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

package dryrun

import (
    "encoding/json"
    "fmt"
    "os"
    "path/filepath"

    cfgpkg "github.com/jan/fm-rds-tx/internal/config"
)

type FrameSummary struct {
    Mode           string    `json:"mode"`
    FrequencyMHz   float64   `json:"frequencyMHz"`
    StereoEnabled  bool      `json:"stereoEnabled"`
    RDSEnabled     bool      `json:"rdsEnabled"`
    SampleRateHz   int       `json:"sampleRateHz"`
    CompositeRate  int       `json:"compositeRateHz"`
    PilotLevel     float64   `json:"pilotLevel"`
    RDSInjection   float64   `json:"rdsInjection"`
    OutputDrive    float64   `json:"outputDrive"`
    PreviewSamples []float64 `json:"previewSamples"`
}

func Generate(cfg cfgpkg.Config) FrameSummary {
    preview := make([]float64, 16)
    base := cfg.Audio.Gain * cfg.FM.OutputDrive
    for i := range preview {
        sign := 1.0
        if i%2 == 1 {
            sign = -1.0
        }
        preview[i] = sign * base * float64(i+1) / 16.0
    }
    return FrameSummary{
        Mode:           "dry-run",
        FrequencyMHz:   cfg.FM.FrequencyMHz,
        StereoEnabled:  cfg.FM.StereoEnabled,
        RDSEnabled:     cfg.RDS.Enabled,
        SampleRateHz:   cfg.Audio.SampleRate,
        CompositeRate:  cfg.FM.CompositeRateHz,
        PilotLevel:     cfg.FM.PilotLevel,
        RDSInjection:   cfg.FM.RDSInjection,
        OutputDrive:    cfg.FM.OutputDrive,
        PreviewSamples: preview,
    }
}

func WriteJSON(path string, frame FrameSummary) error {
    data, err := json.MarshalIndent(frame, "", "  ")
    if err != nil {
        return fmt.Errorf("marshal dry-run frame: %w", err)
    }
    if path == "" || path == "-" {
        _, err = os.Stdout.Write(append(data, '\n'))
        return err
    }
    if err := os.MkdirAll(filepath.Dir(path), 0o755); err != nil {
        return fmt.Errorf("create output dir: %w", err)
    }
    if err := os.WriteFile(path, append(data, '\n'), 0o644); err != nil {
        return fmt.Errorf("write dry-run frame: %w", err)
    }
    return nil
}