package main

import (
	"crypto/sha256"
	"encoding/hex"
	"encoding/json"
	"fmt"
	"os"
	"strconv"
	"time"

	"git.rootprojects.org/root/hashcash"
)

func help() {
	fmt.Println("Usage:")
	fmt.Println("\thashcash new [subject *] [difficulty 10] [expires in 5m]")
	fmt.Println("\thashcash parse <hashcash>")
	fmt.Println("\thashcash solve <hashcash>")
	fmt.Println("\thashcash hash <hashcash>")
	fmt.Println("\thashcash verify <hashcash> [subject *]")
}

func main() {
	args := os.Args[:]
	nargs := len(args)

	if nargs < 2 {
		help()
		os.Exit(1)
		return
	}

	switch args[1] {
	case "new":
		var subject string
		if nargs >= 3 {
			subject = args[2]
		}

		var difficulty int
		if nargs >= 4 {
			var err error
			difficulty, err = strconv.Atoi(args[3])
			if nil != err {
				help()
				os.Exit(1)
				return
			}
		}

		var expIn time.Duration
		if nargs >= 5 {
			var err error
			expIn, err = time.ParseDuration(args[4])
			if nil != err {
				fmt.Println(err)
				help()
				os.Exit(1)
				return
			}
		} else {
			expIn = 5 * time.Minute
		}

		h := hashcash.New(hashcash.Hashcash{
			Subject:    subject,
			Difficulty: difficulty,
			ExpiresAt:  time.Now().Add(expIn),
		})

		fmt.Println(h.String())
		return
	case "parse":
		var token string
		if 3 != nargs {
			help()
			os.Exit(1)
			return
		}
		token = args[2]
		h, err := hashcash.Parse(token)
		if nil != err {
			fmt.Fprintf(os.Stderr, "%s\n", err)
			return
		}
		b, _ := json.MarshalIndent(h, "", "  ")
		fmt.Println(string(b))
		return
	case "solve":
		var token string
		if 3 != nargs {
			help()
			os.Exit(1)
			return
		}
		token = args[2]
		h, err := hashcash.Parse(token)
		if nil != err {
			fmt.Fprintf(os.Stderr, "%s\n", err)
			os.Exit(1)
			return
		}
		err = h.Solve(22)
		if nil != err {
			fmt.Fprintf(os.Stderr, "%s\n", err)
			os.Exit(1)
			return
		}

		fmt.Println(h.String())
		return
	case "hash":
		var token string
		if 3 != nargs {
			help()
			os.Exit(1)
			return
		}
		token = args[2]
		hash := sha256.Sum256([]byte(token))
		fmt.Println(hex.EncodeToString(hash[:]))
		return
	case "verify":
		var token string
		if nargs < 3 {
			help()
			os.Exit(1)
			return
		}
		token = args[2]
		h, err := hashcash.Parse(token)
		if nil != err {
			fmt.Fprintf(os.Stderr, "%s\n", err)
			return
		}

		subject := "*"
		if nargs >= 4 {
			subject = args[3]
		}

		err = h.Verify(subject)
		if nil != err {
			fmt.Fprintf(os.Stderr, "%s\n", err)
			return
		}

		var duration string
		dur := h.ExpiresAt.Sub(time.Now())
		if dur > 365*24*time.Hour {
			duration = "...a long, long time"
		} else {
			duration = dur.Truncate(time.Second).String()
		}
		fmt.Println("valid for", duration)
		return
	default:
		help()
		os.Exit(1)
	}
}