Added a module to coalesce adjacent same-speaker segments

internal/config/config.go

@@ -14,9 +14,13 @@ const (
 	DefaultInputReader           = "json-files"
 	DefaultOutputModules         = "json"
 	DefaultPreprocessingModules  = "validate-raw,normalize-speakers,trim-text"
-	DefaultPostprocessingModules = "detect-overlaps,resolve-overlaps,detect-overlaps,autocorrect,assign-ids,validate-output"
+	DefaultPostprocessingModules = "detect-overlaps,resolve-overlaps,coalesce,detect-overlaps,autocorrect,assign-ids,validate-output"
 	DefaultOverlapWordRunGap     = 0.75
+	DefaultWordRunReorderWindow  = 0.4
+	DefaultCoalesceGap           = 3.0
+	DefaultCoalesceGapValue      = "3.0"
 	OverlapWordRunGapEnv         = "SERIATIM_OVERLAP_WORD_RUN_GAP"
+	WordRunReorderWindowEnv      = "SERIATIM_OVERLAP_WORD_RUN_REORDER_WINDOW"
 )
 
 // MergeOptions captures raw CLI option values before validation.
@@ -30,6 +34,7 @@ type MergeOptions struct {
 	OutputModules         string
 	PreprocessingModules  string
 	PostprocessingModules string
+	CoalesceGap           string
 }
 
 // Config is the validated runtime configuration for a merge invocation.
@@ -44,6 +49,8 @@ type Config struct {
 	PreprocessingModules  []string
 	PostprocessingModules []string
 	OverlapWordRunGap     float64
+	WordRunReorderWindow  float64
+	CoalesceGap           float64
 }
 
 // NewMergeConfig validates raw merge options and returns normalized config.
@@ -54,6 +61,8 @@ func NewMergeConfig(opts MergeOptions) (Config, error) {
 		PreprocessingModules:  nil,
 		PostprocessingModules: nil,
 		OverlapWordRunGap:     DefaultOverlapWordRunGap,
+		WordRunReorderWindow:  DefaultWordRunReorderWindow,
+		CoalesceGap:           DefaultCoalesceGap,
 	}
 
 	if cfg.InputReader == "" {
@@ -119,6 +128,14 @@ func NewMergeConfig(opts MergeOptions) (Config, error) {
 	if err != nil {
 		return Config{}, err
 	}
+	cfg.WordRunReorderWindow, err = parseWordRunReorderWindow()
+	if err != nil {
+		return Config{}, err
+	}
+	cfg.CoalesceGap, err = parseCoalesceGap(opts.CoalesceGap)
+	if err != nil {
+		return Config{}, err
+	}
 
 	return cfg, nil
 }
@@ -198,21 +215,45 @@ func requireFile(path string, flag string) error {
 }
 
 func parseOverlapWordRunGap() (float64, error) {
-	value := strings.TrimSpace(os.Getenv(OverlapWordRunGapEnv))
+	return parsePositiveFloatEnv(OverlapWordRunGapEnv, DefaultOverlapWordRunGap)
+}
+
+func parseWordRunReorderWindow() (float64, error) {
+	return parsePositiveFloatEnv(WordRunReorderWindowEnv, DefaultWordRunReorderWindow)
+}
+
+func parseCoalesceGap(value string) (float64, error) {
+	value = strings.TrimSpace(value)
 	if value == "" {
-		return DefaultOverlapWordRunGap, nil
+		return DefaultCoalesceGap, nil
 	}
 
 	gap, err := strconv.ParseFloat(value, 64)
 	if err != nil {
-		return 0, fmt.Errorf("%s must be a positive number of seconds: %w", OverlapWordRunGapEnv, err)
+		return 0, fmt.Errorf("--coalesce-gap must be a non-negative number of seconds: %w", err)
 	}
-	if gap <= 0 {
-		return 0, fmt.Errorf("%s must be positive", OverlapWordRunGapEnv)
+	if gap < 0 {
+		return 0, fmt.Errorf("--coalesce-gap must be non-negative")
 	}
 	return gap, nil
 }
 
+func parsePositiveFloatEnv(name string, defaultValue float64) (float64, error) {
+	value := strings.TrimSpace(os.Getenv(name))
+	if value == "" {
+		return defaultValue, nil
+	}
+
+	parsed, err := strconv.ParseFloat(value, 64)
+	if err != nil {
+		return 0, fmt.Errorf("%s must be a positive number of seconds: %w", name, err)
+	}
+	if parsed <= 0 {
+		return 0, fmt.Errorf("%s must be positive", name)
+	}
+	return parsed, nil
+}
+
 func contains(values []string, target string) bool {
 	for _, value := range values {
 		if value == target {