package inspect

import (
	"context"
	"crypto/tls"
	"errors"
	"io"
	"net"
	"net/url"
	"os"
	"strings"
	"time"

	"github.com/mattn/go-isatty"
	"github.com/spf13/cobra"
	"src.lwithers.me.uk/go/rsa/pkg/inspect"
	"src.lwithers.me.uk/go/stdinprompt"
)

var (
	outputFormat string = "text"
	display      func(src string, info []inspect.Info)
	noPEMData    = errors.New("no PEM data found")
)

// Register the "inspect" subcommand.
func Register(root *cobra.Command) {
	cmd := &cobra.Command{
		Use:   "inspect source [source2 …]",
		Short: "Inspect files and TLS servers",
		Long: `Allows inspection of RSA keys, X.509 certificates, CRLs and CSRs. Pass
it a list of sources. Valid sources are:
 • filenames
 • ‘-’ for stdin
 • host:port for extracting the server's certificate chain from a TLS handshake
 • https://addr.example/ as per host:port

The output will by default be human-readable formatted text for the terminal,
but JSON and YAML are also supported through the --output flag.`,

		RunE: Inspect,
		Args: cobra.MinimumNArgs(1),
	}

	if isatty.IsTerminal(1) {
		outputFormat = "coloured"
	}

	cmd.Flags().StringVarP(&outputFormat, "output", "o", outputFormat,
		"Output format (coloured, text, json, yaml)")

	root.AddCommand(cmd)
}

// Inspect PEM data from files or TLS handshakes.
func Inspect(cmd *cobra.Command, args []string) error {
	setupAura(false)
	switch outputFormat {
	case "coloured":
		setupAura(true)
		display = displayText
	case "text":
		display = displayText
	case "json":
		display = displayStructured
		defer displayStructuredJSON()
	case "yaml":
		display = displayStructured
		defer displayStructuredYAML()
	default:
		return errors.New("invalid --output format (try: coloured, text, json or yaml)")
	}

	ok := true
	for _, arg := range args {
		switch {
		case arg == "-":
			ok = inspectStdin() && ok

		case strings.HasPrefix(arg, "https://"):
			ok = inspectHTTPS(arg) && ok

		case strings.IndexByte(arg, '/') == -1 && strings.IndexByte(arg, ':') != -1:
			_, _, err := net.SplitHostPort(arg)
			if err == nil {
				ok = inspectHost(arg) && ok
				break
			}
			fallthrough

		default:
			ok = inspectFile(arg) && ok
		}
	}
	if !ok {
		os.Exit(1)
	}
	return nil
}

func inspectStdin() (ok bool) {
	in := stdinprompt.New()
	raw, err := io.ReadAll(in)
	if err != nil {
		displayErr(err, "-")
		return false
	}

	info := inspect.LoadPEM(raw)
	if len(info) == 0 {
		displayErr(noPEMData, "-")
		return false
	}

	display("(stdin)", info)
	return true
}

func inspectHTTPS(addr string) (ok bool) {
	u, err := url.Parse(addr)
	if err != nil {
		displayErr(err, addr)
		return false
	}

	addr = u.Host
	if _, _, err := net.SplitHostPort(addr); err != nil {
		addr += ":443"
	}
	return inspectHost(addr)
}

func inspectHost(addr string) (ok bool) {
	ctx, cancel := context.WithTimeout(context.Background(), 10*time.Second)
	defer cancel()

	conn, err := tls.Dial("tcp", addr, &tls.Config{
		// we want to skip verification so we can inspect invalid certs too
		InsecureSkipVerify: true,

		// we only enable RSA ciphersuites, but we do allow old ones, again
		// so that we can report about bad / invalid servers
		CipherSuites: []uint16{
			tls.TLS_RSA_WITH_RC4_128_SHA,
			tls.TLS_RSA_WITH_3DES_EDE_CBC_SHA,
			tls.TLS_RSA_WITH_AES_128_CBC_SHA,
			tls.TLS_RSA_WITH_AES_256_CBC_SHA,
			tls.TLS_RSA_WITH_AES_128_CBC_SHA256,
			tls.TLS_RSA_WITH_AES_128_GCM_SHA256,
			tls.TLS_RSA_WITH_AES_256_GCM_SHA384,
			tls.TLS_ECDHE_RSA_WITH_RC4_128_SHA,
			tls.TLS_ECDHE_RSA_WITH_3DES_EDE_CBC_SHA,
			tls.TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA,
			tls.TLS_ECDHE_RSA_WITH_AES_256_CBC_SHA,
			tls.TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA256,
			tls.TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256,
			tls.TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384,
			tls.TLS_ECDHE_RSA_WITH_CHACHA20_POLY1305_SHA256,
			tls.TLS_AES_128_GCM_SHA256,
			tls.TLS_AES_256_GCM_SHA384,
			tls.TLS_CHACHA20_POLY1305_SHA256,
		},

		// we enable TLSv1.0 so that we can complain about it
		MinVersion: tls.VersionTLS10,
	})
	if err != nil {
		displayErr(err, addr)
		return false
	}

	if err := conn.HandshakeContext(ctx); err != nil {
		displayErr(err, addr)
		return false
	}

	display(addr, inspect.ConnectionState(conn.ConnectionState()))
	return true
}

func inspectFile(filename string) (ok bool) {
	raw, err := os.ReadFile(filename)
	if err != nil {
		displayErr(err, filename)
		return false
	}

	info := inspect.LoadPEM(raw)
	if len(info) == 0 {
		displayErr(noPEMData, filename)
		return false
	}

	display(filename, info)
	return true
}

func displayYAML(src string, info []inspect.Info) {
}