package main

import (
	"errors"
	"flag"
	"strings"
	"unicode"
	"unicode/utf8"
)

const mutationMessageMaxRunes = 240

type mutationMessageCopy struct {
	MessageHelp, NoPromptHelp, Prompt, Invalid string
}

var mutationMessageText = mutationMessageCopy{
	MessageHelp:  "Add a short note describing this change (shown alongside the recorded action).",
	NoPromptHelp: "Skip the optional change description prompt.",
	Prompt:       "Describe this change (optional):",
	Invalid:      "Message must be one line and 240 characters or fewer.",
}

func firstMutationMessage(messages []string) string {
	if len(messages) == 0 {
		return ""
	}
	return messages[0]
}

type mutationMessageFlags struct {
	message  *string
	noPrompt *bool
}

func addMutationMessageFlags(fs *flag.FlagSet) mutationMessageFlags {
	return mutationMessageFlags{
		message:  fs.String("message", "", mutationMessageText.MessageHelp),
		noPrompt: fs.Bool("no-prompt", false, mutationMessageText.NoPromptHelp),
	}
}

func resolveMutationMessage(fs *flag.FlagSet, flags mutationMessageFlags) (string, error) {
	if flagWasSet(fs, "message") {
		return validateMutationMessage(*flags.message)
	}
	if *flags.noPrompt || !interactiveTerminal() {
		return "", nil
	}
	pref, err := configMessagePrompt()
	if err != nil {
		return "", err
	}
	if pref == "off" {
		return "", nil
	}
	return validateMutationMessage(promptLine(stdout, mutationMessageText.Prompt))
}

func validateMutationMessage(message string) (string, error) {
	if !utf8.ValidString(message) || utf8.RuneCountInString(message) > mutationMessageMaxRunes {
		return "", errors.New(mutationMessageText.Invalid)
	}
	for _, r := range message {
		if unicode.IsControl(r) {
			return "", errors.New(mutationMessageText.Invalid)
		}
	}
	return strings.TrimSpace(message), nil
}