//
//  rhimportd
//
//  The Radio Helsinki Rivendell Import Daemon
//
//
//  Copyright (C) 2015-2016 Christian Pointner <equinox@helsinki.at>
//
//  This file is part of rhimportd.
//
//  rhimportd is free software: you can redistribute it and/or modify
//  it under the terms of the GNU General Public License as published by
//  the Free Software Foundation, either version 3 of the License, or
//  any later version.
//
//  rhimportd 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 General Public License for more details.
//
//  You should have received a copy of the GNU General Public License
//  along with rhimportd. If not, see <http://www.gnu.org/licenses/>.
//

package main

import (
	"bytes"
	"encoding/json"
	"io"
	"mime/multipart"
	"net/http"

	"code.helsinki.at/rhrd-go/rddb"
	"code.helsinki.at/rhrd-go/rhimport"
)

type webUploadResponseData struct {
	ResponseCode int    `json:"RESPONSE_CODE"`
	ErrorString  string `json:"ERROR_STRING"`
}

func webUploadErrorResponse(w http.ResponseWriter, code int, errStr string) {
	w.Header().Set("Content-Type", "application/json")
	w.WriteHeader(code)
	encoder := json.NewEncoder(w)
	respdata := webUploadResponseData{code, errStr}
	encoder.Encode(respdata)
}

func webUploadSuccessResponse(w http.ResponseWriter) {
	w.Header().Set("Content-Type", "application/json")
	w.WriteHeader(http.StatusOK)
	encoder := json.NewEncoder(w)
	respdata := webUploadResponseData{http.StatusOK, "success"}
	encoder.Encode(respdata)
}

const (
	webUploadMaxRequestSize = (2 << 30) - 1 // 2GB, (2 << 30) overflows int on 32-bit systems therefore we use 2GB - 1 Byte
)

func webUploadParseForm(w http.ResponseWriter, r *http.Request) (username, sessionid, srcfile string, src *multipart.Part) {
	mpr, err := r.MultipartReader()
	if err != nil {
		rhl.Printf("WebUploadHandler: error while parsing multipart-form: %v", err)
		webUploadErrorResponse(w, http.StatusBadRequest, err.Error())
		return
	}

	for {
		p, err := mpr.NextPart()
		if err == io.EOF {
			return
		}
		if err != nil {
			rhl.Printf("WebUploadHandler: error while parsing multipart-form: %v", err)
			webUploadErrorResponse(w, http.StatusBadRequest, err.Error())
			return
		}
		var dstfield *string
		switch p.FormName() {
		case "LOGIN_NAME":
			dstfield = &username
		case "SESSION_ID":
			dstfield = &sessionid
		case "FILENAME":
			srcfile = p.FileName()
			src = p
			return // don't read any fileds beyond this point because we would need to load the whole file in order to continue parsing
		default:
			rhdl.Printf("WebUploadHandler: ingoring unknown form field: '%s'", p.FormName())
			continue
		}

		var buf bytes.Buffer
		if _, err := io.CopyN(&buf, p, 1<<10); err != nil && err != io.EOF { // 1kB should be enough
			rhl.Printf("WebUploadHandler: error while extracting form field: %v", err)
			webUploadErrorResponse(w, http.StatusBadRequest, err.Error())
			return
		}
		*dstfield = buf.String()
		p.Close()
	}
}

func webUploadHandler(conf *rhimport.Config, db *rddb.DBChan, sessions *rhimport.SessionStoreChan, trusted bool, w http.ResponseWriter, r *http.Request) {
	if r.Method == "GET" {
		http.Redirect(w, r, "/static/upload-form.html", http.StatusTemporaryRedirect)
		return
	}

	if r.Method != "POST" {
		rhl.Printf("WebUploadHandler: got invalid request method")
		webUploadErrorResponse(w, http.StatusMethodNotAllowed, "only POST and GET method are allowed")
		return
	}

	// This is from: stackoverflow.com/questions/26392196
	if r.ContentLength > webUploadMaxRequestSize {
		rhl.Printf("WebUploadHandler: request is too large: %d > %d", r.ContentLength, webUploadMaxRequestSize)
		webUploadErrorResponse(w, http.StatusExpectationFailed, "request too large")
		return
	}
	r.Body = http.MaxBytesReader(w, r.Body, webUploadMaxRequestSize)

	username, sessionid, srcfile, src := webUploadParseForm(w, r)
	if username == "" {
		webUploadErrorResponse(w, http.StatusBadRequest, "missing field LOGIN_NAME")
		return
	}
	if sessionid == "" {
		webUploadErrorResponse(w, http.StatusBadRequest, "missing field SESSION_ID")
		return
	}
	if srcfile == "" || src == nil {
		webUploadErrorResponse(w, http.StatusBadRequest, "missing field FILENAME")
		return
	}

	s, _, code, _ := sessions.Get(username, sessionid)
	if code != http.StatusOK {
		webUploadErrorResponse(w, http.StatusUnauthorized, "session not found")
		return
	}

	cancel, attachmentChan := s.AttachUploader()
	if attachmentChan == nil || cancel == nil {
		webUploadErrorResponse(w, http.StatusForbidden, "upload already in progress")
		return
	}
	defer close(attachmentChan)

	rhl.Printf("WebUploadHandler: starting upload for file '%s'", srcfile)
	for {
		chunk := rhimport.AttachmentChunk{}

		var data [128 * 1024]byte
		n, err := src.Read(data[:])
		if n > 0 {
			chunk.Data = data[:n]
			if err == io.EOF {
				err = nil
			}
		}
		chunk.Error = err
		if err == io.EOF {
			webUploadSuccessResponse(w)
			return
		}

		select {
		case <-cancel:
			rhl.Printf("WebUploadHandler: upload for file '%s' got canceld", srcfile)
			webUploadErrorResponse(w, http.StatusNoContent, "canceled")
			return
		case attachmentChan <- chunk:
		}

		if err != nil {
			webUploadErrorResponse(w, http.StatusInternalServerError, err.Error())
			return
		}
	}
}