package topic

import (
	"context"
	"fmt"
	"log"
	"sync"

	"github.com/jackc/pgconn"
)

type Database interface {
	Exec(ctx context.Context, query string, args ...interface{}) (pgconn.CommandTag, error)
}

type Topic struct {
	CreateTable func(ctx context.Context, db Database) error
	Store       func(ctx context.Context, db Database, packet *Packet) error
}

var registry = struct {
	topics map[string]*Topic
	lock   *sync.Mutex
}{
	topics: map[string]*Topic{},
	lock:   new(sync.Mutex),
}

func Register(topic string, handler *Topic) {
	registry.lock.Lock()
	defer registry.lock.Unlock()

	if _, ok := registry.topics[topic]; ok {
		panic(fmt.Sprintf("attempt to register pht '%s' that has already been registered", topic))
	}

	registry.topics[topic] = handler
}

type Packet struct {
	Topic     string
	Publisher string
	Received  int64 // unix timestamp
	Payload   []byte
}

// Setup ensures all the required tables are created.
func Setup(ctx context.Context, db Database) error {
	registry.lock.Lock()
	defer registry.lock.Unlock()

	for key, topic := range registry.topics {
		log.Println("running CreateTable for", key)
		err := topic.CreateTable(ctx, db)
		if err != nil {
			return err
		}
	}

	return nil
}

func Publish(ctx context.Context, db Database, packet *Packet) error {
	topic, ok := registry.topics[packet.Topic]
	if !ok {
		return fmt.Errorf("topic: no handler for topic '%s' [%x]", packet.Topic, packet.Payload)
	}

	return topic.Store(ctx, db, packet)
}