import csv
import io
import mimetypes
import os
import uuid
from pathlib import Path
from typing import Annotated

from fastapi import APIRouter, Depends, File, Form, HTTPException, Query, UploadFile
from fastapi.responses import FileResponse
from sqlalchemy.ext.asyncio import AsyncSession

from app.config import get_settings
from app.core.audit import write_audit
from app.dependencies import get_current_user, get_db
from app.schemas.transaction import TransactionCreate, TransactionFilter, TransactionUpdate
from app.services.transaction_service import (
    TransactionError,
    create_transaction,
    delete_transaction,
    get_transaction,
    import_csv,
    list_transactions,
    update_transaction,
    _to_response,
)

MAX_IMPORT_FILE_BYTES = 10 * 1024 * 1024  # 10 MB
MAX_IMPORT_ROWS = 50_000

ALLOWED_MIME_TYPES = {
    "image/jpeg",
    "image/png",
    "image/webp",
    "application/pdf",
}
ALLOWED_EXTENSIONS = {".jpg", ".jpeg", ".png", ".webp", ".pdf"}

router = APIRouter()


@router.get("")
async def get_transactions(
    account_id: uuid.UUID | None = None,
    category_id: uuid.UUID | None = None,
    type: str | None = None,
    status: str | None = None,
    date_from: str | None = None,
    date_to: str | None = None,
    search: str | None = None,
    is_recurring: bool | None = None,
    page: int = Query(default=1, ge=1),
    page_size: int = Query(default=50, ge=1, le=200),
    db: AsyncSession = Depends(get_db),
    user=Depends(get_current_user),
):
    from datetime import date
    filters = TransactionFilter(
        account_id=account_id,
        category_id=category_id,
        type=type,
        status=status,
        date_from=date.fromisoformat(date_from) if date_from else None,
        date_to=date.fromisoformat(date_to) if date_to else None,
        search=search,
        is_recurring=is_recurring,
        page=page,
        page_size=page_size,
    )
    return await list_transactions(db, user.id, filters)


@router.post("", status_code=201)
async def create(
    body: TransactionCreate,
    db: AsyncSession = Depends(get_db),
    user=Depends(get_current_user),
):
    try:
        result = await create_transaction(db, user.id, body, user.base_currency)
        await write_audit(db, user_id=user.id, action="transaction_create")
        await db.commit()
        return result
    except TransactionError as e:
        raise HTTPException(status_code=e.status_code, detail=e.detail)


@router.get("/{txn_id}")
async def get_one(
    txn_id: uuid.UUID,
    db: AsyncSession = Depends(get_db),
    user=Depends(get_current_user),
):
    try:
        txn = await get_transaction(db, txn_id, user.id)
        return _to_response(txn)
    except TransactionError as e:
        raise HTTPException(status_code=e.status_code, detail=e.detail)


@router.put("/{txn_id}")
async def update(
    txn_id: uuid.UUID,
    body: TransactionUpdate,
    db: AsyncSession = Depends(get_db),
    user=Depends(get_current_user),
):
    try:
        result = await update_transaction(db, txn_id, user.id, body, user.base_currency)
        await write_audit(db, user_id=user.id, action="transaction_update", resource_type="transaction", resource_id=txn_id)
        await db.commit()
        return result
    except TransactionError as e:
        raise HTTPException(status_code=e.status_code, detail=e.detail)


@router.delete("/{txn_id}", status_code=204)
async def delete(
    txn_id: uuid.UUID,
    db: AsyncSession = Depends(get_db),
    user=Depends(get_current_user),
):
    try:
        await delete_transaction(db, txn_id, user.id)
        await write_audit(db, user_id=user.id, action="transaction_delete", resource_type="transaction", resource_id=txn_id)
        await db.commit()
    except TransactionError as e:
        raise HTTPException(status_code=e.status_code, detail=e.detail)


@router.post("/{txn_id}/attachments")
async def upload_attachment(
    txn_id: uuid.UUID,
    file: UploadFile = File(...),
    db: AsyncSession = Depends(get_db),
    user=Depends(get_current_user),
):
    settings = get_settings()

    # Validate extension
    filename = file.filename or "upload"
    ext = Path(filename).suffix.lower()
    if ext not in ALLOWED_EXTENSIONS:
        raise HTTPException(status_code=400, detail="Unsupported file type. Allowed: JPG, PNG, WebP, PDF")

