From 822ff6d357c0473bb30449a6dd9cf26c48fbcc00 Mon Sep 17 00:00:00 2001
From: Jan Svabenik <jan@svabi.ch>
Date: Thu, 2 Apr 2026 22:32:46 +0200
Subject: [PATCH] feat: add simulated transmit path to main cli

---
 cmd/fmrtx/main.go        | 14 ++++++++++
 docs/README.md           |  6 +++++
 internal/app/sim.go      | 56 ++++++++++++++++++++++++++++++++++++++++
 internal/app/sim_test.go | 26 +++++++++++++++++++
 scripts/check.ps1        |  1 +
 5 files changed, 103 insertions(+)
 create mode 100644 internal/app/sim.go
 create mode 100644 internal/app/sim_test.go

diff --git a/cmd/fmrtx/main.go b/cmd/fmrtx/main.go
index f53fcfd..52419a9 100644
--- a/cmd/fmrtx/main.go
+++ b/cmd/fmrtx/main.go
@@ -6,7 +6,9 @@ import (
     "log"
     "net/http"
     "os"
+    "time"
 
+    apppkg "github.com/jan/fm-rds-tx/internal/app"
     cfgpkg "github.com/jan/fm-rds-tx/internal/config"
     ctrlpkg "github.com/jan/fm-rds-tx/internal/control"
     drypkg "github.com/jan/fm-rds-tx/internal/dryrun"
@@ -17,6 +19,9 @@ func main() {
     printConfig := flag.Bool("print-config", false, "print effective config and exit")
     dryRun := flag.Bool("dry-run", false, "run no-hardware dry-run output")
     dryOutput := flag.String("dry-output", "-", "dry-run output path or - for stdout")
+    simulate := flag.Bool("simulate-tx", false, "run simulated Soapy/backend transmit path")
+    simulateOutput := flag.String("simulate-output", "", "simulated transmit output file")
+    simulateDuration := flag.Duration("simulate-duration", 500*time.Millisecond, "simulated transmit duration")
     flag.Parse()
 
     cfg, err := cfgpkg.Load(*configPath)
@@ -40,6 +45,15 @@ func main() {
         return
     }
 
+    if *simulate {
+        summary, err := apppkg.RunSimulatedTransmit(cfg, *simulateOutput, *simulateDuration)
+        if err != nil {
+            log.Fatalf("simulate-tx failed: %v", err)
+        }
+        fmt.Println(summary)
+        return
+    }
+
     srv := ctrlpkg.NewServer(cfg)
     log.Printf("fm-rds-tx listening on %s", cfg.Control.ListenAddress)
     log.Fatal(http.ListenAndServe(cfg.Control.ListenAddress, srv.Handler()))
diff --git a/docs/README.md b/docs/README.md
index af11eaa..9c7ad33 100644
--- a/docs/README.md
+++ b/docs/README.md
@@ -7,6 +7,7 @@
 - `go run ./cmd/fmrtx -print-config`
 - `go run ./cmd/fmrtx -config docs/config.sample.json`
 - `go run ./cmd/fmrtx --dry-run --dry-output build/dryrun/frame.json`
+- `go run ./cmd/fmrtx --simulate-tx --simulate-output build/sim/simulated-soapy.iqf32 --simulate-duration 250ms`
 - `go run ./cmd/offline -duration 500ms -output build/offline/composite.iqf32`
 
 ### Internal DSP module
@@ -25,6 +26,11 @@ It is intended as a no-hardware smoke path for the CLI and config/control-adjace
 
 The HTTP control plane also exposes `GET /dry-run` for quick inspection of the currently effective no-hardware summary.
 
