package main

import (
	"bytes"
	"io"
	"strings"

	"golang.org/x/net/html/charset"
	"golang.org/x/text/transform"
)

// processHost fetches and parses a single host's WARC record.
func processHost(host Host) ProcessResult {
	warcResult, err := FetchAndParseWARC(host.WarcFilename, host.WarcRecordOffset, int64(host.WarcRecordLength))
	if err != nil {
		return ProcessResult{Err: err, FetchErr: true}
	}

	// Check iframe headers
	iframeAllowed := CheckIframeAllowed(warcResult.HTTPHeaders)

	// Convert body to UTF-8 based on Content-Type header and HTML meta
	contentType := warcResult.HTTPHeaders.Get("Content-Type")
	body := toUTF8(warcResult.Body, contentType)

	// Parse HTML for title and icons
	parsed := ParseHTML(body, host.Protocol, host.Hostname)

	// Sanitize title — strip any remaining invalid UTF-8 bytes
	// (handles pages that lie about encoding or have truncated sequences)
	title := strings.ToValidUTF8(parsed.Title, "")

	return ProcessResult{
		Title:         title,
		IframeAllowed: iframeAllowed,
		Icons:         parsed.Icons,
	}
}

// toUTF8 detects the encoding of the HTML body and converts to UTF-8.
func toUTF8(body []byte, contentType string) []byte {
	// DetermineEncoding checks Content-Type header and <meta> tags
	encoding, _, _ := charset.DetermineEncoding(body, contentType)
	if encoding == nil {
		return body
	}

	reader := transform.NewReader(bytes.NewReader(body), encoding.NewDecoder())
	utf8Body, err := io.ReadAll(reader)
	if err != nil {
		return body
	}
	return utf8Body
}