package routes

import (
	"bytes"
	"crypto/md5"
	"database/sql"
	"errors"
	"fmt"
	"foobar/database"
	"foobar/model"
	"io"
	"mime/multipart"
	"net/http"
	"os"
	"path/filepath"
	"time"

	"github.com/google/uuid"
)

var maxFileSize int64 = 32 * 1000 * 1000

func fileUpload(w http.ResponseWriter, r *http.Request) (redirectURL, error) {

	boxURL, err := GetBoxURL(r)
	if err != nil {
		return noRedirect, err
	}

	tx := database.MustBeginTx()
	defer tx.Rollback()

	box, err := database.SelectBox(boxURL)
	if err != nil {
		if errors.Is(err, sql.ErrNoRows) { // this is a new URL the user wants to claim for themselves
			editCode := r.FormValue("edit_code")
			if editCode == "" {
				return noRedirect, newUserError(
					"Missing edit code. Box can't be created without it",
				)
			}
			var (
				id            = uuid.New()
				createdAt     = time.Now()
				lastUpdatedAt = createdAt
				header        = readmeTemplate
			)
			newBox := model.NewBox(
				id, boxURL, editCode, header, false, false, createdAt, lastUpdatedAt,
			)
			err = database.InsertBox(tx, newBox, editCode, header)
			if err != nil {
				return noRedirect, err
			}
			box = newBox
		} else {
			return noRedirect, err
		}
	}

	filesCtx, err := GetFilesFromUploadRequest(r)
	if err != nil {
		return noRedirect, err
	}

	var files []model.File

	for _, file := range filesCtx {

		bytes, err := readFileBytes(file.FileHeader())
		if err != nil {
			return noRedirect, err
		}

		mime := model.FileMime(http.DetectContentType(bytes))

		if file.Filename() == "README.md" {

			editCode := r.FormValue("edit_code")
			if editCode == "" {
				return noRedirect, newUserError(
					"Missing edit code. README can't be updated. " +
						"If you're not attempting to update the header, we'd " +
						"suggest changing \"README.md\" to a new filename.",
				)
			}

			if editCode != box.EditCode() {
				return noRedirect, newUserError(
					"Wrong edit code.",
				)
			}

			md := mdToHTML(bytes)

			err := database.UpdateHeader(tx, box.ID(), md)
			if err != nil {
				return noRedirect, err
			}

			if err := tx.Commit(); err != nil {
				return noRedirect, err
			}

			// FIXME: we're ignoring all other uploaded files
			return redirectURL(fmt.Sprintf("/box/%s", box.Url())), nil

		} else {

			err = copyBytesToDisk(file.ID(), bytes)
			if err != nil {
				return "", err
			}

			checksum := calculateMD5(bytes)

			newFile := model.NewFile(
				file.ID(), file.Filename(), file.Size(),
				file.UploadedDate(), mime, checksum,
			)

			files = append(files, newFile)
		}
	}

	for _, file := range files {
		err = database.InsertFile(tx, box.ID(), file)
		if err != nil {
			return noRedirect, err
		}
	}

	if err = tx.Commit(); err != nil {
		return noRedirect, err
	}

	return redirectURL(fmt.Sprintf("/box/%s/inside", box.Url())), nil
}

func calculateMD5(fileBytes []byte) model.MD5Checksum {
	return md5.Sum(fileBytes)
}

func readFileBytes(fileHeader *multipart.FileHeader) ([]byte, error) {
	fileReader, err := fileHeader.Open()
	if err != nil {
		panic(err)
	}
	defer fileReader.Close()

	fileBytes, err := io.ReadAll(fileReader)
	if err != nil {
		return nil, err
	}
	return fileBytes, nil
}

func copyBytesToDisk(fileId uuid.UUID, fileBytes []byte) error {
	fileWriter, err := os.Create(filepath.Join(
		staticDir, "box", fmt.Sprintf(fileId.String())),
	)
	if err != nil {
		return err
	}
	defer fileWriter.Close()

	_, err = io.Copy(fileWriter, bytes.NewReader(fileBytes))
	if err != nil {
		return err
	}
	return nil
}

func GetFilesFromUploadRequest(r *http.Request) ([]model.FileUploadContext, error) {

	err := r.ParseMultipartForm(int64(maxFileSize))
	if err != nil {
		return nil, err
	}

	headers, ok := r.MultipartForm.File["file"]
	if !ok {
		return nil, newUserError("no file")
	}

	var (
		files []model.FileUploadContext
	)

	for _, header := range headers {
		var (
			id           = uuid.New()
			uploadedDate = time.Now()
			size         = header.Size
			filename     = model.Filename(header.Filename)
			mime         = model.MimeFromHeader(header.Header)
		)

		fileUpload := model.NewFileUploadContext(id, uploadedDate, size, filename, mime, header)
		files = append(files, fileUpload)
	}
	return files, nil

}