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plugin.go
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plugin.go
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// Licensed to the Apache Software Foundation (ASF) under one
// or more contributor license agreements. See the NOTICE file
// distributed with this work for additional information
// regarding copyright ownership. The ASF licenses this file
// to you 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 plugin
import (
"fmt"
"os"
"os/exec"
"runtime"
"strings"
"syscall"
)
var ValidPluginFilenamePrefixes = []string{"pulsarctl"}
var DefaultPluginsPaths = []string{"~/.pulsarctl/plugins"}
// Handler is capable of parsing command line arguments
// and performing executable filename lookups to search
// for valid plugin files, and execute found plugins.
type Handler interface {
// exists at the given filename, or a boolean false.
// Lookup will iterate over a list of given prefixes
// in order to recognize valid plugin filenames.
// The first filepath to match a prefix is returned.
Lookup(filename string) (string, bool)
// Execute receives an executable's filepath, a slice
// of arguments, and a slice of environment variables
// to relay to the executable.
Execute(executablePath string, cmdArgs, environment []string) error
}
// DefaultPluginHandler implements PluginHandler
type DefaultPluginHandler struct {
ValidPrefixes []string
}
// NewDefaultPluginHandler instantiates the DefaultPluginHandler with a list of
// given filename prefixes used to identify valid plugin filenames.
func NewDefaultPluginHandler(validPrefixes []string) *DefaultPluginHandler {
return &DefaultPluginHandler{
ValidPrefixes: validPrefixes,
}
}
// Lookup implements PluginHandler
func (h *DefaultPluginHandler) Lookup(filename string) (string, bool) {
// add default plugins dir
currentDir, _ := os.Getwd()
defaultPath := currentDir + "/plugins"
DefaultPluginsPaths = append(DefaultPluginsPaths, defaultPath)
for _, p := range DefaultPluginsPaths {
_ = os.Setenv("PATH", os.Getenv("PATH")+":"+p)
}
for _, prefix := range h.ValidPrefixes {
path, err := exec.LookPath(fmt.Sprintf("%s-%s", prefix, filename))
if err != nil || len(path) == 0 {
continue
}
return path, true
}
return "", false
}
// Execute implements PluginHandler
func (h *DefaultPluginHandler) Execute(executablePath string, cmdArgs, environment []string) error {
// Windows does not support exec syscall.
if runtime.GOOS == "windows" {
cmd := exec.Command(executablePath, cmdArgs...)
cmd.Stdout = os.Stdout
cmd.Stderr = os.Stderr
cmd.Stdin = os.Stdin
cmd.Env = environment
err := cmd.Run()
if err == nil {
os.Exit(0)
}
return err
}
// invoke cmd binary relaying the environment and args given
// append executablePath to cmdArgs, as execve will make first argument the "binary name".
return syscall.Exec(executablePath, append([]string{executablePath}, cmdArgs...), environment)
}
// HandlePluginCommand receives a pluginHandler and command-line arguments and attempts to find
// a plugin executable on the PATH that satisfies the given arguments.
func HandlePluginCommand(pluginHandler Handler, cmdArgs []string) error {
remainingArgs := []string{} // all "non-flag" arguments
for idx := range cmdArgs {
if strings.HasPrefix(cmdArgs[idx], "-") {
break
}
remainingArgs = append(remainingArgs, strings.Replace(cmdArgs[idx], "-", "_", -1))
}
foundBinaryPath := ""
// attempt to find binary, starting at longest possible name with given cmdArgs
for len(remainingArgs) > 0 {
path, found := pluginHandler.Lookup(strings.Join(remainingArgs, "-"))
if !found {
remainingArgs = remainingArgs[:len(remainingArgs)-1]
continue
}
foundBinaryPath = path
break
}
if len(foundBinaryPath) == 0 {
return nil
}
// invoke cmd binary relaying the current environment and args given
if err := pluginHandler.Execute(foundBinaryPath, cmdArgs[len(remainingArgs):], os.Environ()); err != nil {
return err
}
return nil
}