package main

import (
	"flag"
	"fmt"
	"os"
	"strconv"
)

const (
	flagBalance = "balance"
	flagCreate  = "create"
	flagSend    = "send"
	flagLedger  = "ledger"
)

type CLI struct{}

// Run parses command line arguments and processes commands
func (cli *CLI) Run() {
	cli.validateArgs()

	// Valid CLI flags
	getBalanceCmd := flag.NewFlagSet(flagBalance, flag.ExitOnError)
	createBlockchainCmd := flag.NewFlagSet(flagCreate, flag.ExitOnError)
	sendCmd := flag.NewFlagSet(flagSend, flag.ExitOnError)
	printChainCmd := flag.NewFlagSet(flagLedger, flag.ExitOnError)

	getBalanceAddress := getBalanceCmd.String("address", "", "The address to get the balance of")
	createBlockchainAddress := createBlockchainCmd.String("address", "", "The address to send the genesis block reward to")
	sendFrom := sendCmd.String("from", "", "Source wallet address")
	sendTo := sendCmd.String("to", "", "Destination wallet address")
	sendAmount := sendCmd.Int("amount", 0, "Amount to send")

	switch os.Args[1] {
	case flagBalance:
		if err := getBalanceCmd.Parse(os.Args[2:]); err != nil {
			exitWithError(err)
		}
	case flagCreate:
		if err := createBlockchainCmd.Parse(os.Args[2:]); err != nil {
			exitWithError(err)
		}
	case flagLedger:
		if err := printChainCmd.Parse(os.Args[2:]); err != nil {
			exitWithError(err)
		}
	case flagSend:
		if err := sendCmd.Parse(os.Args[2:]); err != nil {
			exitWithError(err)
		}
	default:
		cli.printUsage()
		os.Exit(1)
	}

	if getBalanceCmd.Parsed() {
		if *getBalanceAddress == "" {
			getBalanceCmd.Usage()
			os.Exit(1)
		}
		cli.getBalance(*getBalanceAddress)
	}

	if createBlockchainCmd.Parsed() {
		if *createBlockchainAddress == "" {
			createBlockchainCmd.Usage()
			os.Exit(1)
		}
		cli.createBlockchain(*createBlockchainAddress)
	}

	if printChainCmd.Parsed() {
		cli.printChain()
	}

	if sendCmd.Parsed() {
		if *sendFrom == "" || *sendTo == "" || *sendAmount <= 0 {
			sendCmd.Usage()
			os.Exit(1)
		}
		cli.send(*sendFrom, *sendTo, *sendAmount)
	}
}

// createBlockchain creates a new blockchain with a genesis block
func (cli *CLI) createBlockchain(address string) {
	bc := CreateBlockchain(address)
	bc.db.Close()
	fmt.Println("Done!")
}

// printChain outputs the entire ledger
func (cli *CLI) printChain() {
	bc := NewBlockchain()
	defer bc.db.Close()

	bci := bc.Iterator()

	for {
		block := bci.Next()
		fmt.Printf("Prev. hash: %x\n", block.PrevBlockHash)
		fmt.Printf("Hash: %x\n", block.Hash)
		pow := NewProofOfWork(block)
		fmt.Printf("PoW: %s\n", strconv.FormatBool(pow.Validate()))
		fmt.Println()

		if len(block.PrevBlockHash) == 0 {
			break
		}
	}
}

// getBalance retrieves the transaction balance for an address
func (cli *CLI) getBalance(address string) {
	bc := NewBlockchain()
	defer bc.db.Close()

	balance := 0
	UTXOs := bc.FindUTXO(address)

	for _, out := range UTXOs {
		balance += out.Value
	}

	fmt.Printf("Balance of '%s': %d\n", address, balance)
}

// send Triggers a transaction exchange
func (cli *CLI) send(from, to string, amount int) {
	bc := NewBlockchain()
	defer bc.db.Close()

	tx := NewUTXOTransaction(from, to, amount, bc)
	bc.MineBlock([]*Transaction{tx})
	fmt.Println("Success!")
}

// printUsage prints the usage of the cli app
func (cli *CLI) printUsage() {
	fmt.Println("Usage:")
	fmt.Println("\t" + flagBalance + " -address ADDRESS\tGet balance of ADDRESS")
	fmt.Println("\t" + flagCreate + " -address ADDRESS\tCreate a blockchain and send genesis block reward to ADDRESS")
	fmt.Println("\t" + flagLedger + "\t\t\tprint all the blocks of the blockchain")
	fmt.Println("\t" + flagSend + " -from FROM -to TO -amount AMOUNT\tSend AMOUNT of coins from FROM address to TO address")
}

// validateArgs just makes sure that we've got a couple arguments
func (cli *CLI) validateArgs() {
	if len(os.Args) < 2 {
		cli.printUsage()
		os.Exit(1)
	}
}

func exitWithError(err error) {
	fmt.Println(err)
	os.Exit(1)
}