Adds service binding resolver

bindings/init_test.go

@@ -0,0 +1,14 @@
+package bindings_test
+
+import (
+	"testing"
+
+	"github.com/sclevine/spec"
+	"github.com/sclevine/spec/report"
+)
+
+func TestUnitBindings(t *testing.T) {
+	suite := spec.New("packit/bindings", spec.Report(report.Terminal{}))
+	suite("Resolver", testResolver)
+	suite.Run(t)
+}

bindings/resolver.go

@@ -0,0 +1,133 @@
+package bindings
+
+import (
+	"fmt"
+	"github.com/pkg/errors"
+	"io/ioutil"
+	"os"
+	"path/filepath"
+	"strings"
+)
+
+// Binding represents metadata related to an external service.
+type Binding struct {
+
+	// Name is the name of the binding, given by the binding directory name.
+	Name string
+
+	// Path is the path to the binding directory.
+	Path string
+
+	// Type is the type of the binding, given by the content of the 'type' file within the binding directory.
+	Type string
+
+	// Provider is the provider of the binding, given by the content of the 'provider' file within the binding
+	// directory.
+	Provider string
+
+	// Secret is the primary content of the binding. Keys are given by each file name within the binding directory
+	// (other than 'type' or 'provider'), and corresponding values are given by the content of each file.
+	Secret map[string][]byte // TODO: place in custom buffer class
+}
+
+// Resolver resolves service bindings.
+type Resolver struct {
+	bindingRoot string
+	bindings    []Binding
+}
+
+// NewResolver returns a new service binding resolver. If the SERVICE_BINDING_ROOT environment variable is not set, uses
+// the provided platform directory to resolve bindings at `<platformDir>/bindings`.
+func NewResolver(platformDir string) *Resolver {
+	root := os.Getenv("SERVICE_BINDING_ROOT")
+	if root == "" {
+		root = filepath.Join(platformDir, "bindings")
+	}
+
+	return &Resolver{
+		bindingRoot: root,
+	}
+}
+
+// Resolve returns all bindings matching the given type and optional provider (case-insensitive). To match on type only,
+// provider may be an empty string. Returns an error if there are problems loading bindings from the file system.
+func (r *Resolver) Resolve(typ string, provider string) ([]Binding, error) {
+	if r.bindings == nil {
+		bindings, err := loadBindings(r.bindingRoot)
+		if err != nil {
+			return nil, errors.Wrapf(err, "loading bindings from '%s'", r.bindingRoot)
+		}
+		r.bindings = bindings
+	}
+
+	var resolved []Binding
+	for _, bind := range r.bindings {
+		if (strings.ToLower(bind.Type) == strings.ToLower(typ)) &&
+			(provider == "" || strings.ToLower(bind.Provider) == strings.ToLower(provider)) {
+			resolved = append(resolved, bind)
+		}
+	}
+	return resolved, nil
+}
+
+// ResolveOne returns a single binding matching the given type and optional provider (case-insensitive). To match on
+// type only, provider may be an empty string. Returns an error if the number of matched bindings is not exactly one, or
+// if there are problems loading bindings from the file system.
