"""API routes for approval requests — /api/v1/approvals.

Endpoints: create, list (filterable), get detail, approve, reject, expire.
"""

from __future__ import annotations

import logging
import uuid
from datetime import UTC, datetime
from typing import Any

from fastapi import APIRouter, Depends, HTTPException, Query
from pydantic import BaseModel, Field
from sqlalchemy import select
from sqlalchemy.ext.asyncio import AsyncSession

from app.core.approval import (
    APPROVAL_STATUSES,
    ApprovalRequest,
    create_approval_request,
    expire_approval_request,
    resolve_approval_request,
)
from app.core.db import get_db
from app.deps import get_current_user, require_permission

logger = logging.getLogger(__name__)

router = APIRouter(prefix="/api/v1/approvals", tags=["approvals"])


# ─── Schemas ───


class ApprovalCreate(BaseModel):
    """Create an approval request."""

    entity_type: str = Field(..., min_length=1, max_length=80)
    entity_id: str = Field(..., min_length=1)
    action: str = Field(..., min_length=1, max_length=120)
    requested_by: str | None = None
    requested_by_type: str = Field("agent", pattern="^(user|agent|system)$")
    approver_id: str | None = None
    approver_group: str | None = Field(None, max_length=120)
    expires_at: str | None = None
    metadata: dict[str, Any] = Field(default_factory=dict)


class ApprovalResolve(BaseModel):
    """Approve or reject an approval request."""

    comment: str | None = Field(None, max_length=2000)


class ApprovalResponse(BaseModel):
    """Approval request response."""

    id: str
    tenant_id: str
    entity_type: str
    entity_id: str
    action: str
    requested_by: str
    requested_by_type: str
    approver_id: str | None = None
    approver_group: str | None = None
    status: str
    comment: str | None = None
    created_at: str | None = None
    resolved_at: str | None = None
    expires_at: str | None = None
    metadata: dict[str, Any] = Field(default_factory=dict)


class ApprovalListResponse(BaseModel):
    """Paginated approval request list."""

    items: list[ApprovalResponse]
    total: int


# ─── Helpers ───


def _to_response(r: ApprovalRequest) -> ApprovalResponse:
    return ApprovalResponse(
        id=str(r.id),
        tenant_id=str(r.tenant_id),
        entity_type=r.entity_type,
        entity_id=str(r.entity_id),
        action=r.action,
        requested_by=str(r.requested_by),
        requested_by_type=r.requested_by_type,
        approver_id=str(r.approver_id) if r.approver_id else None,
        approver_group=r.approver_group,
        status=r.status,
        comment=r.comment,
        created_at=r.created_at.isoformat() if r.created_at else None,
        resolved_at=r.resolved_at.isoformat() if r.resolved_at else None,
        expires_at=r.expires_at.isoformat() if r.expires_at else None,
        metadata=r.request_metadata or {},
    )


def _parse_uuid(value: str, field: str) -> uuid.UUID:
    try:
        return uuid.UUID(value)
    except (ValueError, TypeError):
        raise HTTPException(status_code=400, detail=f"Invalid {field}") from None


# ─── Endpoints ───


@router.post(
    "",
    dependencies=[Depends(require_permission("approvals:write"))],
    response_model=ApprovalResponse,
    status_code=201,
)
async def create_approval(
    data: ApprovalCreate,
    current_user: dict[str, Any] = Depends(get_current_user),
    db: AsyncSession = Depends(get_db),
):
    """Create a new approval request."""
    tenant_id = uuid.UUID(current_user["tenant_id"])
    entity_id = _parse_uuid(data.entity_id, "entity_id")
    requested_by = (
        _parse_uuid(data.requested_by, "requested_by")
        if data.requested_by
        else uuid.UUID(current_user["user_id"])
    )
    approver_id = _parse_uuid(data.approver_id, "approver_id") if data.approver_id else None
    expires_at = None
    if data.expires_at:
        try:
            expires_at = datetime.fromisoformat(data.expires_at.replace("Z", "+00:00"))
        except ValueError:
            raise HTTPException(status_code=400, detail="Invalid expires_at") from None

    req = await create_approval_request(
        db,
        tenant_id,
        entity_type=data.entity_type,
        entity_id=entity_id,
        action=data.action,
        requested_by=requested_by,
        requested_by_type=data.requested_by_type,
        approver_id=approver_id,
        approver_group=data.approver_group,
        expires_at=expires_at,
        metadata=data.metadata,
    )
    await db.commit()
    return _to_response(req)


