package main

import (
	"crypto/sha256"
	"embed"
	"flag"
	"fmt"
	"io/fs"
	"log"
	"net/http"
	"os"
	"strconv"
	"strings"

	"github.com/bumi/lnme/ln"
	"github.com/bumi/lnme/lnurl"
	"github.com/didip/tollbooth/v6"
	"github.com/didip/tollbooth/v6/limiter"
	"github.com/knadh/koanf"
	"github.com/knadh/koanf/parsers/toml"
	"github.com/knadh/koanf/providers/basicflag"
	"github.com/knadh/koanf/providers/env"
	"github.com/knadh/koanf/providers/file"
	"github.com/labstack/echo/v4"
	"github.com/labstack/echo/v4/middleware"
)

const DEFAULT_LISTEN = ":1323"

// Middleware for request limited to prevent too many requests
// TODO: move to file
func LimitMiddleware(lmt *limiter.Limiter) echo.MiddlewareFunc {
	return func(next echo.HandlerFunc) echo.HandlerFunc {
		return echo.HandlerFunc(func(c echo.Context) error {
			httpError := tollbooth.LimitByRequest(lmt, c.Response(), c.Request())
			if httpError != nil {
				return c.String(httpError.StatusCode, httpError.Message)
			}
			return next(c)
		})
	}
}

var stdOutLogger = log.New(os.Stdout, "", log.LstdFlags)

type Invoice struct {
	Value int64  `json:"value"`
	Memo  string `json:"memo"`
}

//go:embed files/assets/*
var embeddedAssets embed.FS

//go:embed files/root/index.html
var indexPage string

func main() {
	cfg := LoadConfig()

	e := echo.New()

	// Serve static files if configured
	if cfg.String("static-path") != "" {
		e.Static("/", cfg.String("static-path"))
		// Serve default page
	} else if !cfg.Bool("disable-website") {
		stdOutLogger.Print("Running embedded page")
		e.GET("/", func(c echo.Context) error {
			return c.HTML(200, indexPage)
		})
	}
	assetSubdir, err := fs.Sub(embeddedAssets, "files/assets")
	if err != nil {
		log.Fatal(err)
	}
	// Embed static files and serve those on /lnme (e.g. /lnme/lnme.js)
	assetHandler := http.FileServer(http.FS(assetSubdir))
	e.GET("/lnme/*", echo.WrapHandler(http.StripPrefix("/lnme/", assetHandler)))

	// CORS settings
	if !cfg.Bool("disable-cors") {
		e.Use(middleware.CORS())
	}

	// Recover middleware recovers from panics anywhere in the request chain
	e.Use(middleware.Recover())

	// Request limit per second. DoS protection
	if cfg.Int("request-limit") > 0 {
		limiter := tollbooth.NewLimiter(cfg.Float64("request-limit"), nil)
		e.Use(LimitMiddleware(limiter))
	}

	// Setup lightning client
	stdOutLogger.Printf("Connecting to %s", cfg.String("lnd-address"))
	lndOptions := ln.LNDoptions{
		Address:      cfg.String("lnd-address"),
		CertFile:     cfg.String("lnd-cert-path"),
		CertHex:      cfg.String("lnd-cert"),
		MacaroonFile: cfg.String("lnd-macaroon-path"),
		MacaroonHex:  cfg.String("lnd-macaroon"),
		TorExePath:   cfg.String("tor-exe-path"),
	}
	lnClient, err := ln.NewLNDclient(lndOptions)
	if err != nil {
		stdOutLogger.Print("Error initializing LND client:")
		panic(err)
	}

	// Endpoint URLs compatible to the LND REST API v1
	//
	// Create new invoice
	e.POST("/v1/invoices", func(c echo.Context) error {
		i := new(Invoice)
		if err := c.Bind(i); err != nil {
			stdOutLogger.Printf("Bad request: %s", err)
			return c.JSON(http.StatusBadRequest, "Bad request")
		}

		invoice, err := lnClient.AddInvoice(i.Value, i.Memo, nil, cfg.Bool("enable-private-channels"))
		if err != nil {
			stdOutLogger.Printf("Error creating invoice: %s", err)
			return c.JSON(http.StatusInternalServerError, "Error adding invoice")
		}

		return c.JSON(http.StatusOK, invoice)
	})

	// Get next BTC onchain address
	e.POST("/v1/newaddress", func(c echo.Context) error {
		address, err := lnClient.NewAddress()
		if err != nil {
			stdOutLogger.Printf("Error getting a new BTC address: %s", err)
			return c.JSON(http.StatusInternalServerError, "Error getting address")
		}
		return c.JSON(http.StatusOK, address)
	})

	// Check invoice status
	e.GET("/v1/invoice/:paymentHash", func(c echo.Context) error {
		paymentHash := c.Param("paymentHash")
		invoice, err := lnClient.GetInvoice(paymentHash)

		if err != nil {
			stdOutLogger.Printf("Error looking up invoice: %s", err)
			return c.JSON(http.StatusInternalServerError, "Error fetching invoice")
		}

		return c.JSON(http.StatusOK, invoice)
	})

	if !cfg.Bool("disable-ln-address") {
		lnurlHandler := func(c echo.Context) error {
			host := c.Request().Host
			proto := c.Scheme()
			// TODO: support RFC7239 Forwarded header
			if c.Request().Header.Get("X-Forwarded-Host") != "" {
				host = c.Request().Header.Get("X-Forwarded-Host")
			}
			if c.Request().Header.Get("X-Forwarded-Proto") != "" {
				proto = c.Request().Header.Get("X-Forwarded-Proto")
			}
			name := c.Param("name")
			lightningAddress := name + "@" + host
			lnurlMetadata := "[[\"text/identifier\", \"" + lightningAddress + "\"], [\"text/plain\", \"Sats for " + lightningAddress + "\"]]"
			lnurlpCommentAllowed := cfg.Int64("lnurlp-comment-allowed")