    # Verify transaction ownership
    try:
        txn = await get_transaction(db, txn_id, user.id)
    except TransactionError as e:
        raise HTTPException(status_code=e.status_code, detail=e.detail)

    current_refs: list = txn.get("attachment_refs", []) if isinstance(txn, dict) else []
    # Fetch raw model for JSONB mutation
    from sqlalchemy import select
    from app.db.models.transaction import Transaction as TxnModel
    result = await db.execute(
        select(TxnModel).where(TxnModel.id == txn_id, TxnModel.user_id == user.id)
    )
    txn_row = result.scalar_one_or_none()
    if not txn_row:
        raise HTTPException(status_code=404, detail="Transaction not found")

    current_refs = list(txn_row.attachment_refs or [])
    if len(current_refs) >= settings.max_attachments_per_txn:
        raise HTTPException(status_code=400, detail=f"Maximum {settings.max_attachments_per_txn} attachments per transaction")

    # Read and size-check
    content = await file.read(settings.max_attachment_bytes + 1)
    if len(content) > settings.max_attachment_bytes:
        raise HTTPException(status_code=413, detail="File too large (max 10 MB)")

    # Sniff MIME from content
    import magic  # python-magic
    detected_mime = magic.from_buffer(content[:2048], mime=True)
    if detected_mime not in ALLOWED_MIME_TYPES:
        raise HTTPException(status_code=400, detail="File content does not match an allowed type (JPEG, PNG, WebP, PDF)")

    # Store file
    attachment_id = str(uuid.uuid4())
    user_upload_dir = Path(settings.upload_dir) / str(user.id)
    user_upload_dir.mkdir(parents=True, exist_ok=True)
    stored_name = f"{attachment_id}{ext}"
    stored_path = user_upload_dir / stored_name
    stored_path.write_bytes(content)

    # Update attachment_refs
    ref = {
        "id": attachment_id,
        "filename": filename,
        "mime_type": detected_mime,
        "size": len(content),
        "stored_name": stored_name,
    }
    from sqlalchemy import update as sql_update
    import copy
    new_refs = copy.copy(current_refs)
    new_refs.append(ref)
    await db.execute(
        sql_update(TxnModel)
        .where(TxnModel.id == txn_id)
        .values(attachment_refs=new_refs)
    )
    await write_audit(db, user_id=user.id, action="transaction_update", resource_type="transaction", resource_id=txn_id, metadata={"attachment_added": attachment_id})
    await db.commit()
    return ref


@router.get("/{txn_id}/attachments/{attachment_id}")
async def download_attachment(
    txn_id: uuid.UUID,
    attachment_id: str,
    db: AsyncSession = Depends(get_db),
    user=Depends(get_current_user),
):
    settings = get_settings()

    from sqlalchemy import select
    from app.db.models.transaction import Transaction as TxnModel
    result = await db.execute(
        select(TxnModel).where(TxnModel.id == txn_id, TxnModel.user_id == user.id)
    )
    txn_row = result.scalar_one_or_none()
    if not txn_row:
        raise HTTPException(status_code=404, detail="Transaction not found")

    ref = next((r for r in (txn_row.attachment_refs or []) if r["id"] == attachment_id), None)
    if not ref:
        raise HTTPException(status_code=404, detail="Attachment not found")

    path = Path(settings.upload_dir) / str(user.id) / ref["stored_name"]
    if not path.exists():
        raise HTTPException(status_code=404, detail="Attachment file missing")

    return FileResponse(
        path=str(path),
        media_type=ref["mime_type"],
        filename=ref["filename"],
    )


@router.delete("/{txn_id}/attachments/{attachment_id}", status_code=204)
async def delete_attachment(
    txn_id: uuid.UUID,
    attachment_id: str,
    db: AsyncSession = Depends(get_db),
    user=Depends(get_current_user),
):
    settings = get_settings()

    from sqlalchemy import select, update as sql_update
    from app.db.models.transaction import Transaction as TxnModel
    result = await db.execute(
        select(TxnModel).where(TxnModel.id == txn_id, TxnModel.user_id == user.id)
    )
    txn_row = result.scalar_one_or_none()
    if not txn_row:
        raise HTTPException(status_code=404, detail="Transaction not found")

    refs = list(txn_row.attachment_refs or [])
    ref = next((r for r in refs if r["id"] == attachment_id), None)
    if not ref:
        raise HTTPException(status_code=404, detail="Attachment not found")

