portion of code for HeavenManga extension(Tachiyomi)

HeavenManga.kt

...
import org.jsoup.Jsoup
....

class HeavenManga : ParsedHttpSource() {

    ...

    override val baseUrl = "http://heavenmanga.com"

    ...

// selector of getting the link to the first page of a chapter
private fun chapterPageSelector() = "a#l"

    // skip the page that asks for viewing or downloading of image(pages) 
    // and go directly to the page
    override fun pageListRequest(chapter: SChapter): Request {
        val url = chapter.url
        val newUrl = chapterUrl(url)

        return GET(newUrl, headers)
    }
    
    // displaying chapter details and viewing its pages
    override fun chapterFromElement(element: Element): SChapter {
        val urlElement = element.select("a").first()
        val timeElement = element.select("span").first()
        val time = timeElement.text()
        val date = time.replace("--", "-")
        val url = urlElement.attr("href")

        val chapter = SChapter.create()
        chapter.setUrlWithoutDomain(chapterUrl(url))
        chapter.name = urlElement.text()
        chapter.date_upload = parseChapterDate(date.toString())
        return chapter
    }
    
    // getting the direct link of a chapter
    private fun chapterUrl(pageUrl: String): String {
        val element = getUrlContents(pageUrl)
        return element.select(chapterPageSelector()).attr("href")
    }

    // get contents of a url as Document
    private fun getUrlContents(url: String): Document = Jsoup.connect(url).timeout(0).get()
    
    // the following method deals with search results and filtering of genre and alphabetic order
    override fun searchMangaRequest(page: Int, query: String, filters: FilterList): Request {
        val search_url = "$baseUrl/buscar/$query.html"

        // Filter
        if(query.isBlank()) {
            (if (filters.isEmpty()) getFilterList() else filters).forEach { filter ->
                when(filter) {
                    is GenreFilter -> {
                        return GET(baseUrl + filter.toUriPart(), headers)
                    }
                    is AlphabeticoFilter -> {
                        return GET(baseUrl + filter.toUriPart(), headers)
                    }
                }
            }
        }

        return GET(search_url, headers)
    }
    
    /**
    * count all pages(images) from the select tag
    **/
    override fun pageListParse(document: Document): List<Page> {
        val pages = mutableListOf<Page>()
        document.select(".chaptercontrols > select").first().getElementsByTag("option").forEach {
            pages.add(Page(pages.size, it.attr("value")))
        }
        pages.getOrNull(0)?.imageUrl = imageUrlParse(document)
        return pages
    }

    // TODO: learn how to deal with filtering genres
    // Array.from(document.querySelectorAll('.categorias a')).map(a => `Pair("${a.textContent}", "${a.getAttribute('href')}")`).join(',\n')
    // on http://heavenmanga.com/top/
    private class GenreFilter : UriPartFilter("Géneros", arrayOf(
        ...
    ))

    // Array.from(document.querySelectorAll('.letras a')).map(a => `Pair("${a.textContent}", "${a.getAttribute('href')}")`).join(',\n')
    // on http://heavenmanga.com/top/
    private class AlphabeticoFilter : UriPartFilter("Alfabético", arrayOf(
        ...
    ))
    
    // display filters
    override fun getFilterList() = FilterList(
        GenreFilter(),
        AlphabeticoFilter()
    )
    
    // easy way to display filter name and use its value
    private open class UriPartFilter(displayName: String, val vals: Array<Pair<String, String>>) :
        Filter.Select<String>(displayName, vals.map { it.first }.toTypedArray()) {
        fun toUriPart() = vals[state].second
    }
    
....

debug apk file -> tachiyomi-es.heavenmanga-v1.2.1-debug.apk