package tmpls

import (
	"errors"
	"html/template"
	"io/fs"
	"net/http"
	"os"
	"path/filepath"
	"strings"

	"github.com/gin-gonic/gin/render"
)

var ErrNoTmpl = errors.New("no such template in map")

// TmplMap is a map of templates that implements
// the render.HTMLRender interface
type Map map[string]*template.Template

// Instance returns a Tmpl instance for the given template
func (m Map) Instance(name string, data interface{}) render.Render {
	tmpl, ok := m[name]
	if !ok {
		return nil
	}
	return Tmpl{
		Template: tmpl,
		data:     data,
	}
}

// Tmpl implements the render.Render interface
type Tmpl struct {
	*template.Template
	data interface{}
}

// Render renders the template to response writer
func (t Tmpl) Render(res http.ResponseWriter) error {
	if t.Template == nil {
		return ErrNoTmpl
	}
	return t.Execute(res, t.data)
}

// WriteContentType sets content type to HTML
func (t Tmpl) WriteContentType(res http.ResponseWriter) {
	res.Header().Set("Content-Type", "text/html; charset=utf-8")
}

func FromFS(f fs.FS, root, ext string, fm template.FuncMap) (Map, error) {
	tmpls := Map{}
	err := fs.WalkDir(f, root, func(path string, d fs.DirEntry, err error) error {
		if err != nil {
			return err
		}
		if d.IsDir() || path == filepath.Join(root, "base"+ext) {
			return nil
		}

		tmplName := strings.TrimPrefix(path, root+"/")
		tmplName = strings.TrimSuffix(tmplName, ext)

		tmpl := template.New(filepath.Base(path))

		if fm != nil {
			tmpl = tmpl.Funcs(fm)
		}

		tmpl, err = tmpl.ParseFS(f, path, filepath.Join(root, "base"+ext))
		if err != nil {
			return err
		}

		tmpls[tmplName] = tmpl

		return nil
	})
	return tmpls, err
}

func FromDir(baseDir, ext string, fm template.FuncMap) (Map, error) {
	dir := filepath.Dir(baseDir)
	root := filepath.Base(baseDir)
	return FromFS(os.DirFS(dir), root, ext, fm)
}