handler.go

package handlers

import (
	"fmt"
	"net/http"
	"runtime"
)

// HandlerFunc is the function signature for use in Handler
type HandlerFunc func(c *Context, wr http.ResponseWriter, req *http.Request) (string, error)

// Handler encapsulates our handlers so we can pass a type save context and
// still conform to the http.Handler interface
type Handler struct {
	*Context
	Func HandlerFunc
}

// ServeHTTP gets the request context, calls the actual handler func and
// handles it's returned error, if any
func (h Handler) ServeHTTP(wr http.ResponseWriter, req *http.Request) {
	c := RequestContext(h.Context, wr, req)

	// catch handler panics
	defer func() {
		r := recover()
		if r == nil {
			return
		}

		// stack (copied from net/http/server.go:1284)
		const size = 64 << 10
		buf := make([]byte, size)
		buf = buf[:runtime.Stack(buf, false)]
		c.Logger.Errorf("panic recovered: %v\n%s", r, buf)

		c.Metrics.Panics.Inc()
		http.Error(c.Wr, errInternalServerError.Error(), http.StatusInternalServerError)
	}()

	// run the actual handler
	tpl, origErr := h.Func(c, wr, req)

	// if there's no error, write 200 OK and display the template if any
	if origErr == nil {
		wr.WriteHeader(200)
		if tpl != "" {
			h.handleErr(c, c.View.Display(wr, tpl), false)
		}
		return
	}

	// otherwise handle that motherfucker
	de := NewDebugError(origErr)
	err := de.Underlying()

	if tpl == "" {
		wr.Header().Set("Content-Type", "text/plain; charset=utf-8")
	}

	switch e := err.(type) {
	case Redirector:
		http.Redirect(wr, req, e.Path(), e.Status())
		return
	case *UserError:
		wr.WriteHeader(e.Status())
		if tpl == "" {
			fmt.Fprint(wr, e)
		} else {
			c.View.AddError(e)
		}
	case Error:
		c.Logger.Errorf("Status: %d - %v", e.Status(), de)
		wr.WriteHeader(e.Status())
		if tpl == "" {
			fmt.Fprint(wr, e)
		} else {
			c.View.AddError(e)
		}
	default:
		wr.WriteHeader(http.StatusInternalServerError)
		h.handleErr(c, de, tpl != "")
	}

	if tpl == "" {
		return
	}

	h.handleErr(c, c.View.Display(wr, tpl), false)
}

func (h Handler) handleErr(c *Context, err error, inView bool) {
	if err == nil {
		return
	}
	err = NewDebugError(err)
	if inView {
		c.Logger.Error(err)
		if c.Debug {
			c.View.AddError(err)
		} else {
			c.View.AddError(errInternalServerError)
		}
	} else {
		c.Logger.Error(err)
		http.Error(c.Wr, errInternalServerError.Error(), http.StatusInternalServerError)
	}
}