    # Delete file
    path = Path(settings.upload_dir) / str(user.id) / ref["stored_name"]
    try:
        path.unlink(missing_ok=True)
    except OSError:
        pass

    new_refs = [r for r in refs if r["id"] != attachment_id]
    await db.execute(
        sql_update(TxnModel)
        .where(TxnModel.id == txn_id)
        .values(attachment_refs=new_refs)
    )
    await write_audit(db, user_id=user.id, action="transaction_update", resource_type="transaction", resource_id=txn_id, metadata={"attachment_deleted": attachment_id})
    await db.commit()


_RECEIPT_PROMPT = (
    "You are a receipt parser. Extract information from this receipt and return ONLY a JSON object "
    "with exactly these keys (use null for any field you cannot determine):\n"
    '{"merchant": "store name", "amount": 0.00, "currency": "GBP", '
    '"date": "YYYY-MM-DD", "description": "brief description", '
    '"category": "one of: Food & Drink, Transport, Shopping, Entertainment, Health, Travel, Bills & Utilities, Other"}\n'
    "Return ONLY the JSON object. No markdown, no explanation, no code fences."
)


async def _call_ai_parse(file_bytes: bytes, mime_type: str, user_row) -> dict:
    """Call the configured AI provider and return parsed receipt fields."""
    import base64
    import json
    import httpx
    from app.core.security import decrypt_field

    if not user_row.ai_provider or not user_row.ai_api_key_enc:
        raise HTTPException(status_code=400, detail="No AI provider configured. Add your API key in Settings → AI.")

    api_key = decrypt_field(user_row.ai_api_key_enc)
    b64 = base64.standard_b64encode(file_bytes).decode()
    custom_base_url = (user_row.ai_base_url or "").rstrip("/")
    custom_model = (user_row.ai_model or "").strip()

    try:
        if user_row.ai_provider == "anthropic":
            base_url = custom_base_url or "https://api.anthropic.com"
            model = custom_model or "claude-haiku-4-5-20251001"
            if mime_type == "application/pdf":
                content_block = {"type": "document", "source": {"type": "base64", "media_type": "application/pdf", "data": b64}}
            else:
                content_block = {"type": "image", "source": {"type": "base64", "media_type": mime_type, "data": b64}}
            async with httpx.AsyncClient(timeout=60) as client:
                resp = await client.post(
                    f"{base_url}/v1/messages",
                    headers={"x-api-key": api_key, "anthropic-version": "2023-06-01", "content-type": "application/json"},
                    json={"model": model, "max_tokens": 512, "messages": [{"role": "user", "content": [content_block, {"type": "text", "text": _RECEIPT_PROMPT}]}]},
                )
            resp.raise_for_status()
            text = resp.json()["content"][0]["text"].strip()

        elif user_row.ai_provider == "openai":
            base_url = custom_base_url or "https://api.openai.com"
            model = custom_model or "gpt-4o-mini"
            if mime_type == "application/pdf" and not custom_base_url:
                raise HTTPException(status_code=400, detail="PDF parsing is not supported with the OpenAI provider. Use an image format or switch to Anthropic.")
            async with httpx.AsyncClient(timeout=60) as client:
                resp = await client.post(
                    f"{base_url}/v1/chat/completions",
                    headers={"Authorization": f"Bearer {api_key}", "content-type": "application/json"},
                    json={"model": model, "max_tokens": 512, "messages": [{"role": "user", "content": [
                        {"type": "image_url", "image_url": {"url": f"data:{mime_type};base64,{b64}"}},
                        {"type": "text", "text": _RECEIPT_PROMPT},
                    ]}]},
                )
            resp.raise_for_status()
            text = resp.json()["choices"][0]["message"]["content"].strip()

        else:
            raise HTTPException(status_code=400, detail="Unknown provider")

    except httpx.HTTPStatusError as e:
        raise HTTPException(status_code=502, detail=f"AI provider error: {e.response.status_code}")
    except httpx.RequestError:
        raise HTTPException(status_code=502, detail="Could not reach AI provider")

    if text.startswith("```"):
        text = text.split("```")[1]
        if text.startswith("json"):
            text = text[4:]
        text = text.strip()

    try:
        parsed = json.loads(text)
    except json.JSONDecodeError:
        raise HTTPException(status_code=502, detail="AI returned an unexpected response. Try again.")

    return {
        "merchant":    parsed.get("merchant"),
        "amount":      parsed.get("amount"),
        "currency":    parsed.get("currency"),
        "date":        parsed.get("date"),
        "description": parsed.get("description"),
        "category":    parsed.get("category"),
        "raw":         text,
    }


