package diff

import (
	"errors"
	"fmt"
	"os"
	"os/exec"
	"regexp"
	"strings"
)

func Prompt(value, theirs, mine string) string {
	// TODO: create tmp file with the corresponding contents
	// open tmp file using the $EDITOR environment variable
	// parse and return output of tmp file after $EDITOR execution has been completed
	value = strings.ReplaceAll(value, "\r\n", "\n")
	theirs = strings.ReplaceAll(theirs, "\r\n", "\n")
	mine = strings.ReplaceAll(mine, "\r\n", "\n")
	file, err := os.CreateTemp("", "gitw-*")
	if err != nil {
		fmt.Fprintln(os.Stderr, err)
		return value
	}
	defer os.Remove(file.Name())

	// prepare file contents
	if _, err := file.WriteString(value); err != nil {
		fmt.Fprintln(os.Stderr, err)
		os.Exit(-1)
	}
	if _, err := file.WriteString("\n\n--- theirs ---\n\n"); err != nil {
		fmt.Fprintln(os.Stderr, err)
		os.Exit(-1)
	}
	if _, err := file.WriteString(theirs); err != nil {
		fmt.Fprintln(os.Stderr, err)
		os.Exit(-1)
	}
	if _, err := file.WriteString("\n\n--- mine ---\n\n"); err != nil {
		fmt.Fprintln(os.Stderr, err)
		os.Exit(-1)
	}
	if _, err := file.WriteString(mine); err != nil {
		fmt.Fprintln(os.Stderr, err)
		os.Exit(-1)
	}
	file.Close()

	cmd := exec.Command(os.Getenv("EDITOR"), file.Name())
	cmd.Stdin = os.Stdin
	cmd.Stdout = os.Stdout
	cmd.Stderr = os.Stderr
	if err := cmd.Run(); err != nil {
		fmt.Fprintln(os.Stderr, err)
		return value
	}
	contents, err := os.ReadFile(file.Name())
	if err != nil {
		fmt.Fprintln(os.Stderr, err)
		os.Exit(-1)
	}
	// TODO: what should I do with the '\r' characters? Who and when should they be handled?
	re := regexp.MustCompile("(?s)^(.*)--- theirs ---")
	matches := re.FindAllStringSubmatch(string(contents), -1)
	if len(matches) > 0 && len(matches[0]) == 2 {
		return matches[0][1]
	} else {
		fmt.Fprintln(os.Stderr, errors.New("No matches found, could not read merged value. Aborting."))
		os.Exit(-1)
		return "" // just to make compiler happy
	}
}