package narco

import (
	"fmt"
	"log"
	"net/http"
	"os"
	"runtime"

	"github.com/codemodus/chain"
	"golang.org/x/net/context"
)

type StackResponseFormatter func(err interface{}, stack []byte) string

func GoFormatStack(err interface{}, stack []byte) string {
	return fmt.Sprintf("Server internal error: %s\n%s", err, stack)
}

func HtmlFormatStack(err interface{}, stack []byte) string {
	return fmt.Sprintf(`<h2>Server internal error: %s</h2><pre>%s</pre>`, err, stack)
}

type Recoverer struct {
	Logger              *log.Logger
	ShowStackInResponse StackResponseFormatter
	StackOtherGoroutine bool
}

func NewRecoverer() *Recoverer {
	return &Recoverer{
		Logger:              log.New(os.Stdout, "[narco] ", log.LstdFlags),
		ShowStackInResponse: nil,
		StackOtherGoroutine: false,
	}
}

func (rec *Recoverer) Wrap() func(chain.Handler) chain.Handler {
	return func(other chain.Handler) chain.Handler {
		return chain.HandlerFunc(func(ctx context.Context, rw http.ResponseWriter, req *http.Request) {
			defer func() {
				err := recover()
				if err == nil {
					return
				}
				stack := make([]byte, 8*1024)
				stack = stack[:runtime.Stack(stack, rec.StackOtherGoroutine)]
				rec.Logger.Printf("PANIC: %s\n%s", err, stack)

				var message string
				if rec.ShowStackInResponse != nil {
					message = rec.ShowStackInResponse(err, stack)
				} else {
					message = http.StatusText(http.StatusInternalServerError)
				}
				Error(ctx, rw, message, http.StatusInternalServerError)
			}()

			other.ServeHTTPContext(ctx, rw, req)
		})
	}
}