/*
Copyright 2015 Google Inc. All rights reserved.

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 input

import (
	"bufio"
	"bytes"
	"fmt"
	"github.com/google/git-appraise/repository"
	"io/ioutil"
	"os"
	"os/exec"
)

// LaunchEditor launches the default editor configured for the given repo. This
// method blocks until the editor command has returned.
//
// The specified filename should be a temporary file and provided as a relative path
// from the repo (e.g. "FILENAME" will be converted to ".git/FILENAME"). This file
// will be deleted after the editor is closed and its contents have been read.
//
// This method returns the text that was read from the temporary file, or
// an error if any step in the process failed.
func LaunchEditor(repo repository.Repo, fileName string) (string, error) {
	editor, err := repo.GetCoreEditor()
	if err != nil {
		return "", fmt.Errorf("Unable to detect default git editor: %v\n", err)
	}

	path := fmt.Sprintf("%s/.git/%s", repo.GetPath(), fileName)

	cmd, err := startInlineCommand(editor, path)
	if err != nil {
		// Running the editor directly did not work. This might mean that
		// the editor string is not a path to an executable, but rather
		// a shell command (e.g. "emacsclient --tty"). As such, we'll try
		// to run the command through bash, and if that fails, try with sh
		args := []string{"-c", fmt.Sprintf("%s %q", editor, path)}
		cmd, err = startInlineCommand("bash", args...)
		if err != nil {
			cmd, err = startInlineCommand("sh", args...)
		}
	}
	if err != nil {
		return "", fmt.Errorf("Unable to start editor: %v\n", err)
	}

	if err := cmd.Wait(); err != nil {
		return "", fmt.Errorf("Editing finished with error: %v\n", err)
	}

	output, err := ioutil.ReadFile(path)
	if err != nil {
		os.Remove(path)
		return "", fmt.Errorf("Error reading edited file: %v\n", err)
	}
	os.Remove(path)
	return string(output), err
}

// FromFile loads and returns the contents of a given file. If - is passed
// through, much like git, it will read from stdin. This can be piped data,
// unless there is a tty in which case the user will be prompted to enter a
// message.
func FromFile(fileName string) (string, error) {
	if fileName == "-" {
		stat, err := os.Stdin.Stat()
		if err != nil {
			return "", fmt.Errorf("Error reading from stdin: %v\n", err)
		}
		if (stat.Mode() & os.ModeCharDevice) == 0 {
			// There is no tty. This will allow us to read piped data instead.
			output, err := ioutil.ReadAll(os.Stdin)
			if err != nil {
				return "", fmt.Errorf("Error reading from stdin: %v\n", err)
			}
			return string(output), err
		}

		fmt.Printf("(reading comment from standard input)\n")
		var output bytes.Buffer
		s := bufio.NewScanner(os.Stdin)
		for s.Scan() {
			output.Write(s.Bytes())
			output.WriteRune('\n')
		}
		return output.String(), nil
	}

	output, err := ioutil.ReadFile(fileName)
	if err != nil {
		return "", fmt.Errorf("Error reading file: %v\n", err)
	}
	return string(output), err
}

func startInlineCommand(command string, args ...string) (*exec.Cmd, error) {
	cmd := exec.Command(command, args...)
	cmd.Stdin = os.Stdin
	cmd.Stdout = os.Stdout
	cmd.Stderr = os.Stderr
	err := cmd.Start()
	return cmd, err
}