"""Documents router: CRUD for reference documents, items, and item versions."""

from __future__ import annotations

import difflib
import logging
import uuid

from fastapi import APIRouter, Depends, HTTPException, Query, status
from sqlalchemy import func, select
from sqlalchemy.ext.asyncio import AsyncSession

from app.database import get_db
from app.models.document import Document, DocumentItem, ItemVersion
from app.models.user import DuniterIdentity
from app.schemas.document import (
    DocumentCreate,
    DocumentFullOut,
    DocumentItemCreate,
    DocumentItemOut,
    DocumentItemUpdate,
    DocumentOut,
    DocumentUpdate,
    ItemReorderRequest,
    ItemVersionCreate,
    ItemVersionOut,
)
from app.services import document_service
from app.services.auth_service import get_current_identity

logger = logging.getLogger(__name__)

router = APIRouter()


# ── Helpers ─────────────────────────────────────────────────────────────────


async def _get_document_by_slug(db: AsyncSession, slug: str) -> Document:
    """Fetch a document by slug or raise 404."""
    result = await db.execute(select(Document).where(Document.slug == slug))
    doc = result.scalar_one_or_none()
    if doc is None:
        raise HTTPException(status_code=status.HTTP_404_NOT_FOUND, detail="Document introuvable")
    return doc


async def _get_item(db: AsyncSession, document_id: uuid.UUID, item_id: uuid.UUID) -> DocumentItem:
    """Fetch a document item by ID within a document, or raise 404."""
    result = await db.execute(
        select(DocumentItem).where(
            DocumentItem.id == item_id,
            DocumentItem.document_id == document_id,
        )
    )
    item = result.scalar_one_or_none()
    if item is None:
        raise HTTPException(status_code=status.HTTP_404_NOT_FOUND, detail="Item introuvable")
    return item


# ── Document routes ─────────────────────────────────────────────────────────


@router.get("/", response_model=list[DocumentOut])
async def list_documents(
    db: AsyncSession = Depends(get_db),
    doc_type: str | None = Query(default=None, description="Filtrer par type de document"),
    status_filter: str | None = Query(default=None, alias="status", description="Filtrer par statut"),
    skip: int = Query(default=0, ge=0),
    limit: int = Query(default=50, ge=1, le=200),
) -> list[DocumentOut]:
    """List all reference documents, with optional filters."""
    stmt = select(Document)

    if doc_type is not None:
        stmt = stmt.where(Document.doc_type == doc_type)
    if status_filter is not None:
        stmt = stmt.where(Document.status == status_filter)

    stmt = stmt.order_by(Document.created_at.desc()).offset(skip).limit(limit)
    result = await db.execute(stmt)
    documents = result.scalars().all()

    # Compute items_count for each document
    out = []
    for doc in documents:
        count_result = await db.execute(
            select(func.count()).select_from(DocumentItem).where(DocumentItem.document_id == doc.id)
        )
        items_count = count_result.scalar() or 0
        doc_out = DocumentOut.model_validate(doc)
        doc_out.items_count = items_count
        out.append(doc_out)

    return out


@router.post("/", response_model=DocumentOut, status_code=status.HTTP_201_CREATED)
async def create_document(
    payload: DocumentCreate,
    db: AsyncSession = Depends(get_db),
    identity: DuniterIdentity = Depends(get_current_identity),
) -> DocumentOut:
    """Create a new reference document."""
    # Check slug uniqueness
    existing = await db.execute(select(Document).where(Document.slug == payload.slug))
    if existing.scalar_one_or_none() is not None:
        raise HTTPException(
            status_code=status.HTTP_409_CONFLICT,
            detail="Un document avec ce slug existe deja",
        )

    doc = Document(**payload.model_dump())
    db.add(doc)
    await db.commit()
    await db.refresh(doc)

    doc_out = DocumentOut.model_validate(doc)
    doc_out.items_count = 0
    return doc_out


@router.get("/{slug}", response_model=DocumentOut)
async def get_document(
    slug: str,
    db: AsyncSession = Depends(get_db),
) -> DocumentOut:
    """Get a single document by its slug."""
    doc = await _get_document_by_slug(db, slug)

    count_result = await db.execute(
        select(func.count()).select_from(DocumentItem).where(DocumentItem.document_id == doc.id)
    )
    items_count = count_result.scalar() or 0

    doc_out = DocumentOut.model_validate(doc)
    doc_out.items_count = items_count
    return doc_out


@router.put("/{slug}", response_model=DocumentOut)
async def update_document(
    slug: str,
    payload: DocumentUpdate,
    db: AsyncSession = Depends(get_db),
    identity: DuniterIdentity = Depends(get_current_identity),
) -> DocumentOut:
    """Update a document's metadata (title, status, description, version)."""
    doc = await _get_document_by_slug(db, slug)

    update_data = payload.model_dump(exclude_unset=True)
    for field, value in update_data.items():
        setattr(doc, field, value)

    await db.commit()
    await db.refresh(doc)

    count_result = await db.execute(
        select(func.count()).select_from(DocumentItem).where(DocumentItem.document_id == doc.id)
    )
    items_count = count_result.scalar() or 0

    doc_out = DocumentOut.model_validate(doc)
    doc_out.items_count = items_count
    return doc_out


