package responsemodifers

import (
	"embed"
	"fmt"
	"html/template"
	"io"
	"ladder/proxychain"
	"log"

	"github.com/go-shiori/dom"
	"github.com/markusmobius/go-trafilatura"
)

//go:embed generate_readable_outline.html
var templateFS embed.FS

// GenerateReadableOutline creates an reader-friendly distilled representation of the article.
// This is a reliable way of bypassing soft-paywalled articles, where the content is hidden, but still present in the DOM.
func GenerateReadableOutline() proxychain.ResponseModification {

	// get template only once, and resuse for subsequent calls
	f := "generate_readable_outline.html"
	tmpl, err := template.ParseFS(templateFS, f)
	if err != nil {
		panic(fmt.Errorf("tx.GenerateReadableOutline Error: %s not found", f))
	}

	return func(chain *proxychain.ProxyChain) error {

		// ===========================================================
		// 1. extract dom contents using reading mode algo
		// ===========================================================
		opts := trafilatura.Options{
			IncludeImages: true,
			IncludeLinks:  true,
			//FavorPrecision:     true,
			FallbackCandidates: nil, // TODO: https://github.com/markusmobius/go-trafilatura/blob/main/examples/chained/main.go
			// implement fallbacks from	"github.com/markusmobius/go-domdistiller" and 	"github.com/go-shiori/go-readability"
			OriginalURL: chain.Request.URL,
		}

		result, err := trafilatura.Extract(chain.Response.Body, opts)
		if err != nil {
			return err
		}

		doc := trafilatura.CreateReadableDocument(result)
		distilledHTML := dom.OuterHTML(doc)

		// ============================================================================
		// 2. render generate_readable_outline.html template using metadata from step 1
		// ============================================================================
		data := map[string]interface{}{
			"Success": true,
			"Params":  chain.Request.URL,
			//"Title":   result.Metadata.Title, // todo: modify CreateReadableDocument so we don't have <h1> titles duplicated?
			"Date":   result.Metadata.Date.String(),
			"Author": result.Metadata.Author,
			"Body":   distilledHTML,
		}

		// ============================================================================
		// 3. queue sending the response back to the client by replacing the response body
		// (the response body will be read as a stream in proxychain.Execute() later on.)
		// ============================================================================
		pr, pw := io.Pipe() // pipe io.writer contents into io.reader

		// Use a goroutine for writing to the pipe so we don't deadlock the request
		go func() {
			defer pw.Close()

			err := tmpl.Execute(pw, data) // <- render template

			if err != nil {
				log.Printf("WARN: GenerateReadableOutline template rendering error: %s\n", err)
			}
		}()

		chain.Context.Set("content-type", "text/html")
		chain.Response.Body = pr // <- replace reponse body reader with our new reader from pipe
		return nil
	}
}