hamlab/internal/api/play.go

package api

// Playing a video the browser cannot play as it is: POST /api/files/play starts an HLS
// re-encode on this machine (internal/media), GET …/play/{id}/index.m3u8 and the segments
// feed the player, GET …/play/{id} is its progress, DELETE ends it. /api/files/play-caps
// says which codecs this machine can make and on what. Root mode (?sudo=1) reads the file
// and runs ffmpeg as root, through the same sudo the file reads use.

import (
	"context"
	"encoding/json"
	"errors"
	"io"
	"log"
	"net/http"
	"path/filepath"
	"strings"
	"time"

	"hamlab/internal/files"
	"hamlab/internal/media"
)

const playLimit = 3 // re-encodes at once on one machine; a GPU does two or three, a CPU one

type playCaps struct {
	Codecs    []playCodec     `json:"codecs"`
	Qualities []media.Quality `json:"qualities"`
	Error     string          `json:"error,omitempty"`
}

type playCodec struct {
	media.Codec
	Engine string `json:"engine,omitempty"` // "" when nothing here encodes it
}

// playCapsHandler: GET /api/files/play-caps[?sudo=1]
func (s *Server) playCapsHandler(w http.ResponseWriter, r *http.Request) {
	root := r.URL.Query().Get("sudo") == "1"
	if root && s.fsSudo == nil {
		jsonErr(w, 403, "root access needs passwordless sudo on the host")
		return
	}
	caps, err := s.thumbs.capsFor(r.Context(), root, false)
	pc := playCaps{Codecs: []playCodec{}, Qualities: media.Qualities}
	if err != nil {
		pc.Error = err.Error()
	} else if caps.Error != "" {
		pc.Error = caps.Error
	}
	for _, c := range media.Codecs {
		x := playCodec{Codec: c}
		if pc.Error == "" {
			x.Engine = media.EngineFor(caps, c.ID)
		}
		pc.Codecs = append(pc.Codecs, x)
	}
	jsonOK(w, 200, pc)
}

// playStart: POST /api/files/play[?sudo=1] {path, codec, quality}
func (s *Server) playStart(w http.ResponseWriter, r *http.Request) {
	fsys, ok := s.fsFor(w, r)
	if !ok {
		return
	}
	root := r.URL.Query().Get("sudo") == "1"
	var body struct{ Path, Codec, Quality string }
	if err := json.NewDecoder(io.LimitReader(r.Body, 64<<10)).Decode(&body); err != nil {
		jsonErr(w, 400, "bad request")
		return
	}
	p, err := files.Clean(body.Path)
	if err != nil {
		jsonErr(w, 400, err.Error())
		return
	}
	if media.Kind(p) != "video" {
		jsonErr(w, 415, "not a video")
		return
	}
	if err := media.ValidChoice(body.Codec, body.Quality); err != nil {
		jsonErr(w, 400, err.Error())
		return
	}
	if _, err := fsys.Stat(r.Context(), p); err != nil {
		fsErr(w, err)
		return
	}
	caps, err := s.thumbs.capsFor(r.Context(), root, false)
	if err != nil {
		jsonErr(w, 503, err.Error())
		return
	}
	if caps.Error != "" {
		jsonErr(w, 503, caps.Error)
		return
	}
	ictx, cancel := context.WithTimeout(r.Context(), 30*time.Second)
	src, err := media.Inspect(ictx, caps, p, root)
	cancel()
	if err != nil {
		playErr(w, err)
		return
	}
	st, err := s.plays.Open(r.Context(), caps, root, p, body.Codec, body.Quality, src)
	if err != nil {
		playErr(w, err)
		return
	}
	log.Printf("files: play %s as %s %s on %s (from %s)", p, st.Codec, st.Quality, st.Engine, clientIP(r))
	jsonOK(w, 200, map[string]any{"stream": st, "url": "/api/files/play/" + st.ID + "/index.m3u8"})
}

func playErr(w http.ResponseWriter, err error) {
	var de *media.DecodeError
	switch {
	case errors.As(err, &de):
		jsonErr(w, 422, de.Msg)
	case strings.Contains(err.Error(), "already being re-encoded"):
		jsonErr(w, 429, err.Error())
	case strings.HasPrefix(err.Error(), "unknown ") || strings.HasPrefix(err.Error(), "nothing on this machine encodes"):
		jsonErr(w, 400, err.Error())
	case errors.Is(err, context.DeadlineExceeded):
		jsonErr(w, 504, "the file took too long to read")
	default:
		jsonErr(w, 500, err.Error())
	}
}

// playStatus: GET /api/files/play/{id}
func (s *Server) playStatus(w http.ResponseWriter, r *http.Request) {
	st, ok := s.plays.Find(r.PathValue("id"))
	if !ok {
		jsonErr(w, 404, "no such stream")
		return
	}
	jsonOK(w, 200, st.Status())
}

// playStop: DELETE /api/files/play/{id}, or POST …/close — the form a page can send on its
// way out (navigator.sendBeacon), so a phone closing the tab releases the machine at once.
func (s *Server) playStop(w http.ResponseWriter, r *http.Request) {
	s.plays.Close(r.PathValue("id"))
	w.WriteHeader(204)
}

// playFile: GET /api/files/play/{id}/{file} — the playlist, the init segment, a segment.
// A seekable stream's playlist is written whole, up front; a segment of it that isn't on disk
// yet is waited for, or re-encoded from there if the encode isn't heading that way (a seek).
func (s *Server) playFile(w http.ResponseWriter, r *http.Request) {
	st, ok := s.plays.Find(r.PathValue("id"))
	if !ok {
		jsonErr(w, 404, "no such stream")
		return
	}
	name := r.PathValue("file")
	p, ok := st.File(name)
	if !ok {
		jsonErr(w, 404, "not a stream file")
		return
	}
	w.Header().Set("Cache-Control", "no-store")
	w.Header().Set("X-Content-Type-Options", "nosniff")
	if st.Seekable {
		if name == "index.m3u8" {
			w.Header().Set("Content-Type", "application/vnd.apple.mpegurl")
			_, _ = w.Write(st.Playlist())
			return
		}
		if i, isSeg := media.SegmentIndex(name); isSeg {
			sp, err := st.Segment(r.Context(), i)
			switch {
			case errors.Is(err, media.ErrNotInFilm):
				jsonErr(w, 404, err.Error())
				return
			case r.Context().Err() != nil:
				return // the player moved on
			case err != nil:
				jsonErr(w, 503, err.Error())
				return
			}
			p = sp
		}
	}
	switch filepath.Ext(p) {
	case ".m3u8":
		w.Header().Set("Content-Type", "application/vnd.apple.mpegurl")
	default:
		w.Header().Set("Content-Type", "video/mp4")
	}
	http.ServeFile(w, r, p)
}