package main

import (
	"bufio"
	"bytes"
	"errors"
	"fmt"
	"io"
	"io/ioutil"
	"os"
	"os/exec"
	"strings"
)

const defaultCommitFileMsgTpl = `%s

# Please enter the description for your commit(s). Lines starting with '#' will
# be ignored, and an empty message aborts the commit.`

func tmpFileMsg(tpl string, args ...interface{}) (string, error) {
	editor := os.Getenv("EDITOR")
	if editor == "" {
		return "", errors.New("EDITOR not set, please set it or use -msg in order to create your commit message")
	} else if _, err := os.Stat(editor); err != nil {
		return "", fmt.Errorf("could not stat EDITOR %q: %w", editor, err)
	}

	tmpf, err := ioutil.TempFile("", "dehub.*.txt")
	if err != nil {
		return "", fmt.Errorf("could not open temp file: %w", err)
	}
	tmpfName := tmpf.Name()
	defer os.Remove(tmpfName)

	tmpBody := bytes.NewBufferString(fmt.Sprintf(tpl, args...))

	_, err = io.Copy(tmpf, tmpBody)
	tmpf.Close()
	if err != nil {
		return "", fmt.Errorf("could not write helper message to temp file %q: %w", tmpfName, err)
	}

	cmd := exec.Command(editor, tmpfName)
	cmd.Stdin = os.Stdin
	cmd.Stdout = os.Stdout
	cmd.Stderr = os.Stderr
	if err := cmd.Run(); err != nil {
		return "", fmt.Errorf("error running '%s %q': %w", editor, tmpfName, err)
	}

	body, err := ioutil.ReadFile(tmpfName)
	if err != nil {
		return "", fmt.Errorf("error retrieving message body from %q: %w", tmpfName, err)
	}

	bodyFiltered := new(bytes.Buffer)
	bodyBR := bufio.NewReader(bytes.NewBuffer(body))
	for {
		line, err := bodyBR.ReadString('\n')
		if errors.Is(err, io.EOF) {
			break
		} else if err != nil {
			return "", fmt.Errorf("error reading from buffered body: %w", err)
		}

		if !strings.HasPrefix(strings.TrimSpace(line), "#") {
			bodyFiltered.WriteString(line)
		}
	}

	return strings.TrimSpace(bodyFiltered.String()), nil
}