// Package html renders an internal.AggregatorWriter as a complete,
// standalone HTML document built around the same table fragment produced by
// pretty.PrettyPrinter.RenderHTML. The document includes the Bootstrap 5.3
// stylesheet via CDN and embeds the raw table fragment without HTML-escaping
// it so the result opens directly in a browser.
package html

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

	"github.com/nmoniz/any2anexoj/internal"
	"github.com/nmoniz/any2anexoj/internal/writing/pretty"
)

// bootstrapCSSURL is the jsDelivr CDN URL for Bootstrap 5.3.3.
const bootstrapCSSURL = "https://cdn.jsdelivr.net/npm/bootstrap@5.3.3/dist/css/bootstrap.min.css"

// bootstrapIntegrity is the official SRI hash for Bootstrap 5.3.3 css.
const bootstrapIntegrity = "sha384-QWTKZyjpPEjISv5WaRU9OFeRpok6YctnYmDr5pNlyT2bRjXh0JMhjY6hW+ALEwIH"

// HTMLWriter writes a complete HTML document for an AggregatorWriter.
type HTMLWriter struct {
	output  io.Writer
	printer *pretty.PrettyPrinter
	title   string
	lang    string
}

// NewHTMLWriter builds an HTMLWriter that writes a complete HTML document to
// w. The printer is used purely as a source for the raw <table> fragment via
// RenderHTML; this writer never invokes Render or any method that writes to
// printer's own io.Writer.
func NewHTMLWriter(w io.Writer, printer *pretty.PrettyPrinter, title, lang string) *HTMLWriter {
	return &HTMLWriter{
		output:  w,
		printer: printer,
		title:   title,
		lang:    lang,
	}
}

// documentTemplate renders the full HTML page. The table fragment is typed as
// template.HTML so the template engine emits it verbatim without escaping
// the angle brackets in the <table> markup.
var documentTemplate = template.Must(template.New("html").Parse(`<!DOCTYPE html>
<html lang="{{.Lang}}">
<head>
<meta charset="utf-8">
<meta name="viewport" content="width=device-width, initial-scale=1">
<title>{{.Title}}</title>
<link rel="stylesheet" href="{{.CSSURL}}" integrity="{{.Integrity}}" crossorigin="anonymous">
</head>
<body>
<main class="container-fluid py-4">
<h1>{{.Title}}</h1>
<div class="table-responsive">
{{.TableFragment}}
</div>
<p class="text-muted small">Generated at {{.GeneratedAt}}</p>
</main>
</body>
</html>
`))

// Render writes a complete standalone HTML document for aw to the configured
// output. The same HTMLWriter may be reused; each call rebuilds the table
// fragment from aw so the rendered <tr> count reflects aw's current items and
// no rows are duplicated across invocations.
func (hw *HTMLWriter) Render(aw *internal.AggregatorWriter) error {
	if hw.printer == nil {
		return fmt.Errorf("html: nil printer")
	}
	fragment := hw.printer.RenderHTML(aw)
	data := struct {
		Lang          string
		Title         string
		CSSURL        string
		Integrity     string
		TableFragment template.HTML
		GeneratedAt   string
	}{
		Lang:          hw.lang,
		Title:         hw.title,
		CSSURL:        bootstrapCSSURL,
		Integrity:     bootstrapIntegrity,
		TableFragment: template.HTML(fragment),
		GeneratedAt:   time.Now().UTC().Format(time.RFC3339),
	}
	if err := documentTemplate.Execute(hw.output, data); err != nil {
		return fmt.Errorf("render html document: %w", err)
	}
	return nil
}