app/api/routes_download.py

"""
============================================
Download Routes
- English .txt  → chapter.content
- Hindi .txt    → chapter.content_hindi (already translated during scraping)
============================================
"""

import io
import logging
from fastapi import APIRouter, Depends, HTTPException
from fastapi.responses import StreamingResponse
from sqlalchemy.ext.asyncio import AsyncSession

from app.database.connection import get_db_session
from app.database.crud import (
    get_novel_by_id,
    get_chapters_for_novel,
    get_chapter_count,
    get_total_word_count,
)

logger = logging.getLogger(__name__)
router = APIRouter(prefix="/api/download", tags=["Download"])


def _build_txt(novel, chapters, lang="english") -> bytes:
    """Build .txt file content for given language."""
    lines = []

    if lang == "hindi":
        title = novel.title_hindi or novel.title
    else:
        title = novel.title

    lines.append("=" * 60)
    lines.append(f"  {title}")
    if lang == "hindi":
        lines.append(f"  ({novel.title})")
    lines.append("=" * 60)
    lines.append(f"  Source: {novel.url}")
    lines.append(f"  Chapters: {len(chapters)}")
    total_words = sum(ch.word_count for ch in chapters)
    lines.append(f"  Total Words: {total_words:,}")
    lines.append(f"  Language: {'Hindi 🇮🇳' if lang == 'hindi' else 'English'}")
    lines.append(f"  Generated by Novel Scraper Pro")
    lines.append("=" * 60)
    lines.append("")

    for chapter in chapters:
        if lang == "hindi":
            ch_title = chapter.title_hindi or chapter.title
            ch_content = chapter.content_hindi or chapter.content
            ch_label = f"अध्याय {chapter.chapter_number}"
        else:
            ch_title = chapter.title
            ch_content = chapter.content
            ch_label = f"Chapter {chapter.chapter_number}"

        lines.append("-" * 50)
        lines.append(f"  {ch_label}: {ch_title}")
        lines.append("-" * 50)
        lines.append("")
        lines.append(ch_content)
        lines.append("")

    lines.append("=" * 60)
    lines.append("  उपन्यास समाप्त" if lang == "hindi" else "  END OF NOVEL")
    lines.append("=" * 60)

    return "\n".join(lines).encode("utf-8")


@router.get("/{novel_id}/info")
async def get_download_info(novel_id: int, db: AsyncSession = Depends(get_db_session)):
    novel = await get_novel_by_id(db, novel_id)
    if not novel:
        raise HTTPException(status_code=404, detail="Novel not found")
    chapter_count = await get_chapter_count(db, novel_id)
    word_count = await get_total_word_count(db, novel_id)
    return {
        "novel_id": novel_id,
        "title": novel.title,
        "status": novel.status.value,
        "chapter_count": chapter_count,
        "word_count": word_count,
        "estimated_pages": word_count // 250 if word_count else 0,
        "downloadable": chapter_count > 0,
    }


@router.get("/{novel_id}/txt")
async def download_english(novel_id: int, db: AsyncSession = Depends(get_db_session)):
    """Download novel as English .txt"""
    novel = await get_novel_by_id(db, novel_id)
    if not novel:
        raise HTTPException(status_code=404, detail="Novel not found")
    chapters = await get_chapters_for_novel(db, novel_id)
    if not chapters:
        raise HTTPException(status_code=404, detail="No chapters found!")

    file_bytes = _build_txt(novel, chapters, lang="english")
    safe = "".join(c for c in novel.title if c.isalnum() or c in ' -_').strip()[:80]

    return StreamingResponse(
        io.BytesIO(file_bytes),
        media_type="text/plain; charset=utf-8",
        headers={
            "Content-Disposition": f'attachment; filename="{safe}_English.txt"',
            "Content-Length": str(len(file_bytes)),
        },
    )


@router.get("/{novel_id}/txt-hindi")
async def download_hindi(novel_id: int, db: AsyncSession = Depends(get_db_session)):
    """
    Download novel as Hindi .txt
    Translation already done during scraping — instant download!
    """
    novel = await get_novel_by_id(db, novel_id)
    if not novel:
        raise HTTPException(status_code=404, detail="Novel not found")
    chapters = await get_chapters_for_novel(db, novel_id)
    if not chapters:
        raise HTTPException(status_code=404, detail="No chapters found!")

    hindi_chapters = [ch for ch in chapters if ch.content_hindi]
    if not hindi_chapters:
        raise HTTPException(
            status_code=404,
            detail="Hindi translation nahi mili! Purane chapters dobara scrape karo."
        )

    file_bytes = _build_txt(novel, hindi_chapters, lang="hindi")
    safe = "".join(c for c in novel.title if c.isalnum() or c in ' -_').strip()[:80]

    logger.info(f"Hindi download: '{novel.title}' - {len(hindi_chapters)} chapters")

    return StreamingResponse(
        io.BytesIO(file_bytes),
        media_type="text/plain; charset=utf-8",
        headers={
            "Content-Disposition": f'attachment; filename="{safe}_Hindi.txt"',
            "Content-Length": str(len(file_bytes)),
        },
    )


@router.get("/{novel_id}/chapters")
async def list_chapters(novel_id: int, db: AsyncSession = Depends(get_db_session)):
    novel = await get_novel_by_id(db, novel_id)
    if not novel:
        raise HTTPException(status_code=404, detail="Novel not found")
    chapters = await get_chapters_for_novel(db, novel_id)
    return {
        "novel_id": novel_id,
        "title": novel.title,
        "total_chapters": len(chapters),
        "chapters": [
            {
                "number": ch.chapter_number,
                "title": ch.title,
                "title_hindi": ch.title_hindi,
                "word_count": ch.word_count,
                "hindi_available": bool(ch.content_hindi),
                "url": ch.url,
                "scraped_at": ch.scraped_at.isoformat() if ch.scraped_at else None,
            }
            for ch in chapters
        ],
    }