package filesharing

import (
	"crypto/rand"
	"cwtch.im/cwtch/model"
	"cwtch.im/cwtch/model/attr"
	"cwtch.im/cwtch/peer"
	"cwtch.im/cwtch/protocol/files"
	"encoding/hex"
	"encoding/json"
	"errors"
	"fmt"
	"git.openprivacy.ca/openprivacy/log"
	"io"
	"math"
	path "path/filepath"
	"strconv"
)

// Functionality groups some common UI triggered functions for contacts...
type Functionality struct {
}

// FunctionalityGate returns contact.Functionality always
func FunctionalityGate(experimentMap map[string]bool) (*Functionality, error) {
	if experimentMap["filesharing"] == true {
		return new(Functionality), nil
	}
	return nil, errors.New("filesharing is not enabled")
}

// OverlayMessage presents the canonical format of the File Sharing functionality Overlay Message
// This is the format that the UI will parse to display the message
type OverlayMessage struct {
	Name  string `json:"f"`
	Hash  string `json:"h"`
	Nonce string `json:"n"`
	Size  uint64 `json:"s"`
}

// DownloadFile given a profile, a conversation handle and a file sharing key, start off a download process
// to downloadFilePath
func (f *Functionality) DownloadFile(profile peer.CwtchPeer, handle string, downloadFilePath string, manifestFilePath string, key string) {

	// Store local.filesharing.filekey.manifest as the location of the manifest
	profile.SetScopedZonedAttribute(attr.LocalScope, attr.FilesharingZone, fmt.Sprintf("%s.manifest", key), manifestFilePath)

	// Store local.filesharing.filekey as the location of the download
	profile.SetScopedZonedAttribute(attr.LocalScope, attr.FilesharingZone, key, downloadFilePath)

	// Get the value of conversation.filesharing.filekey.manifest.size from `handle`
	profile.SendScopedZonedGetValToContact(handle, attr.ConversationScope, attr.FilesharingZone, fmt.Sprintf("%s.manifest.size", key))
}

// ShareFile given a profile and a conversation handle, sets up a file sharing process to share the file
// at filepath
func (f *Functionality) ShareFile(filepath string, profile peer.CwtchPeer, handle string) error {
	manifest, err := files.CreateManifest(filepath)
	if err != nil {
		return err
	}

	var nonce [24]byte
	if _, err := io.ReadFull(rand.Reader, nonce[:]); err != nil {
		log.Errorf("Cannot read from random: %v\n", err)
		return err
	}

	message := OverlayMessage{
		Name:  path.Base(manifest.FileName),
		Hash:  hex.EncodeToString(manifest.RootHash),
		Nonce: hex.EncodeToString(nonce[:]),
		Size:  manifest.FileSizeInBytes,
	}

	data, _ := json.Marshal(message)

	wrapper := model.MessageWrapper{
		Overlay: model.OverlayFileSharing,
		Data:    string(data),
	}

	wrapperJSON, _ := json.Marshal(wrapper)
	key := fmt.Sprintf("%x.%x", manifest.RootHash, nonce)
	serializedManifest, _ := json.Marshal(manifest)

	// Store the size of the manifest (in chunks) as part of the public scope so contacts who we share the file with
	// can fetch the manifest as if it were a file.
	// manifest.FileName gets redacted in filesharing_subsystem (to remove the system-specific file hierarchy),
	// but we need to *store* the full path because the sender also uses it to locate the file
	lenDiff := len(filepath) - len(path.Base(filepath))
	profile.SetScopedZonedAttribute(attr.ConversationScope, attr.FilesharingZone, fmt.Sprintf("%s.manifest.size", key), strconv.Itoa(int(math.Ceil(float64(len(serializedManifest)-lenDiff)/float64(files.DefaultChunkSize)))))

	profile.ShareFile(key, string(serializedManifest))

	profile.SendMessage(handle, string(wrapperJSON))

	return nil
}