package storage

import (
	"context"
	"crypto/md5"
	"encoding/base64"
	"encoding/json"
	"fmt"
	"io/ioutil"
	"log"
	"os"
	"path/filepath"

	"github.com/emersion/go-vcard"
	"github.com/emersion/go-webdav/carddav"

	"git.sr.ht/~sircmpwn/tokidoki/auth"
)

type filesystemBackend struct {
	path string
}

var nilBackend carddav.Backend = (*filesystemBackend)(nil)

func NewFilesystem(path string) (carddav.Backend, error) {
	info, err := os.Stat(path)
	if err != nil {
		return nilBackend, fmt.Errorf("failed to create filesystem backend: %s", err.Error())
	}
	if !info.IsDir() {
		return nilBackend, fmt.Errorf("base path for filesystem backend must be a directory")
	}
	return &filesystemBackend{
		path: path,
	}, nil
}

func (b *filesystemBackend) pathForContext(ctx context.Context) (string, error) {
	raw := ctx.Value(auth.AuthCtxKey)
	if raw == nil {
		return b.path, nil
	}
	authCtx, ok := raw.(*auth.AuthContext)
	if !ok {
		panic("Invalid data in auth context!")
	}
	//TODO sanitize user name or at least check if valid dir name?
	path := filepath.Join(b.path, authCtx.UserName)

	_, err := os.Stat(path)
	if os.IsNotExist(err) {
		err = os.Mkdir(path, 0755)
		if err != nil {
			return "", fmt.Errorf("error creating '%s': %s", path, err.Error())
		}
	}
	return path, nil
}

func etagForFile(path string) (string, error) {
	data, err := ioutil.ReadFile(path)
	if err != nil {
		return "", err
	}
	csum := md5.Sum(data)
	return base64.StdEncoding.EncodeToString(csum[:]), nil
}

func vcardFromFile(path string) (*vcard.Card, error) {
	f, err := os.Open(path)
	if err != nil {
		return nil, err
	}
	defer f.Close()

	dec := vcard.NewDecoder(f)
	card, err := dec.Decode()
	if err != nil {
		return nil, err
	}

	return &card, nil
}

func createDefaultAddressBook(path string) error {
	// TODO what should the default address book look like?
	defaultAB := carddav.AddressBook{
		Path:                 "/default",
		Name:                 "My contacts",
		Description:          "Default address book",
		MaxResourceSize:      1024,
		SupportedAddressData: []carddav.AddressDataType{},
	}
	blob, err := json.MarshalIndent(defaultAB, "", "  ")
	if err != nil {
		return fmt.Errorf("error creating default address book: %s", err.Error())
	}
	err = os.WriteFile(path, blob, 0644)
	if err != nil {
		return fmt.Errorf("error writing default address book: %s", err.Error())
	}
	return nil
}

func (b *filesystemBackend) AddressBook(ctx context.Context) (*carddav.AddressBook, error) {
	path, err := b.pathForContext(ctx)
	if err != nil {
		return nil, err
	}
	path = filepath.Join(path, "default.json")
	_, err = os.Stat(path)
	if os.IsNotExist(err) {
		err = createDefaultAddressBook(path)
		if err != nil {
			return nil, err
		}
	} else if err != nil {
		return nil, fmt.Errorf("error opening address book: %s", err.Error())
	}

	data, err := ioutil.ReadFile(path)
	if err != nil {
		return nil, fmt.Errorf("error opening address book: %s", err.Error())
	}
	var addressBook carddav.AddressBook
	err = json.Unmarshal(data, &addressBook)
	if err != nil {
		return nil, fmt.Errorf("error reading address book: %s", err.Error())
	}

	return &addressBook, nil
}

func (b *filesystemBackend) GetAddressObject(ctx context.Context, path string, req *carddav.AddressDataRequest) (*carddav.AddressObject, error) {
	basePath, err := b.pathForContext(ctx)
	if err != nil {
		return nil, err
	}
	path = filepath.Join(basePath, path)

	info, err := os.Stat(path)
	if err != nil {
		return nil, err
	}

	card, err := vcardFromFile(path)
	if err != nil {
		return nil, err
	}

	etag, err := etagForFile(path)
	if err != nil {
		return nil, err
	}

	obj := carddav.AddressObject{
		Path: "/" + filepath.Base(path),
		ModTime: info.ModTime(),
		ETag: etag,
		Card: *card,
	}
	return &obj, nil
}

func (b *filesystemBackend) ListAddressObjects(ctx context.Context, req *carddav.AddressDataRequest) ([]carddav.AddressObject, error) {
	result := []carddav.AddressObject{}

	path, err := b.pathForContext(ctx)
	if err != nil {
		return result, err
	}

	err = filepath.Walk(path, func(filename string, info os.FileInfo, err error) error {
		// TODO this heuristic will not work for all clients
		if filepath.Ext(filename) != ".vcf" {
			return nil
		}

		card, err := vcardFromFile(filename)
		if err != nil {
			return err
		}

		etag, err := etagForFile(filename)
		if err != nil {
			return err
		}

		obj := carddav.AddressObject{
			Path: "/" + filepath.Base(filename),
			ModTime: info.ModTime(),
			ETag: etag,
			Card: *card,
		}
		result = append(result, obj)
		return nil
	})
	if err != nil {
		panic(err)
	}

	return result, nil
}

func (*filesystemBackend) QueryAddressObjects(ctx context.Context, query *carddav.AddressBookQuery) ([]carddav.AddressObject, error) {
	// TODO
	log.Println("QueryAddressObjects called, not implemented")
	return []carddav.AddressObject{}, nil
}

func (b *filesystemBackend) PutAddressObject(ctx context.Context, path string, card vcard.Card) (loc string, err error) {
	basePath, err := b.pathForContext(ctx)
	if err != nil {
		return "", err
	}
	path = filepath.Join(basePath, path)
	f, err := os.OpenFile(path, os.O_RDWR|os.O_CREATE, 0644)
	if err != nil {
		return "", err
	}
	defer f.Close()

	enc := vcard.NewEncoder(f)
	err = enc.Encode(card)
	if err != nil {
		return "", err
	}

	return path, nil
}

func (b *filesystemBackend) DeleteAddressObject(ctx context.Context, path string) error {
	basePath, err := b.pathForContext(ctx)
	if err != nil {
		return err
	}
	path = filepath.Join(basePath, path)
	//TODO does this need more security/sanity checks?
	err = os.Remove(path)
	if err != nil {
		return err
	}
	return nil
}