

@@ -19,6 +19,7 @@ import (
 	"log"
 	"mongodb/openapi/tools/cli/internal/cli/flag"
 	"mongodb/openapi/tools/cli/internal/cli/usage"
+	"mongodb/openapi/tools/cli/internal/openapi"
 	"os"
 
 	"github.com/spf13/cobra"
@@ -29,14 +30,24 @@ const (
 )
 
 type Opts struct {
+	Merger        openapi.Merger
 	basePath      string
 	outputPath    string
 	externalPaths []string
 }
 
 func (o *Opts) Run(_ []string) error {
-	// To add in follow up PR: CLOUDP-225849
-	return o.saveFile([]byte("test"))
+	federated, err := o.Merger.MergeOpenAPISpecs(o.externalPaths)
+	if err != nil {
+		return err
+	}
+
+	federatedBytes, err := federated.Spec.MarshalJSON()
+	if err != nil {
+		return err
+	}
+
+	return o.saveFile(federatedBytes)
 }
 
 func (o *Opts) PreRunE(_ []string) error {
@@ -48,7 +59,9 @@ func (o *Opts) PreRunE(_ []string) error {
 		return fmt.Errorf("no external OAS detected. Please, use the flag %s to include at least one OAS", flag.External)
 	}
 
-	return nil
+	m, err := openapi.NewOasDiff(o.basePath)
+	o.Merger = m
+	return err
 }
 
 func (o *Opts) saveFile(data []byte) error {

tools/cli/internal/openapi/errors/path_conflict_error.go

@@ -0,0 +1,11 @@
+package errors
+
+import "fmt"
+
+type PathConflictError struct {
+	Entry string
+}
+
+func (e PathConflictError) Error() string {
+	return fmt.Sprintf("there was a conflict with the path: %q", e.Entry)
+}

tools/cli/internal/openapi/oasdiff.go

@@ -0,0 +1,78 @@
+package openapi
+
+import (
+	"log"
+	"mongodb/openapi/tools/cli/internal/openapi/errors"
+
+	"github.com/tufin/oasdiff/diff"
+	"github.com/tufin/oasdiff/load"
+)
+
+type OasDiff struct {
+	base     *load.SpecInfo
+	external *load.SpecInfo
+	config   *diff.Config
+	specDiff *diff.Diff
+	parser   Parser
+}
+
+func NewOasDiff(base string) (*OasDiff, error) {
+	parser := NewOpenAPI3()
+	baseSpec, err := parser.CreateOpenAPISpecFromPath(base)
+	if err != nil {
+		return nil, err
+	}
+
+	return &OasDiff{
+		base:   baseSpec,
+		parser: parser,
+		config: &diff.Config{
+			IncludePathParams: true,
+		},
+	}, nil
+}
+
+func (o *OasDiff) MergeOpenAPISpecs(paths []string) (*load.SpecInfo, error) {
+	for _, p := range paths {
+		spec, err := o.parser.CreateOpenAPISpecFromPath(p)
+		if err != nil {
+			return nil, err
+		}
+
+		specDiff, err := diff.Get(o.config, o.base.Spec, spec.Spec)
+		if err != nil {
+			log.Fatalf("error in calculating the diff of the specs: %s", err)
+			return nil, err
+		}
+
+		o.specDiff = specDiff
+		o.external = spec
+		err = o.mergeSpecIntoBase()
+		if err != nil {
+			return nil, err
+		}
+	}
+
+	return o.base, nil
+}
+
+func (o OasDiff) mergeSpecIntoBase() error {
+	return o.mergePaths()
+}
+
+func (o OasDiff) mergePaths() error {
+	pathsToMerge := o.external.Spec.Paths
+	basePaths := o.base.Spec.Paths
+	for k, v := range pathsToMerge {
+		if _, ok := basePaths[k]; !ok {
+			basePaths[k] = v
+		} else {
+			return errors.PathConflictError{
+				Entry: k,
+			}
+		}
+	}
+
+	o.base.Spec.Paths = basePaths
+	return nil
+}

tools/cli/internal/openapi/openapi.go

@@ -0,0 +1,13 @@
+package openapi
+
+import (
+	"github.com/tufin/oasdiff/load"
+)
+
+type Merger interface {
+	MergeOpenAPISpecs([]string) (*load.SpecInfo, error)
+}
+
+type Parser interface {
+	CreateOpenAPISpecFromPath(string) (*load.SpecInfo, error)
+}

tools/cli/internal/openapi/openapi3.go

@@ -0,0 +1,31 @@
+package openapi
+
+import (
+	"github.com/getkin/kin-openapi/openapi3"
+	"github.com/tufin/oasdiff/load"
+)
+
+type OpenAPI3 struct {
+	IsExternalRefsAllowed    bool
+	CircularReferenceCounter int
+}
+
+func NewOpenAPI3() *OpenAPI3 {
+	return &OpenAPI3{
+		IsExternalRefsAllowed:    true,
+		CircularReferenceCounter: 10,
+	}
+}
+
+func (o *OpenAPI3) CreateOpenAPISpecFromPath(path string) (*load.SpecInfo, error) {
+	openapi3.CircularReferenceCounter = o.CircularReferenceCounter
+	loader := openapi3.NewLoader()
+	loader.IsExternalRefsAllowed = o.IsExternalRefsAllowed
+
+	spec, err := load.LoadSpecInfo(loader, load.NewSource(path))
+	if err != nil {
+		return nil, err
+	}
+
+	return spec, nil
+}