breakpilot-lehrer/backend-lehrer/recording/transcription.py

"""
Recording API - Transcription Routes.

Start transcription, get status, download VTT/SRT subtitle files.
"""

import uuid
from datetime import datetime
from typing import Optional

from fastapi import APIRouter, HTTPException
from fastapi.responses import PlainTextResponse

from .models import (
    TranscriptionRequest,
    TranscriptionStatusResponse,
)
from .helpers import (
    _recordings_store,
    _transcriptions_store,
    log_audit,
    format_vtt_time,
    format_srt_time,
)

router = APIRouter(tags=["Recordings"])


# ==========================================
# TRANSCRIPTION ENDPOINTS
# ==========================================

@router.post("/{recording_id}/transcribe", response_model=TranscriptionStatusResponse)
async def start_transcription(recording_id: str, request: TranscriptionRequest):
    """
    Start transcription for a recording.

    Queues the recording for processing by the transcription worker.
    """
    recording = _recordings_store.get(recording_id)
    if not recording:
        raise HTTPException(status_code=404, detail="Recording not found")

    if recording["status"] == "deleted":
        raise HTTPException(status_code=400, detail="Cannot transcribe deleted recording")

    # Check if transcription already exists
    existing = next(
        (t for t in _transcriptions_store.values()
         if t["recording_id"] == recording_id and t["status"] != "failed"),
        None
    )
    if existing:
        raise HTTPException(
            status_code=409,
            detail=f"Transcription already exists with status: {existing['status']}"
        )

    # Create transcription entry
    transcription_id = str(uuid.uuid4())
    now = datetime.utcnow()

    transcription = {
        "id": transcription_id,
        "recording_id": recording_id,
        "language": request.language,
        "model": request.model,
        "status": "pending",
        "full_text": None,
        "word_count": None,
        "confidence_score": None,
        "vtt_path": None,
        "srt_path": None,
        "json_path": None,
        "error_message": None,
        "processing_started_at": None,
        "processing_completed_at": None,
        "processing_duration_seconds": None,
        "created_at": now.isoformat(),
        "updated_at": now.isoformat()
    }

    _transcriptions_store[transcription_id] = transcription

    # Update recording status
    recording["status"] = "processing"
    recording["updated_at"] = now.isoformat()

    # Log transcription start
    log_audit(
        action="transcription_started",
        recording_id=recording_id,
        transcription_id=transcription_id,
        metadata={"language": request.language, "model": request.model}
    )

    # TODO: Queue job to Redis/Valkey for transcription worker

    return TranscriptionStatusResponse(
        id=transcription_id,
        recording_id=recording_id,
        status="pending",
        language=request.language,
        model=request.model,
        word_count=None,
        confidence_score=None,
        processing_duration_seconds=None,
        error_message=None,
        created_at=now,
        completed_at=None
    )


@router.get("/{recording_id}/transcription", response_model=TranscriptionStatusResponse)
async def get_transcription_status(recording_id: str):
    """
    Get transcription status for a recording.
    """
    transcription = next(
        (t for t in _transcriptions_store.values() if t["recording_id"] == recording_id),
        None
    )
    if not transcription:
        raise HTTPException(status_code=404, detail="No transcription found for this recording")

    return TranscriptionStatusResponse(
        id=transcription["id"],
        recording_id=transcription["recording_id"],
        status=transcription["status"],
        language=transcription["language"],
        model=transcription["model"],
        word_count=transcription.get("word_count"),
        confidence_score=transcription.get("confidence_score"),
        processing_duration_seconds=transcription.get("processing_duration_seconds"),
        error_message=transcription.get("error_message"),
        created_at=datetime.fromisoformat(transcription["created_at"]),
        completed_at=(
            datetime.fromisoformat(transcription["processing_completed_at"])
            if transcription.get("processing_completed_at") else None
        )
    )


@router.get("/{recording_id}/transcription/text")
async def get_transcription_text(recording_id: str):
    """
    Get the full transcription text.
    """
    transcription = next(
        (t for t in _transcriptions_store.values() if t["recording_id"] == recording_id),
        None
    )
    if not transcription:
        raise HTTPException(status_code=404, detail="No transcription found for this recording")

    if transcription["status"] != "completed":
        raise HTTPException(
            status_code=400,
            detail=f"Transcription not ready. Status: {transcription['status']}"
        )

    return {
        "transcription_id": transcription["id"],
        "recording_id": recording_id,
        "language": transcription["language"],
        "text": transcription.get("full_text", ""),
        "word_count": transcription.get("word_count", 0)
    }


@router.get("/{recording_id}/transcription/vtt")
async def get_transcription_vtt(recording_id: str):
    """
    Download transcription as WebVTT subtitle file.
    """
    transcription = next(
        (t for t in _transcriptions_store.values() if t["recording_id"] == recording_id),
        None
    )
    if not transcription:
        raise HTTPException(status_code=404, detail="No transcription found for this recording")

    if transcription["status"] != "completed":
        raise HTTPException(
            status_code=400,
            detail=f"Transcription not ready. Status: {transcription['status']}"
        )

    # Generate VTT content
    vtt_content = "WEBVTT\n\n"
    text = transcription.get("full_text", "")

    if text:
        sentences = text.replace(".", ".\n").split("\n")
        time_offset = 0
        for sentence in sentences:
            sentence = sentence.strip()
            if sentence:
                start = format_vtt_time(time_offset)
                time_offset += 3000
                end = format_vtt_time(time_offset)
                vtt_content += f"{start} --> {end}\n{sentence}\n\n"

    return PlainTextResponse(
        content=vtt_content,
        media_type="text/vtt",
        headers={"Content-Disposition": f"attachment; filename=transcript_{recording_id}.vtt"}
    )


@router.get("/{recording_id}/transcription/srt")
async def get_transcription_srt(recording_id: str):
    """
    Download transcription as SRT subtitle file.
    """
    transcription = next(
        (t for t in _transcriptions_store.values() if t["recording_id"] == recording_id),
        None
    )
    if not transcription:
        raise HTTPException(status_code=404, detail="No transcription found for this recording")

    if transcription["status"] != "completed":
        raise HTTPException(
            status_code=400,
            detail=f"Transcription not ready. Status: {transcription['status']}"
        )

    # Generate SRT content
    srt_content = ""
    text = transcription.get("full_text", "")

    if text:
        sentences = text.replace(".", ".\n").split("\n")
        time_offset = 0
        index = 1
        for sentence in sentences:
            sentence = sentence.strip()
            if sentence:
                start = format_srt_time(time_offset)
                time_offset += 3000
                end = format_srt_time(time_offset)
                srt_content += f"{index}\n{start} --> {end}\n{sentence}\n\n"
                index += 1

    return PlainTextResponse(
        content=srt_content,
        media_type="text/plain",
        headers={"Content-Disposition": f"attachment; filename=transcript_{recording_id}.srt"}
    )