// Package editor encapsulates working with external text editor.
package editor

import (
	"bufio"
	"context"
	"errors"
	"fmt"
	"io/ioutil"
	"os"
	"os/exec"
	"path/filepath"
	"runtime"
	"strings"

	"github.com/kopia/kopia/repo/logging"
)

var log = logging.GetContextLoggerFunc("editor")

// EditLoop launches OS-specific editor (VI, notepad.exe or anoter editor configured through environment variables)
// It creates a temporary file with 'initial' contents and repeatedly invokes the editor until the provided 'parse' function
// returns nil result indicating success. The 'parse' function is passed the contents of edited files without # line comments.
func EditLoop(ctx context.Context, fname, initial string, parse func(updated string) error) error {
	tmpDir, err := ioutil.TempDir("", "kopia")
	if err != nil {
		return err
	}

	tmpFile := filepath.Join(tmpDir, fname)
	defer os.RemoveAll(tmpDir) //nolint:errcheck

	if err := ioutil.WriteFile(tmpFile, []byte(initial), 0600); err != nil {
		return err
	}

	for {
		if err := editFile(ctx, tmpFile); err != nil {
			return err
		}

		txt, err := readAndStripComments(tmpFile)
		if err != nil {
			return err
		}

		err = parse(txt)
		if err == nil {
			return nil
		}

		log(ctx).Errorf("%v", err)
		fmt.Print("Reopen editor to fix? (Y/n) ")

		var shouldReopen string

		_, _ = fmt.Scanf("%s", &shouldReopen)

		if strings.HasPrefix(strings.ToLower(shouldReopen), "n") {
			return errors.New("aborted")
		}
	}
}

func readAndStripComments(fname string) (string, error) {
	f, err := os.Open(fname) //nolint:gosec
	if err != nil {
		return "", err
	}
	defer f.Close() //nolint:errcheck

	var result []string

	s := bufio.NewScanner(f)
	for s.Scan() {
		l := s.Text()
		l = strings.TrimSpace(strings.Split(l, "#")[0])

		if l != "" {
			result = append(result, l)
		}
	}

	return strings.Join(result, "\n"), nil
}

func editFile(ctx context.Context, file string) error {
	editor, editorArgs := getEditorCommand()

	var args []string
	args = append(args, editorArgs...)
	args = append(args, file)

	cmd := exec.Command(editor, args...) //nolint:gosec
	cmd.Stderr = os.Stderr
	cmd.Stdin = os.Stdin
	cmd.Stdout = os.Stdout

	log(ctx).Debugf("launching editor %q on file %q", editor, file)

	err := cmd.Run()
	if err != nil {
		log(ctx).Errorf("unable to launch editor: %v", err)
	}

	return nil
}

func getEditorCommand() (cmd string, args []string) {
	editor := os.Getenv("VISUAL")
	if editor == "" {
		editor = os.Getenv("EDITOR")
	}

	if editor != "" {
		return parseEditor(editor)
	}

	if runtime.GOOS == "windows" {
		return "notepad.exe", nil
	}

	return "vi", nil
}

func parseEditor(s string) (cmd string, args []string) {
	// quoted editor path
	if s[0] == '"' {
		p := strings.Index(s[1:], "\"")
		if p == -1 {
			// invalid
			return s, nil
		}

		return s[1 : p+1], strings.Split(strings.TrimSpace(s[p+1:]), " ")
	}

	parts := strings.Split(s, " ")

	return parts[0], parts[1:]
}