+func (r *Resolver) ResolveOne(typ string, provider string) (Binding, error) {
+	binds, err := r.Resolve(typ, provider)
+	if err != nil {
+		return Binding{}, err
+	}
+	if len(binds) != 1 {
+		return Binding{}, fmt.Errorf("found %d bindings for type '%s' and provider '%s' but expected exactly 1", len(binds), typ, provider)
+	}
+	return binds[0], nil
+}
+
+func loadBindings(bindingRoot string) ([]Binding, error) {
+	files, err := ioutil.ReadDir(bindingRoot)
+	if err != nil {
+		return nil, err
+	}
+
+	var bindings []Binding
+	for _, file := range files {
+		binding, err := loadBinding(bindingRoot, file.Name())
+		if err != nil {
+			return nil, err
+		}
+		bindings = append(bindings, binding)
+	}
+	return bindings, nil
+}
+
+func loadBinding(bindingRoot, name string) (Binding, error) {
+	binding := Binding{
+		Name:   name,
+		Path:   filepath.Join(bindingRoot, name),
+		Secret: map[string][]byte{},
+	}
+
+	files, err := ioutil.ReadDir(binding.Path)
+	if err != nil {
+		return Binding{}, nil
+	}
+
+	for _, file := range files {
+		content, err := os.ReadFile(filepath.Join(binding.Path, file.Name()))
+		if err != nil {
+			return Binding{}, err
+		}
+
+		switch file.Name() {
+		case "type":
+			binding.Type = string(content)
+		case "provider":
+			binding.Provider = string(content)
+		default:
+			binding.Secret[file.Name()] = content
+		}
+	}
+
+	return binding, nil
+}

bindings/resolver_test.go

@@ -0,0 +1,249 @@
+package bindings_test
+
+import (
+	"github.com/paketo-buildpacks/packit/bindings"
+	"github.com/sclevine/spec"
+	"os"
+	"path/filepath"
+	"testing"
+
+	. "github.com/onsi/gomega"
+)
+
+func testResolver(t *testing.T, context spec.G, it spec.S) {
+	var Expect = NewWithT(t).Expect
+
+	context("NewResolver", func() {
+		var (
+			bindingRoot string
+			platformDir string
+		)
+
+		it.Before(func() {
+			var err error
+
+			bindingRoot, err = os.MkdirTemp("", "bindings")
+			Expect(err).NotTo(HaveOccurred())
+
+			err = os.MkdirAll(filepath.Join(bindingRoot, "some-binding"), os.ModePerm)
+			Expect(err).NotTo(HaveOccurred())
+
+			err = os.WriteFile(filepath.Join(bindingRoot, "some-binding", "type"), []byte("some-type"), os.ModePerm)
+			Expect(err).NotTo(HaveOccurred())
+
+			platformDir, err = os.MkdirTemp("", "bindings")
+			Expect(err).NotTo(HaveOccurred())
+
+			err = os.MkdirAll(filepath.Join(platformDir, "bindings", "some-binding"), os.ModePerm)
+			Expect(err).NotTo(HaveOccurred())
+
+			err = os.WriteFile(filepath.Join(platformDir, "bindings", "some-binding", "type"), []byte("some-type"), os.ModePerm)
+			Expect(err).NotTo(HaveOccurred())
+		})
+
+		context("SERVICE_BINDING_ROOT is set", func() {
+			it.Before(func() {
+				Expect(os.Setenv("SERVICE_BINDING_ROOT", bindingRoot)).To(Succeed())
+			})
+
+			it("uses env var value for binding root", func() {
+				resolver := bindings.NewResolver(platformDir)
+
+				binds, err := resolver.Resolve("some-type", "")
+				Expect(err).NotTo(HaveOccurred())
+				Expect(binds).To(ConsistOf(
+					bindings.Binding{
+						Name:   "some-binding",
+						Path:   filepath.Join(bindingRoot, "some-binding"),
+						Type:   "some-type",
+						Secret: map[string][]byte{},
+					},
+				))
+			})
+
+		})
+
+		context("SERVICE_BINDING_ROOT is unset", func() {
+			it.Before(func() {
