feat: Implement comprehensive export functionality

- Create TranscriptionExporter utility supporting TXT, SRT, VTT, JSON, TSV formats
- Implement proper timestamp formatting for subtitle formats
- Update GUI export dialog with all supported formats
- Integrate exporter with main window
- Add robust error handling for export operations
- Phase 4 complete: Full export capabilities ready

farsi_transcriber/ui/main_window.py

@@ -23,6 +23,7 @@ from PyQt6.QtWidgets import (
 from PyQt6.QtGui import QFont
 
 from farsi_transcriber.models.whisper_transcriber import FarsiTranscriber
+from farsi_transcriber.utils.export import TranscriptionExporter
 
 
 class TranscriptionWorker(QThread):
@@ -239,24 +240,35 @@ class MainWindow(QMainWindow):
 
     def on_export(self):
         """Handle export button click"""
-        if not hasattr(self, "last_result"):
+        if not self.last_result:
             QMessageBox.warning(self, "Warning", "No transcription to export.")
             return
 
-        file_path, file_format = QFileDialog.getSaveFileName(
+        file_path, file_filter = QFileDialog.getSaveFileName(
             self,
             "Export Transcription",
             "",
-            "Text Files (*.txt);;SRT Files (*.srt);;JSON Files (*.json)",
+            "Text Files (*.txt);;SRT Subtitles (*.srt);;WebVTT Subtitles (*.vtt);;JSON (*.json);;TSV (*.tsv)",
         )
 
         if file_path:
             try:
-                # TODO: Implement export logic in Phase 4
+                file_path = Path(file_path)
-                with open(file_path, "w", encoding="utf-8") as f:
+
-                    f.write(self.results_text.toPlainText())
+                # Determine format from file extension
+                suffix = file_path.suffix.lower().lstrip(".")
+                if not suffix:
+                    # Default to txt if no extension
+                    suffix = "txt"
+                    file_path = file_path.with_suffix(".txt")
+
+                # Export using the appropriate format
+                TranscriptionExporter.export(self.last_result, file_path, suffix)
+
                 QMessageBox.information(
-                    self, "Success", f"Results exported to {Path(file_path).name}"
+                    self,
+                    "Success",
+                    f"Transcription exported successfully to:\n{file_path.name}",
                 )
             except Exception as e:
                 QMessageBox.critical(

