package database

import (
	"encoding/json"
	"fmt"
	"io"
	"log"
	"os"

	"git.phc.dm.unipi.it/phc/storage/store"
	"golang.org/x/exp/slices"
)

type MonitorWidget struct {
	Type  string `json:"type"`
	Value any    `json:"value"`
}

type DashboardState struct {
	Widgets []MonitorWidget `json:"widgets"`
}

type Database interface {
	// Dashboard DashboardState

	GetDashboardState() (DashboardState, error)
	SetDashboardState(DashboardState) error

	// Bucket Operations

	CreateBucket(bucket string, options ...any) error
	DeleteBucket(bucket string) error

	AllBuckets() ([]string, error)

	// Bucket Object Operations

	CreateBucketObject(bucket string, r io.Reader) (string, error)
	DeleteBucketObject(bucket, id string) error

	GetBucketObject(bucket, id string, w io.Writer) error
	SetBucketObject(bucket, id string, r io.Reader) error

	AllBucketObjects(bucket string) ([]string, error)
}

type jsonBucket struct {
	Name    string   `json:"name"`
	Path    string   `json:"path"`
	Objects []string `json:"objects"`
}

type jsonDB struct {
	file string

	PrefixSize int `json:"prefixSize"`

	DashboardState DashboardState         `json:"dashboardState"`
	Buckets        map[string]*jsonBucket `json:"buckets"`
}

func NewJSON(file string) Database {
	db := &jsonDB{
		file:       file,
		PrefixSize: 2,
		DashboardState: DashboardState{
			Widgets: []MonitorWidget{},
		},
		Buckets: map[string]*jsonBucket{},
	}

	err := db.load()
	if err != nil {
		panic(err)
	}

	return db
}

func (db *jsonDB) setup() error {
	if _, err := os.Stat(db.file); !os.IsNotExist(err) {
		return nil
	}

	log.Printf("missing %q, creating empty database file", db.file)

	f, err := os.Create(db.file)
	defer f.Close()
	if err != nil {
		return err
	}

	enc := json.NewEncoder(f)
	enc.SetIndent("", "    ")
	if err := enc.Encode(&db); err != nil {
		return err
	}

	return nil
}

func (db *jsonDB) store() error {
	f, err := os.Create(db.file)
	defer f.Close()
	if err != nil {
		return err
	}

	enc := json.NewEncoder(f)
	enc.SetIndent("", "    ")
	if err := enc.Encode(&db); err != nil {
		return err
	}

	return nil
}

func (db *jsonDB) load() error {
	if err := db.setup(); err != nil {
		return err
	}

	f, err := os.Open(db.file)
	defer f.Close()
	if err != nil {
		return err
	}

	if err := json.NewDecoder(f).Decode(&db); err != nil {
		return err
	}

	return nil
}

func (db *jsonDB) GetDashboardState() (DashboardState, error) {
	db.load()

	return db.DashboardState, nil
}

func (db *jsonDB) SetDashboardState(state DashboardState) error {
	db.load()
	db.DashboardState = state

	db.store()
	return nil
}

func (db *jsonDB) CreateBucket(bucket string, options ...any) error {
	db.load()

	if _, found := db.Buckets[bucket]; found {
		return fmt.Errorf("bucket named %q already present", bucket)
	}

	bi := &jsonBucket{
		Name:    bucket,
		Path:    bucket + "/",
		Objects: []string{},
	}
	if len(options) > 0 {
		bi.Path = options[0].(string)
	}

	db.Buckets[bucket] = bi

	db.store()
	return nil
}

func (db *jsonDB) DeleteBucket(bucket string) error {
	db.load()

	if _, found := db.Buckets[bucket]; !found {
		return fmt.Errorf("bucket named %q not found", bucket)
	}

	delete(db.Buckets, bucket)

	log.Printf("The bucket named %q was removed but its files are still on disk", bucket)

	db.store()
	return nil
}

func (db *jsonDB) AllBuckets() ([]string, error) {
	db.load()

	buckets := make([]string, 0, len(db.Buckets))

	for _, b := range db.Buckets {
		buckets = append(buckets, b.Name)
	}

	return buckets, nil
}

func (db *jsonDB) CreateBucketObject(bucket string, r io.Reader) (string, error) {
	db.load()

	b, found := db.Buckets[bucket]
	if !found {
		return "", fmt.Errorf("bucket named %q not found", bucket)
	}

	id, err := store.Create(b.Path, db.PrefixSize, r)
	if err != nil {
		return "", err
	}

	b.Objects = append(b.Objects, id)

	db.store()
	return id, err
}

func (db *jsonDB) SetBucketObject(bucket, id string, r io.Reader) error {
	db.load()

	b, found := db.Buckets[bucket]
	if !found {
		return fmt.Errorf("bucket named %q not found", bucket)
	}

	db.store()
	return store.Update(b.Path, db.PrefixSize, id, r)
}

func (db *jsonDB) GetBucketObject(bucket, id string, w io.Writer) error {
	db.load()

	b, found := db.Buckets[bucket]
	if !found {
		return fmt.Errorf("bucket named %q not found", bucket)
	}

	return store.Read(b.Path, db.PrefixSize, id, w)
}

func (db *jsonDB) DeleteBucketObject(bucket, id string) error {
	db.load()

	b, found := db.Buckets[bucket]
	if !found {
		return fmt.Errorf("bucket named %q not found", bucket)
	}

	if err := store.Delete(b.Path, db.PrefixSize, id); err != nil {
		return err
	}

	i := slices.Index(b.Objects, id)
	b.Objects = append(b.Objects[:i], b.Objects[i+1:]...)

	db.store()
	return nil
}

func (db *jsonDB) AllBucketObjects(bucket string) ([]string, error) {
	db.load()

	b, found := db.Buckets[bucket]
	if !found {
		return nil, fmt.Errorf("bucket named %q not found", bucket)
	}

	objects, err := store.All(b.Path)
	if err != nil {
		return nil, err
	}

	b.Objects = objects

	db.store()
	return b.Objects, nil
}