+				Expect(os.Unsetenv("SERVICE_BINDING_ROOT")).To(Succeed())
+			})
+
+			it("uses '<platform>/bindings' for binding root", func() {
+				resolver := bindings.NewResolver(platformDir)
+
+				binds, err := resolver.Resolve("some-type", "")
+				Expect(err).NotTo(HaveOccurred())
+				Expect(binds).To(ConsistOf(
+					bindings.Binding{
+						Name:   "some-binding",
+						Path:   filepath.Join(platformDir, "bindings", "some-binding"),
+						Type:   "some-type",
+						Secret: map[string][]byte{},
+					},
+				))
+			})
+
+		})
+
+	})
+
+	context("resolving bindings", func() {
+		var bindingRoot string
+		var resolver *bindings.Resolver
+
+		it.Before(func() {
+			var err error
+			bindingRoot, err = os.MkdirTemp("", "bindings")
+			Expect(err).NotTo(HaveOccurred())
+			Expect(os.Setenv("SERVICE_BINDING_ROOT", bindingRoot)).To(Succeed())
+
+			resolver = bindings.NewResolver("")
+
+			err = os.MkdirAll(filepath.Join(bindingRoot, "binding-1A"), os.ModePerm)
+			Expect(err).NotTo(HaveOccurred())
+
+			err = os.WriteFile(filepath.Join(bindingRoot, "binding-1A", "type"), []byte("type-1"), os.ModePerm)
+			Expect(err).NotTo(HaveOccurred())
+
+			err = os.WriteFile(filepath.Join(bindingRoot, "binding-1A", "provider"), []byte("provider-1A"), os.ModePerm)
+			Expect(err).NotTo(HaveOccurred())
+
+			err = os.WriteFile(filepath.Join(bindingRoot, "binding-1A", "username"), []byte("username-1A"), os.ModePerm)
+			Expect(err).NotTo(HaveOccurred())
+
+			err = os.WriteFile(filepath.Join(bindingRoot, "binding-1A", "password"), []byte("password-1A"), os.ModePerm)
+			Expect(err).NotTo(HaveOccurred())
+
+			err = os.MkdirAll(filepath.Join(bindingRoot, "binding-1B"), os.ModePerm)
+			Expect(err).NotTo(HaveOccurred())
+
+			err = os.WriteFile(filepath.Join(bindingRoot, "binding-1B", "type"), []byte("type-1"), os.ModePerm)
+			Expect(err).NotTo(HaveOccurred())
+
+			err = os.WriteFile(filepath.Join(bindingRoot, "binding-1B", "provider"), []byte("provider-1B"), os.ModePerm)
+			Expect(err).NotTo(HaveOccurred())
+
+			err = os.WriteFile(filepath.Join(bindingRoot, "binding-1B", "username"), []byte("username-1B"), os.ModePerm)
+			Expect(err).NotTo(HaveOccurred())
+
+			err = os.WriteFile(filepath.Join(bindingRoot, "binding-1B", "password"), []byte("password-1B"), os.ModePerm)
+			Expect(err).NotTo(HaveOccurred())
+
+			err = os.MkdirAll(filepath.Join(bindingRoot, "binding-2"), os.ModePerm)
+			Expect(err).NotTo(HaveOccurred())
+
+			err = os.WriteFile(filepath.Join(bindingRoot, "binding-2", "type"), []byte("type-2"), os.ModePerm)
+			Expect(err).NotTo(HaveOccurred())
+
+			err = os.WriteFile(filepath.Join(bindingRoot, "binding-2", "provider"), []byte("provider-2"), os.ModePerm)
+			Expect(err).NotTo(HaveOccurred())
+
+			err = os.WriteFile(filepath.Join(bindingRoot, "binding-2", "username"), []byte("username-2"), os.ModePerm)
+			Expect(err).NotTo(HaveOccurred())
+
+			err = os.WriteFile(filepath.Join(bindingRoot, "binding-2", "password"), []byte("password-2"), os.ModePerm)
+			Expect(err).NotTo(HaveOccurred())
+		})
+
+		it.After(func() {
+			Expect(os.RemoveAll(bindingRoot)).To(Succeed())
+			Expect(os.Unsetenv("SERVICE_BINDING_ROOT")).To(Succeed())
+		})
+
+		context("Resolve", func() {
+			it("resolves by type only (case-insensitive)", func() {
+				binds, err := resolver.Resolve("TyPe-1", "")
