// Vikunja is a to-do list application to facilitate your life.
// Copyright 2018-present Vikunja and contributors. All rights reserved.
//
// This program is free software: you can redistribute it and/or modify
// it under the terms of the GNU Affero General Public License as published by
// the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.
//
// This program is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
// GNU Affero General Public License for more details.
//
// You should have received a copy of the GNU Affero General Public License
// along with this program.  If not, see <https://www.gnu.org/licenses/>.

package v1

import (
	"errors"
	"io"
	"mime"
	"net/http"
	"strconv"
	"strings"

	"code.vikunja.io/api/pkg/config"
	"code.vikunja.io/api/pkg/db"
	"code.vikunja.io/api/pkg/models"
	auth2 "code.vikunja.io/api/pkg/modules/auth"
	"code.vikunja.io/api/pkg/web"

	"github.com/labstack/echo/v5"
)

// attachmentUploadError represents a structured error for attachment upload failures
type attachmentUploadError struct {
	Code    int    `json:"code,omitempty"`
	Message string `json:"message"`
}

// toAttachmentUploadError converts an error to a structured attachmentUploadError
func toAttachmentUploadError(err error) attachmentUploadError {
	// Try to get structured error info from HTTPErrorProcessor
	if httpErr, ok := err.(web.HTTPErrorProcessor); ok {
		errDetails := httpErr.HTTPError()
		return attachmentUploadError{
			Code:    errDetails.Code,
			Message: errDetails.Message,
		}
	}
	// Fall back to just the error message
	return attachmentUploadError{
		Message: err.Error(),
	}
}

// UploadTaskAttachment handles everything needed for the upload of a task attachment
// @Summary Upload a task attachment
// @Description Upload a task attachment. You can pass multiple files with the files form param.
// @tags task
// @Accept mpfd
// @Produce json
// @Param id path int true "Task ID"
// @Param files formData string true "The file, as multipart form file. You can pass multiple."
// @Security JWTKeyAuth
// @Success 200 {object} models.Message "Attachments were uploaded successfully."
// @Failure 403 {object} models.Message "No access to the task."
// @Failure 404 {object} models.Message "The task does not exist."
// @Failure 500 {object} models.Message "Internal error"
// @Router /tasks/{id}/attachments [put]
func UploadTaskAttachment(c *echo.Context) error {

	var taskAttachment models.TaskAttachment
	if err := c.Bind(&taskAttachment); err != nil {
		return echo.NewHTTPError(http.StatusBadRequest, "No task ID provided").Wrap(err)
	}

	// Permissions check
	auth, err := auth2.GetAuthFromClaims(c)
	if err != nil {
		return err
	}

	s := db.NewSession()
	defer s.Close()

	can, err := taskAttachment.CanCreate(s, auth)
	if err != nil {
		_ = s.Rollback()
		return err
	}
	if !can {
		return echo.ErrForbidden
	}

	// Multipart form
	form, err := c.MultipartForm()
	if err != nil {
		_ = s.Rollback()
		if errors.Is(err, http.ErrNotMultipart) {
			return echo.NewHTTPError(http.StatusBadRequest, "No multipart form provided").Wrap(err)
		}
		return err
	}

	type result struct {
		Errors  []attachmentUploadError  `json:"errors"`
		Success []*models.TaskAttachment `json:"success"`
	}
	r := &result{}
	fileHeaders := form.File["files"]
	for _, file := range fileHeaders {
		// We create a new attachment object here to have a clean start
		ta := &models.TaskAttachment{
			TaskID: taskAttachment.TaskID,
		}

		f, err := file.Open()
		if err != nil {
			r.Errors = append(r.Errors, toAttachmentUploadError(err))
			continue
		}
		defer f.Close()

		err = ta.NewAttachment(s, f, file.Filename, uint64(file.Size), auth)
		if err != nil {
			r.Errors = append(r.Errors, toAttachmentUploadError(err))
			continue
		}
		r.Success = append(r.Success, ta)
	}

