package haberdasherserver

import (
	"context"
	"encoding/binary"
	"encoding/json"
	"fmt"
	"math/rand"
	"os"

	"github.com/boltdb/bolt"
	"github.com/twitchtv/twirp"

	pb "haberdasher-twirp/haberdasher"
)

const dbBucket = "hats"

type Server struct {
	DBPath string
}

type Hat struct {
	Inches int32  `json:"inches"`
	Color  string `json:"color"`
	Name   string `json:"name"`
}

type HatQuery struct {
	Limit int32
}

type Store struct {
	db *bolt.DB
}

func HatToHatModel(h *pb.Hat) Hat {
	return Hat{
		Inches: h.Inches,
		Color:  h.Color,
		Name:   h.Name,
	}
}

func HatModelToHat(h Hat) *pb.Hat {
	return &pb.Hat{
		Inches: h.Inches,
		Color:  h.Color,
		Name:   h.Name,
	}
}

func HatsModelToHats(hs []Hat) (hats *pb.Hats) {
	hats = &pb.Hats{}
	for _, h := range hs {
		hat := HatModelToHat(h)
		hats.Hats = append(hats.Hats, hat)
	}
	return hats
}

func HatQueryToHatQueryModel(q *pb.HatQuery) HatQuery {
	return HatQuery{
		Limit: q.Limit,
	}
}

func (s *Server) MakeHat(ctx context.Context, size *pb.Size) (hat *pb.Hat, err error) {
	st, _ := NewStore(s.DBPath, 0600, nil)
	defer st.Close()

	if size.Inches <= 0 {
		return nil, twirp.InvalidArgumentError("inches", "I can't make a hat that small!")
	}

	h := Hat{
		Inches: size.Inches,
		Color:  []string{"white", "black", "red", "blue"}[rand.Intn(4)],
		Name:   []string{"bowler", "baseball cap", "top hat", "derby"}[rand.Intn(3)],
	}

	fmt.Printf("made hat: %+v\n", h)

	st.SaveHat(h)

	return HatModelToHat(h), nil
}

func (s *Server) ListHats(ctx context.Context, q *pb.HatQuery) (hats *pb.Hats, err error) {
	st, _ := NewStore(s.DBPath, 0600, nil)
	defer st.Close()

	hs, err := st.ListHats(HatQueryToHatQueryModel(q))

	return HatsModelToHats(hs), nil
}

func itob(v uint64) []byte {
	b := make([]byte, 8)
	binary.BigEndian.PutUint64(b, uint64(v))
	return b
}

func btoi(b []byte) uint64 {
	return binary.BigEndian.Uint64(b)
}

func NewStore(path string, mode os.FileMode, options *bolt.Options) (s *Store, err error) {
	s = &Store{}
	s.db, err = bolt.Open(path, mode, options)
	if err != nil {
		fmt.Printf("bolt open: %s", err)
	}

	s.db.Update(func(tx *bolt.Tx) error {
		if _, err := tx.CreateBucket([]byte(dbBucket)); err != nil {
			return fmt.Errorf("create bucket: %s", err)
		}
		return nil
	})

	return s, err
}

func (s *Store) SaveHat(h Hat) (err error) {
	return s.db.Update(func(tx *bolt.Tx) error {
		b := tx.Bucket([]byte("hats"))

		id, _ := b.NextSequence()

		buf, err := json.Marshal(h)
		if err != nil {
			return fmt.Errorf("json marshal: %s", err)
		}

		return b.Put(itob(id), buf)
	})
}

func (s *Store) ListHats(q HatQuery) (hats []Hat, err error) {
	var hat Hat
	var i int

	s.db.View(func(tx *bolt.Tx) error {
		b := tx.Bucket([]byte("hats"))

		c := b.Cursor()

		for k, v := c.Last(); k != nil && i < int(q.Limit); k, v = c.Prev() {
			if err := json.Unmarshal(v, &hat); err != nil {
				return fmt.Errorf("json unmarshal: %s", err)
			}
			h := hat
			hats = append(hats, h)
			i++
		}

		return nil
	})

	return hats, nil
}

func (s *Store) Close() (err error) {
	return s.db.Close()
}