+## Simulated transmit
+
+`--simulate-tx` runs the offline generator through the Soapy-oriented simulated backend path and writes an IQ-style artifact to disk.
+This is the current closest no-hardware stand-in for the future transmit pipeline in the main application path.
+
 ## Offline generation
 
 `cmd/offline` generates a deterministic no-hardware IQ/composite-style file using the repository's output backend path.
diff --git a/internal/app/sim.go b/internal/app/sim.go
new file mode 100644
index 0000000..6950fe0
--- /dev/null
+++ b/internal/app/sim.go
@@ -0,0 +1,56 @@
+package app
+
+import (
+    "context"
+    "encoding/binary"
+    "fmt"
+    "path/filepath"
+    "time"
+
+    cfgpkg "github.com/jan/fm-rds-tx/internal/config"
+    offpkg "github.com/jan/fm-rds-tx/internal/offline"
+    "github.com/jan/fm-rds-tx/internal/output"
+    "github.com/jan/fm-rds-tx/internal/platform"
+)
+
+func RunSimulatedTransmit(cfg cfgpkg.Config, outPath string, duration time.Duration) (string, error) {
+    if outPath == "" {
+        outPath = filepath.Join("build", "sim", "simulated-soapy.iqf32")
+    }
+
+    fileBackend, err := output.NewFileBackend(outPath, binary.LittleEndian, output.BackendInfo{
+        Name:        "simulated-soapy-file",
+        Description: "simulated soapy sink to file",
+    })
+    if err != nil {
+        return "", err
+    }
+    defer fileBackend.Close(context.Background())
+
+    soapyCfg := platform.SoapyConfig{
+        BackendConfig: output.BackendConfig{
+            SampleRateHz: float64(cfg.FM.CompositeRateHz),
+            Channels:     2,
+            IQLevel:      float32(cfg.FM.OutputDrive),
+        },
+        Driver:         "simulated",
+        Device:         cfg.Backend.Device,
+        CenterFreqHz:   cfg.FM.FrequencyMHz * 1_000_000,
+        Simulated:      true,
+        SimulationPath: outPath,
+    }
+    backend := platform.NewSoapyBackend(soapyCfg, platform.NewSimulatedDriver(fileBackend))
+    if err := backend.Configure(context.Background(), soapyCfg.BackendConfig); err != nil {
+        return "", err
+    }
+
+    gen := offpkg.NewGenerator(cfg)
+    frame := gen.GenerateFrame(duration)
+    if _, err := backend.Write(context.Background(), frame); err != nil {
+        return "", err
+    }
+    if err := backend.Flush(context.Background()); err != nil {
+        return "", err
+    }
+    return fmt.Sprintf("simulated transmit: backend=%s output=%s duration=%s", backend.Info().Name, outPath, duration), nil
+}
diff --git a/internal/app/sim_test.go b/internal/app/sim_test.go
new file mode 100644
index 0000000..fe86b5c
--- /dev/null
+++ b/internal/app/sim_test.go
@@ -0,0 +1,26 @@
+package app
+
+import (
+    "os"
+    "path/filepath"
+    "strings"
+    "testing"
+    "time"
+
+    cfgpkg "github.com/jan/fm-rds-tx/internal/config"
+)
+
+func TestRunSimulatedTransmit(t *testing.T) {
+    cfg := cfgpkg.Default()
+    out := filepath.Join(t.TempDir(), "simulated.iqf32")
+    summary, err := RunSimulatedTransmit(cfg, out, 20*time.Millisecond)
+    if err != nil {
+        t.Fatalf("RunSimulatedTransmit failed: %v", err)
+    }
+    if !strings.Contains(summary, "simulated transmit") {
+        t.Fatalf("unexpected summary: %s", summary)
+    }
+    if info, err := os.Stat(out); err != nil || info.Size() == 0 {
+        t.Fatalf("expected non-empty output file, err=%v", err)
+    }
+}
diff --git a/scripts/check.ps1 b/scripts/check.ps1
index d165dca..f1d63d2 100644
--- a/scripts/check.ps1
+++ b/scripts/check.ps1
@@ -1,6 +1,7 @@
 $ErrorActionPreference = "Stop"
 go test ./...
 go run ./cmd/fmrtx --dry-run --dry-output build/dryrun/frame.json
+go run ./cmd/fmrtx --simulate-tx --simulate-output build/sim/simulated-soapy.iqf32 --simulate-duration 250ms
 go run ./cmd/offline -duration 500ms -output build/offline/composite.iqf32
 Push-Location internal
 go test ./...