/*
Copyright 2017 Vector Creations Ltd

Licensed under the Apache License, Version 2.0 (the "License");
you may not use this file except in compliance with the License.
You may obtain a copy of the License at

    http://www.apache.org/licenses/LICENSE-2.0

Unless required by applicable law or agreed to in writing, software
distributed under the License is distributed on an "AS IS" BASIS,
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
See the License for the specific language governing permissions and
limitations under the License.
*/

package main

import (
	"bytes"
	"compress/gzip"
	"encoding/json"
	"fmt"
	"io/ioutil"
	"net/http"
	"os"
	"path/filepath"
	"strconv"
	"time"
)

var maxPayloadSize = 1024 * 1024 * 55 // 55 MB

type submitServer struct {
}

type payload struct {
	Text      string     `json:"text"`
	Version   string     `json:"version"`
	UserAgent string     `json:"user_agent"`
	Logs      []logEntry `json:"logs"`
}

type logEntry struct {
	ID    string `json:"id"`
	Lines string `json:"lines"`
}

func (s *submitServer) ServeHTTP(w http.ResponseWriter, req *http.Request) {
	if req.Method != "POST" && req.Method != "OPTIONS" {
		respond(405, w)
		return
	}
	// Set CORS
	w.Header().Set("Access-Control-Allow-Origin", "*")
	w.Header().Set("Access-Control-Allow-Methods", "POST, OPTIONS")
	w.Header().Set("Access-Control-Allow-Headers", "Origin, X-Requested-With, Content-Type, Accept")
	if req.Method == "OPTIONS" {
		respond(200, w)
		return
	}
	if length, err := strconv.Atoi(req.Header.Get("Content-Length")); err != nil || length > maxPayloadSize {
		respond(413, w)
		return
	}
	var p payload
	if err := json.NewDecoder(req.Body).Decode(&p); err != nil {
		respond(400, w)
		return
	}

	if err := saveReport(p); err != nil {
		respond(500, w)
		return
	}

	respond(200, w)
}

func saveReport(p payload) error {
	// Dump bug report to disk as form:
	//  "bugreport-20170115-112233.log.gz" => user text, version, user agent, # logs
	//  "bugreport-20170115-112233-0.log.gz" => most recent log
	//  "bugreport-20170115-112233-1.log.gz" => ...
	//  "bugreport-20170115-112233-N.log.gz" => oldest log
	t := time.Now().UTC()
	prefix := t.Format("2006-01-02/150405")
	summary := fmt.Sprintf(
		"%s\n\nNumber of logs: %d\nVersion: %s\nUser-Agent: %s\n", p.Text, len(p.Logs), p.Version, p.UserAgent,
	)
	if err := gzipAndSave([]byte(summary), prefix, "details.log.gz"); err != nil {
		return err
	}
	for i, log := range p.Logs {
		if err := gzipAndSave([]byte(log.Lines), prefix, fmt.Sprintf("logs-%d.log.gz", i)); err != nil {
			return err // TODO: Rollback?
		}
	}
	return nil
}

func respond(code int, w http.ResponseWriter) {
	w.WriteHeader(code)
	w.Write([]byte("{}"))
}

func gzipAndSave(data []byte, dirname, fpath string) error {
	_ = os.MkdirAll(filepath.Join("bugs", dirname), os.ModePerm)
	fpath = filepath.Join("bugs", dirname, fpath)

	if _, err := os.Stat(fpath); err == nil {
		return fmt.Errorf("file already exists") // the user can just retry
	}
	var b bytes.Buffer
	gz := gzip.NewWriter(&b)
	if _, err := gz.Write(data); err != nil {
		return err
	}
	if err := gz.Flush(); err != nil {
		return err
	}
	if err := gz.Close(); err != nil {
		return err
	}
	if err := ioutil.WriteFile(fpath, b.Bytes(), 0644); err != nil {
		return err
	}
	return nil
}