package main

import (
	"context"
	"crypto/tls"
	"crypto/x509"
	"encoding/pem"
	"fmt"
	"net/mail"
	"os"
	"strings"
	"time"

	log "github.com/sirupsen/logrus"
	cli "github.com/urfave/cli/v3"
)

func main() {
	cmd := &cli.Command{
		Name:    "too-soon",
		Usage:   "check if certificates expire too soon",
		Version: "0.1",
		Authors: []any{
			&mail.Address{Name: "Vincent Batts", Address: "vbatts@hashbangbash.com"},
		},
		Flags: []cli.Flag{
			&cli.IntFlag{
				Name:  "days",
				Value: 20,
				Usage: "days within range to alert about",
			},
			&cli.BoolFlag{
				Name:    "debug",
				Aliases: []string{"D"},
				Value:   false,
				Usage:   "output debug verbose info",
			},
		},
		Before: func(ctx context.Context, cmd *cli.Command) (context.Context, error) {
			if cmd.Bool("debug") {
				log.SetLevel(log.DebugLevel)
			}
			return ctx, nil
		},
		Commands: []*cli.Command{
			&cli.Command{
				Name:      "pem",
				Usage:     "check if PEM certificate files expire too soon",
				Action:    fPEMCheck,
				ArgsUsage: "[PEM files...]",
			},
			&cli.Command{
				Name:      "remote",
				Usage:     "check if certificate on a remote host expires too soon",
				Action:    fHostCheck,
				ArgsUsage: "[host/host:port...]",
			},
		},
		Action: func(ctx context.Context, cmd *cli.Command) error {
			cli.ShowAppHelpAndExit(cmd, 1)
			return nil
		},
	}

	if err := cmd.Run(context.Background(), os.Args); err != nil {
		log.Fatal(err)
	}
}

func fHostCheck(ctx context.Context, cmd *cli.Command) error {
	numAlert := 0
	numHostErr := 0
	for i := 0; i <= cmd.Args().Len(); i++ {
		host := cmd.Args().Get(i)
		if host == "" {
			break
		}

		// TODO use the url.Parse package to do this, incase there is a protocol and path on there as well
		port := "443"
		if strings.Contains(host, ":") {
			chunks := strings.Split(host, ":")
			host = chunks[0]
			port = chunks[1]
		}
		// connect to the domain:port/tcp
		dest := fmt.Sprintf("%s:%s", host, port)
		conn, err := tls.Dial("tcp", dest, &tls.Config{
			InsecureSkipVerify: true, // TODO add a flag to force this
		})
		if err != nil {
			numHostErr++
			log.Errorf("%q connection failed: %s", dest, err)
			continue
		}
		defer conn.Close()

		log.Debugf("server: %s", conn.ConnectionState().ServerName)
		log.Debugf("version: %d", conn.ConnectionState().Version)
		for _, cert := range conn.ConnectionState().PeerCertificates {
			log.Debugf(" -- cert serial: %x", cert.SerialNumber)
			if len(cert.DNSNames) == 0 {
				log.Debugf(" -- cert: skipping as there are no DNS names")
				continue
			}

			hours := time.Duration(cmd.Int("days") * -24)
			alertTime := cert.NotAfter.Add(hours * time.Hour)
			today := time.Now()
			if today.After(alertTime) {
				if today.After(cert.NotAfter) {
					log.Warnf("%q(%x) : TIME TO RENEW CERTIFICATE (already expired!)", dest, cert.SerialNumber)
				} else {
					log.Warnf("%q(%x) : TIME TO RENEW CERTIFICATE (expires in less than %d days)", dest, cert.SerialNumber, cmd.Int("days"))
				}
				log.Warnf("%q(%x) : %v", dest, cert.SerialNumber, cert.NotAfter)
				log.Warnf("%q(%x) : %v", dest, cert.SerialNumber, cert.DNSNames)
				numAlert++
			} else {
				log.Debugf("%q(%x) : %v", dest, cert.SerialNumber, cert.NotAfter)
				log.Debugf("%q(%x) : %v", dest, cert.SerialNumber, cert.DNSNames)
			}
		}
	}
	if numAlert != 0 {
		return cli.Exit("domain certificates need to be renewed", numAlert)
	}
	return nil
}

func fPEMCheck(ctx context.Context, cmd *cli.Command) error {
	numAlert := 0
	for i := 0; i <= cmd.Args().Len(); i++ {
		file := cmd.Args().Get(i)
		if file == "" {
			break
		}

		var certs []*x509.Certificate

		buf, err := os.ReadFile(file)
		if err != nil {
			log.Errorf("%q could not be read: %s", file, err)
			continue
		}

		more := true
		for more {
			block, rest := pem.Decode(buf)
			cert, err := x509.ParseCertificate(block.Bytes)
			if err != nil {
				log.Errorf("%q cert could not be parsed: %s", file, err)
				continue
			}
			certs = append(certs, cert)

			if len(rest) == 0 {
				more = false
			}
			// reset the buffer if there is more
			buf = rest
		}

		for _, cert := range certs {
			if len(cert.DNSNames) == 0 {
				continue
			}

			hours := time.Duration(cmd.Int("days") * -24)
			alertTime := cert.NotAfter.Add(hours * time.Hour)
			today := time.Now()
			if today.After(alertTime) {
				if today.After(cert.NotAfter) {
					log.Warnf("%q : TIME TO RENEW CERTIFICATE (already expired!)", file)
				} else {
					log.Warnf("%q : TIME TO RENEW CERTIFICATE (expires in less than %d days)", file, cmd.Int("days"))
				}
				log.Warnf("%q : %v", file, cert.NotAfter)
				log.Warnf("%q : %v", file, cert.DNSNames)
				numAlert++
			} else {
				log.Debugf("%q : %v", file, cert.NotAfter)
				log.Debugf("%q : %v", file, cert.DNSNames)
			}
		}
	}
	if numAlert != 0 {
		return cli.Exit("certificates need to be renewed", numAlert)
	}
	return nil
}