from typing import List, Optional, Dict, Any
import random
import os
import shutil
import asyncio

from sqlalchemy import select

from sqlalchemy.ext.asyncio import AsyncSession

from app.core.logging import get_logger
from app.db.models.ratio_task import RatioInstance, RatioRelation
from app.db.models import Dataset, DatasetFiles
from app.db.session import AsyncSessionLocal

logger = get_logger(__name__)


class RatioTaskService:
    """Service for Ratio Task DB operations."""

    def __init__(self, db: AsyncSession):
        self.db = db

    async def create_task(
        self,
        *,
        name: str,
        description: Optional[str],
        totals: int,
        ratio_method: str,
        config: List[Dict[str, Any]],
        target_dataset_id: Optional[str] = None,
    ) -> RatioInstance:
        """Create a ratio task instance and its relations.

        config item format: {"dataset_id": str, "counts": int, "filter_conditions": str}
        """
        logger.info(f"Creating ratio task: name={name}, method={ratio_method}, totals={totals}, items={len(config or [])}")

        instance = RatioInstance(
            name=name,
            description=description,
            ratio_method=ratio_method,
            totals=totals,
            target_dataset_id=target_dataset_id,
            status="PENDING",
        )
        self.db.add(instance)
        await self.db.flush()  # populate instance.id

        for item in config or []:
            relation = RatioRelation(
                ratio_instance_id=instance.id,
                source_dataset_id=item.get("dataset_id"),
                counts=int(item.get("counts", 0)),
                filter_conditions=item.get("filter_conditions"),
            )
            self.db.add(relation)

        await self.db.commit()
        await self.db.refresh(instance)
        logger.info(f"Ratio task created: {instance.id}")
        return instance

    # ========================= Execution (Background) ========================= #

    @staticmethod
    async def execute_dataset_ratio_task(instance_id: str) -> None:
        """Execute a ratio task in background.

        Supported ratio_method:
        - DATASET: randomly select counts files from each source dataset
        - TAG: randomly select counts files matching relation.filter_conditions tags

        Steps:
        - Mark instance RUNNING
        - For each relation: fetch ACTIVE files, optionally filter by tags
        - Copy selected files into target dataset
        - Update dataset statistics and mark instance SUCCESS/FAILED
        """
        async with AsyncSessionLocal() as session:  # type: AsyncSession
            try:
                # Load instance and relations
                inst_res = await session.execute(select(RatioInstance).where(RatioInstance.id == instance_id))
                instance: Optional[RatioInstance] = inst_res.scalar_one_or_none()
                if not instance:
                    logger.error(f"Ratio instance not found: {instance_id}")
                    return
                logger.info(f"start execute ratio task: {instance_id}")

                rel_res = await session.execute(
                    select(RatioRelation).where(RatioRelation.ratio_instance_id == instance_id)
                )
                relations: List[RatioRelation] = list(rel_res.scalars().all())

                # Mark running
                instance.status = "RUNNING"

                if instance.ratio_method not in {"DATASET", "TAG"}:
                    logger.info(f"Instance {instance_id} ratio_method={instance.ratio_method} not supported yet")
                    instance.status = "SUCCESS"
                    return

                # Load target dataset
                ds_res = await session.execute(select(Dataset).where(Dataset.id == instance.target_dataset_id))
                target_ds: Optional[Dataset] = ds_res.scalar_one_or_none()
                if not target_ds:
                    logger.error(f"Target dataset not found for instance {instance_id}")
                    instance.status = "FAILED"
                    return

                # Preload existing target file paths for deduplication
                existing_path_rows = await session.execute(
                    select(DatasetFiles.file_path).where(DatasetFiles.dataset_id == target_ds.id)
                )
                existing_paths = set(p for p in existing_path_rows.scalars().all() if p)

                added_count = 0
                added_size = 0

                for rel in relations:
                    if not rel.source_dataset_id or not rel.counts or rel.counts <= 0:
                        continue

                    # Fetch all files for the source dataset (ACTIVE only)
                    files_res = await session.execute(
                        select(DatasetFiles).where(
                            DatasetFiles.dataset_id == rel.source_dataset_id,
                            DatasetFiles.status == "ACTIVE",
                        )
                    )
                    files = list(files_res.scalars().all())

                    # TAG mode: filter by tags according to relation.filter_conditions
                    if instance.ratio_method == "TAG":
                        required_tags = RatioTaskService._parse_required_tags(rel.filter_conditions)
                        if required_tags:
                            files = [f for f in files if RatioTaskService._file_contains_tags(f, required_tags)]

                    if not files:
                        continue

                    pick_n = min(rel.counts or 0, len(files))
                    chosen = random.sample(files, pick_n) if pick_n < len(files) else files

