// Copyright © 2023 Roberto Hidalgo <event-gateway@un.rob.mx>
// SPDX-License-Identifier: Apache-2.0
package source

import (
	"fmt"

	"git.rob.mx/nidito/chinampa/pkg/logger"
	"git.rob.mx/nidito/event-gateway/internal/config"
	"git.rob.mx/nidito/event-gateway/internal/source/types"
)

var log = logger.Sub("event-gateway.manager")

type Manager struct {
	Sources   map[types.Kind]config.Source
	Config    config.Loader
	Ready     bool
	listeners map[string]*config.Listener
}

func (m *Manager) AddSource(src config.Source) {
	if m.Sources == nil {
		m.Sources = map[types.Kind]config.Source{}
	}
	m.Sources[src.Kind()] = src
}

func (m *Manager) Listen(cfg config.Loader) error {
	m.Config = cfg
	for _, src := range m.Sources {
		src.Initialize()
	}

	if err := m.watchConfig(); err != nil {
		return fmt.Errorf("could not initialize config loading: %s", err)
	}

	return nil
}

func (m *Manager) watchConfig() error {
	updates := make(chan []*config.Listener, 1)
	go func() {
		for {
			listeners := <-updates
			log.Debugf("manager got updated listeners with count %d", len(listeners))
			if err := m.onUpdate(listeners); err != nil {
				log.Errorf("could not process updated listeners: %s", err)
			}
		}
	}()

	log.Debugf("Loading configuration with %s", m.Config)
	res, err := m.Config.Load()
	if err != nil {
		return fmt.Errorf("error loading config using %s: %s", m.Config, err)
	}
	log.Debugf("Loaded configuration with %s, starting watch", m.Config)

	updates <- res
	m.Config.Watch(updates)

	return nil
}

func (m *Manager) onUpdate(listeners []*config.Listener) error {
	updated := map[string]*config.Listener{}
	for _, l := range listeners {
		src, srcExists := m.Sources[l.Source.Kind]
		if !srcExists {
			return fmt.Errorf("unknown source kind <%s> for %s: %+v", l.Source.Kind, l.ID, l)
		}

		if l.Event == nil {
			return fmt.Errorf("sink configuration for %s not provided: %+v", l.ID, l)
		}

		action := "registered"
		if existing, exists := m.listeners[l.ID]; exists {
			if l.Hash == existing.Hash {
				log.Infof("Same configuration for %s, will not reload", l.ID)
				updated[l.ID] = l
				continue
			}
			log.Infof("Reloading configuration for %s", l.ID)
			src.Deregister(l.ID)
			action = "reloaded"
		} else {
			log.Debugf("registering %s with source %s", l.ID, l.Source.Kind)
		}

		if err := src.Register(l); err != nil {
			log.Errorf("could not register %s with source %s: %s", l.Source.Kind, l.ID, err)
		}
		log.Infof("%s %s in source %s", action, l.ID, l.Source.Kind)
		updated[l.ID] = l
	}

	for id, l := range m.listeners {
		if _, exists := updated[id]; !exists {
			log.Infof("Deleting listener for %s as it's no longer in configuration", l.ID)
			m.Sources[l.Source.Kind].Deregister(id)
		}
	}

	m.listeners = updated
	m.Ready = true

	return nil
}