@router.get(
    "",
    dependencies=[Depends(require_permission("approvals:read"))],
    response_model=ApprovalListResponse,
)
async def list_approvals(
    status: str | None = Query(None),
    entity_type: str | None = Query(None),
    entity_id: str | None = Query(None),
    requested_by: str | None = Query(None),
    limit: int = Query(50, ge=1, le=200),
    offset: int = Query(0, ge=0),
    current_user: dict[str, Any] = Depends(get_current_user),
    db: AsyncSession = Depends(get_db),
):
    """List approval requests with optional filters."""
    tenant_id = uuid.UUID(current_user["tenant_id"])
    query = select(ApprovalRequest).where(ApprovalRequest.tenant_id == tenant_id)
    count_query = (
        select(__import__("sqlalchemy").func.count())
        .select_from(ApprovalRequest)
        .where(ApprovalRequest.tenant_id == tenant_id)
    )

    if status:
        query = query.where(ApprovalRequest.status == status)
        count_query = count_query.where(ApprovalRequest.status == status)
    if entity_type:
        query = query.where(ApprovalRequest.entity_type == entity_type)
        count_query = count_query.where(ApprovalRequest.entity_type == entity_type)
    if entity_id:
        eid = _parse_uuid(entity_id, "entity_id")
        query = query.where(ApprovalRequest.entity_id == eid)
        count_query = count_query.where(ApprovalRequest.entity_id == eid)
    if requested_by:
        rid = _parse_uuid(requested_by, "requested_by")
        query = query.where(ApprovalRequest.requested_by == rid)
        count_query = count_query.where(ApprovalRequest.requested_by == rid)

    total = (await db.execute(count_query)).scalar() or 0
    result = await db.execute(
        query.order_by(ApprovalRequest.created_at.desc()).limit(limit).offset(offset)
    )
    items = list(result.scalars().all())
    return ApprovalListResponse(items=[_to_response(r) for r in items], total=total)


@router.get(
    "/{request_id}",
    dependencies=[Depends(require_permission("approvals:read"))],
    response_model=ApprovalResponse,
)
async def get_approval(
    request_id: str,
    current_user: dict[str, Any] = Depends(get_current_user),
    db: AsyncSession = Depends(get_db),
):
    """Get a single approval request by ID."""
    tenant_id = uuid.UUID(current_user["tenant_id"])
    rid = _parse_uuid(request_id, "request_id")
    result = await db.execute(
        select(ApprovalRequest).where(
            ApprovalRequest.id == rid,
            ApprovalRequest.tenant_id == tenant_id,
        )
    )
    req = result.scalar_one_or_none()
    if req is None:
        raise HTTPException(status_code=404, detail="Approval request not found")
    return _to_response(req)


@router.post(
    "/{request_id}/approve",
    dependencies=[Depends(require_permission("approvals:approve"))],
    response_model=ApprovalResponse,
)
async def approve_approval(
    request_id: str,
    body: ApprovalResolve,
    current_user: dict[str, Any] = Depends(get_current_user),
    db: AsyncSession = Depends(get_db),
):
    """Approve a pending approval request."""
    tenant_id = uuid.UUID(current_user["tenant_id"])
    rid = _parse_uuid(request_id, "request_id")
    req = await resolve_approval_request(
        db,
        tenant_id,
        rid,
        decision="approved",
        approver_id=uuid.UUID(current_user["user_id"]),
        comment=body.comment,
    )
    if req is None:
        raise HTTPException(status_code=404, detail="Approval request not found or not pending")
    await db.commit()
    return _to_response(req)


@router.post(
    "/{request_id}/reject",
    dependencies=[Depends(require_permission("approvals:approve"))],
    response_model=ApprovalResponse,
)
async def reject_approval(
    request_id: str,
    body: ApprovalResolve,
    current_user: dict[str, Any] = Depends(get_current_user),
    db: AsyncSession = Depends(get_db),
):
    """Reject a pending approval request."""
    tenant_id = uuid.UUID(current_user["tenant_id"])
    rid = _parse_uuid(request_id, "request_id")
    req = await resolve_approval_request(
        db,
        tenant_id,
        rid,
        decision="rejected",
        approver_id=uuid.UUID(current_user["user_id"]),
        comment=body.comment,
    )
    if req is None:
        raise HTTPException(status_code=404, detail="Approval request not found or not pending")
    await db.commit()
    return _to_response(req)


@router.post(
    "/{request_id}/expire",
    dependencies=[Depends(require_permission("approvals:write"))],
    response_model=ApprovalResponse,
)
async def expire_approval(
    request_id: str,
    current_user: dict[str, Any] = Depends(get_current_user),
    db: AsyncSession = Depends(get_db),
):
    """Mark a pending approval request as expired (system only)."""
    tenant_id = uuid.UUID(current_user["tenant_id"])
    rid = _parse_uuid(request_id, "request_id")
    req = await expire_approval_request(db, tenant_id, rid)
    if req is None:
        raise HTTPException(status_code=404, detail="Approval request not found or not pending")
    await db.commit()
    return _to_response(req)