# ── Document Item routes ────────────────────────────────────────────────────


@router.post("/{slug}/items", response_model=DocumentItemOut, status_code=status.HTTP_201_CREATED)
async def add_item(
    slug: str,
    payload: DocumentItemCreate,
    db: AsyncSession = Depends(get_db),
    identity: DuniterIdentity = Depends(get_current_identity),
) -> DocumentItemOut:
    """Add a new item (clause, rule, etc.) to a document."""
    doc = await _get_document_by_slug(db, slug)

    # Determine sort_order: max existing + 1
    max_order_result = await db.execute(
        select(func.max(DocumentItem.sort_order)).where(DocumentItem.document_id == doc.id)
    )
    max_order = max_order_result.scalar() or 0

    item = DocumentItem(
        document_id=doc.id,
        sort_order=max_order + 1,
        **payload.model_dump(),
    )
    db.add(item)
    await db.commit()
    await db.refresh(item)

    return DocumentItemOut.model_validate(item)


@router.get("/{slug}/items", response_model=list[DocumentItemOut])
async def list_items(
    slug: str,
    db: AsyncSession = Depends(get_db),
) -> list[DocumentItemOut]:
    """List all items in a document, ordered by sort_order."""
    doc = await _get_document_by_slug(db, slug)

    result = await db.execute(
        select(DocumentItem)
        .where(DocumentItem.document_id == doc.id)
        .order_by(DocumentItem.sort_order)
    )
    items = result.scalars().all()
    return [DocumentItemOut.model_validate(item) for item in items]


# NOTE: reorder must be declared BEFORE /{slug}/items/{item_id} routes
# to avoid "reorder" being parsed as a UUID path parameter.


@router.put("/{slug}/items/reorder", response_model=list[DocumentItemOut])
async def reorder_items(
    slug: str,
    payload: ItemReorderRequest,
    db: AsyncSession = Depends(get_db),
    identity: DuniterIdentity = Depends(get_current_identity),
) -> list[DocumentItemOut]:
    """Reorder items in a document by updating their sort_order values."""
    doc = await _get_document_by_slug(db, slug)

    items = await document_service.reorder_items(
        doc.id,
        [(entry.item_id, entry.sort_order) for entry in payload.items],
        db,
    )

    return [DocumentItemOut.model_validate(item) for item in items]


@router.get("/{slug}/items/{item_id}", response_model=DocumentItemOut)
async def get_item(
    slug: str,
    item_id: uuid.UUID,
    db: AsyncSession = Depends(get_db),
) -> DocumentItemOut:
    """Get a single item with its version history."""
    doc = await _get_document_by_slug(db, slug)
    item = await _get_item(db, doc.id, item_id)
    return DocumentItemOut.model_validate(item)


@router.post(
    "/{slug}/items/{item_id}/versions",
    response_model=ItemVersionOut,
    status_code=status.HTTP_201_CREATED,
)
async def propose_version(
    slug: str,
    item_id: uuid.UUID,
    payload: ItemVersionCreate,
    db: AsyncSession = Depends(get_db),
    identity: DuniterIdentity = Depends(get_current_identity),
) -> ItemVersionOut:
    """Propose a new version of a document item.

    Automatically computes a unified diff between the current text and the proposed text.
    """
    doc = await _get_document_by_slug(db, slug)
    item = await _get_item(db, doc.id, item_id)

    # Compute diff
    diff_lines = difflib.unified_diff(
        item.current_text.splitlines(keepends=True),
        payload.proposed_text.splitlines(keepends=True),
        fromfile="actuel",
        tofile="propose",
    )
    diff_text = "".join(diff_lines) or None

    version = ItemVersion(
        item_id=item.id,
        proposed_text=payload.proposed_text,
        diff_text=diff_text,
        rationale=payload.rationale,
        proposed_by_id=identity.id,
    )
    db.add(version)
    await db.commit()
    await db.refresh(version)

    return ItemVersionOut.model_validate(version)


# ── Item update & delete ───────────────────────────────────────────────────


@router.put("/{slug}/items/{item_id}", response_model=DocumentItemOut)
async def update_item(
    slug: str,
    item_id: uuid.UUID,
    payload: DocumentItemUpdate,
    db: AsyncSession = Depends(get_db),
    identity: DuniterIdentity = Depends(get_current_identity),
) -> DocumentItemOut:
    """Update an item's text, title, position, or item_type."""
    doc = await _get_document_by_slug(db, slug)
    item = await _get_item(db, doc.id, item_id)

    update_data = payload.model_dump(exclude_unset=True)
    for field, value in update_data.items():
        setattr(item, field, value)

    await db.commit()
    await db.refresh(item)

    return DocumentItemOut.model_validate(item)


@router.delete("/{slug}/items/{item_id}", status_code=status.HTTP_204_NO_CONTENT)
async def delete_item(
    slug: str,
    item_id: uuid.UUID,
    db: AsyncSession = Depends(get_db),
    identity: DuniterIdentity = Depends(get_current_identity),
) -> None:
    """Delete a document item.