			if amount := c.QueryParam("amount"); amount == "" {
				lnurlPayResponse1 := lnurl.LNURLPayResponse1{
					LNURLResponse:   lnurl.LNURLResponse{Status: "OK"},
					Callback:        fmt.Sprintf("%s://%s%s", proto, host, c.Request().URL.Path),
					MinSendable:     1000,
					MaxSendable:     100000000,
					EncodedMetadata: lnurlMetadata,
					CommentAllowed:  lnurlpCommentAllowed,
					Tag:             "payRequest",
				}
				return c.JSON(http.StatusOK, lnurlPayResponse1)
			} else {
				stdOutLogger.Printf("New LightningAddress request amount: %s", amount)
				msats, err := strconv.ParseInt(amount, 10, 64)
				if err != nil || msats < 1000 {
					stdOutLogger.Printf("Invalid amount: %s", amount)
					return c.JSON(http.StatusOK, lnurl.LNURLErrorResponse{Status: "ERROR", Reason: "Invalid Amount"})
				}
				sats := msats / 1000 // we need sats
				comment := c.QueryParam("comment")
				if commentLength := int64(len(comment)); commentLength > lnurlpCommentAllowed {
					stdOutLogger.Printf("Invalid comment length: %d", commentLength)
					return c.JSON(http.StatusOK, lnurl.LNURLErrorResponse{Status: "ERROR", Reason: "Invalid comment length"})
				}
				metadataHash := sha256.Sum256([]byte(lnurlMetadata))
				invoice, err := lnClient.AddInvoice(sats, comment, metadataHash[:], cfg.Bool("enable-private-channels"))
				if err != nil {
					stdOutLogger.Printf("Error creating invoice: %s", err)
					return c.JSON(http.StatusOK, lnurl.LNURLErrorResponse{Status: "ERROR", Reason: "Server Error"})
				}
				lnurlPayResponse2 := lnurl.LNURLPayResponse2{
					LNURLResponse: lnurl.LNURLResponse{Status: "OK"},
					PR:            invoice.PaymentRequest,
					Routes:        make([][]lnurl.RouteInfo, 0),
					Disposable:    false,
					SuccessAction: &lnurl.SuccessAction{Tag: "message", Message: "Thanks, payment received!"},
				}
				return c.JSON(http.StatusOK, lnurlPayResponse2)
			}
		}
		e.GET("/.well-known/lnurlp/:name", lnurlHandler)
		e.GET("/lnurlp/:name", lnurlHandler)
	}

	// Debug test endpoint
	e.GET("/ping", func(c echo.Context) error {
		return c.JSON(http.StatusOK, "pong")
	})

	port := cfg.String("port")
	// Special case for PORT instead of LNME_PORT due to cloud-providers
	if os.Getenv("PORT") != "" {
		port = os.Getenv("PORT")
	}
	listen := cfg.String("listen")
	if listen != "" && port != "" {
		log.Fatalf("Port and listen options are mutually exclusive, please just use listen.")
	}
	if listen == "" {
		if port != "" {
			stdOutLogger.Printf("Please use listen instead of deprecated port setting.")
			listen = fmt.Sprintf(":%s", port)
		} else {
			listen = DEFAULT_LISTEN
		}
	}

	e.Logger.Fatal(e.Start(listen))
}

func LoadConfig() *koanf.Koanf {
	k := koanf.New(".")

	f := flag.NewFlagSet("LnMe", flag.ExitOnError)
	f.String("lnd-address", "localhost:10009", "The host and port of the LND gRPC server.")
	f.String("lnd-macaroon-path", "~/.lnd/data/chain/bitcoin/mainnet/invoice.macaroon", "Path to the LND macaroon file.")
	f.String("lnd-macaroon", "", "HEX string of LND macaroon file.")
	f.String("lnd-cert-path", "~/.lnd/tls.cert", "Path to the LND tls.cert file.")
	f.String("lnd-cert", "", "HEX string of LND tls cert file.")
	f.Int64("lnurlp-comment-allowed", 210, "Allowed length of LNURL-pay comments.")
	f.Bool("disable-website", false, "Disable default embedded website.")
	f.Bool("disable-ln-address", false, "Disable Lightning Address handling")
	f.Bool("disable-cors", false, "Disable CORS headers.")
	f.Bool("enable-private-channels", false, "Adds private routing hints to invoices")
	f.Float64("request-limit", 5, "Request limit per second.")
	f.String("static-path", "", "Path to a static assets directory.")
	f.String("port", "", "Port to bind on (deprecated - use listen).")
	f.String("listen", "", fmt.Sprintf("Address to bind on. (default \"%s\")", DEFAULT_LISTEN))
	f.String("tor-exe-path", "tor", "Path to the Tor executable. Used when connecting through Tor. (default: tor)")
	var configPath string
	f.StringVar(&configPath, "config", "config.toml", "Path to a .toml config file.")
	f.Parse(os.Args[1:])

	// Load config from flags, including defaults
	if err := k.Load(basicflag.Provider(f, "."), nil); err != nil {
		log.Fatalf("Error loading config: %v", err)
	}

	// Load config from environment variables
	k.Load(env.Provider("LNME_", ".", func(s string) string {
		return strings.Replace(strings.ToLower(strings.TrimPrefix(s, "LNME_")), "_", "-", -1)
	}), nil)

	// Load config from file if available
	if configPath != "" {
		if _, err := os.Stat(configPath); err == nil {
			if err := k.Load(file.Provider(configPath), toml.Parser()); err != nil {
				log.Fatalf("Error loading config file: %v", err)
			}
		}
	}

	return k
}
