// Copyright 2019 The Fuchsia Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

package execution

import (
	"context"
	"fmt"
	"io"
	"os"
	"os/exec"
	"strings"
)

// Executor supports chaining subcommand execution and error handling.
type Executor struct {
	stdout io.Writer
	stderr io.Writer
	dir    string
}

// NewExecutor returns a new Executor that writes to stdout and stderr.
func NewExecutor(stdout, stderr io.Writer, dir string) *Executor {
	return &Executor{stdout: stdout, stderr: stderr, dir: dir}
}

// Exec runs the command at path with args.
func (e Executor) Exec(ctx context.Context, path string, args ...string) error {
	cmd := exec.CommandContext(ctx, path, args...)
	cmd.Env = os.Environ()
	cmd.Stdout = e.stdout
	cmd.Stderr = e.stderr
	cmd.Dir = e.dir
	return cmd.Run()
}

// ExecAll runs all given commands. Upon encountering an error after execution
// stops and the error is returned. Returns an error if an element in cmds is
// empty.
func (e Executor) ExecAll(ctx context.Context, cmds [][]string) error {
	for i, cmd := range cmds {
		if len(cmd) == 0 {
			return fmt.Errorf("forbidden empty list in cmds at position %d", i)
		}
		if err := e.Exec(ctx, cmd[0], cmd[1:]...); err != nil {
			return fmt.Errorf("failed to exec cmd: %s; %v", strings.Join(cmd, " "), err)
		}
	}
	return nil
}