"""Lightweight development backend for UI work.

This avoids importing heavy ML dependencies so the UI can run during frontend
development without installing large Python packages (torch/whisperx/etc.).
Use this when you only need the health/file streaming endpoints.
"""
from fastapi import FastAPI, Request, HTTPException
from fastapi.middleware.cors import CORSMiddleware
from fastapi.responses import StreamingResponse
from pathlib import Path

from routers import audio

app = FastAPI(title="TalkEdit Dev Backend", version="0.0.1")

app.add_middleware(
    CORSMiddleware,
    allow_origins=["*"],
    allow_credentials=True,
    allow_methods=["*"],
    allow_headers=["*"],
    expose_headers=["Content-Range", "Accept-Ranges", "Content-Length"],
)


MIME_MAP = {
    ".mp4": "video/mp4",
    ".mkv": "video/x-matroska",
    ".mov": "video/quicktime",
    ".avi": "video/x-msvideo",
    ".webm": "video/webm",
    ".m4a": "audio/mp4",
    ".wav": "audio/wav",
    ".mp3": "audio/mpeg",
    ".flac": "audio/flac",
}


app.include_router(audio.router)

@app.get("/health")
async def health():
    return {"status": "ok"}


@app.get("/file")
async def serve_local_file(request: Request, path: str):
    file_path = Path(path)
    if not file_path.is_file():
        raise HTTPException(status_code=404, detail=f"File not found: {path}")

    file_size = file_path.stat().st_size
    content_type = MIME_MAP.get(file_path.suffix.lower(), "application/octet-stream")

    range_header = request.headers.get("range")
    if range_header:
        range_spec = range_header.replace("bytes=", "")
        start_str, end_str = range_spec.split("-")
        start = int(start_str) if start_str else 0
        end = int(end_str) if end_str else file_size - 1
        end = min(end, file_size - 1)
        content_length = end - start + 1

        def iter_range():
            with open(file_path, "rb") as f:
                f.seek(start)
                remaining = content_length
                while remaining > 0:
                    chunk = f.read(min(65536, remaining))
                    if not chunk:
                        break
                    remaining -= len(chunk)
                    yield chunk

        return StreamingResponse(
            iter_range(),
            status_code=206,
            media_type=content_type,
            headers={
                "Content-Range": f"bytes {start}-{end}/{file_size}",
                "Accept-Ranges": "bytes",
                "Content-Length": str(content_length),
            },
        )

    def iter_file():
        with open(file_path, "rb") as f:
            while chunk := f.read(65536):
                yield chunk

    return StreamingResponse(
        iter_file(),
        media_type=content_type,
        headers={
            "Accept-Ranges": "bytes",
            "Content-Length": str(file_size),
        },
    )