package server

import (
	"archive/zip"
	"crypto/rand"
	"encoding/hex"
	"fmt"
	"io"
	"mime"
	"mime/multipart"
	"net/http"
	"net/url"
	"os"
	"path/filepath"
	"strings"

	"github.com/gin-contrib/gzip"
	"github.com/gin-gonic/gin"
)

const uploadRoot = "data/uploads"

type boxFile struct {
	Name         string
	Size         int64
	SizeLabel    string
	MimeType     string
	IconPath     string
	DownloadPath string
}

func Run(addr string) error {
	router := gin.Default()
	router.LoadHTMLGlob("templates/*.html")

	router.GET("/", func(ctx *gin.Context) {
		ctx.HTML(http.StatusOK, "index.html", gin.H{})
	})

	router.GET("/box/:id", func(ctx *gin.Context) {
		boxID := ctx.Param("id")
		if !validBoxID(boxID) {
			ctx.String(http.StatusBadRequest, "Invalid box id")
			return
		}

		files, err := listBoxFiles(boxID)
		if err != nil {
			ctx.String(http.StatusNotFound, "Box not found")
			return
		}

		ctx.HTML(http.StatusOK, "box.html", gin.H{
			"BoxID":       boxID,
			"Files":       files,
			"FileCount":   len(files),
			"DownloadAll": "/box/" + boxID + "/download",
		})
	})

	router.GET("/box/:id/download", func(ctx *gin.Context) {
		boxID := ctx.Param("id")
		if !validBoxID(boxID) {
			ctx.String(http.StatusBadRequest, "Invalid box id")
			return
		}

		files, err := listBoxFiles(boxID)
		if err != nil {
			ctx.String(http.StatusNotFound, "Box not found")
			return
		}

		ctx.Header("Content-Type", "application/zip")
		ctx.Header("Content-Disposition", fmt.Sprintf(`attachment; filename="warpbox-%s.zip"`, boxID))

		zipWriter := zip.NewWriter(ctx.Writer)
		defer zipWriter.Close()

		for _, file := range files {
			if err := addFileToZip(zipWriter, boxID, file.Name); err != nil {
				ctx.Status(http.StatusInternalServerError)
				return
			}
		}
	})

	router.GET("/box/:id/files/:filename", func(ctx *gin.Context) {
		boxID := ctx.Param("id")
		filename, ok := safeFilename(ctx.Param("filename"))
		if !validBoxID(boxID) || !ok {
			ctx.String(http.StatusBadRequest, "Invalid file")
			return
		}

		path := filepath.Join(boxPath(boxID), filename)
		if !strings.HasPrefix(path, boxPath(boxID)+string(filepath.Separator)) {
			ctx.String(http.StatusBadRequest, "Invalid file")
			return
		}

		if _, err := os.Stat(path); err != nil {
			ctx.String(http.StatusNotFound, "File not found")
			return
		}

		ctx.FileAttachment(path, filename)
	})

	router.POST("/box", func(ctx *gin.Context) {
		boxID, err := newBoxID()
		if err != nil {
			ctx.JSON(http.StatusInternalServerError, gin.H{"error": "Could not create upload box"})
			return
		}

		if err := os.MkdirAll(boxPath(boxID), 0755); err != nil {
			ctx.JSON(http.StatusInternalServerError, gin.H{"error": "Could not prepare upload box"})
			return
		}

		ctx.JSON(http.StatusOK, gin.H{
			"box_id":  boxID,
			"box_url": "/box/" + boxID,
		})
	})

	router.POST("/box/:id/upload", func(ctx *gin.Context) {
		boxID := ctx.Param("id")
		if !validBoxID(boxID) {
			ctx.JSON(http.StatusBadRequest, gin.H{"error": "Invalid box id"})
			return
		}

		file, err := ctx.FormFile("file")
		if err != nil {
			ctx.JSON(http.StatusBadRequest, gin.H{"error": "No file received"})
			return
		}

		savedFile, err := saveUploadedFile(ctx, boxID, file)
		if err != nil {
			ctx.JSON(http.StatusBadRequest, gin.H{"error": err.Error()})
			return
		}

		ctx.JSON(http.StatusOK, gin.H{
			"box_id":  boxID,
			"box_url": "/box/" + boxID,
			"file":    savedFile,
		})
	})

	router.POST("/upload", func(ctx *gin.Context) {
		form, err := ctx.MultipartForm()
		if err != nil {
			ctx.JSON(http.StatusBadRequest, gin.H{"error": "No files received"})
			return
		}

		files := form.File["files"]
		if len(files) == 0 {
			ctx.JSON(http.StatusBadRequest, gin.H{"error": "No files received"})
			return
		}

		boxID, err := newBoxID()
		if err != nil {
			ctx.JSON(http.StatusInternalServerError, gin.H{"error": "Could not create upload box"})
			return
		}

		if err := os.MkdirAll(boxPath(boxID), 0755); err != nil {
			ctx.JSON(http.StatusInternalServerError, gin.H{"error": "Could not prepare upload box"})
			return
		}

		savedFiles := make([]gin.H, 0, len(files))

		for _, file := range files {
			savedFile, err := saveUploadedFile(ctx, boxID, file)
			if err != nil {
				ctx.JSON(http.StatusBadRequest, gin.H{"error": err.Error()})
				return
			}

			savedFiles = append(savedFiles, savedFile)
		}

		ctx.JSON(http.StatusOK, gin.H{
			"box_id":  boxID,
			"box_url": "/box/" + boxID,
			"files":   savedFiles,
		})
	})

