// Copyright (C) 2019 The Syncthing Authors.
//
// This Source Code Form is subject to the terms of the Mozilla Public
// License, v. 2.0. If a copy of the MPL was not distributed with this file,
// You can obtain one at https://mozilla.org/MPL/2.0/.

// Command stcrashreceiver is a trivial HTTP server that allows two things:
//
// - uploading files (crash reports) named like a SHA256 hash using a PUT request
// - checking whether such file exists using a HEAD request
//
// Typically this should be deployed behind something that manages HTTPS.
package main

import (
	"context"
	"encoding/json"
	"fmt"
	"io"
	"log"
	"net/http"
	"os"
	"path/filepath"
	"regexp"
	"strings"

	"github.com/alecthomas/kong"
	raven "github.com/getsentry/raven-go"
	"github.com/prometheus/client_golang/prometheus/promhttp"
	_ "github.com/syncthing/syncthing/lib/automaxprocs"
	"github.com/syncthing/syncthing/lib/build"
	"github.com/syncthing/syncthing/lib/sha256"
	"github.com/syncthing/syncthing/lib/ur"
)

const maxRequestSize = 1 << 20 // 1 MiB

type cli struct {
	Dir            string `help:"Parent directory to store crash and failure reports in" env:"REPORTS_DIR" default:"."`
	DSN            string `help:"Sentry DSN" env:"SENTRY_DSN"`
	Listen         string `help:"HTTP listen address" default:":8080" env:"LISTEN_ADDRESS"`
	MaxDiskFiles   int    `help:"Maximum number of reports on disk" default:"100000" env:"MAX_DISK_FILES"`
	MaxDiskSizeMB  int64  `help:"Maximum disk space to use for reports" default:"1024" env:"MAX_DISK_SIZE_MB"`
	SentryQueue    int    `help:"Maximum number of reports to queue for sending to Sentry" default:"64" env:"SENTRY_QUEUE"`
	DiskQueue      int    `help:"Maximum number of reports to queue for writing to disk" default:"64" env:"DISK_QUEUE"`
	MetricsListen  string `help:"HTTP listen address for metrics" default:":8081" env:"METRICS_LISTEN_ADDRESS"`
	IngorePatterns string `help:"File containing ignore patterns (regexp)" env:"IGNORE_PATTERNS" type:"existingfile"`
}

func main() {
	var params cli
	kong.Parse(&params)

	mux := http.NewServeMux()

	ds := &diskStore{
		dir:      filepath.Join(params.Dir, "crash_reports"),
		inbox:    make(chan diskEntry, params.DiskQueue),
		maxFiles: params.MaxDiskFiles,
		maxBytes: params.MaxDiskSizeMB << 20,
	}
	go ds.Serve(context.Background())

	ss := &sentryService{
		dsn:   params.DSN,
		inbox: make(chan sentryRequest, params.SentryQueue),
	}
	go ss.Serve(context.Background())

	var ip *ignorePatterns
	if params.IngorePatterns != "" {
		var err error
		ip, err = loadIgnorePatterns(params.IngorePatterns)
		if err != nil {
			log.Fatalf("Failed to load ignore patterns: %v", err)
		}
	}

	cr := &crashReceiver{
		store:  ds,
		sentry: ss,
		ignore: ip,
	}

	mux.Handle("/", cr)
	mux.HandleFunc("/ping", func(w http.ResponseWriter, req *http.Request) {
		w.Write([]byte("OK"))
	})

	if params.MetricsListen != "" {
		mmux := http.NewServeMux()
		mmux.Handle("/metrics", promhttp.Handler())
		go func() {
			if err := http.ListenAndServe(params.MetricsListen, mmux); err != nil {
				log.Fatalln("HTTP serve metrics:", err)
			}
		}()
	}

	if params.DSN != "" {
		mux.HandleFunc("/newcrash/failure", handleFailureFn(params.DSN, filepath.Join(params.Dir, "failure_reports"), ip))
	}

	log.SetOutput(os.Stdout)
	if err := http.ListenAndServe(params.Listen, mux); err != nil {
		log.Fatalln("HTTP serve:", err)
	}
}

func handleFailureFn(dsn, failureDir string, ignore *ignorePatterns) func(w http.ResponseWriter, req *http.Request) {
	return func(w http.ResponseWriter, req *http.Request) {
		result := "failure"
		defer func() {
			metricFailureReportsTotal.WithLabelValues(result).Inc()
		}()

		lr := io.LimitReader(req.Body, maxRequestSize)
		bs, err := io.ReadAll(lr)
		req.Body.Close()
		if err != nil {
			http.Error(w, err.Error(), 500)
			return
		}

		if ignore.match(bs) {
			result = "ignored"
			return
		}

		var reports []ur.FailureReport
		err = json.Unmarshal(bs, &reports)
		if err != nil {
			http.Error(w, err.Error(), 400)
			return
		}
		if len(reports) == 0 {
			// Shouldn't happen
			log.Printf("Got zero failure reports")
			return
		}

		version, err := build.ParseVersion(reports[0].Version)
		if err != nil {
			http.Error(w, err.Error(), 400)
			return
		}
		for _, r := range reports {
			pkt := packet(version, "failure")
			pkt.Message = r.Description
			pkt.Extra = raven.Extra{
				"count": r.Count,
			}
			for k, v := range r.Extra {
				pkt.Extra[k] = v
			}
			if r.Goroutines != "" {
				url, err := saveFailureWithGoroutines(r.FailureData, failureDir)
				if err != nil {
					log.Println("Saving failure report:", err)
					http.Error(w, "Internal server error", http.StatusInternalServerError)
					return
				}
				pkt.Extra["goroutinesURL"] = url
			}
			message := sanitizeMessageLDB(r.Description)
			pkt.Fingerprint = []string{message}

			if err := sendReport(dsn, pkt, userIDFor(req)); err != nil {
				log.Println("Failed to send failure report:", err)
			} else {
				log.Println("Sent failure report:", r.Description)
				result = "success"
			}
		}
	}
}

func saveFailureWithGoroutines(data ur.FailureData, failureDir string) (string, error) {
	bs := make([]byte, len(data.Description)+len(data.Goroutines))
	copy(bs, data.Description)
	copy(bs[len(data.Description):], data.Goroutines)
	id := fmt.Sprintf("%x", sha256.Sum256(bs))
	path := fullPathCompressed(failureDir, id)
	err := compressAndWrite(bs, path)
	if err != nil {
		return "", err
	}
	return reportServer + path, nil
}

type ignorePatterns struct {
	patterns []*regexp.Regexp
}

func loadIgnorePatterns(path string) (*ignorePatterns, error) {
	bs, err := os.ReadFile(path)
	if err != nil {
		return nil, err
	}

	var patterns []*regexp.Regexp
	for _, line := range strings.Split(string(bs), "\n") {
		line = strings.TrimSpace(line)
		if line == "" {
			continue
		}
		re, err := regexp.Compile(line)
		if err != nil {
			return nil, err
		}
		patterns = append(patterns, re)
	}

	log.Printf("Loaded %d ignore patterns", len(patterns))
	return &ignorePatterns{patterns: patterns}, nil
}

func (i *ignorePatterns) match(report []byte) bool {
	if i == nil {
		return false
	}
	for _, re := range i.patterns {
		if re.Match(report) {
			return true
		}
	}
	return false
}