package main

import (
	"bufio"
	"errors"
	"flag"
	"fmt"
	"io"
	"os"
	"path/filepath"
	"strings"
	"text/tabwriter"

	"send/internal/auth"
	"send/internal/config"
)

const tokenUsage = `send token - manage upload credentials

Usage:
  send token add <name> [options]        generate a token
  send token add <name> --token -        read a chosen one from stdin
  send token list [options]
  send token rm <name> [options]

A token grants its own size and lifetime limits. Any limit left unset is
inherited from the running server's defaults, so a token with no options
behaves exactly like the anonymous tier but may claim vanity names.

Options:
`

func tokenCommand(args []string) error {
	// Asking for help is not a subcommand, and neither is asking for nothing.
	if len(args) == 0 || isHelp(args[0]) {
		tokenUsageTo(os.Stdout)
		if len(args) == 0 {
			return errors.New("token: expected add, list or rm")
		}
		return flag.ErrHelp
	}
	sub, rest := args[0], args[1:]

	// The name is positional and must come first; stdlib flag stops parsing at
	// the first non-flag argument.
	name := ""
	if len(rest) > 0 && (len(rest[0]) == 0 || rest[0][0] != '-') {
		name, rest = rest[0], rest[1:]
	}

	var opts tokenOptions
	fs := opts.register()
	fs.SetOutput(os.Stderr)

	if err := fs.Parse(rest); err != nil {
		if errors.Is(err, flag.ErrHelp) {
			fs.PrintUsage(os.Stdout, tokenUsage)
			return flag.ErrHelp
		}
		return err
	}
	if opts.tokensPath == "" {
		opts.tokensPath = opts.dataDir + "/tokens.json"
	}

	// Match the server's permissions for anything this command has to create.
	setUmask()

	file, err := auth.Load(opts.tokensPath)
	if err != nil {
		return err
	}
	warnIfUnusedDataDir(opts.dataDir, opts.tokensPath)

	switch sub {
	case "add":
		if name == "" {
			return errors.New("token add: a name is required")
		}
		return tokenAdd(file, name, opts)
	case "list":
		return tokenList(file)
	case "rm", "remove", "delete":
		if name == "" {
			return errors.New("token rm: a name is required")
		}
		if err := file.Remove(name); err != nil {
			return err
		}
		fmt.Printf("Removed token %q.\n", name)
		return nil
	default:
		return fmt.Errorf("token: unknown subcommand %q", sub)
	}
}

// warnIfUnusedDataDir flags the most likely mistake with this command: pointing
// --data somewhere the server does not read, so a freshly minted token is never
// seen and every request comes back 401. A data directory the server has opened
// always has an objects/ subdirectory.
func warnIfUnusedDataDir(dataDir, tokensPath string) {
	if _, err := os.Stat(filepath.Join(dataDir, "objects")); err == nil {
		return
	}
	fmt.Fprintf(os.Stderr,
		"note: %s has no objects/ directory, so no server has used it.\n"+
			"      Tokens written to %s are only read by a server started with --data %s\n\n",
		dataDir, tokensPath, dataDir)
}

// tokenOptions are the flags every token subcommand shares.
type tokenOptions struct {
	dataDir    string
	tokensPath string
	maxSize    string
	maxExpiry  string
	defExpiry  string
	chosen     string
	vanity     bool
	admin      bool
}

func (o *tokenOptions) register() *config.Set {
	fs := config.NewSet("send token", config.EnvPrefix)
	fs.String(&o.dataDir, "data", "d", "./data", "DIR", "directory holding the data")
	fs.String(&o.tokensPath, "tokens", "", "", "FILE", "token file location (default <data>/tokens.json)")
	fs.String(&o.maxSize, "max-size", "s", "", "SIZE", "per-upload cap for this token; 'unlimited' to remove it")
	fs.String(&o.maxExpiry, "max-expiry", "e", "", "DURATION", "longest lifetime this token may request; 'never' to remove the cap")
	fs.String(&o.defExpiry, "default-expiry", "", "", "DURATION", "lifetime applied when this token does not ask for one")
	fs.String(&o.chosen, "token", "t", "", "VALUE",
		"use this token instead of a generated one; \"-\" reads it from standard input")
	fs.Bool(&o.vanity, "vanity", "", false, "allow this token to claim custom names")
	fs.Bool(&o.admin, "admin", "", false, "allow this token to delete anyone's files")
	return fs
}