	compressed := router.Group("/", gzip.Gzip(gzip.DefaultCompression))
	compressed.Static("/static", "./static")

	return router.Run(addr)
}

func newBoxID() (string, error) {
	bytes := make([]byte, 16)
	if _, err := rand.Read(bytes); err != nil {
		return "", err
	}

	return hex.EncodeToString(bytes), nil
}

func validBoxID(boxID string) bool {
	if len(boxID) != 32 {
		return false
	}

	for _, character := range boxID {
		if !strings.ContainsRune("0123456789abcdef", character) {
			return false
		}
	}

	return true
}

func boxPath(boxID string) string {
	return filepath.Join(uploadRoot, boxID)
}

func listBoxFiles(boxID string) ([]boxFile, error) {
	entries, err := os.ReadDir(boxPath(boxID))
	if err != nil {
		return nil, err
	}

	files := make([]boxFile, 0, len(entries))
	for _, entry := range entries {
		if entry.IsDir() {
			continue
		}

		info, err := entry.Info()
		if err != nil {
			return nil, err
		}

		name := entry.Name()
		mimeType := mimeTypeForFile(filepath.Join(boxPath(boxID), name), name)
		files = append(files, boxFile{
			Name:         name,
			Size:         info.Size(),
			SizeLabel:    formatBytes(info.Size()),
			MimeType:     mimeType,
			IconPath:     iconForMimeType(mimeType, name),
			DownloadPath: "/box/" + boxID + "/files/" + url.PathEscape(name),
		})
	}

	return files, nil
}

func addFileToZip(zipWriter *zip.Writer, boxID string, filename string) error {
	path := filepath.Join(boxPath(boxID), filename)
	source, err := os.Open(path)
	if err != nil {
		return err
	}
	defer source.Close()

	destination, err := zipWriter.Create(filename)
	if err != nil {
		return err
	}

	_, err = io.Copy(destination, source)
	return err
}

func saveUploadedFile(ctx *gin.Context, boxID string, file *multipart.FileHeader) (gin.H, error) {
	filename, ok := safeFilename(file.Filename)
	if !ok {
		return nil, fmt.Errorf("Invalid filename")
	}

	boxPath := boxPath(boxID)
	if err := os.MkdirAll(boxPath, 0755); err != nil {
		return nil, fmt.Errorf("Could not prepare upload box")
	}

	filename = uniqueFilename(boxPath, filename)
	destination := filepath.Join(boxPath, filename)
	if err := ctx.SaveUploadedFile(file, destination); err != nil {
		return nil, fmt.Errorf("Could not save uploaded file")
	}

	return gin.H{
		"name": filename,
		"size": file.Size,
	}, nil
}

func safeFilename(name string) (string, bool) {
	filename := filepath.Base(name)
	filename = strings.TrimSpace(filename)
	return filename, filename != "" && filename != "." && filename != string(filepath.Separator)
}

func uniqueFilename(directory string, filename string) string {
	if _, err := os.Stat(filepath.Join(directory, filename)); os.IsNotExist(err) {
		return filename
	}

	extension := filepath.Ext(filename)
	base := strings.TrimSuffix(filename, extension)
	for count := 2; ; count++ {
		candidate := fmt.Sprintf("%s-%d%s", base, count, extension)
		if _, err := os.Stat(filepath.Join(directory, candidate)); os.IsNotExist(err) {
			return candidate
		}
	}
}

func mimeTypeForFile(path string, filename string) string {
	if mimeType := mime.TypeByExtension(strings.ToLower(filepath.Ext(filename))); mimeType != "" {
		return mimeType
	}

	file, err := os.Open(path)
	if err != nil {
		return "application/octet-stream"
	}
	defer file.Close()

	buffer := make([]byte, 512)
	bytesRead, err := file.Read(buffer)
	if err != nil && err != io.EOF {
		return "application/octet-stream"
	}

	return http.DetectContentType(buffer[:bytesRead])
}

func iconForMimeType(mimeType string, filename string) string {
	extension := strings.ToLower(filepath.Ext(filename))

	switch {
	case strings.HasPrefix(mimeType, "image/"):
		return "/static/img/sprites/bitmap.png"
	case strings.HasPrefix(mimeType, "video/"):
		return "/static/img/icons/netshow_notransm-1.png"
	case strings.HasPrefix(mimeType, "audio/"):
		return "/static/img/icons/netshow_notransm-1.png"
	case strings.HasPrefix(mimeType, "text/") || extension == ".md":
		return "/static/img/sprites/notepad_file-1.png"
	case strings.Contains(mimeType, "zip") || strings.Contains(mimeType, "compressed") || extension == ".rar" || extension == ".7z" || extension == ".tar" || extension == ".gz":
		return "/static/img/icons/Windows Icons - PNG/zipfldr.dll_14_101-0.png"
	case extension == ".ttf" || extension == ".otf" || extension == ".woff" || extension == ".woff2":
		return "/static/img/sprites/font.png"
	case extension == ".pdf":
		return "/static/img/sprites/journal.png"
	case extension == ".html" || extension == ".css" || extension == ".js":
		return "/static/img/sprites/frame_web-0.png"
	default:
		return "/static/img/sprites/freepad.png"
	}
}

func formatBytes(bytes int64) string {
	units := []string{"B", "KB", "MB", "GB"}
	size := float64(bytes)
	unitIndex := 0

	for size >= 1024 && unitIndex < len(units)-1 {
		size /= 1024
		unitIndex++
	}

	if unitIndex == 0 {
		return fmt.Sprintf("%d %s", bytes, units[unitIndex])
	}

	return fmt.Sprintf("%.1f %s", size, units[unitIndex])
}