+				Expect(err).NotTo(HaveOccurred())
+
+				Expect(binds).To(ConsistOf(
+					bindings.Binding{
+						Name:     "binding-1A",
+						Path:     filepath.Join(bindingRoot, "binding-1A"),
+						Type:     "type-1",
+						Provider: "provider-1A",
+						Secret: map[string][]byte{
+							"username": []byte("username-1A"),
+							"password": []byte("password-1A"),
+						},
+					},
+					bindings.Binding{
+						Name:     "binding-1B",
+						Path:     filepath.Join(bindingRoot, "binding-1B"),
+						Type:     "type-1",
+						Provider: "provider-1B",
+						Secret: map[string][]byte{
+							"username": []byte("username-1B"),
+							"password": []byte("password-1B"),
+						},
+					},
+				))
+			})
+
+			it("resolves by type and provider (case-insensitive)", func() {
+				binds, err := resolver.Resolve("TyPe-1", "PrOvIdEr-1B")
+				Expect(err).NotTo(HaveOccurred())
+
+				Expect(binds).To(ConsistOf(
+					bindings.Binding{
+						Name:     "binding-1B",
+						Path:     filepath.Join(bindingRoot, "binding-1B"),
+						Type:     "type-1",
+						Provider: "provider-1B",
+						Secret: map[string][]byte{
+							"username": []byte("username-1B"),
+							"password": []byte("password-1B"),
+						},
+					},
+				))
+			})
+
+			it("returns errors encountered while reading binding", func() {
+				err := os.MkdirAll(filepath.Join(bindingRoot, "bad-binding"), os.ModePerm)
+				Expect(err).NotTo(HaveOccurred())
+
+				err = os.WriteFile(filepath.Join(bindingRoot, "bad-binding", "type"), []byte("bad-type"), 000)
+
+				_, err = resolver.Resolve("bad-type", "")
+				Expect(err).To(MatchError(HavePrefix("loading bindings from '%s': open %s: permission denied", bindingRoot, filepath.Join(bindingRoot, "bad-binding", "type"))))
+			})
+		})
+
+		context("ResolveOne", func() {
+			it("resolves one binding (case-insensitive)", func() {
+				bind, err := resolver.ResolveOne("TyPe-2", "")
+				Expect(err).NotTo(HaveOccurred())
+				Expect(bind).To(Equal(bindings.Binding{
+					Name:     "binding-2",
+					Path:     filepath.Join(bindingRoot, "binding-2"),
+					Type:     "type-2",
+					Provider: "provider-2",
+					Secret: map[string][]byte{
+						"username": []byte("username-2"),
+						"password": []byte("password-2"),
+					},
+				}))
+			})
+
+			it("returns an error if no matches", func() {
+				_, err := resolver.ResolveOne("non-existent-type", "non-existent-provider")
+				Expect(err).To(MatchError("found 0 bindings for type 'non-existent-type' and provider 'non-existent-provider' but expected exactly 1"))
+			})
+
+			it("returns an error if more than one match", func() {
+				_, err := resolver.ResolveOne("TyPe-1", "")
+				Expect(err).To(MatchError("found 2 bindings for type 'TyPe-1' and provider '' but expected exactly 1"))
+			})
+
+			it("returns errors encountered while reading binding", func() {
+				err := os.MkdirAll(filepath.Join(bindingRoot, "bad-binding"), os.ModePerm)
+				Expect(err).NotTo(HaveOccurred())
+
+				err = os.WriteFile(filepath.Join(bindingRoot, "bad-binding", "type"), []byte("bad-type"), 000)
+
+				_, err = resolver.Resolve("bad-type", "")
+				Expect(err).To(MatchError(HavePrefix("loading bindings from '%s': open %s: permission denied", bindingRoot, filepath.Join(bindingRoot, "bad-binding", "type"))))
+			})
+
+		})
+	})
+}