package classes

import (
	"context"

	chatcontracts "git.golem15.com/golem15/sm-chat-plugin/contracts"
	userclasses "git.golem15.com/golem15/sm-user-plugin/classes"
	"gorm.io/gorm"
)

var _ chatcontracts.Context = (*ChatContext)(nil)

// The BM chat context: one context of type bm with id 1, whose members are
// the members of one user group.
const (
	// ChatContextType is the context alias (context_type) jz.bm registers on
	// golem15.chat.
	ChatContextType = "bm"
	// ChatContextID is the id of the one BM chat context.
	ChatContextID uint = 1
	// ChatGeneralName is the name of the group conversation and its channel.
	ChatGeneralName = "ogólny"
	// ChatGeneralSlug is the slug of the adopted channel.
	ChatGeneralSlug = "ogolny"
	// ChatBroadcastChannel is the host channel golem15.chat publishes created
	// events to. It must never be empty: an empty host channel silences the
	// conversation channels too. No client can subscribe to it, because the
	// chat authorizer only admits chat:conversation:{id}.
	ChatBroadcastChannel = "chat:context:1"
)

// ChatContext is the golem15.chat context of the BM chat. Membership is the
// user group named by group; nobody oversees other people's chats, so a
// moderator reads no DM and edits no foreign message.
type ChatContext struct {
	db             *gorm.DB
	group          string
	moderatorGroup string
}

// NewChatContext returns the BM chat context over db for the chat group
// code group and the moderator group code moderatorGroup.
func NewChatContext(db *gorm.DB, group, moderatorGroup string) *ChatContext {
	return &ChatContext{db: db, group: group, moderatorGroup: moderatorGroup}
}

func (c *ChatContext) ID() uint                 { return ChatContextID }
func (c *ChatContext) Type() string             { return ChatContextType }
func (c *ChatContext) ChatEnabled() bool        { return true }
func (c *ChatContext) GroupName() string        { return ChatGeneralName }
func (c *ChatContext) BroadcastChannel() string { return ChatBroadcastChannel }

// CanActFor is the default: a user acts only for themself.
func (c *ChatContext) CanActFor(ctx context.Context, actorID, memberID uint) bool {
	return chatcontracts.DefaultCanActFor(ctx, actorID, memberID)
}

// CanOverseeChats is always false. golem15.chat grants an overseer read
// access to every conversation and edits of other people's messages, which
// no BM user gets; moderators delete through a narrower hook.
func (c *ChatContext) CanOverseeChats(context.Context, uint) (bool, error) {
	return false, nil
}

// HasMember reports whether userID is in the chat group.
func (c *ChatContext) HasMember(ctx context.Context, userID uint) (bool, error) {
	if userID == 0 || c.group == "" {
		return false, nil
	}
	return userclasses.HasGroupCode(ctx, c.db, userID, c.group)
}

// Members lists the ids of the chat group's users that are not deleted.
func (c *ChatContext) Members(ctx context.Context) ([]uint, error) {
	ids := []uint{}
	if c.group == "" {
		return ids, nil
	}
	err := c.db.WithContext(ctx).
		Table("users_groups").
		Joins("JOIN user_groups ON user_groups.id = users_groups.user_group_id").
		Joins("JOIN users ON users.id = users_groups.user_id").
		Where("user_groups.code = ? AND users.deleted_at IS NULL", c.group).
		Distinct().
		Order("users_groups.user_id").
		Pluck("users_groups.user_id", &ids).Error
	if err != nil {
		return nil, err
	}
	return ids, nil
}