package webui

import (
	"embed"
	"errors"
	"html/template"
	"io"
	"path"
	"strings"
	"time"
)

//go:embed templates/*.gohtml static/admin.css static/admin.js
var embeddedFiles embed.FS

type Renderer struct {
	templates *template.Template
}

func NewRenderer() (*Renderer, error) {
	templates, err := template.New("admin").
		Option("missingkey=error").
		Funcs(template.FuncMap{
			"displayTime": displayTime,
			"machineTime": machineTime,
			"pathPart":    pathPart,
		}).
		ParseFS(embeddedFiles, "templates/*.gohtml")
	if err != nil {
		return nil, errors.New("parse admin templates")
	}
	return &Renderer{templates: templates}, nil
}

func (r *Renderer) Execute(
	writer io.Writer,
	name string,
	data any,
) error {
	if r == nil || r.templates == nil {
		return errors.New("admin renderer is not configured")
	}
	if err := r.templates.ExecuteTemplate(writer, name, data); err != nil {
		return errors.New("render admin template")
	}
	return nil
}

func staticFile(name string) ([]byte, error) {
	if name != "admin.css" && name != "admin.js" {
		return nil, errors.New("unknown admin static file")
	}
	content, err := embeddedFiles.ReadFile("static/" + name)
	if err != nil {
		return nil, errors.New("read admin static file")
	}
	return content, nil
}

func displayTime(value time.Time) string {
	if value.IsZero() {
		return "尚未记录"
	}
	return value.Local().Format("2006-01-02 15:04")
}

func machineTime(value time.Time) string {
	if value.IsZero() {
		return ""
	}
	return value.UTC().Format(time.RFC3339)
}

func pathPart(value string) string {
	return pathEscape(strings.TrimSpace(value))
}

func pathEscape(value string) string {
	// Keep IDs as one opaque path component.
	if value == "" || value == "." || value == ".." ||
		path.Base(value) != value || strings.ContainsAny(value, `/\`) {
		return "invalid"
	}
	return value
}