farsi_transcriber/utils/export.py

@@ -0,0 +1,164 @@
+"""
+Export utilities for transcription results
+
+Supports multiple export formats: TXT, SRT, JSON, TSV, VTT
+"""
+
+import json
+from datetime import timedelta
+from pathlib import Path
+from typing import Dict, List
+
+
+class TranscriptionExporter:
+    """Export transcription results in various formats"""
+
+    @staticmethod
+    def export_txt(result: Dict, file_path: Path) -> None:
+        """
+        Export transcription as plain text file.
+
+        Args:
+            result: Transcription result dictionary
+            file_path: Output file path
+        """
+        text = result.get("full_text", "") or result.get("text", "")
+
+        with open(file_path, "w", encoding="utf-8") as f:
+            f.write(text)
+
+    @staticmethod
+    def export_srt(result: Dict, file_path: Path) -> None:
+        """
+        Export transcription as SRT subtitle file.
+
+        Args:
+            result: Transcription result dictionary
+            file_path: Output file path
+        """
+        segments = result.get("segments", [])
+
+        with open(file_path, "w", encoding="utf-8") as f:
+            for i, segment in enumerate(segments, 1):
+                start = TranscriptionExporter._format_srt_time(segment.get("start", 0))
+                end = TranscriptionExporter._format_srt_time(segment.get("end", 0))
+                text = segment.get("text", "").strip()
+
+                if text:
+                    f.write(f"{i}\n")
+                    f.write(f"{start} --> {end}\n")
+                    f.write(f"{text}\n\n")
+
+    @staticmethod
+    def export_vtt(result: Dict, file_path: Path) -> None:
+        """
+        Export transcription as WebVTT subtitle file.
+
+        Args:
+            result: Transcription result dictionary
+            file_path: Output file path
+        """
+        segments = result.get("segments", [])
+
+        with open(file_path, "w", encoding="utf-8") as f:
+            f.write("WEBVTT\n\n")
+
+            for segment in segments:
+                start = TranscriptionExporter._format_vtt_time(segment.get("start", 0))
+                end = TranscriptionExporter._format_vtt_time(segment.get("end", 0))
+                text = segment.get("text", "").strip()
+
+                if text:
+                    f.write(f"{start} --> {end}\n")
+                    f.write(f"{text}\n\n")
+
+    @staticmethod
+    def export_json(result: Dict, file_path: Path) -> None:
+        """
+        Export transcription as JSON file.
+
+        Args:
+            result: Transcription result dictionary
+            file_path: Output file path
+        """
+        with open(file_path, "w", encoding="utf-8") as f:
+            json.dump(result, f, ensure_ascii=False, indent=2)
+
+    @staticmethod
+    def export_tsv(result: Dict, file_path: Path) -> None:
+        """
+        Export transcription as TSV (tab-separated values) file.
+
+        Args:
+            result: Transcription result dictionary
+            file_path: Output file path
+        """
+        segments = result.get("segments", [])
+
+        with open(file_path, "w", encoding="utf-8") as f:
+            # Write header
+            f.write("Index\tStart\tEnd\tDuration\tText\n")
+
+            for i, segment in enumerate(segments, 1):
+                start = segment.get("start", 0)
+                end = segment.get("end", 0)
+                duration = end - start
+                text = segment.get("text", "").strip()
+
+                if text:
+                    f.write(
+                        f"{i}\t{start:.2f}\t{end:.2f}\t{duration:.2f}\t{text}\n"
+                    )
+
+    @staticmethod
+    def export(
+        result: Dict, file_path: Path, format_type: str = "txt"
+    ) -> None:
+        """
+        Export transcription in specified format.
+
+        Args:
+            result: Transcription result dictionary
+            file_path: Output file path
+            format_type: Export format ('txt', 'srt', 'vtt', 'json', 'tsv')
+
+        Raises:
+            ValueError: If format is not supported
+        """
+        format_type = format_type.lower()
+
+        exporters = {
+            "txt": TranscriptionExporter.export_txt,
+            "srt": TranscriptionExporter.export_srt,
+            "vtt": TranscriptionExporter.export_vtt,
+            "json": TranscriptionExporter.export_json,
+            "tsv": TranscriptionExporter.export_tsv,
+        }
+
+        if format_type not in exporters:
+            raise ValueError(
+                f"Unsupported format: {format_type}. "
+                f"Supported formats: {list(exporters.keys())}"
+            )
+
+        exporters[format_type](result, file_path)
+
+    @staticmethod
+    def _format_srt_time(seconds: float) -> str:
+        """Format time for SRT format (HH:MM:SS,mmm)"""
+        td = timedelta(seconds=seconds)
+        hours, remainder = divmod(int(td.total_seconds()), 3600)
+        minutes, secs = divmod(remainder, 60)
+        milliseconds = int((seconds % 1) * 1000)
+
+        return f"{hours:02d}:{minutes:02d}:{secs:02d},{milliseconds:03d}"
+
+    @staticmethod
+    def _format_vtt_time(seconds: float) -> str:
+        """Format time for VTT format (HH:MM:SS.mmm)"""
+        td = timedelta(seconds=seconds)
+        hours, remainder = divmod(int(td.total_seconds()), 3600)
+        minutes, secs = divmod(remainder, 60)
+        milliseconds = int((seconds % 1) * 1000)
+
+        return f"{hours:02d}:{minutes:02d}:{secs:02d}.{milliseconds:03d}"