package bm

import (
	"context"
	"database/sql"
	"errors"

	chatcontracts "git.golem15.com/golem15/sm-chat-plugin/contracts"
	chanclasses "git.golem15.com/golem15/sm-chatchannels-plugin/classes"
	"git.golem15.com/golem15/summercms/modules/backpack"
	"git.golem15.com/golem15/summercms/modules/lagoon"
	"git.golem15.com/jakub/sm-bm-plugin/classes"
	"gorm.io/gorm"
)

// The chat config keys and their fallbacks (config/config.yaml).
const (
	configChatGroup          = "jz.bm.chat.group"
	configChatModeratorGroup = "jz.bm.chat.moderator_group"
	configChatMaxUpload      = "jz.bm.chat.max_upload_bytes"
	configChatMaxEmbeds      = "jz.bm.chat.max_embeds"

	defaultChatGroup          = "studenci"
	defaultChatModeratorGroup = "moderatorzy"
	defaultChatMaxUpload      = 62914560
	defaultChatMaxEmbeds      = 3
)

// registerChat makes jz.bm the host of the BM chat: it registers the bm
// context alias on golem15.chat's registry and installs the channel access
// policy. Without golem15.chat it does nothing, so jz.bm keeps working (and
// its tests keep activating) without the chat plugins; jz.bm does not
// Require them.
func (p *Plugin) registerChat(app *backpack.App) error {
	if app == nil || !app.HasPlugin("golem15.chat") {
		return nil
	}
	reg, ok := app.Lookup[*chatcontracts.Registry]()
	if !ok || reg == nil {
		return errors.New("jz.bm: golem15.chat must be listed before jz.bm in summer.yaml")
	}
	if err := reg.Add(p.ID(), chatcontracts.Registration{Alias: classes.ChatContextType, Loader: p.loadChatContext}); err != nil {
		return err
	}
	return p.installChatAccess(app)
}

// loadChatContext is the loader of the bm alias. The only context is id 1;
// any other id is unknown, which golem15.chat answers with its not-a-member
// error.
func (p *Plugin) loadChatContext(ctx context.Context, db *gorm.DB, id uint) (chatcontracts.Context, error) {
	return classes.ChatContextLoader(p.chatGroup, p.chatModeratorGroup)(ctx, db, id)
}

// installChatAccess installs BM's access policy on golem15.chatchannels'
// channel service. The service is published from chatchannels' own
// database hook, which runs before this one because chatchannels boots
// first; under a database-less boot (tests, route:list) neither runs.
func (p *Plugin) installChatAccess(app *backpack.App) error {
	if app == nil || !app.HasPlugin("golem15.chatchannels") {
		return nil
	}
	return lagoon.OnDatabase(app, func(_ *sql.DB, _ *gorm.DB) error {
		svc, ok := app.Lookup[*chanclasses.ChannelService]()
		if !ok || svc == nil {
			return errors.New("jz.bm: golem15.chatchannels must be listed before jz.bm in summer.yaml")
		}
		svc.SetAccessResolver(classes.NewChatAccess(p.database, p.chatGroup(), nil))
		return nil
	})
}

// database returns the published application database, or nil.
func (p *Plugin) database() *gorm.DB {
	if p.app == nil {
		return nil
	}
	db, _ := p.app.Lookup[*gorm.DB]()
	return db
}

// chatGroup is the code of the user group whose members are in the chat.
func (p *Plugin) chatGroup() string {
	return p.configString(configChatGroup, defaultChatGroup)
}

// chatModeratorGroup is the code of the user group whose members moderate
// the chat's channels.
func (p *Plugin) chatModeratorGroup() string {
	return p.configString(configChatModeratorGroup, defaultChatModeratorGroup)
}

// chatMaxUploadBytes is the total attachment size of one message.
func (p *Plugin) chatMaxUploadBytes() int {
	return p.configInt(configChatMaxUpload, defaultChatMaxUpload)
}

// chatMaxEmbeds is the number of entity embeds one message may carry.
func (p *Plugin) chatMaxEmbeds() int {
	return p.configInt(configChatMaxEmbeds, defaultChatMaxEmbeds)
}

func (p *Plugin) configString(key, fallback string) string {
	if p.app == nil || p.app.Config == nil {
		return fallback
	}
	if v := p.app.Config.String(key); v != "" {
		return v
	}
	return fallback
}

func (p *Plugin) configInt(key string, fallback int) int {
	if p.app == nil || p.app.Config == nil {
		return fallback
	}
	if v := p.app.Config.Int(key); v > 0 {
		return v
	}
	return fallback
}