fm-rds-tx/internal/control/control.go

package control

import (
	"encoding/json"
	"net/http"
	"sync"

	"github.com/jan/fm-rds-tx/internal/config"
	drypkg "github.com/jan/fm-rds-tx/internal/dryrun"
	"github.com/jan/fm-rds-tx/internal/platform"
)

// TXController is an optional interface the Server uses to start/stop TX.
type TXController interface {
	StartTX() error
	StopTX() error
	TXStats() map[string]any
}

type Server struct {
	mu   sync.RWMutex
	cfg  config.Config
	tx   TXController
	drv  platform.SoapyDriver // optional, for runtime stats
}

type ConfigPatch struct {
	FrequencyMHz     *float64 `json:"frequencyMHz,omitempty"`
	OutputDrive      *float64 `json:"outputDrive,omitempty"`
	ToneLeftHz       *float64 `json:"toneLeftHz,omitempty"`
	ToneRightHz      *float64 `json:"toneRightHz,omitempty"`
	ToneAmplitude    *float64 `json:"toneAmplitude,omitempty"`
	PS               *string  `json:"ps,omitempty"`
	RadioText        *string  `json:"radioText,omitempty"`
	PreEmphasisTauUS *float64 `json:"preEmphasisTauUS,omitempty"`
	LimiterEnabled   *bool    `json:"limiterEnabled,omitempty"`
	LimiterCeiling   *float64 `json:"limiterCeiling,omitempty"`
}

func NewServer(cfg config.Config) *Server {
	return &Server{cfg: cfg}
}

func (s *Server) SetTXController(tx TXController) {
	s.mu.Lock()
	s.tx = tx
	s.mu.Unlock()
}

func (s *Server) SetDriver(drv platform.SoapyDriver) {
	s.mu.Lock()
	s.drv = drv
	s.mu.Unlock()
}

func (s *Server) Handler() http.Handler {
	mux := http.NewServeMux()
	mux.HandleFunc("/healthz", s.handleHealth)
	mux.HandleFunc("/status", s.handleStatus)
	mux.HandleFunc("/dry-run", s.handleDryRun)
	mux.HandleFunc("/config", s.handleConfig)
	mux.HandleFunc("/runtime", s.handleRuntime)
	mux.HandleFunc("/tx/start", s.handleTXStart)
	mux.HandleFunc("/tx/stop", s.handleTXStop)
	return mux
}

func (s *Server) handleHealth(w http.ResponseWriter, _ *http.Request) {
	w.Header().Set("Content-Type", "application/json")
	_ = json.NewEncoder(w).Encode(map[string]any{"ok": true})
}

func (s *Server) handleStatus(w http.ResponseWriter, _ *http.Request) {
	s.mu.RLock()
	cfg := s.cfg
	s.mu.RUnlock()

	w.Header().Set("Content-Type", "application/json")
	_ = json.NewEncoder(w).Encode(map[string]any{
		"service":             "fm-rds-tx",
		"backend":             cfg.Backend.Kind,
		"frequencyMHz":        cfg.FM.FrequencyMHz,
		"stereoEnabled":       cfg.FM.StereoEnabled,
		"rdsEnabled":          cfg.RDS.Enabled,
		"preEmphasisTauUS":    cfg.FM.PreEmphasisTauUS,
		"limiterEnabled":      cfg.FM.LimiterEnabled,
		"fmModulationEnabled": cfg.FM.FMModulationEnabled,
	})
}

func (s *Server) handleRuntime(w http.ResponseWriter, _ *http.Request) {
	s.mu.RLock()
	drv := s.drv
	tx := s.tx
	s.mu.RUnlock()

	result := map[string]any{}
	if drv != nil {
		result["driver"] = drv.Stats()
	}
	if tx != nil {
		result["engine"] = tx.TXStats()
	}
	w.Header().Set("Content-Type", "application/json")
	_ = json.NewEncoder(w).Encode(result)
}

