package util

import (
	"errors"
	"strings"
)

var (
	//Errors for ParseRole
	ErrInvalidRole = errors.New("Invalid role has been provided.")
	//Errors for ParseEmoji
	ErrInvalidEmoji = errors.New("Invalid emoji has been provided.")
	//Errors for ParseMessageLink
	ErrNotValidURL   = errors.New("Invalid URL has been provided (expecting message link).")
	ErrNotDiscordURL = errors.New("Invalid Discord URL has been provided (expecting message link).")
	ErrNotMessageURL = errors.New("Invalid Discord message link has been provided.")
)

type ParsedMessageLink struct {
	GuildID   string
	ChannelID string
	MessageID string
}

func ParseRole(roleString string) (string, error) {
	if !strings.HasPrefix(roleString, "<@&") || !strings.HasSuffix(roleString, ">") {
		return "", ErrInvalidRole
	}
	return roleString[3 : len(roleString)-1], nil
}

func ParseEmoji(emojiString string) (string, error) {
	if strings.HasPrefix(emojiString, "<:") && strings.HasSuffix(emojiString, ">") {
		return emojiString[2 : len(emojiString)-1], nil
	}
	//TODO: We assume people aren't ill-intended and everything are actually emoji for now.
	//The alternative would be to keep a list of all possible emoji which is overkill.
	return emojiString, nil
}

func ParseMessageLink(messageLink string) (ParsedMessageLink, error) {
	if !strings.HasPrefix(messageLink, "https://") {
		return ParsedMessageLink{}, ErrNotValidURL
	}
	split := strings.Split(messageLink, "/")
	if split[2] != "discordapp.com" && split[2] != "canary.discordapp.com" && split[2] != "ptb.discordapp.com" {
		return ParsedMessageLink{}, ErrNotDiscordURL
	}
	if len(split) < 7 || split[3] != "channels" {
		return ParsedMessageLink{}, ErrNotMessageURL
	}
	return ParsedMessageLink{
		GuildID:   split[4],
		ChannelID: split[5],
		MessageID: split[6],
	}, nil
}