Allow downstream projects to import func-e

* Define an api that allows go projects to use func-e as a library

Takes #434 forward

Fixes: #433

Signed-off-by: Arko Dasgupta <arko@tetrate.io>

api/run.go

@@ -0,0 +1,111 @@
+// Copyright 2022 Tetrate
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+// Package api allows go projects to use func-e as a library.
+package api
+
+import (
+	"context"
+	"io"
+	"os"
+	"runtime"
+
+	"github.com/tetratelabs/func-e/internal/cmd"
+	"github.com/tetratelabs/func-e/internal/globals"
+	"github.com/tetratelabs/func-e/internal/version"
+)
+
+// HomeDir is an absolute path which most importantly contains "versions"
+// installed from EnvoyVersionsURL. Defaults to "${HOME}/.func-e"
+func HomeDir(homeDir string) RunOption {
+	return func(o *runOpts) {
+		o.homeDir = homeDir
+	}
+}
+
+// EnvoyVersionsURL is the path to the envoy-versions.json.
+// Defaults to "https://archive.tetratelabs.io/envoy/envoy-versions.json"
+func EnvoyVersionsURL(envoyVersionsURL string) RunOption {
+	return func(o *runOpts) {
+		o.envoyVersionsURL = envoyVersionsURL
+	}
+}
+
+// EnvoyVersion overrides the version of Envoy to run. Defaults to the
+// contents of "$HomeDir/versions/version".
+//
+// When that file is missing, it is generated from ".latestVersion" from the
+// EnvoyVersionsURL. Its value can be in full version major.minor.patch format,
+// e.g. 1.18.1 or without patch component, major.minor, e.g. 1.18.
+func EnvoyVersion(envoyVersion string) RunOption {
+	return func(o *runOpts) {
+		o.envoyVersion = envoyVersion
+	}
+}
+
+// Out is where status messages are written. Defaults to os.Stdout
+func Out(out io.Writer) RunOption {
+	return func(o *runOpts) {
+		o.out = out
+	}
+}
+
+// RunOption is configuration for Run.
+type RunOption func(*runOpts)
+
+type runOpts struct {
+	homeDir          string
+	envoyVersion     string
+	envoyVersionsURL string
+	out              io.Writer
+}
+
+// Run downloads Envoy and runs it as a process with the arguments
+// passed to it. Use RunOption for configuration options.
+func Run(ctx context.Context, args []string, options ...RunOption) error {
+	ro := &runOpts{
+		homeDir:          globals.DefaultHomeDir,
+		envoyVersion:     "", // default to lookup
+		envoyVersionsURL: globals.DefaultEnvoyVersionsURL,
+		out:              os.Stdout,
+	}
+	for _, option := range options {
+		option(ro)
+	}
+
+	o := globals.GlobalOpts{
+		HomeDir:          ro.homeDir,
+		EnvoyVersion:     version.PatchVersion(ro.envoyVersion),
+		EnvoyVersionsURL: ro.envoyVersion,
+		Out:              ro.out,
+	}
+
+	funcECmd := cmd.NewApp(&o)
+
+	funcERunArgs := []string{"func-e", "--platform", runtime.GOOS + "/" + runtime.GOARCH, "run"}
+	funcERunArgs = append(funcERunArgs, args...)
+
+	errChan := make(chan error)
+	go func() {
+		errChan <- funcECmd.RunContext(ctx, funcERunArgs)
+	}()
+
+	// Wait for run to exit or an explicit stop.
+	select {
+	case <-ctx.Done():
+		return nil
+	case err := <-errChan:
+		return err
+	}
+}

api/run_test.go

@@ -0,0 +1,55 @@
+// Copyright 2022 Tetrate
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package api
+
+import (
+	"bytes"
+	"context"
+	"os"
+	"path/filepath"
+	"testing"
+	"time"
+
+	"github.com/stretchr/testify/require"
+
+	"github.com/tetratelabs/func-e/internal/test"
+	"github.com/tetratelabs/func-e/internal/version"
+)
+
+var (
+	runArgs = []string{"--version"}
+)
+
+func TestRun(t *testing.T) {
+
+	tmpDir := t.TempDir()
+	envoyVersion := version.LastKnownEnvoy
+	versionsServer := test.RequireEnvoyVersionsTestServer(t, envoyVersion)
+	defer versionsServer.Close()
+	envoyVersionsURL := versionsServer.URL + "/envoy-versions.json"
+	b := bytes.NewBufferString("")
+
+	require.Equal(t, 0, b.Len())
+
+	ctx := context.Background()
+	ctx, cancel := context.WithTimeout(ctx, 2*time.Second)
+	defer cancel()
+	err := Run(ctx, runArgs, Out(b), HomeDir(tmpDir), EnvoyVersionsURL(envoyVersionsURL))
+	require.NoError(t, err)
+
+	require.NotEqual(t, 0, b.Len())
+	_, err = os.Stat(filepath.Join(tmpDir, "versions"))
+	require.NoError(t, err)
+}