package render

import (
	"fmt"
	"html/template"
	"io"

	"slidewalk/internal/parser"
	"slidewalk/web"
)

var pageTemplate = template.Must(template.ParseFS(web.Templates, "templates/page.html.tmpl"))

// Page is the data needed to render a full slide deck as one HTML page.
type Page struct {
	// Title is used as the document's <title>.
	Title string
	// Slides are the deck's slides, in presentation order.
	Slides []parser.Slide
	// DevReload, when true, includes the dev-only live-reload client script
	// that listens for change notifications from the dev server. It must
	// stay false for static exports.
	DevReload bool
}

// slideView is the per-slide data exposed to the page template. Index is
// the slide's 1-based position, used as the data-slide attribute.
type slideView struct {
	Index       int
	Title       string
	Class       string
	Notes       string
	Incremental bool
	HTML        template.HTML
}

// pageView is the top-level data exposed to the page template.
type pageView struct {
	Title     string
	Slides    []slideView
	DevReload bool
}

// Render writes page as a single self-contained HTML document to w, with
// one <section data-slide="n"> per slide in presentation order.
//
// Render is the shared assembly step behind both the dev server
// (internal/watch) and the static exporter (internal/export): both call it
// to turn parsed slides into the final page, so the markup is only ever
// built in one place.
func Render(w io.Writer, page Page) error {
	views := make([]slideView, len(page.Slides))
	for i, s := range page.Slides {
		views[i] = slideView{
			Index:       i + 1,
			Title:       s.Title,
			Class:       s.Class,
			Notes:       s.Notes,
			Incremental: s.Incremental,
			HTML:        s.HTML,
		}
	}

	data := pageView{Title: page.Title, Slides: views, DevReload: page.DevReload}
	if err := pageTemplate.Execute(w, data); err != nil {
		return fmt.Errorf("rendering page: %w", err)
	}
	return nil
}