@router.post("/parse-receipt")
async def parse_receipt_upload(
    file: UploadFile = File(...),
    db: AsyncSession = Depends(get_db),
    user=Depends(get_current_user),
):
    """Upload a receipt image and parse it with AI — no existing transaction required."""
    from app.db.models.user import User as UserModel

    settings = get_settings()
    filename = file.filename or "upload"
    ext = Path(filename).suffix.lower()
    if ext not in ALLOWED_EXTENSIONS:
        raise HTTPException(status_code=400, detail="Unsupported file type. Allowed: JPG, PNG, WebP, PDF")

    content = await file.read(settings.max_attachment_bytes + 1)
    if len(content) > settings.max_attachment_bytes:
        raise HTTPException(status_code=413, detail="File too large (max 10 MB)")

    import magic
    mime_type = magic.from_buffer(content[:2048], mime=True)
    if mime_type not in ALLOWED_MIME_TYPES:
        raise HTTPException(status_code=400, detail="File content does not match an allowed type")

    user_row = await db.get(UserModel, user.id)
    return await _call_ai_parse(content, mime_type, user_row)


@router.post("/{txn_id}/attachments/{attachment_id}/parse")
async def parse_attachment(
    txn_id: uuid.UUID,
    attachment_id: str,
    db: AsyncSession = Depends(get_db),
    user=Depends(get_current_user),
):
    """Parse an already-uploaded attachment with AI."""
    from sqlalchemy import select
    from app.db.models.transaction import Transaction as TxnModel
    from app.db.models.user import User as UserModel

    settings = get_settings()
    user_row = await db.get(UserModel, user.id)

    result = await db.execute(select(TxnModel).where(TxnModel.id == txn_id, TxnModel.user_id == user.id))
    txn_row = result.scalar_one_or_none()
    if not txn_row:
        raise HTTPException(status_code=404, detail="Transaction not found")

    ref = next((r for r in (txn_row.attachment_refs or []) if r["id"] == attachment_id), None)
    if not ref:
        raise HTTPException(status_code=404, detail="Attachment not found")

    path = Path(settings.upload_dir) / str(user.id) / ref["stored_name"]
    if not path.exists():
        raise HTTPException(status_code=404, detail="Attachment file missing")

    return await _call_ai_parse(path.read_bytes(), ref["mime_type"], user_row)


@router.post("/import")
async def import_transactions(
    file: UploadFile = File(...),
    account_id: uuid.UUID = Form(...),
    date_col: str = Form(default="date"),
    description_col: str = Form(default="description"),
    amount_col: str = Form(default="amount"),
    db: AsyncSession = Depends(get_db),
    user=Depends(get_current_user),
):
    if not file.filename or not file.filename.lower().endswith(".csv"):
        raise HTTPException(status_code=400, detail="Only CSV files are supported")

    content = await file.read(MAX_IMPORT_FILE_BYTES + 1)
    if len(content) > MAX_IMPORT_FILE_BYTES:
        raise HTTPException(status_code=413, detail="File too large (max 10 MB)")
    try:
        text = content.decode("utf-8-sig")  # handle BOM
    except UnicodeDecodeError:
        text = content.decode("latin-1")

    reader = csv.DictReader(io.StringIO(text))
    rows = []
    for row in reader:
        if len(rows) >= MAX_IMPORT_ROWS:
            raise HTTPException(status_code=400, detail=f"File contains too many rows (max {MAX_IMPORT_ROWS:,})")
        mapped = {}
        # Flexible column mapping
        for key, col in [("date", date_col), ("description", description_col), ("amount", amount_col)]:
            val = row.get(col) or row.get(col.lower()) or row.get(col.upper())
            if val is not None:
                mapped[key] = val.strip()
        if "date" in mapped and "amount" in mapped:
            mapped.setdefault("description", "Imported transaction")
            rows.append(mapped)

    if not rows:
        raise HTTPException(status_code=400, detail="No valid rows found. Check column names.")

    result = await import_csv(db, user.id, account_id, rows, user.base_currency)
    await write_audit(db, user_id=user.id, action="import_data", metadata=result)
    await db.commit()
    return result


@router.get("/import/template")
async def import_template():
    from fastapi.responses import Response
    csv_content = "date,description,amount,merchant,notes\n2026-01-15,Tesco Groceries,-45.67,Tesco,\n2026-01-14,Salary,2500.00,Employer,January salary\n"
    return Response(
        content=csv_content,
        media_type="text/csv",
        headers={"Content-Disposition": "attachment; filename=import_template.csv"},
    )