package state

import (
	"errors"

	"github.com/diamondburned/arikawa/discord"
	"github.com/diamondburned/arikawa/gateway"
)

// Store is the state storage. It should handle mutex itself, and it should only
// concern itself with the local state.
type Store interface {
	StoreGetter
	StoreModifier
}

// All methods in StoreGetter will be wrapped by the State. If the State can't
// find anything in the storage, it will call the API itself and automatically
// add what's missing into the storage.
//
// Methods that return with a slice should pay attention to race conditions that
// would mutate the underlying slice (and as a result the returned slice as
// well). The best way to avoid this is to copy the whole slice, like
// DefaultStore does.
type StoreGetter interface {
	Me() (*discord.User, error)

	// Channel should check for both DM and guild channels.
	Channel(id discord.Snowflake) (*discord.Channel, error)
	Channels(guildID discord.Snowflake) ([]discord.Channel, error)
	PrivateChannels() ([]discord.Channel, error)

	Emoji(guildID, emojiID discord.Snowflake) (*discord.Emoji, error)
	Emojis(guildID discord.Snowflake) ([]discord.Emoji, error)

	Guild(id discord.Snowflake) (*discord.Guild, error)
	Guilds() ([]discord.Guild, error)

	Member(guildID, userID discord.Snowflake) (*discord.Member, error)
	Members(guildID discord.Snowflake) ([]discord.Member, error)

	Message(channelID, messageID discord.Snowflake) (*discord.Message, error)
	Messages(channelID discord.Snowflake) ([]discord.Message, error)
	MaxMessages() int // used to know if the state is filled or not.

	// These don't get fetched from the API, it's Gateway only.
	Presence(guildID, userID discord.Snowflake) (*discord.Presence, error)
	Presences(guildID discord.Snowflake) ([]discord.Presence, error)

	Role(guildID, roleID discord.Snowflake) (*discord.Role, error)
	Roles(guildID discord.Snowflake) ([]discord.Role, error)
}

type StoreModifier interface {
	MyselfSet(me *discord.User) error

	// ChannelSet should switch on Type to know if it's a private channel or
	// not.
	ChannelSet(*discord.Channel) error
	ChannelRemove(*discord.Channel) error

	// EmojiSet should delete all old emojis before setting new ones.
	EmojiSet(guildID discord.Snowflake, emojis []discord.Emoji) error

	GuildSet(*discord.Guild) error
	GuildRemove(id discord.Snowflake) error

	MemberSet(guildID discord.Snowflake, member *discord.Member) error
	MemberRemove(guildID, userID discord.Snowflake) error

	MessageSet(*discord.Message) error
	MessageRemove(channelID, messageID discord.Snowflake) error

	PresenceSet(guildID discord.Snowflake, presence *discord.Presence) error
	PresenceRemove(guildID, userID discord.Snowflake) error

	RoleSet(guildID discord.Snowflake, role *discord.Role) error
	RoleRemove(guildID, roleID discord.Snowflake) error

	// This should reset all the state to zero/null.
	Reset() error
}

// ErrStoreNotFound is an error that a store can use to return when something
// isn't in the storage. There is no strict restrictions on what uses this (the
// default one does, though), so be advised.
var ErrStoreNotFound = errors.New("item not found in store")

// Helper functions

func handleGuildCreate(s *State, guild *gateway.GuildCreateEvent) {
	if err := s.Store.GuildSet(&guild.Guild); err != nil {
		s.stateErr(err, "Failed to set guild in Ready")
	}

	// Handle guild emojis
	if guild.Emojis != nil {
		if err := s.Store.EmojiSet(guild.ID, guild.Emojis); err != nil {
			s.stateErr(err, "Failed to set guild emojis")
		}
	}

	// Handle guild member
	for i := range guild.Members {
		if err := s.Store.MemberSet(guild.ID, &guild.Members[i]); err != nil {
			s.stateErr(err, "Failed to set guild member in Ready")
		}
	}

	// Handle guild channels
	for i := range guild.Channels {
		if err := s.Store.ChannelSet(&guild.Channels[i]); err != nil {
			s.stateErr(err, "Failed to set guild channel in Ready")
		}
	}

	// Handle guild presences
	for i := range guild.Presences {
		if err := s.Store.PresenceSet(guild.ID, &guild.Presences[i]); err != nil {
			s.stateErr(err, "Failed to set guild presence in Ready")
		}
	}
}