gophertype/pkg/responses/templates.go

package responses

import (
	"errors"
	"fmt"
	"html/template"
	"io/ioutil"
	"log"
	"net/http"
	"os"
	"strings"

	"git.kirsle.net/apps/gophertype/pkg/bundled"
)

// GetTemplate returns the template file's data, wherever it is.
// Checks the embedded bindata, then the user root on disk, then error.
// If it can be found, returns the contents or error.
func GetFile(path string) ([]byte, error) {
	// Check bindata.
	if b, err := bundled.Asset(path); err == nil {
		return b, nil
	}

	// Check the filesystem. TODO
	if b, err := ioutil.ReadFile("./pvt-www/" + path); err == nil {
		return b, nil
	} else {
		return []byte{}, err
	}
}

// GetFileExists checks if the file exists but doesn't return its data.
func GetFileExists(path string) bool {
	// Check bindata.
	if _, err := bundled.AssetInfo(path); err == nil {
		return true
	}

	// Check the filesystem. TODO
	if _, err := os.Stat(path); err == nil {
		return true
	}

	return false
}

/*
ResolveFile searches for the existence of a file from a fuzzy URL path.

`path` is a request path like "/about"

This function would return e.g. "about.gohtml" as being a file path that is
sure to return data in GetFile().

Path finding rules follow expected behavior from dominant web servers:

- If the exact path is found, return it immediately.
- Try assuming a ".gohtml" or ".md" file extension for the path.
- Try checking if the path is a directory with an "index.gohtml" inside it, etc.
*/
func ResolveFile(path string) (string, error) {
	// Ensure the path doesn't begin with a slash.
	path = strings.TrimLeft(path, "/")

	// Try the exact path.
	if GetFileExists(path) {
		return path, nil
	}

	// Try fuzzy file matches.
	var tries = []string{
		path + ".gohtml",
		path + ".md",
		path + "/index.gohtml",
		path + "/index.html",
	}
	for _, try := range tries {
		path = strings.TrimLeft(try, "/")
		if GetFileExists(path) {
			return path, nil
		}
	}

	return "", errors.New("not found")
}

// RenderTemplate renders a Go HTML template.
// The io.Writer can be an http.ResponseWriter.
func RenderTemplate(w http.ResponseWriter, tmpl string, vars interface{}) error {
	w.Header().Set("Content-Type", "text/html; charset=utf-8")

	// Look for the built-in template.
	if b, err := GetFile(tmpl); err == nil {
		t, err := template.New(tmpl).Parse(string(b))
		if err != nil {
			return fmt.Errorf("bundled template '%s': %s", tmpl, err)
		}

		// We found the template. Can we find the layout html?
		if layout, err := GetFile(".layout.gohtml"); err == nil {
			_, err := t.New("layout").Parse(string(layout))
			if err != nil {
				fmt.Errorf("RenderTemplate(.layout.gohtml): %s", err)
			}
		} else {
			log.Printf("RenderTemplate: .layout.gohtml not found to wrap %s", tmpl)
		}

		fmt.Printf("Render Templ: %s", tmpl)
		if err := t.ExecuteTemplate(w, "layout", vars); err != nil {
			log.Printf("RenderTemplate(%s): %s", tmpl, err)
		}
		log.Println("Done")
		return nil
	} else {
		Panic(w, http.StatusInternalServerError, err.Error())
	}

	return nil
}