    Refuses deletion if the item has any active votes (status 'voting').
    """
    doc = await _get_document_by_slug(db, slug)
    item = await _get_item(db, doc.id, item_id)

    # Check for active votes on this item's versions
    active_versions_result = await db.execute(
        select(func.count()).select_from(ItemVersion).where(
            ItemVersion.item_id == item.id,
            ItemVersion.status == "voting",
        )
    )
    active_count = active_versions_result.scalar() or 0
    if active_count > 0:
        raise HTTPException(
            status_code=status.HTTP_409_CONFLICT,
            detail="Impossible de supprimer un element avec des votes en cours",
        )

    await db.delete(item)
    await db.commit()


# ── Version accept & reject ────────────────────────────────────────────────


@router.put(
    "/{slug}/items/{item_id}/versions/{version_id}/accept",
    response_model=DocumentItemOut,
)
async def accept_version(
    slug: str,
    item_id: uuid.UUID,
    version_id: uuid.UUID,
    db: AsyncSession = Depends(get_db),
    identity: DuniterIdentity = Depends(get_current_identity),
) -> DocumentItemOut:
    """Accept a proposed version and apply it to the document item.

    Replaces the item's current_text with the version's proposed_text
    and rejects all other pending/voting versions for this item.
    """
    doc = await _get_document_by_slug(db, slug)
    # Verify item belongs to document
    await _get_item(db, doc.id, item_id)

    try:
        updated_item = await document_service.apply_version(item_id, version_id, db)
    except ValueError as exc:
        raise HTTPException(status_code=status.HTTP_404_NOT_FOUND, detail=str(exc))

    return DocumentItemOut.model_validate(updated_item)


@router.put(
    "/{slug}/items/{item_id}/versions/{version_id}/reject",
    response_model=ItemVersionOut,
)
async def reject_version(
    slug: str,
    item_id: uuid.UUID,
    version_id: uuid.UUID,
    db: AsyncSession = Depends(get_db),
    identity: DuniterIdentity = Depends(get_current_identity),
) -> ItemVersionOut:
    """Reject a proposed version."""
    doc = await _get_document_by_slug(db, slug)
    # Verify item belongs to document
    await _get_item(db, doc.id, item_id)

    try:
        version = await document_service.reject_version(item_id, version_id, db)
    except ValueError as exc:
        raise HTTPException(status_code=status.HTTP_404_NOT_FOUND, detail=str(exc))

    return ItemVersionOut.model_validate(version)


# ── Version listing ────────────────────────────────────────────────────────


@router.get(
    "/{slug}/items/{item_id}/versions",
    response_model=list[ItemVersionOut],
)
async def list_versions(
    slug: str,
    item_id: uuid.UUID,
    db: AsyncSession = Depends(get_db),
) -> list[ItemVersionOut]:
    """List all versions for a document item."""
    doc = await _get_document_by_slug(db, slug)
    await _get_item(db, doc.id, item_id)

    result = await db.execute(
        select(ItemVersion)
        .where(ItemVersion.item_id == item_id)
        .order_by(ItemVersion.created_at.desc())
    )
    versions = result.scalars().all()
    return [ItemVersionOut.model_validate(v) for v in versions]


# ── Document full view ─────────────────────────────────────────────────────


@router.get("/{slug}/full", response_model=DocumentFullOut)
async def get_document_full(
    slug: str,
    db: AsyncSession = Depends(get_db),
) -> DocumentFullOut:
    """Get a document with all its items (not just count)."""
    doc = await document_service.get_document_with_items(slug, db)
    if doc is None:
        raise HTTPException(status_code=status.HTTP_404_NOT_FOUND, detail="Document introuvable")

    return DocumentFullOut.model_validate(doc)


# ── Document archive to sanctuary ──────────────────────────────────────────


@router.post("/{slug}/archive", status_code=status.HTTP_201_CREATED)
async def archive_document(
    slug: str,
    db: AsyncSession = Depends(get_db),
    identity: DuniterIdentity = Depends(get_current_identity),
) -> dict:
    """Archive a document to the sanctuary (IPFS + on-chain hash).

    Serializes the full document text and sends it through the sanctuary pipeline.
    """
    entry = await document_service.archive_document(slug, db)
    return {
        "message": "Document archive avec succes",
        "sanctuary_entry_id": str(entry.id),
        "content_hash": entry.content_hash,
        "ipfs_cid": entry.ipfs_cid,
        "chain_tx_hash": entry.chain_tx_hash,
    }