error-pages/internal/http/handlers/index/handler.go

package index

import (
	"strconv"

	"github.com/tarampampam/error-pages/internal/config"
	"github.com/tarampampam/error-pages/internal/http/core"
	"github.com/tarampampam/error-pages/internal/options"
	"github.com/tarampampam/error-pages/internal/tpl"
	"github.com/valyala/fasthttp"
)

type (
	templatePicker interface {
		// Pick the template name for responding.
		Pick() string
	}

	renderer interface {
		Render(content []byte, props tpl.Properties) ([]byte, error)
	}
)

// NewHandler creates handler for the index page serving.
func NewHandler(cfg *config.Config, p templatePicker, rdr renderer, opt options.ErrorPage) fasthttp.RequestHandler {
	return func(ctx *fasthttp.RequestCtx) {
		pageCode, httpCode := opt.Default.PageCode, int(opt.Default.HTTPCode)

		if returnCode, ok := extractCodeToReturn(ctx); ok {
			pageCode, httpCode = strconv.Itoa(returnCode), returnCode
		}

		core.RespondWithErrorPage(ctx, cfg, p, rdr, pageCode, httpCode, opt)
	}
}

func extractCodeToReturn(ctx *fasthttp.RequestCtx) (int, bool) { // for the Ingress support
	var ch = ctx.Request.Header.Peek(core.CodeHeader)

	if len(ch) > 0 && len(ch) <= 3 {
		if code, err := strconv.Atoi(string(ch)); err == nil {
			if code > 0 && code <= 599 {
				return code, true
			}
		}
	}

	return 0, false
}