// Package handlebars the HandlebarsEngine's functionality
package handlebars

import (
	"fmt"
	"io"
	"io/ioutil"
	"os"
	"path/filepath"
	"strings"
	"sync"

	"github.com/aymerick/raymond"
	"github.com/kataras/iris/config"
)

type (
	// Engine the Handlebars engine
	Engine struct {
		Config        *config.Template
		templateCache map[string]*raymond.Template
		mu            sync.Mutex
	}
)

// New creates and returns the Handlebars template engine
func New(c config.Template) *Engine {
	s := &Engine{Config: &c, templateCache: make(map[string]*raymond.Template, 0)}
	return s
}

// BuildTemplates builds the handlebars templates
func (e *Engine) BuildTemplates() error {
	if e.Config.Extensions == nil || len(e.Config.Extensions) == 0 {
		e.Config.Extensions = []string{".html"}
	}

	// register the global helpers
	if e.Config.Handlebars.Helpers != nil {
		raymond.RegisterHelpers(e.Config.Handlebars.Helpers)
	}
	var templateErr error

	dir := e.Config.Directory
	filepath.Walk(dir, func(path string, info os.FileInfo, err error) error {
		if info == nil || info.IsDir() {
			return nil
		}

		rel, err := filepath.Rel(dir, path)
		if err != nil {
			return err
		}

		ext := ""
		if strings.Index(rel, ".") != -1 {
			ext = filepath.Ext(rel)
		}

		for _, extension := range e.Config.Extensions {
			if ext == extension {

				buf, err := ioutil.ReadFile(path)
				contents := string(buf)

				if err != nil {
					templateErr = err
					break
				}

				name := filepath.ToSlash(rel)

				tmpl, err := raymond.Parse(contents)
				if err != nil {
					templateErr = err
					continue
				}
				e.mu.Lock()
				e.templateCache[name] = tmpl
				e.mu.Unlock()

				break
			}
		}
		return nil
	})
	return templateErr

}
func (e *Engine) fromCache(relativeName string) *raymond.Template {
	e.mu.Lock()
	tmpl, ok := e.templateCache[relativeName]
	if ok {
		e.mu.Unlock()
		return tmpl
	}
	e.mu.Unlock()
	return nil
}

// ExecuteWriter executes a templates and write its results to the out writer
func (e *Engine) ExecuteWriter(out io.Writer, name string, binding interface{}, layout string) error {
	if tmpl := e.fromCache(name); tmpl != nil {
		res, err := tmpl.Exec(binding)
		_, err = fmt.Fprint(out, res)
		return err
	}

	return fmt.Errorf("[IRIS TEMPLATES] Template with name %s doesn't exists in the dir %s", name, e.Config.Directory)
}