package filesharing

import (
	"crypto/rand"
	"encoding/hex"
	"encoding/json"
	"errors"
	"fmt"
	"io"
	"math"
	"os"
	path "path/filepath"
	"regexp"
	"strconv"
	"strings"
	"time"

	"cwtch.im/cwtch/model"
	"cwtch.im/cwtch/model/attr"
	"cwtch.im/cwtch/peer"
	"cwtch.im/cwtch/protocol/files"
	"git.openprivacy.ca/openprivacy/log"
)

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

// FunctionalityGate returns filesharing if enabled in the given experiment map
// Note: Experiment maps are currently in libcwtch-go
func FunctionalityGate(experimentMap map[string]bool) (*Functionality, error) {
	if experimentMap["filesharing"] {
		return new(Functionality), nil
	}
	return nil, errors.New("filesharing is not enabled")
}

func PreviewFunctionalityGate(experimentMap map[string]bool) (*Functionality, error) {
	if experimentMap["filesharing"] == true && experimentMap["filesharing-images"] == true {
		return new(Functionality), nil
	}
	return nil, errors.New("image previews are 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"`
}

func (om *OverlayMessage) FileKey() string {
	return fmt.Sprintf("%s.%s", om.Hash, om.Nonce)
}

// checks file size and file name. *DOES NOT* check user settings or contact state
func (om *OverlayMessage) ShouldAutoDL() bool {
	lname := strings.ToLower(om.Name)
	return om.Size <= 20971520 && (strings.HasSuffix(lname, "jpg") || strings.HasSuffix(lname, "jpeg") || strings.HasSuffix(lname, "png") || strings.HasSuffix(lname, "gif") || strings.HasSuffix(lname, "webp") || strings.HasSuffix(lname, "bmp"))
}

// 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, conversationID int, 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.path as the location of the download
	profile.SetScopedZonedAttribute(attr.LocalScope, attr.FilesharingZone, fmt.Sprintf("%s.path", key), downloadFilePath)

	// Get the value of conversation.filesharing.filekey.manifest.size from `handle`
	profile.SendScopedZonedGetValToContact(conversationID, 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, conversationID int) 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.LocalScope, attr.FilesharingZone, fmt.Sprintf("%s.ts", key), strconv.FormatInt(time.Now().Unix(), 10))
	profile.SetScopedZonedAttribute(attr.ConversationScope, attr.FilesharingZone, fmt.Sprintf("%s.manifest", key), string(serializedManifest))
	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(conversationID, string(wrapperJSON))

	return nil
}

func GenerateDownloadPath(basePath, fileName string) (filePath, manifestPath string) {
	// avoid all kina funky shit
	re := regexp.MustCompile(`[^A-Za-z0-9._-]`)
	filePath = re.ReplaceAllString(filePath, "")
	// avoid hidden files on linux
	for strings.HasPrefix(filePath, ".") {
		filePath = strings.TrimPrefix(filePath, ".")
	}
	// avoid empties
	if strings.TrimSpace(filePath) == "" {
		filePath = "untitled"
	}
	// if you like it, put a / on it
	if !strings.HasSuffix(basePath, string(os.PathSeparator)) {
		basePath = fmt.Sprintf("%s%s", basePath, string(os.PathSeparator))
	}
	filePath = fmt.Sprintf("%s%s", basePath, fileName)
	manifestPath = fmt.Sprintf("%s.manifest", filePath)

	// if file is named "file", iterate "file", "file (2)", "file (3)", ... until DNE
	// if file is named "file.ext", iterate "file.ext", "file (2).ext", "file (3).ext", ... until DNE
	parts := strings.Split(fileName, ".")
	fileNameBase := parts[0]
	fileNameExt := ""
	if len(parts) > 1 {
		fileNameBase = strings.Join(parts[0:len(parts)-1], ".")
		fileNameExt = fmt.Sprintf(".%s", parts[len(parts)-1])
	}

	for i := 2; ; i++ {
		if _, err := os.Open(filePath); os.IsNotExist(err) {
			if _, err := os.Open(manifestPath); os.IsNotExist(err) {
				return
			}
		}
		filePath = fmt.Sprintf("%s%s (%d)%s", basePath, fileNameBase, i, fileNameExt)
		manifestPath = fmt.Sprintf("%s.manifest", filePath)
	}
}