func (s *Server) handleTXStart(w http.ResponseWriter, r *http.Request) {
	if r.Method != http.MethodPost {
		http.Error(w, "method not allowed", http.StatusMethodNotAllowed)
		return
	}
	s.mu.RLock()
	tx := s.tx
	s.mu.RUnlock()
	if tx == nil {
		http.Error(w, "tx controller not available", http.StatusServiceUnavailable)
		return
	}
	if err := tx.StartTX(); err != nil {
		http.Error(w, err.Error(), http.StatusConflict)
		return
	}
	w.Header().Set("Content-Type", "application/json")
	_ = json.NewEncoder(w).Encode(map[string]any{"ok": true, "action": "started"})
}

func (s *Server) handleTXStop(w http.ResponseWriter, r *http.Request) {
	if r.Method != http.MethodPost {
		http.Error(w, "method not allowed", http.StatusMethodNotAllowed)
		return
	}
	s.mu.RLock()
	tx := s.tx
	s.mu.RUnlock()
	if tx == nil {
		http.Error(w, "tx controller not available", http.StatusServiceUnavailable)
		return
	}
	if err := tx.StopTX(); err != nil {
		http.Error(w, err.Error(), http.StatusInternalServerError)
		return
	}
	w.Header().Set("Content-Type", "application/json")
	_ = json.NewEncoder(w).Encode(map[string]any{"ok": true, "action": "stopped"})
}

func (s *Server) handleDryRun(w http.ResponseWriter, _ *http.Request) {
	s.mu.RLock()
	cfg := s.cfg
	s.mu.RUnlock()
	w.Header().Set("Content-Type", "application/json")
	_ = json.NewEncoder(w).Encode(drypkg.Generate(cfg))
}

func (s *Server) handleConfig(w http.ResponseWriter, r *http.Request) {
	switch r.Method {
	case http.MethodGet:
		s.mu.RLock()
		cfg := s.cfg
		s.mu.RUnlock()
		w.Header().Set("Content-Type", "application/json")
		_ = json.NewEncoder(w).Encode(cfg)
	case http.MethodPost:
		// TODO: config changes only update the control server's copy.
		// The running Engine/Generator holds its own snapshot and won't
		// pick up these changes until restarted. Wire up a hot-reload
		// path or document this limitation clearly for operators.
		var patch ConfigPatch
		if err := json.NewDecoder(r.Body).Decode(&patch); err != nil {
			http.Error(w, err.Error(), http.StatusBadRequest)
			return
		}

		s.mu.Lock()
		next := s.cfg
		if patch.FrequencyMHz != nil {
			next.FM.FrequencyMHz = *patch.FrequencyMHz
		}
		if patch.OutputDrive != nil {
			next.FM.OutputDrive = *patch.OutputDrive
		}
		if patch.ToneLeftHz != nil {
			next.Audio.ToneLeftHz = *patch.ToneLeftHz
		}
		if patch.ToneRightHz != nil {
			next.Audio.ToneRightHz = *patch.ToneRightHz
		}
		if patch.ToneAmplitude != nil {
			next.Audio.ToneAmplitude = *patch.ToneAmplitude
		}
		if patch.PS != nil {
			next.RDS.PS = *patch.PS
		}
		if patch.RadioText != nil {
			next.RDS.RadioText = *patch.RadioText
		}
		if patch.PreEmphasisTauUS != nil {
			next.FM.PreEmphasisTauUS = *patch.PreEmphasisTauUS
		}
		if patch.LimiterEnabled != nil {
			next.FM.LimiterEnabled = *patch.LimiterEnabled
		}
		if patch.LimiterCeiling != nil {
			next.FM.LimiterCeiling = *patch.LimiterCeiling
		}
		if err := next.Validate(); err != nil {
			s.mu.Unlock()
			http.Error(w, err.Error(), http.StatusBadRequest)
			return
		}
		s.cfg = next
		s.mu.Unlock()

		w.Header().Set("Content-Type", "application/json")
		_ = json.NewEncoder(w).Encode(map[string]any{"ok": true})
	default:
		http.Error(w, "method not allowed", http.StatusMethodNotAllowed)
	}
}