package handlers

import (
	"encoding/json"
	"log"
	"net/http"
	"os"

	"aroll/store"
	"aroll/transcode"
	"aroll/ws"
)

type exportRequest struct {
	Filename string              `json:"filename"`
	Segments []transcode.Segment `json:"segments"`
	Duration float64             `json:"duration"`
}

type updateTimeLine struct {
	Type     string              `json:"type"`
	Segments []transcode.Segment `json:"segments"`
	Duration float64             `json:"duration"`
}

func ExportHandler(st *store.Store, hub *ws.Hub) http.HandlerFunc {
	return func(w http.ResponseWriter, r *http.Request) {
		if r.Method != http.MethodPost {
			http.Error(w, "method not allowed", http.StatusMethodNotAllowed)
			return
		}

		var req exportRequest
		if err := json.NewDecoder(r.Body).Decode(&req); err != nil {
			http.Error(w, "bad JSON: "+err.Error(), http.StatusBadRequest)
			return
		}

		if len(req.Segments) == 0 {
			http.Error(w, "no segments", http.StatusBadRequest)
			return
		}

		inPath, ok := st.Path(req.Filename)
		if !ok {
			http.Error(w, "file not found", http.StatusNotFound)
			return
		}

		go func() {
			/* ToDo: Make sure that other video formats gets transcoded */
			outputKey := "output-" + store.NewID() + ".mp4"
			outPath := st.Allocate(outputKey)

			if err := transcode.ExportSegments(inPath, outPath, req.Segments, hub.Broadcast); err != nil {
				os.Remove(outPath)
				broadcastError(hub, err.Error())
				return
			}

			doneMsg, _ := json.Marshal(map[string]string{
				"type":    "done",
				"message": outputKey,
			})
			hub.Broadcast(doneMsg)

			// Build normalized segments for the exported video: timestamps start at 0
			// with no gaps, so the timeline reflects the exported file's layout.
			var normalized []transcode.Segment
			cursor := 0.0
			for _, seg := range req.Segments {
				dur := seg.End - seg.Start
				normalized = append(normalized, transcode.Segment{Start: cursor, End: cursor + dur})
				cursor += dur
			}
			timelineMsg, _ := json.Marshal(updateTimeLine{
				Type:     "timeline",
				Segments: normalized,
				Duration: cursor,
			})
			hub.Broadcast(timelineMsg)
		}()

		w.WriteHeader(http.StatusAccepted)
		log.Println("Export handler works")
	}
}