Implemented an initial transcript merge stage

internal/builtin/input.go

@@ -2,7 +2,9 @@ package builtin
 
 import (
 	"context"
+	"encoding/json"
 	"fmt"
+	"os"
 
 	"gitea.maximumdirect.net/eric/seriatim/internal/config"
 	"gitea.maximumdirect.net/eric/seriatim/internal/model"
@@ -22,10 +24,92 @@ func (jsonFilesReader) Read(ctx context.Context, cfg config.Config) ([]model.Raw
 
 	raw := make([]model.RawTranscript, 0, len(cfg.InputFiles))
 	for _, inputFile := range cfg.InputFiles {
-		raw = append(raw, model.RawTranscript{Source: inputFile})
+		transcript, err := readRawTranscript(inputFile)
+		if err != nil {
+			return nil, nil, err
+		}
+		raw = append(raw, transcript)
 	}
 
 	return raw, []report.Event{
-		report.Info("input", "json-files", fmt.Sprintf("accepted %d input file(s)", len(raw))),
+		report.Info("input", "json-files", fmt.Sprintf("decoded %d input file(s)", len(raw))),
 	}, nil
 }
+
+type rawTranscriptFile struct {
+	Segments json.RawMessage `json:"segments"`
+}
+
+type rawSegmentFile struct {
+	Start json.RawMessage `json:"start"`
+	End   json.RawMessage `json:"end"`
+	Text  json.RawMessage `json:"text"`
+}
+
+func readRawTranscript(path string) (model.RawTranscript, error) {
+	data, err := os.ReadFile(path)
+	if err != nil {
+		return model.RawTranscript{}, fmt.Errorf("read input file %q: %w", path, err)
+	}
+
+	var parsed rawTranscriptFile
+	if err := json.Unmarshal(data, &parsed); err != nil {
+		return model.RawTranscript{}, fmt.Errorf("parse input file %q: %w", path, err)
+	}
+	if parsed.Segments == nil || isJSONNull(parsed.Segments) {
+		return model.RawTranscript{}, fmt.Errorf("input file %q must contain top-level segments array", path)
+	}
+
+	var rawSegments []rawSegmentFile
+	if err := json.Unmarshal(parsed.Segments, &rawSegments); err != nil {
+		return model.RawTranscript{}, fmt.Errorf("input file %q top-level segments must be an array: %w", path, err)
+	}
+
+	segments := make([]model.RawSegment, 0, len(rawSegments))
+	for index, segment := range rawSegments {
+		if segment.Start == nil || isJSONNull(segment.Start) {
+			return model.RawTranscript{}, fmt.Errorf("input file %q segment %d missing numeric start", path, index)
+		}
+		if segment.End == nil || isJSONNull(segment.End) {
+			return model.RawTranscript{}, fmt.Errorf("input file %q segment %d missing numeric end", path, index)
+		}
+		if segment.Text == nil || isJSONNull(segment.Text) {
+			return model.RawTranscript{}, fmt.Errorf("input file %q segment %d missing string text", path, index)
+		}
+
+		var start float64
+		if err := json.Unmarshal(segment.Start, &start); err != nil {
+			return model.RawTranscript{}, fmt.Errorf("input file %q segment %d start must be numeric", path, index)
+		}
+		var end float64
+		if err := json.Unmarshal(segment.End, &end); err != nil {
+			return model.RawTranscript{}, fmt.Errorf("input file %q segment %d end must be numeric", path, index)
+		}
+		var text string
+		if err := json.Unmarshal(segment.Text, &text); err != nil {
+			return model.RawTranscript{}, fmt.Errorf("input file %q segment %d text must be a string", path, index)
+		}
+
+		if start < 0 {
+			return model.RawTranscript{}, fmt.Errorf("input file %q segment %d has negative start", path, index)
+		}
+		if end < start {
+			return model.RawTranscript{}, fmt.Errorf("input file %q segment %d has end before start", path, index)
+		}
+
+		segments = append(segments, model.RawSegment{
+			Start: start,
+			End:   end,
+			Text:  text,
+		})
+	}
+
+	return model.RawTranscript{
+		Source:   path,
+		Segments: segments,
+	}, nil
+}
+
+func isJSONNull(value json.RawMessage) bool {
+	return string(value) == "null"
+}