                    # Copy into target dataset with de-dup by target path
                    for f in chosen:
                        src_path = f.file_path
                        new_path = src_path
                        needs_copy = False
                        src_prefix = f"/dataset/{rel.source_dataset_id}"
                        if isinstance(src_path, str) and src_path.startswith(src_prefix):
                            dst_prefix = f"/dataset/{target_ds.id}"
                            new_path = src_path.replace(src_prefix, dst_prefix, 1)
                            needs_copy = True

                        # De-dup by target path
                        if new_path in existing_paths:
                            continue

                        # Perform copy only when needed
                        if needs_copy:
                            dst_dir = os.path.dirname(new_path)
                            await asyncio.to_thread(os.makedirs, dst_dir, exist_ok=True)
                            await asyncio.to_thread(shutil.copy2, src_path, new_path)

                        new_file = DatasetFiles(
                            dataset_id=target_ds.id,  # type: ignore
                            file_name=f.file_name,
                            file_path=new_path,
                            file_type=f.file_type,
                            file_size=f.file_size,
                            check_sum=f.check_sum,
                            tags=f.tags,
                            dataset_filemetadata=f.dataset_filemetadata,
                            status="ACTIVE",
                        )
                        session.add(new_file)
                        existing_paths.add(new_path)
                        added_count += 1
                        added_size += int(f.file_size or 0)

                    # Periodically flush to avoid huge transactions
                    await session.flush()

                # Update target dataset statistics
                target_ds.file_count = (target_ds.file_count or 0) + added_count  # type: ignore
                target_ds.size_bytes = (target_ds.size_bytes or 0) + added_size  # type: ignore
                # If target dataset has files, mark it ACTIVE
                if (target_ds.file_count or 0) > 0:  # type: ignore
                    target_ds.status = "ACTIVE"

                # Done
                instance.status = "SUCCESS"
                logger.info(f"Dataset ratio execution completed: instance={instance_id}, files={added_count}, size={added_size}")

            except Exception as e:
                logger.exception(f"Dataset ratio execution failed for {instance_id}: {e}")
                try:
                    # Try mark failed
                    inst_res = await session.execute(select(RatioInstance).where(RatioInstance.id == instance_id))
                    instance = inst_res.scalar_one_or_none()
                    if instance:
                        instance.status = "FAILED"
                finally:
                    pass
            finally:
                await session.commit()

    # ------------------------- helpers for TAG filtering ------------------------- #

    @staticmethod
    def _parse_required_tags(conditions: Optional[str]) -> set[str]:
        """Parse filter_conditions into a set of required tag strings.

        Supports simple separators: comma, semicolon, space. Empty/None -> empty set.
        """
        if not conditions:
            return set()
        raw = conditions.replace("\n", " ")
        seps = [",", ";", " "]
        tokens = [raw]
        for sep in seps:
            nxt = []
            for t in tokens:
                nxt.extend(t.split(sep))
            tokens = nxt
        return {t.strip() for t in tokens if t and t.strip()}

    @staticmethod
    def _file_contains_tags(f: DatasetFiles, required: set[str]) -> bool:
        if not required:
            return True
        tags = f.tags
        if not tags:
            return False
        try:
            # tags could be a list of strings or list of objects with 'name'
            tag_names = set()
            if isinstance(tags, list):
                for item in tags:
                    if isinstance(item, str):
                        tag_names.add(item)
                    elif isinstance(item, dict):
                        name = item.get("name") or item.get("label") or item.get("tag")
                        if isinstance(name, str):
                            tag_names.add(name)
            elif isinstance(tags, dict):
                # flat dict of name->... treat keys as tags
                tag_names = set(map(str, tags.keys()))
            else:
                return False
            logger.info(f">>>>>{tags}>>>>>{required}, {tag_names}")
            return required.issubset(tag_names)
        except Exception:
            return False

    @staticmethod
    async def get_new_file(f, rel: RatioRelation, target_ds: Dataset) -> DatasetFiles:
        new_path = f.file_path
        src_prefix = f"/dataset/{rel.source_dataset_id}"
        if isinstance(f.file_path, str) and f.file_path.startswith(src_prefix):
            dst_prefix = f"/dataset/{target_ds.id}"
            new_path = f.file_path.replace(src_prefix, dst_prefix, 1)
            dst_dir = os.path.dirname(new_path)
            # Ensure directory and copy the file in a thread to avoid blocking the event loop
            await asyncio.to_thread(os.makedirs, dst_dir, exist_ok=True)
            await asyncio.to_thread(shutil.copy2, f.file_path, new_path)

        new_file = DatasetFiles(
            dataset_id=target_ds.id,  # type: ignore
            file_name=f.file_name,
            file_path=new_path,
            file_type=f.file_type,
            file_size=f.file_size,
            check_sum=f.check_sum,
            tags=f.tags,
            dataset_filemetadata=f.dataset_filemetadata,
            status="ACTIVE",
        )
        return new_file