// isHelp recognises the spellings people actually type.
func isHelp(arg string) bool {
	switch arg {
	case "help", "-h", "--help":
		return true
	}
	return false
}

func tokenUsageTo(w io.Writer) {
	var opts tokenOptions
	opts.register().PrintUsage(w, tokenUsage)
}

func tokenAdd(file *auth.File, name string, opts tokenOptions) error {
	chosen := opts.chosen
	if chosen == "-" {
		read, err := readSecret()
		if err != nil {
			return err
		}
		chosen = read
	}

	var (
		t      *auth.Token
		secret string
		err    error
	)
	if chosen != "" {
		t, err = auth.NewChosen(name, chosen)
		secret = chosen
	} else {
		t, secret, err = auth.NewGenerated(name)
	}
	if err != nil {
		return err
	}
	t.AllowVanity = opts.vanity
	t.Admin = opts.admin
	// Only options actually given are recorded; everything else stays absent
	// so it keeps tracking the server's defaults.
	if opts.maxSize != "" {
		t.MaxSize = &opts.maxSize
	}
	if opts.maxExpiry != "" {
		t.MaxExpiry = &opts.maxExpiry
	}
	if opts.defExpiry != "" {
		t.DefaultExpiry = &opts.defExpiry
	}
	if err := file.Add(t); err != nil {
		return err
	}

	if chosen != "" {
		fmt.Printf("Added token %q to %s\n\n", name, file.Path())
		fmt.Println("It is stored under a slow key derivation, so a leak of the token")
		fmt.Println("file does not hand over the passphrase itself. Guessing it online is")
		fmt.Println("rate limited, but a weak choice is still a weak choice.")
		return nil
	}
	fmt.Printf("Added token %q to %s\n\n", name, file.Path())
	fmt.Printf("  %s\n\n", secret)
	fmt.Println("This is the only time it is shown; only its hash is stored.")
	fmt.Println("Send it as:  Authorization: Bearer <token>")
	return nil
}

// readSecret reads a token from standard input, so it need not appear in a
// shell history or in the process list.
func readSecret() (string, error) {
	line, err := bufio.NewReader(os.Stdin).ReadString('\n')
	if err != nil && !errors.Is(err, io.EOF) {
		return "", err
	}
	secret := strings.TrimRight(line, "\r\n")
	if secret == "" {
		return "", errors.New("no token on standard input")
	}
	return secret, nil
}

func tokenList(file *auth.File) error {
	tokens := file.List()
	if len(tokens) == 0 {
		fmt.Printf("No tokens in %s\n", file.Path())
		return nil
	}
	w := tabwriter.NewWriter(os.Stdout, 0, 0, 2, ' ', 0)
	fmt.Fprintln(w, "NAME\tKIND\tMAX SIZE\tMAX EXPIRY\tDEFAULT\tVANITY\tADMIN\tCREATED")
	for _, t := range tokens {
		fmt.Fprintf(w, "%s\t%s\t%s\t%s\t%s\t%s\t%s\t%s\n",
			t.Name, kind(t),
			inherited(t.MaxSize), inherited(t.MaxExpiry), inherited(t.DefaultExpiry),
			yesNo(t.AllowVanity), yesNo(t.Admin),
			t.Created.Format("2006-01-02"))
	}
	return w.Flush()
}

func kind(t *auth.Token) string {
	if t.Chosen() {
		return "chosen"
	}
	return "generated"
}

func inherited(s *string) string {
	if s == nil {
		return "(default)"
	}
	return *s
}

func yesNo(b bool) string {
	if b {
		return "yes"
	}
	return "no"
}