	if err := s.Commit(); err != nil {
		_ = s.Rollback()
		return err
	}

	return c.JSON(http.StatusOK, r)
}

// GetTaskAttachment returns a task attachment to download for the user
// @Summary Get one attachment.
// @Description Get one attachment for download. **Returns json on error.**
// @tags task
// @Produce octet-stream
// @Param id path int true "Task ID"
// @Param attachmentID path int true "Attachment ID"
// @Param preview_size query string false "The size of the preview image. Can be sm = 100px, md = 200px, lg = 400px or xl = 800px. If provided, a preview image will be returned if the attachment is an image."
// @Security JWTKeyAuth
// @Success 200 {file} blob "The attachment file."
// @Failure 403 {object} models.Message "No access to this task."
// @Failure 404 {object} models.Message "The task does not exist."
// @Failure 500 {object} models.Message "Internal error"
// @Router /tasks/{id}/attachments/{attachmentID} [get]
func GetTaskAttachment(c *echo.Context) error {

	var taskAttachment models.TaskAttachment
	if err := c.Bind(&taskAttachment); err != nil {
		return echo.NewHTTPError(http.StatusBadRequest, "No task ID provided").Wrap(err)
	}

	// Permissions check
	auth, err := auth2.GetAuthFromClaims(c)
	if err != nil {
		return err
	}

	s := db.NewSession()
	defer s.Close()

	can, _, err := taskAttachment.CanRead(s, auth)
	if err != nil {
		_ = s.Rollback()
		return err
	}
	if !can {
		return echo.ErrForbidden
	}

	// Get the attachment incl file
	err = taskAttachment.ReadOne(s, auth)
	if err != nil {
		_ = s.Rollback()
		return err
	}

	// Open the file so its content is available for preview generation and download
	err = taskAttachment.File.LoadFileByID()
	if err != nil {
		_ = s.Rollback()
		return err
	}

	// If the preview query parameter is set, get the preview (cached or generate)
	previewSize := models.GetPreviewSizeFromString(c.QueryParam("preview_size"))
	if previewSize != models.PreviewSizeUnknown && strings.HasPrefix(taskAttachment.File.Mime, "image") {
		previewFileBytes := taskAttachment.GetPreview(previewSize)
		if previewFileBytes != nil {
			return c.Blob(http.StatusOK, "image/png", previewFileBytes)
		}
	}

	if err := s.Commit(); err != nil {
		_ = s.Rollback()
		return err
	}

	mimeToReturn := taskAttachment.File.Mime
	if mimeToReturn == "" {
		mimeToReturn = "application/octet-stream"
	}

	c.Response().Header().Set("Content-Disposition", mime.FormatMediaType("attachment", map[string]string{
		"filename": taskAttachment.File.Name,
	}))
	c.Response().Header().Set("Content-Type", mimeToReturn)
	c.Response().Header().Set("Content-Length", strconv.FormatUint(taskAttachment.File.Size, 10))
	c.Response().Header().Set("Last-Modified", taskAttachment.File.Created.UTC().Format(http.TimeFormat))
	// Override the global no-store directive so browsers can cache attachments.
	// no-cache allows caching but requires revalidation via If-Modified-Since.
	c.Response().Header().Set("Cache-Control", "no-cache")

	if config.FilesType.GetString() == "s3" {
		// Check If-Modified-Since and return 304 if the file hasn't changed.
		// http.ServeContent handles this automatically for local files.
		if ifModSince := c.Request().Header.Get("If-Modified-Since"); ifModSince != "" {
			if t, parseErr := http.ParseTime(ifModSince); parseErr == nil && !taskAttachment.File.Created.UTC().After(t) {
				return c.NoContent(http.StatusNotModified)
			}
		}

		// s3 files cannot use http.ServeContent as it requires a Seekable file
		// so we stream the file content directly to the response
		_, err = io.Copy(c.Response(), taskAttachment.File.File)
		return err
	}

	http.ServeContent(c.Response(), c.Request(), taskAttachment.File.Name, taskAttachment.File.Created, taskAttachment.File.File.(io.ReadSeeker))
	return nil
}