package client

import (
	"encoding/binary"
	"fmt"
	"net/http"
	"time"

	"git.tijl.dev/tijl/shortify/pkg/generation"
	bolt "go.etcd.io/bbolt"
)

type Client struct {
	serverURL  string
	httpClient *http.Client
	prefix     uint16
	gen        *generation.Generator

	db         *bolt.DB
	retryQueue chan shortenJob
	stopRetry  chan struct{}
}

// NewClient with persistence and retry queue
func NewClient(serverURL string, folder string) (*Client, error) {
	httpClient, baseURL, err := createHTTPClient(serverURL)
	if err != nil {
		return nil, err
	}

	db, err := bolt.Open(folder+"/"+dbFileName, 0600, &bolt.Options{Timeout: 1 * time.Second})
	if err != nil {
		return nil, err
	}

	cli := &Client{
		serverURL:  baseURL,
		httpClient: httpClient,
		db:         db,
		retryQueue: make(chan shortenJob, 1000),
		stopRetry:  make(chan struct{}),
	}

	// Create buckets if not exist
	err = db.Update(func(tx *bolt.Tx) error {
		_, err := tx.CreateBucketIfNotExists([]byte(bucketPrefix))
		if err != nil {
			return err
		}
		_, err = tx.CreateBucketIfNotExists([]byte(bucketRetryJobs))
		return err
	})
	if err != nil {
		return nil, err
	}

	// Load or get prefix
	var prefix uint16
	err = db.View(func(tx *bolt.Tx) error {
		b := tx.Bucket([]byte(bucketPrefix))
		v := b.Get([]byte("prefix"))
		if v == nil {
			return nil
		}
		if len(v) != 2 {
			return fmt.Errorf("invalid prefix length in db")
		}
		prefix = binary.BigEndian.Uint16(v)
		return nil
	})
	if err != nil {
		return nil, err
	}

	// If prefix not found, register new one and save it
	if prefix == 0 {
		prefix, err = cli.registerPrefix()
		if err != nil {
			return nil, err
		}
		err = db.Update(func(tx *bolt.Tx) error {
			b := tx.Bucket([]byte(bucketPrefix))
			buf := make([]byte, 2)
			binary.BigEndian.PutUint16(buf, prefix)
			return b.Put([]byte("prefix"), buf)
		})
		if err != nil {
			return nil, err
		}
	}
	cli.prefix = prefix
	cli.gen = generation.NewGenerator(prefix)

	// Load retry jobs from DB into channel
	go cli.loadRetryJobs()

	// Start retry worker
	go cli.retryWorker()

	return cli, nil
}

// Shorten creates a short URL and sends it async to the central server
func (c *Client) Shorten(longURL string) string {
	shortID := c.gen.NextID()

	go c.enqueueJob(shortenJob{
		ID:  shortID,
		URL: longURL,
	})

	return shortID
}