// Package ark knows the text ARK: Survival Evolved's admin console speaks: the commands to send,
// and how to read what comes back from ListPlayers and GetChat.
package ark

import (
	"errors"
	"fmt"
	"regexp"
	"strings"
	"time"
)

// NoResponse is what the server answers to a command that has nothing to say.
const NoResponse = "Server received, But no response!!"

// Player is one person connected to a server.
type Player struct {
	Name    string `json:"name"`
	SteamID string `json:"steam_id"`
}

var playerLine = regexp.MustCompile(`^\s*\d+\.\s+(.*),\s*(\d{15,20})\s*$`)

// ParsePlayers reads the reply to ListPlayers: "0. Name, 76561198000000000" per line. Names may
// contain commas, so the Steam ID is taken from the end of the line.
func ParsePlayers(s string) []Player {
	var out []Player
	for _, line := range strings.Split(s, "\n") {
		if m := playerLine.FindStringSubmatch(strings.TrimRight(line, "\r\x00 ")); m != nil {
			out = append(out, Player{Name: strings.TrimSpace(m[1]), SteamID: m[2]})
		}
	}
	return out
}

// ChatLine is one line from GetChat.
type ChatLine struct {
	Sender    string `json:"sender"`
	Character string `json:"character,omitempty"`
	Message   string `json:"message"`
	Server    bool   `json:"server"` // the server itself speaking (broadcasts, admin messages)
}

var timestamp = regexp.MustCompile(`^\[\d{4}\.\d\d\.\d\d[-_]\d\d\.\d\d\.\d\d\]\s*`)

// ParseChat reads the reply to GetChat. Player lines look like "Steam Name (Character): hello".
func ParseChat(s string) []ChatLine {
	var out []ChatLine
	for _, line := range strings.Split(s, "\n") {
		line = strings.TrimSpace(strings.Trim(line, "\x00"))
		line = timestamp.ReplaceAllString(line, "")
		if line == "" || strings.HasPrefix(line, NoResponse) {
			continue
		}
		cl := ChatLine{Message: line, Server: true}
		if i := strings.Index(line, ": "); i > 0 {
			who := line[:i]
			cl.Message = line[i+2:]
			cl.Sender = who
			if j := strings.LastIndex(who, " ("); j > 0 && strings.HasSuffix(who, ")") {
				cl.Sender = who[:j]
				cl.Character = who[j+2 : len(who)-1]
			}
			cl.Server = cl.Sender == "SERVER"
		}
		out = append(out, cl)
	}
	return out
}

// IsEmptyReply reports whether a reply carries nothing worth showing.
func IsEmptyReply(s string) bool {
	s = strings.TrimSpace(s)
	return s == "" || strings.HasPrefix(s, NoResponse)
}

// ValidSteamID says whether s is a 64-bit Steam ID: digits only, so it can never smuggle anything
// else into a command.
func ValidSteamID(s string) bool {
	if len(s) < 15 || len(s) > 20 {
		return false
	}
	for _, r := range s {
		if r < '0' || r > '9' {
			return false
		}
	}
	return true
}

// Clean makes text safe to put in a command: one line, no control characters, no double quotes.
func Clean(s string) string {
	var sb strings.Builder
	for _, r := range s {
		switch {
		case r == '"':
			sb.WriteRune('\'')
		case r == '\n' || r == '\r' || r == '\t':
			sb.WriteRune(' ')
		case r < 0x20 || r == 0x7f:
		default:
			sb.WriteRune(r)
		}
	}
	out := strings.TrimSpace(sb.String())
	if r := []rune(out); len(r) > 400 {
		out = string(r[:400])
	}
	return out
}

// Command lines with fixed text.
const (
	ListPlayers      = "ListPlayers"
	GetChat          = "GetChat"
	SaveWorld        = "SaveWorld"
	DoExit           = "DoExit"
	DestroyWildDinos = "DestroyWildDinos"
)

// Broadcast shows a message in the middle of every player's screen.
func Broadcast(msg string) (string, error) { return withText("Broadcast", msg) }

// ServerChat posts a line to global chat as SERVER.
func ServerChat(msg string) (string, error) { return withText("ServerChat", msg) }

// SetMOTD changes the message of the day.
func SetMOTD(msg string) (string, error) { return withText("SetMessageOfTheDay", msg) }

func withText(cmd, msg string) (string, error) {
	msg = Clean(msg)
	if msg == "" {
		return "", errors.New("the message is empty")
	}
	return cmd + " " + msg, nil
}

// ServerChatTo whispers a message to one player.
func ServerChatTo(steamID, msg string) (string, error) {
	if !ValidSteamID(steamID) {
		return "", errors.New("not a Steam ID")
	}
	msg = Clean(msg)
	if msg == "" {
		return "", errors.New("the message is empty")
	}
	return fmt.Sprintf(`ServerChatTo "%s" %s`, steamID, msg), nil
}

// ForPlayer builds a command that takes only a Steam ID: KickPlayer, BanPlayer, UnbanPlayer,
// AllowPlayerToJoinNoCheck, DisallowPlayerToJoinNoCheck.
func ForPlayer(cmd, steamID string) (string, error) {
	if !ValidSteamID(steamID) {
		return "", errors.New("not a Steam ID")
	}
	return cmd + " " + steamID, nil
}

var timeOfDay = regexp.MustCompile(`^([01]?\d|2[0-3]):[0-5]\d(:[0-5]\d)?$`)

// SetTimeOfDay sets the in-game clock to HH:MM or HH:MM:SS.
func SetTimeOfDay(t string) (string, error) {
	t = strings.TrimSpace(t)
	if !timeOfDay.MatchString(t) {
		return "", errors.New("time must look like 06:30")
	}
	if strings.Count(t, ":") == 1 {
		t += ":00"
	}
	return "SetTimeOfDay " + t, nil
}

// Reference lists the console commands worth offering as suggestions in a UI.
var Reference = []string{
	"ListPlayers", "GetChat", "SaveWorld", "DoExit", "Broadcast ", "ServerChat ", `ServerChatTo "<steamid>" `,
	`ServerChatToPlayer "<name>" `, "KickPlayer <steamid>", "BanPlayer <steamid>", "UnbanPlayer <steamid>",
	"AllowPlayerToJoinNoCheck <steamid>", "DisallowPlayerToJoinNoCheck <steamid>", "DestroyWildDinos",
	"SetTimeOfDay 12:00", "SetMessageOfTheDay ", "ShowMessageOfTheDay", "GiveItemToPlayer <playerid> <blueprint> 1 0 0",
	"GiveExpToPlayer <playerid> 1000 0 0", "RenamePlayer \"<old>\" <new>", "RenameTribe \"<old>\" <new>",
}

// Duration formats d the way a player would say it ("10 minutes", "30 seconds").
func Duration(d time.Duration) string {
	d = d.Round(time.Second)
	switch {
	case d >= 2*time.Hour:
		return fmt.Sprintf("%d hours", int(d.Hours()))
	case d >= time.Hour:
		return "1 hour"
	case d >= 2*time.Minute:
		return fmt.Sprintf("%d minutes", int(d.Minutes()))
	case d >= time.Minute:
		return "1 minute"
	case d == time.Second:
		return "1 second"
	}
	return fmt.Sprintf("%d seconds", int(d.Seconds()))
}