// Copyright 2023 CloudWeGo Authors
//
// 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 util

import (
	"io"
	"os"
)

// ReadInput defaults to read from stdin.
// If `KITEX_TOOL_STDIN_LOAD_FILE` is a valid path, it reads from the specified file;
// If `KITEX_TOOL_STDIN_DUMP_FILE` is a valid path, it dumps what it read to the file;
// This feature makes it easier to debug kitex tool.
func ReadInput() ([]byte, error) {
	if dumpFileName := os.Getenv("KITEX_TOOL_STDIN_LOAD_FILE"); dumpFileName != "" {
		return os.ReadFile(dumpFileName)
	}
	data, err := io.ReadAll(os.Stdin)
	if err == nil {
		if dumpFileName := os.Getenv("KITEX_TOOL_STDIN_DUMP_FILE"); dumpFileName != "" {
			os.WriteFile(dumpFileName, data, 0o644)
		}
	}
	return data, err
}
