package frontend

import (
	"fmt"
	"time"
	"embed"
	"strings"
	"net/http"
	"net/url"
	"git.noctra.dev/noctra/servtex/backend"
	"git.noctra.dev/noctra/servtex/globals"
)

//go:embed jscss/bootstrap.min.css
//go:embed jscss/custom-view.css
//go:embed jscss/htmx.min.js
//go:embed jscss/htmx-ext-sse.js
//go:embed templates/main.html
var WebFiles embed.FS

// Adds necessary Headers for SSE
func sseHeadersAdd(writer *http.ResponseWriter) {
	(*writer).Header().Set("Content-Type", "text/event-stream")
	(*writer).Header().Set("Cache-Control", "no-cache")
	(*writer).Header().Set("Connection", "keep-alive")
}

// Sends a Ping to keep the connection alive
func ssePing(writer *http.ResponseWriter) {
	sseHeadersAdd(writer)

	fmt.Fprintf((*writer), ": ping\n\n")

	(*writer).(http.Flusher).Flush()
}

// Sends new Event
//
// Reads globals.LatexExec
func sseStatusSend(writer *http.ResponseWriter) {
	sseHeadersAdd(writer)

	fmt.Fprintf((*writer), "event: status\n")
	fmt.Fprintf((*writer), "data: Execution Time:  %s\n", globals.LatexExec.Timestamp)
	fmt.Fprintf((*writer), "data: Execution State: %s\n\n", globals.LatexExec.ExecutionState)

	(*writer).(http.Flusher).Flush()
}

// Sends new Event
//
// Reads globals.LatexExec
func ssePDFSend(writer *http.ResponseWriter) {
	sseHeadersAdd(writer)

	fmt.Fprintf((*writer), "event: pdf\n")
	iframe := fmt.Sprintf(
		`<iframe class="pdf-frame" src="servetex.pdf?ts=%s" hx-sse="connect:/sse/pdf" hx-swap="outerHTML"></iframe>`, 
		url.QueryEscape(backend.GetLocalTimeRFC()),
	)
	fmt.Fprintf((*writer), "data: %s\n\n", iframe)

	(*writer).(http.Flusher).Flush()
}

// Sends new Event
//
// Reads globals.LatexExec
func sseOutputSend(writer *http.ResponseWriter) {
	sseHeadersAdd(writer)

	fmt.Fprintf((*writer), "event: output\n")
	lines := strings.SplitSeq(string(globals.LatexExec.Output), "\n")
	for line := range lines {
		fmt.Fprintf((*writer), "data: %s\n", line)
	}
	fmt.Fprintf((*writer), "\n")

	(*writer).(http.Flusher).Flush()
}

// Server Side Event Handler
//
// Sends a Ping instead of actual data when no new data available to save bandwidth
func SSEventHandler(writer http.ResponseWriter, request *http.Request) {
	lastExecution := ""
	for range time.Tick(time.Second) {
		if lastExecution == globals.LatexExec.Timestamp {
			ssePing(&writer)
		} else {
			sseStatusSend(&writer)
			ssePDFSend(&writer)
			sseOutputSend(&writer)
			// comment out for testing purposes
			lastExecution = globals.LatexExec.Timestamp
		}
	}
}


func PDFHandler(writer http.ResponseWriter, request *http.Request) {
	http.NotFound(writer, request)
}

// Serves the main page of ServTeX
func MainHandler(writer http.ResponseWriter, request *http.Request) {
	writer.Header().Set("Content-Type", "text/html")
	main, _ := WebFiles.ReadFile("templates/main.html")
	writer.Write(main)
}